Develop Reference

Android Studio RecyclerView: Why always ( No adapter attached; skipping layout )

I am a student who currently taking mobile application development. Although my app can run but it doesnt show any activity instead of just give me W/RecyclerView: No adapter attached; skipping layout. I dont know how to solve the issue, so I was hoping can get some guidlines from experts.
Here is my code
MainActivity.java
package my.edu.utar.practicalassignment;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
public class MainActivity extends AppCompatActivity {
private Toolbar tool;
private TextView textView;
private RecyclerView recyclerView;
private Button AddBtn;
RecyclerView.LayoutManager layoutManager;
private FirebaseAuth auth;
private DatabaseReference ref;
private String userID = "";
private ProgressDialog progressDialog;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tool = findViewById(R.id.toolbar);
setSupportActionBar(tool);
//getSupportActionBar().setTitle("Today's Spending");
textView=findViewById(R.id.totalCashBack);
recyclerView =findViewById(R.id.recycle_view);
// recyclerView =(RecyclerView)findViewById(R.id.recycleView);
// layoutManager = new LinearLayoutManager(this);
// recyclerView.setLayoutManager(layoutManager);
AddBtn = findViewById(R.id.add_new);
auth = FirebaseAuth.getInstance();
userID = auth.getCurrentUser().getUid();
ref = FirebaseDatabase.getInstance().getReference().child("expenses").child(userID);
// if(userID !=null){
// try{
// ref = FirebaseDatabase.getInstance().getReference().child("expenses").child(userID);
//
// }catch (NullPointerException ex){
// ex.printStackTrace();
// }
// }
progressDialog = new ProgressDialog(this);
AddBtn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
addItem();
}
});
}
private void addItem() {
AlertDialog.Builder alert = new AlertDialog.Builder(this);
LayoutInflater layout = LayoutInflater.from(this);
View view = layout.inflate(R.layout.input_layout, null);
alert.setView(view);
final AlertDialog dialog = alert.create();
dialog.setCancelable(false);
final Spinner spinnerItem = view.findViewById(R.id.spinner);
ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.category));
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinnerItem.setAdapter(adapter);
final EditText amount = view.findViewById(R.id.insert_amount);
final EditText notes = view.findViewById(R.id.insert_note);
final Button saveButton = view.findViewById(R.id.add_button);
final Button cancelButton = view.findViewById(R.id.cancel_button);
saveButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
String amountGet = amount.getText().toString();
String notesGet = notes.getText().toString();
String categoryGet = spinnerItem.getSelectedItem().toString();
Drawable icon = getResources().getDrawable(R.drawable.error);
if(amountGet.isEmpty()){
amount.setError("Please enter an amount!!!", icon );
return;
}
if(notesGet.isEmpty()){
notes.setError("Please enter a notes!!!", icon );
return;
}
if(categoryGet.equals("Select a Category")){
Toast.makeText(MainActivity.this, "Please select a valid category", Toast.LENGTH_SHORT).show();
}
else{
progressDialog.setMessage("Had added the information into database");
progressDialog.setCanceledOnTouchOutside(false);
progressDialog.show();
String id = ref.push().getKey();
DateFormat format = new SimpleDateFormat("dd-MM-yyyy");
Calendar calendar = Calendar.getInstance();
String date = format.format(calendar.getTime());
Data inform = new Data(categoryGet, date, id, notesGet, Integer.parseInt(amountGet));
ref.child(id).setValue(inform).addOnCompleteListener(new OnCompleteListener<Void>() {
#Override
public void onComplete(#NonNull Task<Void> task) {
if(task.isSuccessful()){
Toast.makeText(MainActivity.this, "Information added successfully", Toast.LENGTH_SHORT).show();
}else{
Toast.makeText(MainActivity.this, "Fail to add the information", Toast.LENGTH_SHORT).show();
}
progressDialog.dismiss();
}
});
}
dialog.dismiss();
}
});
cancelButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
dialog.dismiss();
}
});
}
}
MainActivity.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#000"
android:orientation="vertical"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#ffff00"
android:elevation="4dp" />
<TextView
android:id="#+id/totalCashBack"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="5dp"
android:gravity="center"
android:text=" Total Cash Back = RM 0"
android:textColor="#fff"
android:textSize="20sp"
android:textStyle="bold" />
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recycle_view"
android:layout_width="match_parent"
android:layout_height="556dp" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
</LinearLayout>
<Button
android:id="#+id/add_new"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|end"
android:layout_margin="16dp"
android:backgroundTint="#ffff00"
android:text="Add"
app:fabSize="normal" />
</LinearLayout>
InputLayout.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:elevation="10dp"
app:cardElevation="10dp"
android:layout_margin="10dp"
android:orientation="vertical"
android:layout_height="match_parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:background="#000"
android:layout_margin="10dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:gravity="center">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="What did you had spend on ?"
android:gravity="center"
android:textColor="#fff"
android:textStyle="bold"
android:layout_margin="5dp"
android:textSize="20sp"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<Spinner
android:id="#+id/spinner"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:background="#ffff00"
android:entries="#array/category"/>
<EditText
android:id="#+id/insert_amount"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Please enter a amount:"
android:textColor="#fff"
android:inputType="number"
android:textColorHint="#fff"/>
<EditText
android:id="#+id/insert_note"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Please enter a note:"
android:textColor="#fff"
android:textColorHint="#fff"/>
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<RelativeLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1">
<Button
android:id="#+id/cancel_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Cancel"
android:textAllCaps="false"
android:textColor="#000"
android:textStyle="bold"
android:background="#fff"
android:layout_margin="2dp"/>
</RelativeLayout>
<RelativeLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1">
<Button
android:id="#+id/add_button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Add Transaction"
android:textAllCaps="false"
android:textColor="#000"
android:textStyle="bold"
android:background="#ffff00"
android:layout_margin="2dp"/>
</RelativeLayout>
</LinearLayout>
</LinearLayout>
</androidx.cardview.widget.CardView>
strings.xml
<resources>
<string name="app_name">PracticalAssignment</string>
<string-array name="category">
<item>Select a category</item>
<item>Petrol Spend</item>
<item>Groceries Spend</item>
<item>eWallet Transaction</item>
<item>Other Eligible Spend</item>
</string-array>
</resources>

You have to create an adapter class and add with your recycler view.
The basic snippet to set adapter to recycler view is like bellow
YourAdater adapter = YourAdater();
layoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(layoutManager);
recyclerView.setAdapter(adapter);
for more detail that how to create a RecyclerView AdapterClass you can see this or this

Search In Json Functionality

So, I get some data from a nutrition database and I want to add a search option. I'm new to Android Studio so some advice would help me.
This is the app:
This edittext should search in the database and show after the name of products. Is there an easier way to make this work?
This is the activity layout:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".NutritionDatabase">
<EditText
android:id="#+id/et_dataInput"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:ems="10"
android:hint="Search Database"
android:inputType="textPersonName"
android:layout_marginTop="-58dp"
app:layout_constraintTop_toTopOf="#id/list"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"/>
<ListView
android:id="#+id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="123dp"
app:layout_constraintTop_toTopOf="parent"
tools:layout_editor_absoluteX="0dp" />
<RelativeLayout
android:id="#+id/relativeLayout"
android:layout_width="0dp"
android:layout_height="wrap_content"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="411dp"
android:layout_height="wrap_content"
android:background="#000000" />
<ImageView
android:id="#+id/back_to_home"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:minWidth="40dp"
android:minHeight="45dp"
android:paddingTop="15dp"
android:src="#drawable/ic_back" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingTop="16dp"
android:text="Nutrition Database"
android:textAlignment="center"
android:textColor="#FFFFFFFF"
android:textSize="20sp"
android:textStyle="bold" />
</RelativeLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
This is the java class:
package com.example.myapplication;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
public class NutritionDatabase extends AppCompatActivity {
EditText et_dataInput;
private String TAG = MainActivity.class.getSimpleName();
private ListView lv;
ArrayList<HashMap<String, String>> resultList;
#Override
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);
switch (item.getItemId()) {
case android.R.id.home:
finish();
break;
}
return true;
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_nutrition_database);
et_dataInput=findViewById(R.id.et_dataInput);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
if (getSupportActionBar() != null){
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
resultList = new ArrayList<>();
lv = (ListView) findViewById(R.id.list);
new GetContacts().execute();
}
private class GetContacts extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
Toast.makeText(NutritionDatabase.this,"Json Data is downloading",Toast.LENGTH_LONG).show();
}
#Override
protected Void doInBackground(Void... arg0) {
HttpHandler sh = new HttpHandler();
// Making a request to url and getting response
String url = "https://wger.de/api/v2/ingredient/?language=2&limit=11865";
String jsonStr = sh.makeServiceCall(url);
Log.e(TAG, "Response from url: " + jsonStr);
if (jsonStr != null) {
try {
JSONObject jsonObj = new JSONObject(jsonStr);
// Getting JSON Array node
JSONArray results = jsonObj.getJSONArray("results");
// looping through All Contacts
for (int i = 0; i < results.length(); i++) {
JSONObject c = results.getJSONObject(i);
String name = c.getString("name");
String fat = c.getString("fat");
String protein = c.getString("protein");
String energy = c.getString("energy");
String carbohydrates = c.getString("carbohydrates");
String carbohydrates_sugar = c.getString("carbohydrates_sugar");
String fat_saturated = c.getString("fat_saturated");
String fibres = c.getString("fibres");
String sodium = c.getString("sodium");
// tmp hash map for single contact
HashMap<String, String> result = new HashMap<>();
// adding each child node to HashMap key => value
result.put("name","Name :"+ name);
result.put("fat","Fat :"+ fat);
result.put("protein","Protein :"+ protein);
result.put("energy","Energy :"+ energy);
result.put("carbohydrates","Carbohydrates :"+ carbohydrates);
result.put("carbohydrates_sugar","Carbohydrates from sugar :"+ carbohydrates_sugar);
result.put("fat_saturated","Saturated Fat:"+ fat_saturated);
result.put("fibres","Fibres :"+ fibres);
result.put("sodium","Sodium :"+ sodium);
// adding contact to contact list
resultList.add(result);
}
} catch (final JSONException e) {
Log.e(TAG, "Json parsing error: " + e.getMessage());
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(),
"Json parsing error: " + e.getMessage(),Toast.LENGTH_LONG).show();
}
});
}
} else {
Log.e(TAG, "Couldn't get json from server.");
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(),
"Couldn't get json from server. Check LogCat for possible errors!",
Toast.LENGTH_LONG).show();
}
});
}
return null;
}
#Override
protected void onPostExecute(Void result) {
super.onPostExecute(result);
ListAdapter adapter = new SimpleAdapter(NutritionDatabase.this, resultList,
R.layout.list_item_nutrition, new String[]{ "name","fat","energy","protein","carbohydrates","carbohydrates_sugar","fat_saturated","fibres","sodium"},
new int[]{R.id.name, R.id.fat,R.id.protein,R.id.energy,R.id.carbohydrates,R.id.carbohidrates_sugar,R.id.fat_saturated,R.id.fibres,R.id.sodium});
lv.setAdapter(adapter);
}
}
}
This is the list that I use :
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="#dimen/activity_horizontal_margin">
<TextView
android:paddingTop="10dp"
android:id="#+id/name"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:textColor="#color/colorAccent"
android:text="Name:"/>
<TextView
android:id="#+id/energy"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#5d5d5d"
android:textStyle="bold"
android:paddingTop="10dp"
android:text="Energy:"
/>
<TextView
android:id="#+id/protein"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#5d5d5d"
android:textStyle="bold"
android:text="Protein:"
/>
<TextView
android:id="#+id/carbohydrates"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#5d5d5d"
android:textStyle="bold"
android:text="Carbohydrates:"
/>
<TextView
android:id="#+id/carbohidrates_sugar"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#5d5d5d"
android:textStyle="bold"
android:text="Carbohydrates from sugar:"
/>
<TextView
android:id="#+id/fat"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#5d5d5d"
android:textStyle="bold"
android:text="Fat:"
/>
<TextView
android:id="#+id/fat_saturated"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#5d5d5d"
android:textStyle="bold"
android:text="Saturated Fat:"
/>
<TextView
android:id="#+id/fibres"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#5d5d5d"
android:textStyle="bold"
android:text="Fibres:"
/>
<TextView
android:id="#+id/sodium"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textColor="#5d5d5d"
android:textStyle="bold"
android:text="Sodium:"
/>
</LinearLayout>

Implements NutritionDatabase activity with Filterable class and implements Filterable class method in your NutritionDatabase activity.
#Override
public Filter getFilter() {
return myFilter;
}
Filter myFilter = new Filter() {
#Override
protected FilterResults performFiltering(CharSequence constraint) {
FilterResults filterResults = new FilterResults();
ArrayList<String> tempList = new ArrayList<String>();
//constraint is the result from text you want to filter against.
//objects is your data set you will filter from
if (constraint != null && your_list != null) {
int length = your_list.size();
int i = 0;
while (i < length) {
String item = your_list.get(i);
//do whatever you wanna do here
//adding result set output array
tempList.add(item);
i++;
}
//following two lines is very important
//as publish result can only take FilterResults objects
filterResults.values = tempList;
filterResults.count = tempList.size();
}
return filterResults;
}
#Override
protected void publishResults(CharSequence contraint, FilterResults results) {
your_list = (ArrayList<String>) results.values;
if (results.count > 0) {
your_adapter.notifyDataSetChanged();
} else {
}
}
};
Implement your search edittext like
et_dataInput.addTextChangedListener(new TextWatcher() {
#Override
public void afterTextChanged(Editable arg0) {
// TODO Auto-generated method stub
String text = et_dataInput.getText().toString());
your_adapter.getFilter().filter(text);
}
#Override
public void beforeTextChanged(CharSequence arg0, int arg1,
int arg2, int arg3) {
// TODO Auto-generated method stub
}
#Override
public void onTextChanged(CharSequence arg0, int arg1, int arg2,
int arg3) {
// TODO Auto-generated method stub
}
});
use this code for search name from your list.

Unable to add more than one item in a listview

I am working on a tasks app, for which I created a list view that shows list items consitsting of task names, their priority etc. The data given to the list view is from an sqlite database. I, however, am unable to add more than one item to the list. I have no idea why. I have created a method to do so, but it doesn't seem to work. I don't know if the error is due to the database or my method itself. Even debugging didn't help. Please note that I am using a list adapter since I am using a custom listview.
Code for Activity where list is shown :
package com.example.taskmasterv3;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Context;
import android.database.Cursor;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.widget.ListView;
import android.widget.TextView;
import java.util.ArrayList;
public class TaskSummary extends AppCompatActivity {
ListView lvTaskList;
TextView tvBreak, tvBreakAfterEvery, txt1, txt2, text1, hmm;
TextView break_duration_mins;
ArrayList<SubtaskPartTwo> subtaskList = new ArrayList<>();
String subtname;
String pri;
String time;
DBHelper dbHelper;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_task_summary);
lvTaskList = findViewById(R.id.lvTaskList);
tvBreak = findViewById(R.id.tvBreak);
tvBreakAfterEvery = findViewById(R.id.tvBreakAfterEvery);
txt1 = findViewById(R.id.txt1);
txt2 = findViewById(R.id.txt2);
break_duration_mins = findViewById(R.id.break_duration_mins);
text1 = findViewById(R.id.text1);
hmm = findViewById(R.id.hmm);
dbHelper = new DBHelper(this);
subtname = getIntent().getStringExtra("subtaskname");
pri = getIntent().getStringExtra("pri");
time = getIntent().getStringExtra("time");
// Using adapter for listview :
SubtaskDetailAdapter adapter = new SubtaskDetailAdapter(this, subtaskList);
lvTaskList.setAdapter(adapter);
SubtaskPartTwo subtaskPartTwo = new SubtaskPartTwo(subtname, pri, time);
subtaskList.add(subtaskPartTwo);
adapter.addANewSubTask(subtaskPartTwo);
double working_hours = getIntent().getIntExtra("working_hours", 1);
double working_minutes = getIntent().getIntExtra("working_minutes", 0);
double without_break_hours = getIntent().getIntExtra("without_break_hours", 1);
double without_break_minutes = getIntent().getIntExtra("without_break_minutes", 0);
double break_duration = getIntent().getIntExtra("break_duration", 20);
String a = working_hours + " h";
txt1.setText(a);
String b = working_minutes + " m";
break_duration_mins.setText(b);
String c = break_duration + " m";
txt2.setText(c);
//Mathematics
double g = working_hours * 100;
double h = g + working_minutes;
double i = h + break_duration;
double j = i / 60;
double p = (int) j;
double q = j - p;
double r = q * 60;
without_break_hours = p;
without_break_minutes = r;
String d = without_break_hours + " h";
String e = without_break_minutes + " m";
text1.setText(d);
hmm.setText(e);
}
}
Code for Adapter Class :
package com.example.taskmasterv3;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import java.util.ArrayList;
public class SubtaskDetailAdapter extends ArrayAdapter<SubtaskPartTwo> {
private final Context context;
private ArrayList<SubtaskPartTwo> values;
public boolean deleted;
public SubtaskDetailAdapter(Context context, ArrayList<SubtaskPartTwo> list) {
//since your are using custom view,pass zero and inflate the custom view by overriding getview
super(context, 0 , list);
this.context = context;
this.values = list;
}
#Override
public View getView(int position, #Nullable View convertView, #NonNull ViewGroup parent) {
//check if its null, if so inflate it, else simply reuse it
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.task_summary_item, parent, false);
}
//use convertView to refer the childviews to populate it with data
TextView tvSubtaskName = convertView.findViewById(R.id.tvlolitaskname);
ImageView ivPri = convertView.findViewById(R.id.ivloliPri);
ImageView ivTime = convertView.findViewById(R.id.ivloliTime);
tvSubtaskName.setText(values.get(position).getSubtaskName());
if (values.get(position).getPri() == "h")
{
ivPri.setImageResource(R.drawable.priority_high);
}
if (values.get(position).getPri() == "m")
{
ivPri.setImageResource(R.drawable.priority_med);
}
if (values.get(position).getPri() == "l")
{
ivPri.setImageResource(R.drawable.priority_low);
}
if (values.get(position).getTime() == "more")
{
ivPri.setImageResource(R.drawable.time_symbol_more);
}
if (values.get(position).getPri() == "med")
{
ivPri.setImageResource(R.drawable.time_symbol_med);
}
if (values.get(position).getPri() == "less")
{
ivPri.setImageResource(R.drawable.time_symbol_less);
}
//return the view you inflated
return convertView;
}
//to keep adding the new subtasks try the following
public void addANewSubTask(SubtaskPartTwo newSubTask){
ArrayList<SubtaskPartTwo> newvalues = new ArrayList<>(this.values);
newvalues.add(newSubTask);
this.values = newvalues;
notifyDataSetChanged();
}
}
XML code for listview activity :
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/parent"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/background"
tools:context=".TaskSummary">
<!-- hello -->
<ScrollView
android:id="#+id/scrollView2"
android:layout_width="wrap_content"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<LinearLayout
android:id="#+id/okay"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:orientation="vertical">
<ListView
android:id="#+id/lvTaskList"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="16dp">
</ListView>
</LinearLayout>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="horizontal">
<TextView
android:id="#+id/tvBreak"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="8dp"
android:fontFamily="#font/roboto"
android:text="Total Working Time (Including Breaks)"
android:textColor="#B8AEAE"
android:textSize="20sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:orientation="horizontal">
<TextView
android:id="#+id/txt1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margin="8dp"
android:layout_weight="1"
android:fontFamily="#font/roboto"
android:gravity="right"
android:text="00 h"
android:textColor="#B8AEAE"
android:textSize="20sp" />
<TextView
android:id="#+id/break_duration_mins"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="8dp"
android:layout_marginRight="8dp"
android:layout_marginBottom="8dp"
android:layout_weight="1"
android:gravity="left"
android:text="20 m"
android:textColor="#B8AEAE"
android:textSize="20sp" />
</LinearLayout>
</LinearLayout>
<!-- hello -->
<!-- hello -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="16dp"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="horizontal">
<TextView
android:id="#+id/tvWorktimeWithoutBreak"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_margin="8dp"
android:fontFamily="#font/roboto"
android:text="Work Time Before Each Break"
android:textColor="#B8AEAE"
android:textSize="20sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:orientation="horizontal">
<TextView
android:id="#+id/text1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_margin="8dp"
android:layout_weight="1"
android:fontFamily="#font/roboto"
android:gravity="right"
android:text="00 h"
android:textColor="#B8AEAE"
android:textSize="20sp" />
<TextView
android:id="#+id/hmm"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginTop="8dp"
android:layout_marginRight="8dp"
android:layout_marginBottom="8dp"
android:layout_weight="1"
android:gravity="left"
android:text="20 m"
android:textColor="#B8AEAE"
android:textSize="20sp" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
<!-- hello -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<TextView
android:id="#+id/tvBreakAfterEvery"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginTop="8dp"
android:layout_marginRight="8dp"
android:layout_marginBottom="8dp"
android:fontFamily="#font/roboto"
android:text="Break Duration"
android:textColor="#B8AEAE"
android:textSize="20sp"
app:layout_constraintBottom_toTopOf="#+id/lvTaskList"
app:layout_constraintEnd_toStartOf="#+id/lvTaskList"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="#+id/txt2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_margin="8dp"
android:fontFamily="#font/roboto"
android:gravity="center_horizontal"
android:text="30 m"
android:textColor="#B8AEAE"
android:textSize="20sp" />
</LinearLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">
<Button
android:id="#+id/btnStart"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|center_horizontal"
android:layout_margin="16dp"
android:text="Start" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
</ScrollView>
</androidx.constraintlayout.widget.ConstraintLayout>
EDIT : Database Code
package com.example.taskmasterv3;
public class TaskInfo extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_task_info);
tvTaskName = findViewById(R.id.tvTaskName);
btnProceed = findViewById(R.id.btnProceed);
dbHelper = new DBHelper(this);
tvTaskName.setVisibility(View.INVISIBLE);
if (tvTaskName.getText().equals(""))
{
tvTaskName.setClickable(false);
}
else
{
tvTaskName.setClickable(true);
}
btnSaveTaskName.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
tvTaskName.setVisibility(View.VISIBLE);
tvTaskName.setText(etTaskName.getText().toString().toUpperCase().trim());
etTaskName.setVisibility(View.GONE);
btnSaveTaskName.setVisibility(View.GONE);
btnNewSubtask.setEnabled(true);
}
});
tvTaskName.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String tasksname = tvTaskName.getText().toString().trim();
tvTaskName.setText("");
etTaskName.setVisibility(View.VISIBLE);
etTaskName.setText(tasksname);
btnSaveTaskName.setVisibility(View.VISIBLE);
}
});
btnNewSubtask.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Intent i2 = new Intent(TaskInfo.this, SubtaskActivity.class);
startActivityForResult(i2, ENTER_SUBTASK);
overridePendingTransition(R.anim.slide_in_up, R.anim.slide_out_up);
}
});
// THE DATABASE PART
btnProceed.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Cursor res = dbHelper.getdata();
while(res != null && res.moveToNext()){
subtname = res.getString(0);
pri = res.getString(1);
time = res.getString(2);
}
if (etWorkingHours.getText().toString().isEmpty())
{
etWorkingHours.setText("0");
}
if (etWorkingMinutes.getText().toString().isEmpty())
{
etWorkingMinutes.setText("0");
}
if (etWorkinghrs.getText().toString().isEmpty())
{
etWorkinghrs.setText("0");
}
if (etWorkingMins.getText().toString().isEmpty())
{
etWorkingMins.setText("0");
}
int working_hours = Integer.parseInt(etWorkinghrs.getText().toString().trim());
int working_minutes = Integer.parseInt(etWorkingMins.getText().toString().trim());
int without_break_hours = Integer.parseInt(etWorkingHours.getText().toString().trim());
int without_break_minutes = Integer.parseInt(etWorkingMinutes.getText().toString().trim());
if (etWorkingHours.getText().toString().isEmpty() || etWorkingMinutes.getText().toString().isEmpty() || etWorkinghrs.getText().toString().isEmpty() || etWorkingMins.getText().toString().isEmpty())
{
Toast.makeText(TaskInfo.this, "Field cannot be empty, please try again.", Toast.LENGTH_SHORT).show();
}
else
{
if (working_hours != 0)
{
if (working_hours > without_break_hours)
{
int breaktime = Integer.parseInt(tvBreakTime.getText().toString());
Intent intent = new Intent(TaskInfo.this, TaskSummary.class);
intent.putExtra("working_hours", working_hours);
intent.putExtra("working_minutes", working_minutes);
intent.putExtra("without_break_hours", without_break_hours);
intent.putExtra("without_break_minutes", without_break_minutes);
intent.putExtra("break_duration", breaktime);
intent.putExtra("subtaskname", taskName);
intent.putExtra("priigh", NpriHigh);
intent.putExtra("primed", NpriMed);
intent.putExtra("prilow", NpriLow);
intent.putExtra("timemore", NtimeMore);
intent.putExtra("timemed", NtimeMed);
intent.putExtra("timeless", NtimeLess);
startActivity(intent);
}
if (working_hours == without_break_hours){
if (working_minutes >= without_break_minutes){
int breaktime = Integer.parseInt(tvBreakTime.getText().toString());
Intent intent = new Intent(TaskInfo.this, TaskSummary.class);
intent.putExtra("working_hours", working_hours);
intent.putExtra("working_minutes", working_minutes);
intent.putExtra("without_break_hours", without_break_hours);
intent.putExtra("without_break_minutes", without_break_minutes);
intent.putExtra("break_duration", breaktime);
intent.putExtra("subtaskname", taskName);
intent.putExtra("priigh", NpriHigh);
intent.putExtra("primed", NpriMed);
intent.putExtra("prilow", NpriLow);
intent.putExtra("timemore", NtimeMore);
intent.putExtra("timemed", NtimeMed);
intent.putExtra("timeless", NtimeLess);
intent.putExtra("subtaskname", subtname);
intent.putExtra("pri", pri);
intent.putExtra("time", time);
startActivity(intent);
}
if (working_minutes < without_break_minutes){
Toast.makeText(TaskInfo.this, "Invalid Time Entered", Toast.LENGTH_SHORT).show();
}
}
if (working_hours < without_break_hours){
Toast.makeText(TaskInfo.this, "Invalid Time Entered", Toast.LENGTH_SHORT).show();
}
}
if (working_hours == 0){
if (without_break_hours == 0)
{
if (working_minutes >= without_break_minutes){
int breaktime = Integer.parseInt(tvBreakTime.getText().toString());
Intent intent = new Intent(TaskInfo.this, TaskSummary.class);
intent.putExtra("working_hours", working_hours);
intent.putExtra("working_minutes", working_minutes);
intent.putExtra("without_break_hours", without_break_hours);
intent.putExtra("without_break_minutes", without_break_minutes);
intent.putExtra("break_duration", breaktime);
intent.putExtra("subtaskname", taskName);
intent.putExtra("prihigh", NpriHigh);
intent.putExtra("primed", NpriMed);
intent.putExtra("prilow", NpriLow);
intent.putExtra("timemore", NtimeMore);
intent.putExtra("timemed", NtimeMed);
intent.putExtra("timeless", NtimeLess);
startActivity(intent);
}
if (working_minutes < without_break_minutes){
Toast.makeText(TaskInfo.this, "Invalid Time Entered", Toast.LENGTH_SHORT).show();
}
}
if (without_break_hours != 0)
{
Toast.makeText(TaskInfo.this, "Invalid Time Entered", Toast.LENGTH_SHORT).show();
}
}
}
}
});
boolean delete = getIntent().getBooleanExtra("deleted", false);
if (delete){
}
}
}
}
}

The problem is that you're creating a new ArrayList while the adapter is left using the old one. That's why notifyDataSetChanged() doesn't work because the adapter's backing list has not changed.
To fix this, update the values list directly
public void addANewSubTask(SubtaskPartTwo newSubTask) {
this.values.add(newSubTask);
notifyDataSetChanged();
}
or, add() through the adapter itself.
public void addANewSubTask(SubtaskPartTwo newSubTask) {
add(newSubTask);
notifyDataSetChanged();
}
Even if I add one item, it shows 2 (both the same)
It seems you're adding the new element twice:
SubtaskPartTwo subtaskPartTwo = new SubtaskPartTwo(subtname, pri, time);
subtaskList.add(subtaskPartTwo);
adapter.addANewSubTask(subtaskPartTwo);
Just add via adapter only as it notifies as well. Check other places too for such duplicates.

Listview not showinng the data but showinng the blank position where the value is to be shown

I am parsing a JSON and inflating the listview with it. First listview is showing the correct value but when i am opening another activity from my contributors button, second listview is not showing any value but displays a blank space where the text is to be displayed.
Here is my code...
Main Activity
package com.example.pc.jbossoutreachapp;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
public void getStarted(View view)
{
Intent intent = new Intent(this, repositories.class);
startActivity(intent);
}
}
layout activity.main
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/background"
tools:context=".MainActivity">
<ImageView
android:id="#+id/imageView"
android:layout_width="358dp"
android:layout_height="251dp"
android:contentDescription="#string/ContentDescipt"
app:layout_constraintBottom_toTopOf="#+id/textView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="#drawable/logo" />
<TextView
android:id="#+id/textView"
android:layout_width="0dp"
android:layout_height="31dp"
android:layout_marginBottom="1dp"
android:gravity="center"
android:text="#string/JBoss"
android:textColor="#android:color/holo_red_dark"
android:textSize="#dimen/size"
android:textStyle="bold"
app:fontFamily="sans-serif-smallcaps"
app:layout_constraintBottom_toTopOf="#+id/textView3"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/imageView" />
<TextView
android:id="#+id/textView3"
android:layout_width="0dp"
android:layout_height="25dp"
android:gravity="center"
android:text="#string/JBoss_intro"
android:textSize="18sp"
app:layout_constraintBottom_toTopOf="#+id/button"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/textView" />
<Button
android:id="#+id/button"
android:layout_width="114dp"
android:layout_height="48dp"
android:background="#f0e68c"
android:onClick="getStarted"
android:text="#string/Button"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="#+id/textView3" />
</android.support.constraint.ConstraintLayout>
repositories class
Here the code works fine and the items are shown in the listview
HttpHandler class makes service call and returns Json String.
package com.example.pc.jbossoutreachapp;
import android.app.ProgressDialog;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
public class repositories extends AppCompatActivity {
private String TAG = MainActivity.class.getSimpleName();
private ProgressDialog ProgDialog;
private ListView listview;
private static String url = "https://api.github.com/orgs/JBossOutreach/repos";
ArrayList<HashMap<String,String>> RepoDetails;
public void link(View view)
{
TextView text = findViewById(R.id.Repolink);
String url = text.getText().toString();
Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
startActivity(browserIntent);
}
public void Contributors(View view)
{
listview = findViewById(R.id.list);
TextView name = findViewById(R.id.RepositoryName);
String n = name.getText().toString();
String url1 = "https://api.github.com/repos/JBossOutreach/"+n+"/contributors";
Intent intent = new Intent(this, contributors.class);
Bundle bundle = new Bundle();
bundle.putString("url", url1);
intent.putExtras(bundle);
startActivity(intent);
}
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.repositories);
RepoDetails = new ArrayList<>();
listview = (ListView)findViewById(R.id.list);
new GetContacts().execute();
}
private class GetContacts extends AsyncTask<Void, Void, Void>
{
#Override
protected void onPreExecute() {
super.onPreExecute();
ProgDialog = new ProgressDialog(repositories.this);
ProgDialog.setMessage("Please wait...");
ProgDialog.setCancelable(false);
ProgDialog.show();
}
#Override
protected Void doInBackground(Void... voids) {
HttpHandler sh = new HttpHandler();
String Json_String = sh.makeServiceCall(url);
Log.e(TAG, "Response from url: " + Json_String);
if(Json_String != null)
{
try
{
JSONArray array = new JSONArray(Json_String);
for(int i = 0; i < array.length(); i++)
{
JSONObject ob = array.getJSONObject(i);
String name = ob.getString("name");
JSONObject owner = ob.getJSONObject("owner");
String link = owner.getString("html_url");
HashMap<String, String> contact = new HashMap<>();
contact.put("name", name);
contact.put("link", link+"/"+name);
RepoDetails.add(contact);
}
}
catch(final JSONException e)
{
Log.e(TAG, "Json parsing error: " + e.getMessage());
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(),
"Json Parsing error: " + e.getMessage(), Toast.LENGTH_LONG).show(); }
});
}
}
else
{
Log.e(TAG, "Couldn't get Json from server");
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(),
"Couldn't get json from server ", Toast.LENGTH_LONG).show();
}
});
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
if(ProgDialog.isShowing())
{
ProgDialog.dismiss();
}
ListAdapter adapter = new SimpleAdapter(
repositories.this, RepoDetails, R.layout.repo_list_item, new String[]
{"name", "link"}, new int[]{R.id.RepositoryName, R.id.Repolink});
listview.setAdapter(adapter);
}
}
}
repositories.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/background">
<TextView
android:id="#+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginStart="109dp"
android:layout_marginLeft="109dp"
android:layout_marginTop="0dp"
android:text="#string/Heading1"
android:textSize="24sp"
android:textStyle="bold" />
<ListView
android:id="#+id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginStart="0dp"
android:layout_marginTop="0dp" />
</RelativeLayout>
repo_list_itmen.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="5dp">
<TextView
android:id="#+id/RepositoryName"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:paddingTop="15dp"
android:paddingBottom="8dp"
android:textColor="#color/NameRepo" />
<TextView
android:id="#+id/Repolink"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:onClick="link"
android:paddingBottom="8dp"
android:textColor="#color/colorAccent" />
<Button
android:id="#+id/button2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:onClick="Contributors"
android:text="#string/Contributors" />
</LinearLayout>
contributors class
Problem starts from here no items are displayed but only the blank space for the items are displayed.
package com.example.pc.jbossoutreachapp;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
public class contributors extends AppCompatActivity {
private String TAG = contributors.class.getSimpleName();
ArrayList<HashMap<String, String>> names;
ListView lv;
private ProgressDialog progressDialog;
static String url;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.contributors);
names = new ArrayList<>();
lv = findViewById(R.id.list2);
Bundle bundle = getIntent().getExtras();
System.out.print(url);
url = bundle.getString("url");
new contributors.getcontrib().execute();
}
private class getcontrib extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
progressDialog = new ProgressDialog(contributors.this);
progressDialog.setMessage("Please wait...");
progressDialog.setCancelable(false);
progressDialog.show();
}
#Override
protected Void doInBackground(Void... voids) {
HttpHandler hd = new HttpHandler();
String Json_result = hd.makeServiceCall(url);
Log.e(TAG, "Response from url: " + Json_result);
if (Json_result != null) {
try {
JSONArray array = new JSONArray(Json_result);
for (int i = 0; i < array.length(); i++) {
JSONObject obj = array.getJSONObject(i);
String contributor_name = obj.getString("login");
HashMap<String, String> hashMap = new HashMap<>();
hashMap.put("name", contributor_name);
names.add(hashMap);
}
} catch (final JSONException e) {
Log.e(TAG, "Json parsing error: " + e.getMessage());
runOnUiThread(new Runnable() {
#Override
public void run() {
Toast.makeText(getApplicationContext(),
"Json Parsing error: " + e.getMessage(), Toast.LENGTH_LONG).show();
}
});
}
}
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
if (progressDialog.isShowing()) {
progressDialog.dismiss();
}
ListAdapter adapter = new SimpleAdapter(
contributors.this, names, R.layout.contributor_list_items, new String[]
{"contributors"}, new int[]{R.id.ContributorsName});
((SimpleAdapter) adapter).notifyDataSetChanged();
lv.setAdapter(adapter);
}
}
}
contributors.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#drawable/background">
<TextView
android:id="#+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginStart="109dp"
android:layout_marginLeft="109dp"
android:layout_marginTop="0dp"
android:text="#string/Heading2"
android:textSize="24sp"
android:textStyle="bold" />
<ListView
android:id="#+id/list2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginStart="0dp"
android:layout_marginTop="0dp" />
</RelativeLayout>
contributors_list_items.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android = "http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="5dp">
<TextView
android:id="#+id/ContributorsName"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:paddingTop="15dp"
android:paddingBottom="8dp"
android:textColor="#color/colorPrimaryDark" />
</LinearLayout>

Change your AsyncTask call from
new contributors.getcontrib().execute();
to
new getcontrib().execute();
Edit:
Also, change your adapter initialization code from:
ListAdapter adapter = new SimpleAdapter(
contributors.this, names, R.layout.contributor_list_items, new String[]
{"contributors"}, new int[]{R.id.ContributorsName});
to
ListAdapter adapter = new SimpleAdapter(
contributors.this, names, R.layout.contributor_list_items, new String[]
{"name"}, new int[]{R.id.ContributorsName});
Note: you have added your contributers name in "name" key and not in "contributors" key

Check Ur Response First .
String url1 = "https://api.github.com/repos/JBossOutreach/"+n+"/contributors";
Ur Json Respo
{
"message": "Not Found",
"documentation_url": "https://developer.github.com/v3/repos/#list-contributors"
}

Android studio - don't produce output

i want to create an apps that can scan other ip that are connected to my Lan network. this is my java code,maybe there is an error that cause my codding don't produce the result.
package com.example.admin.ipscanner3;
import android.content.Context;
import android.net.wifi.WifiManager;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;
import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
TextView tvWifiState;
TextView tvScanning, tvResult;
ArrayList<InetAddress> inetAddresses;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tvWifiState = (TextView)findViewById(R.id.WifiState);
tvScanning = (TextView)findViewById(R.id.Scanning);
tvResult = (TextView)findViewById(R.id.Result);
//To prevent memory leaks on devices prior to Android N,
//retrieve WifiManager with
//getApplicationContext().getSystemService(Context.WIFI_SERVICE),
//instead of getSystemService(Context.WIFI_SERVICE)
WifiManager wifiManager =
(WifiManager)
getApplicationContext().getSystemService(Context.WIFI_SERVICE);
tvWifiState.setText(readtvWifiState(wifiManager));
new ScanTask(tvScanning, tvResult).execute();
}
// "android.permission.ACCESS_WIFI_STATE" is needed
private String readtvWifiState(WifiManager wm){
String result = "";
switch (wm.getWifiState()){
case WifiManager.WIFI_STATE_DISABLED:
result = "WIFI_STATE_DISABLED";
break;
case WifiManager.WIFI_STATE_DISABLING:
result = "WIFI_STATE_DISABLING";
break;
case WifiManager.WIFI_STATE_ENABLED:
result = "WIFI_STATE_ENABLED";
break;
case WifiManager.WIFI_STATE_ENABLING:
result = "WIFI_STATE_ENABLING";
break;
case WifiManager.WIFI_STATE_UNKNOWN:
result = "WIFI_STATE_UNKNOWN";
break;
default:
}
return result;
}
private class ScanTask extends AsyncTask<Void, String, Void> {
TextView tvCurrentScanning, tvScanResullt;
ArrayList<String> canonicalHostNames;
public ScanTask(TextView tvCurrentScanning, TextView tvScanResullt) {
this.tvCurrentScanning = tvCurrentScanning;
this.tvScanResullt = tvScanResullt;
}
#Override
protected void onPostExecute(Void aVoid) {
tvCurrentScanning.setText("Finished.");
tvScanResullt.setText("");
for(int i = 0; i < inetAddresses.size(); i++){
tvScanResullt.append(canonicalHostNames.get(i) + "\n");
}
}
#Override
protected Void doInBackground(Void... voids) {
scanInetAddresses();
return null;
}
#Override
protected void onProgressUpdate(String... values) {
tvCurrentScanning.setText(values[0]);
}
private void scanInetAddresses(){
//May be you have to adjust the timeout
final int timeout = 500;
if(inetAddresses == null){
inetAddresses = new ArrayList<>();
}
inetAddresses.clear();
if(canonicalHostNames == null){
canonicalHostNames = new ArrayList<>();
}
canonicalHostNames.clear();
//For demonstration, scan 192.168.1.xxx only
byte[] ip = {(byte) 183, (byte) 171, (byte) 93, 0};
for (int j = 0; j < 255; j++) {
ip[3] = (byte) j;
try {
InetAddress checkAddress = InetAddress.getByAddress(ip);
publishProgress(checkAddress.getCanonicalHostName());
if (checkAddress.isReachable(timeout)) {
inetAddresses.add(checkAddress);
canonicalHostNames.add(checkAddress.getCanonicalHostName());
}
} catch (UnknownHostException e) {
e.printStackTrace();
publishProgress(e.getMessage());
} catch (IOException e) {
e.printStackTrace();
publishProgress(e.getMessage());
}
}
}
}
}
this is my interface/ layout. i think there is no error here.
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.admin.ipscanner3.MainActivity">
<TextView
android:id="#+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginTop="8dp"
android:autoLink="web"
android:text="http://android-er.blogspot.com/"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.502"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.069" />
<TextView
android:id="#+id/WifiState"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:orientation="horizontal"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.144">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Scanning: " />
<TextView
android:id="#+id/Scanning"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textStyle="italic" />
</LinearLayout>
<TextView
android:id="#+id/Result"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:layout_marginEnd="8dp"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.212" />
</android.support.constraint.ConstraintLayout>
i have add this two permission too to get a permission to access the wifi state and the internet.
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.INTERNET"/>