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Why does my Database not exist in the Main-Activity, when I return back to MainActivity?

in the Mainclass Im creating a variable called mDatabase. In the Mainclass there is a button called Database. When I click on it, it opens a new Activity. Then it starts the onCreate-Method of the second class databasegrocery.
When the program executes the command:
mAdapter=new GroceryAdapter(this, activity.getAllItems());
(...) it returns back to Main-Activity to call the method getAllItems().
When im returning to this method, mDatabase is null (mDatabase was already declared and initialized, when the app started with the MainActivity), why?
As Im totally new to android programing its possible that Im trying something stupid,
so I appreciate your help.
(I read something about activity-lifecycles and I saw that the MainActivity is in Stop-Status, when the second Activity is active. So the data from MainActivity is not destroyed, right?)
If you need more information, tell me!
Thank you.
package com.example.grocerylist;
import android.content.ContentValues;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.ItemTouchHelper;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
public class MainActivity extends AppCompatActivity{
public SQLiteDatabase mDatabase;
private EditText mEditTextName;
private EditText mEditTextName2;
private EditText mEditTextName3;
private EditText mEditTextName4;
private EditText mEditTextName5;
private EditText mEditTextName6;
private EditText mEditTextName7;
private EditText mEditTextName8;
private EditText mEditTextName9;
Button buttonIncrease;
Button buttonDecrease;
Button buttonAdd;
Button buttonDatabase;
public databasegrocery database;
Intent IntentDatabase;
private TextView mTextViewAmount;
private int mAmount = 0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
GroceryDBHelper dbHelper = new GroceryDBHelper(this);
mDatabase = dbHelper.getWritableDatabase();
mEditTextName = findViewById(R.id.edittext_name);
mTextViewAmount = findViewById(R.id.textview_amount);
mEditTextName2=findViewById(R.id.edittext_name2);
mEditTextName3=findViewById(R.id.edittext_name3);
mEditTextName4=findViewById(R.id.edittext_name4);
mEditTextName5=findViewById(R.id.edittext_name5);
mEditTextName6=findViewById(R.id.edittext_name6);
mEditTextName7=findViewById(R.id.edittext_name7);
mEditTextName8=findViewById(R.id.edittext_name8);
mEditTextName9=findViewById(R.id.edittext_name9);
IntentDatabase=new Intent(MainActivity.this,databasegrocery.class);
buttonIncrease = findViewById(R.id.button_increase);
buttonDecrease = findViewById(R.id.button_decrease);
buttonAdd = findViewById(R.id.button_add);
buttonDatabase=findViewById(R.id.buttonDatabase);
buttonDatabase.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(IntentDatabase);
}
});
buttonIncrease.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
increase();
}
});
buttonDecrease.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
decrease();
}
});
buttonAdd.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
addItem();
}
});
}
private void increase() {
mAmount++;
mTextViewAmount.setText(String.valueOf(mAmount));
}
private void decrease() {
if (mAmount > 0) {
mAmount--;
mTextViewAmount.setText(String.valueOf(mAmount));
}
}
private void addItem() {
if (mEditTextName.getText().toString().trim().length() == 0 || mAmount == 0) {
return;
}
String name = mEditTextName.getText().toString();
String mkcal1 = mEditTextName2.getText().toString();
String mkcal2=mEditTextName3.getText().toString();
String mFett=mEditTextName4.getText().toString();
String mDavongesaettigtefettsaueren=mEditTextName5.getText().toString();
String mKohlenhydrate=mEditTextName6.getText().toString();
String mZucker=mEditTextName7.getText().toString();
String mEiweiss=mEditTextName8.getText().toString();
String mSalz=mEditTextName9.getText().toString();
//___________________________________________________________________
ContentValues cv = new ContentValues();
cv.put(GroceryContract.GroceryEntry.COLUMN_NAME, name);
cv.put(GroceryContract.GroceryEntry.COLUMN_AMOUNT, mAmount);
//----------------------------------------------------------------------------------------
cv.put(GroceryContract.GroceryEntry.COLUMN_KCAL1, mkcal1);
cv.put(GroceryContract.GroceryEntry.COLUMN_KCAL2, mkcal2);
cv.put(GroceryContract.GroceryEntry.COLUMN_FETT, mFett);
cv.put(GroceryContract.GroceryEntry.COLUMN_DAVONGESAETTIGTEFETTSAEUREN, mDavongesaettigtefettsaueren);
cv.put(GroceryContract.GroceryEntry.COLUMN_Kohlenhydrate, mKohlenhydrate);
cv.put(GroceryContract.GroceryEntry.COLUMN_Zucker, mZucker);
cv.put(GroceryContract.GroceryEntry.COLUMN_EIWEIS, mEiweiss);
cv.put(GroceryContract.GroceryEntry.COLUMN_SALZ, mSalz);
//------------------------------------------------------------------------------------------
mDatabase.insert(GroceryContract.GroceryEntry.TABLE_NAME, null, cv);
databasegrocery.mAdapter.swapCursor(getAllItems());
mEditTextName.getText().clear();
mEditTextName2.getText().clear();
mEditTextName3.getText().clear();
mEditTextName4.getText().clear();
mEditTextName5.getText().clear();
mEditTextName6.getText().clear();
mEditTextName7.getText().clear();
mEditTextName8.getText().clear();
mEditTextName9.getText().clear();
}
public Cursor getAllItems() {
return mDatabase.query(GroceryContract.GroceryEntry.TABLE_NAME, null, null, null, null, null, GroceryContract.GroceryEntry.COLUMN_TIMESTAMP + " ASC");
}
}
package com.example.grocerylist;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
public class databasegrocery extends AppCompatActivity {
public static GroceryAdapter mAdapter;
public MainActivity activity;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.databasegrocery);
activity=new MainActivity();
RecyclerView recyclerView = findViewById(R.id.recyclerview);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
mAdapter = new GroceryAdapter(this, activity.getAllItems());
recyclerView.setAdapter(mAdapter);
}
}

recycler view does not refresh and show data

in my recycler view , when data get added , recycelr view does not show it until user close the activity and open it another time.
I think it has something to do with notifydataetchanger.
please help me with this
the only thing that worked by now was to creating an Intent .
but it makes app to loob very bad
my adaptor
package com.example.myapplication;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.List;
public class Rec_adaptor_aza extends RecyclerView.Adapter<Rec_adaptor_aza.ViewHolder> {
Context context;
public Rec_adaptor_aza(Context context, List<Model_aza> list_aza) {
this.context = context;
this.list_aza = list_aza;
}
List<Model_aza> list_aza;
#NonNull
#Override
public Rec_adaptor_aza.ViewHolder onCreateViewHolder(#NonNull ViewGroup parent, int viewType) {
View view= LayoutInflater.from(context).inflate(R.layout.rec_row_aza,parent,false);
return new ViewHolder(view);
}
#Override
public void onBindViewHolder(#NonNull Rec_adaptor_aza.ViewHolder holder, int position) {
Model_aza modelAza =list_aza.get(position);
holder.txt_name.setText(modelAza.getName_aza());
holder.txt_semat.setText(modelAza.getSemat_aza());
holder.txt_saat_voood.setText(modelAza.getSaaat_vorood_aza());
holder.txt_saat_khoroo.setText(modelAza.getSaat_khorooj_aza());
}
#Override
public int getItemCount() {
return list_aza.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView txt_name,txt_semat,txt_saat_voood,txt_saat_khoroo;
public ViewHolder(#NonNull View itemView) {
super(itemView);
txt_name=itemView.findViewById(R.id.txt__person__name);
txt_semat=itemView.findViewById(R.id.txt__person__semat);
txt_saat_voood=itemView.findViewById(R.id.txt__person__enter);
txt_saat_khoroo=itemView.findViewById(R.id.txt__person__out);
}
}
}
my model class
package com.example.myapplication;
public class Model_aza {
private String name_aza;
private String semat_aza;
private String saaat_vorood_aza;
public String getName_aza() {
return name_aza;
}
public void setName_aza(String name_aza) {
this.name_aza = name_aza;
}
public String getSemat_aza() {
return semat_aza;
}
public void setSemat_aza(String semat_aza) {
this.semat_aza = semat_aza;
}
public String getSaaat_vorood_aza() {
return saaat_vorood_aza;
}
public void setSaaat_vorood_aza(String saaat_vorood_aza) {
this.saaat_vorood_aza = saaat_vorood_aza;
}
public String getSaat_khorooj_aza() {
return saat_khorooj_aza;
}
public void setSaat_khorooj_aza(String saat_khorooj_aza) {
this.saat_khorooj_aza = saat_khorooj_aza;
}
private String saat_khorooj_aza;
}
My activity
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.Toast;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;
import java.util.List;
public class Activity_Gozaresh_giri extends AppCompatActivity {
private static final String TAG = "gozaresh_activity";
List<Model_aza> list_aza;
Rec_adaptor_aza rec_adaptor_aza;
public static Context context;
SQLiteDatabase sqLiteDatabase;
ImageButton btn__add__field, btn__add__field1;
final DataBase_aza dataBase_aza = new DataBase_aza(this);
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_gozaresh_giri);
btn__add__field1 = findViewById(R.id.btn__add__field1);
btn__add__field = findViewById(R.id.btn__add__field);
int id=getIntent().getIntExtra("id",0);
list_aza = new ArrayList<>();
Log.d(TAG, "onCreate: onclicked");
btn__add__field.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
EditText edtname = findViewById(R.id.edt__person__name);
EditText edt_semat_aza = findViewById(R.id.edt__person__semat);
EditText edt_vorood_aza = findViewById(R.id.edt__person__enter);
EditText edt_khorooj_aza = findViewById(R.id.edt__person__out);
String name_aza = edtname.getText().toString();
String semat_aza = edt_semat_aza.getText().toString();
String saat_vorood_aza = edt_vorood_aza.getText().toString();
String saat_khorooj_aza = edt_khorooj_aza.getText().toString();
long result = dataBase_aza.insert_info(name_aza, semat_aza, saat_vorood_aza, saat_khorooj_aza,id);
Toast.makeText(Activity_Gozaresh_giri.this, result + "", Toast.LENGTH_SHORT).show();
}
});
Cursor cursor1 = dataBase_aza.cursor(id);
for (cursor1.moveToFirst(); !cursor1.isAfterLast(); cursor1.moveToNext()) {
Model_aza modelAza = new Model_aza();
modelAza.setName_aza(cursor1.getString(1));
modelAza.setSemat_aza(cursor1.getString(2));
modelAza.setSaaat_vorood_aza(cursor1.getString(3));
modelAza.setSaat_khorooj_aza(cursor1.getString(4));
list_aza.add(modelAza);
}
RecyclerView recyclerView_aza = findViewById(R.id.rec_aza);
recyclerView_aza.setAdapter(new Rec_adaptor_aza(this, list_aza));
recyclerView_aza.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
}
}
my data base
package com.example.myapplication;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import androidx.annotation.Nullable;
public class DataBase_aza extends SQLiteOpenHelper {
public DataBase_aza(#Nullable Context context) {
super(context, "datbase_aza", null, 1);
}
#Override
public void onCreate(SQLiteDatabase db) {
try {
db.execSQL("create table if not exists database_aza (_id integer primary key autoincrement,_name varcher(55) not null,_semat varcher(55) not null, _vorood varcher(6) not null, _khorooj varchar(22) not null, id__item__gozaresh integer(55))");
} catch (Exception e) {
e.printStackTrace();
}
}
#Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
}
public long insert_info(String name, String semat, String vorood, String khorooj, int id) {
ContentValues cv = new ContentValues();
cv.put("_name", name);
cv.put("_semat", semat);
cv.put("_vorood", vorood);
cv.put("_khorooj", khorooj);
cv.put("id__item__gozaresh", id);
SQLiteDatabase sqLiteDatabase = this.getWritableDatabase();
return sqLiteDatabase.insert("database_aza", null, cv);
}
public Cursor cursor(int id) {
SQLiteDatabase sqLiteDatabase = this.getReadableDatabase();
return sqLiteDatabase.rawQuery("SELECT * FROM database_aza where id__item__gozaresh="+id, null);
}
}
I want recycler view to show data as soon as user clicks on add button

after adding entry just notify data set changed to adapter like below
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_gozaresh_giri);
btn__add__field1 = findViewById(R.id.btn__add__field1);
btn__add__field = findViewById(R.id.btn__add__field);
int id=getIntent().getIntExtra("id",0);
list_aza = new ArrayList<>();
Log.d(TAG, "onCreate: onclicked");
rec_adaptor_aza = new Rec_adaptor_aza(this, list_aza);
RecyclerView recyclerView_aza = findViewById(R.id.rec_aza);
recyclerView_aza.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
recyclerView_aza.setAdapter(rec_adaptor_aza);
Cursor cursor1 = dataBase_aza.cursor(id);
for (cursor1.moveToFirst(); !cursor1.isAfterLast(); cursor1.moveToNext()) {
Model_aza modelAza = new Model_aza();
modelAza.setName_aza(cursor1.getString(1));
modelAza.setSemat_aza(cursor1.getString(2));
modelAza.setSaaat_vorood_aza(cursor1.getString(3));
modelAza.setSaat_khorooj_aza(cursor1.getString(4));
list_aza.add(modelAza);
}
rec_adaptor_aza.notifyDataSetChanged();
btn__add__field.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
EditText edtname = findViewById(R.id.edt__person__name);
EditText edt_semat_aza = findViewById(R.id.edt__person__semat);
EditText edt_vorood_aza = findViewById(R.id.edt__person__enter);
EditText edt_khorooj_aza = findViewById(R.id.edt__person__out);
String name_aza = edtname.getText().toString();
String semat_aza = edt_semat_aza.getText().toString();
String saat_vorood_aza = edt_vorood_aza.getText().toString();
String saat_khorooj_aza = edt_khorooj_aza.getText().toString();
long result = dataBase_aza.insert_info(name_aza, semat_aza, saat_vorood_aza, saat_khorooj_aza,id);
rec_adaptor_aza.notifyDataSetChanged(); // change here
Toast.makeText(Activity_Gozaresh_giri.this, result + "", Toast.LENGTH_SHORT).show();
}
});
}

Use it like below:-
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_gozaresh_giri);
btn__add__field1 = findViewById(R.id.btn__add__field1);
btn__add__field = findViewById(R.id.btn__add__field);
int id=getIntent().getIntExtra("id",0);
list_aza = new ArrayList<>();
Rec_adaptor_aza adapter = new Rec_adaptor_aza(this, list_aza); // Add
RecyclerView recyclerView_aza = findViewById(R.id.rec_aza);
recyclerView_aza.setAdapter(adapter);
recyclerView_aza.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
btn__add__field.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
EditText edtname = findViewById(R.id.edt__person__name);
EditText edt_semat_aza = findViewById(R.id.edt__person__semat);
EditText edt_vorood_aza = findViewById(R.id.edt__person__enter);
EditText edt_khorooj_aza = findViewById(R.id.edt__person__out);
String name_aza = edtname.getText().toString();
String semat_aza = edt_semat_aza.getText().toString();
String saat_vorood_aza = edt_vorood_aza.getText().toString();
String saat_khorooj_aza = edt_khorooj_aza.getText().toString();
long result = dataBase_aza.insert_info(name_aza, semat_aza, saat_vorood_aza, saat_khorooj_aza,id);
Model_aza modelAza = new Model_aza(); // Add
modelAza.setName_aza(name_aza);// Add
modelAza.setSemat_aza(semat_aza);// Add
modelAza.setSaaat_vorood_aza(saat_vorood_aza);// Add
modelAza.setSaat_khorooj_aza(saat_khorooj_aza);// Add
list_aza.add(modelAza);// Add
adapter.notifyDataSetChanged();// Add
Toast.makeText(Activity_Gozaresh_giri.this, result + "", Toast.LENGTH_SHORT).show();
}
});
Cursor cursor1 = dataBase_aza.cursor(id);
for (cursor1.moveToFirst(); !cursor1.isAfterLast(); cursor1.moveToNext()) {
Model_aza modelAza = new Model_aza();
modelAza.setName_aza(cursor1.getString(1));
modelAza.setSemat_aza(cursor1.getString(2));
modelAza.setSaaat_vorood_aza(cursor1.getString(3));
modelAza.setSaat_khorooj_aza(cursor1.getString(4));
list_aza.add(modelAza);
}
adapter.notifyDataSetChanged();// Add
}

Just add the below code, in your clickListner, you need to add the same object in your list, and after adding you need to notify the adapter about the inserted item, by using notifyDataSetChanged().
btn__add__field.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
EditText edtname = findViewById(R.id.edt__person__name);
EditText edt_semat_aza = findViewById(R.id.edt__person__semat);
EditText edt_vorood_aza = findViewById(R.id.edt__person__enter);
EditText edt_khorooj_aza = findViewById(R.id.edt__person__out);
String name_aza = edtname.getText().toString();
String semat_aza = edt_semat_aza.getText().toString();
String saat_vorood_aza = edt_vorood_aza.getText().toString();
String saat_khorooj_aza = edt_khorooj_aza.getText().toString();
long result = dataBase_aza.insert_info(name_aza, semat_aza, saat_vorood_aza, saat_khorooj_aza,id);
Toast.makeText(Activity_Gozaresh_giri.this, result + "", Toast.LENGTH_SHORT).show();
/*
* Adding entered data in list*/
Model_aza mm=new Model_aza();
mm.setName_aza(name_aza);
mm.setSemat_aza(semat_aza);
mm.setSaaat_vorood_aza(saat_vorood_aza);
mm.setSaat_khorooj_aza(saat_khorooj_aza);
list_aza.add(mm);
rec_adaptor_aza.notifyDataSetChanged();
}
});

Set layoutmanager before set the adapter to recylerview in your activity, like below
RecyclerView recyclerView_aza = findViewById(R.id.rec_aza);
// set layout manager before set adapter
recyclerView_aza.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
recyclerView_aza.setAdapter(new Rec_adaptor_aza(this, list_aza));

Complete android cardView with db helper and recycleView

I am pretty new to this whole android development but I am looking to create a simple android app making use of a sql database, cardViews and a RecycleView.
The app I have so far works but I am trying to add a button to the DetailedActivity which will allow me to remove the entry from the database.
The desired workflow would be:
Get Data
Select a CardView
Click New Button (will be
delete)
Go back to CardView, Remove entry on which the button has
been pressed and populate the CardView.
RecyclerAdapter.java
package com.example.prabhu.databasedemo;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder> {
static List<DatabaseModel> dbList;
static Context context;
RecyclerAdapter(Context context, List<DatabaseModel> dbList ){
this.dbList = new ArrayList<DatabaseModel>();
this.context = context;
this.dbList = dbList;
}
#Override
public RecyclerAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemLayoutView = LayoutInflater.from(parent.getContext()).inflate(
R.layout.item_row, null);
// create ViewHolder
ViewHolder viewHolder = new ViewHolder(itemLayoutView);
return viewHolder;
}
#Override
public void onBindViewHolder(RecyclerAdapter.ViewHolder holder, int position) {
holder.name.setText(dbList.get(position).getName());
holder.email.setText(dbList.get(position).getEmail());
}
#Override
public int getItemCount() {
return dbList.size();
}
public static class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public TextView name,email;
public ViewHolder(View itemLayoutView) {
super(itemLayoutView);
name = (TextView) itemLayoutView
.findViewById(R.id.rvname);
email = (TextView)itemLayoutView.findViewById(R.id.rvemail);
itemLayoutView.setOnClickListener(this);
}
#Override
public void onClick(View v) {
Intent intent = new Intent(context,DetailsActivity.class);
Bundle extras = new Bundle();
extras.putInt("position",getAdapterPosition());
intent.putExtras(extras);
/*
int i=getAdapterPosition();
intent.putExtra("position", getAdapterPosition());*/
context.startActivity(intent);
Toast.makeText(RecyclerAdapter.context, "you have clicked Row " + getAdapterPosition(), Toast.LENGTH_SHORT).show();
}
}
}
DatabaseHelper.java
package com.example.prabhu.databasedemo;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class DatabaseHelpher extends SQLiteOpenHelper {
private static final String DATABASE_NAME="student";
private static final int DATABASE_VERSION = 1;
private static final String STUDENT_TABLE = "stureg";
private static final String STU_TABLE = "create table "+STUDENT_TABLE +"(name TEXT,email TEXT primary key,roll TEXT,address TEXT,branch TEXT)";
Context context;
public DatabaseHelpher(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
this.context = context;
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(STU_TABLE);
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + STUDENT_TABLE);
// Create tables again
onCreate(db);
}
/* Insert into database*/
public void insertIntoDB(String name,String email,String roll,String address,String branch){
Log.d("insert", "before insert");
// 1. get reference to writable DB
SQLiteDatabase db = this.getWritableDatabase();
// 2. create ContentValues to add key "column"/value
ContentValues values = new ContentValues();
values.put("name", name);
values.put("email", email);
values.put("roll", roll);
values.put("address", address);
values.put("branch", branch);
// 3. insert
db.insert(STUDENT_TABLE, null, values);
// 4. close
db.close();
Toast.makeText(context, "insert value", Toast.LENGTH_SHORT);
Log.i("insert into DB", "After insert");
}
/* Retrive data from database */
public List<DatabaseModel> getDataFromDB(){
List<DatabaseModel> modelList = new ArrayList<DatabaseModel>();
String query = "select * from "+STUDENT_TABLE;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query,null);
if (cursor.moveToFirst()){
do {
DatabaseModel model = new DatabaseModel();
model.setName(cursor.getString(0));
model.setEmail(cursor.getString(1));
model.setRoll(cursor.getString(2));
model.setAddress(cursor.getString(3));
model.setBranch(cursor.getString(4));
modelList.add(model);
}while (cursor.moveToNext());
}
Log.d("student data", modelList.toString());
return modelList;
}
/*delete a row from database*/
public void deleteARow(String email){
SQLiteDatabase db= this.getWritableDatabase();
db.delete(STUDENT_TABLE, "email" + " = ?", new String[] { email });
db.close();
}
}
DatabaseModel.java
package com.example.prabhu.databasedemo;
public class DatabaseModel {
private String name;
private String roll;
private String address;
private String branch;
private String email;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getRoll() {
return roll;
}
public void setRoll(String roll) {
this.roll = roll;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public String getBranch() {
return branch;
}
public void setBranch(String branch) {
this.branch = branch;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
}
MainActivity.java
package com.example.prabhu.databasedemo;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
EditText etName,etRoll,etAddress,etBranch,etEmail;
Button btnSubmit,btngetdata;
DatabaseHelpher helpher;
List<DatabaseModel> dbList;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
dbList= new ArrayList<DatabaseModel>();
etName = (EditText)findViewById(R.id.etName);
etRoll = (EditText)findViewById(R.id.etRoll);
etAddress =(EditText)findViewById(R.id.etAddress);
etBranch = (EditText)findViewById(R.id.etBranch);
etEmail = (EditText)findViewById(R.id.etEmail);
btnSubmit =(Button)findViewById(R.id.btnSubmit);
btngetdata =(Button)findViewById(R.id.btngetdata);
btngetdata.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
startActivity(new Intent(MainActivity.this, SecondActivity.class));
// startActivity(new Intent(MainActivity.this, DetailsActivity.class));
}
});
btnSubmit.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String name=etName.getText().toString();
String email=etEmail.getText().toString();
String roll=etRoll.getText().toString();
String address=etAddress.getText().toString();
String branch=etBranch.getText().toString();
if(name.equals("") || email.equals("") || roll.equals("") ||address.equals("")||branch.equals("")){
Toast.makeText(MainActivity.this,"Please fill all the fields",Toast.LENGTH_SHORT).show();
}else {
helpher = new DatabaseHelpher(MainActivity.this);
helpher.insertIntoDB(name, email, roll, address, branch);
}
etName.setText("");
etRoll.setText("");
etAddress.setText("");
etBranch.setText("");
etEmail.setText("");
Toast.makeText(MainActivity.this, "insert value", Toast.LENGTH_SHORT);
}
});
}
}
SecondActivity.java
package com.example.prabhu.databasedemo;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import java.util.ArrayList;
import java.util.List;
public class SecondActivity extends AppCompatActivity {
DatabaseHelpher helpher;
List<DatabaseModel> dbList;
RecyclerView mRecyclerView;
private RecyclerView.Adapter mAdapter;
private RecyclerView.LayoutManager mLayoutManager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
helpher = new DatabaseHelpher(this);
dbList= new ArrayList<DatabaseModel>();
dbList = helpher.getDataFromDB();
mRecyclerView = (RecyclerView)findViewById(R.id.recycleview);
mRecyclerView.setHasFixedSize(true);
// use a linear layout manager
mLayoutManager = new LinearLayoutManager(this);
mRecyclerView.setLayoutManager(mLayoutManager);
// specify an adapter (see also next example)
mAdapter = new RecyclerAdapter(this,dbList);
mRecyclerView.setAdapter(mAdapter);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_second, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
finish();
return true;
}
return super.onOptionsItemSelected(item);
}
}
DetailedActivity.java
package com.example.prabhu.databasedemo;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class DetailsActivity extends AppCompatActivity {
DatabaseHelpher helpher;
List<DatabaseModel> dbList;
int position;
TextView tvname,tvemail,tvroll,tvaddress,tvbranch;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_details);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
Intent intent = getIntent();
Bundle bundle = intent.getExtras();
// 5. get status value from bundle
position = bundle.getInt("position");
tvname =(TextView)findViewById(R.id.name);
tvemail =(TextView)findViewById(R.id.email);
tvroll =(TextView)findViewById(R.id.roll);
tvaddress =(TextView)findViewById(R.id.address);
tvbranch =(TextView)findViewById(R.id.branch);
helpher = new DatabaseHelpher(this);
dbList= new ArrayList<DatabaseModel>();
dbList = helpher.getDataFromDB();
if(dbList.size()>0){
String name= dbList.get(position).getName();
String email=dbList.get(position).getEmail();
String roll=dbList.get(position).getRoll();
String address=dbList.get(position).getAddress();
String branch=dbList.get(position).getBranch();
tvname.setText(name);
tvemail.setText(email);
tvroll.setText(roll);
tvaddress.setText(address);
tvbranch.setText(branch);
}
Toast.makeText(DetailsActivity.this, dbList.toString(), Toast.LENGTH_SHORT);
}
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_details, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
finish();
return true;
}
return super.onOptionsItemSelected(item);
}
}
I had added a button (findViewByID) in the DetailedAvtivity.java with an OnClickListener. Initially to only show a toast, however, when the button on any detailed view is clicked, nothing happens - no toast.
So really, questions are:
Where do I have to define the button and where do I implement the onClickListener?
How do I make the button delete the entry? For now I am happy to use the email from the email TextView (tvemail) but I will have to go back and refresh the cards as well.
Thanks all in advance

After some time I found the answer. What I was doing was correct but messed the toast command.
Basically what needs to be done is
delButton = (Button) findViewById(R.id.button);
delButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Toast.makeText(getApplicationContext(), tvemail.getText() + " deleted", Toast.LENGTH_SHORT).show();
startActivity(new Intent(DetailsActivity.this, MainActivity.class));
helpher.deleteARow((String) tvemail.getText());
}
});

Retrieve data into EditText from SQL Lite Database

I am currently working on a small application which allows a persons details to be stored in a database and then retrieved into an EditText field. Currently i am able to store a persons name into the database. But i am having trouble retrieving this data.
Any help anyone can give would be greatly appreciated!
Thanks!
DatabaseHelper.java:
package my.example.com.mymedicare;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DatabaseHelper extends SQLiteOpenHelper {
public DatabaseHelper(Context context) {
super(context, "user.db", null, 4);
}
#Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE Users (ID INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL , FullName VARCHAR, Email VARCHAR, Number INTEGER, Age INTEGER, Nurse VARCHAR)");
}
#Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS Users");
// Create tables again
onCreate(db);
}
}
SQLHelper.java:
package my.example.com.mymedicare;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import java.io.File;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
public class SQLHelper {
Context mContext;
DatabaseHelper dbHelper;
public SQLHelper(Context mContext) {
dbHelper = new DatabaseHelper(mContext);
this.mContext = mContext;
}
public boolean insert(String FullName, int i){
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("FullName", FullName);
db.close();
return true;
}
}
Register.java:
package my.example.com.mymedicare;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
public class Register extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
};
public void btnCreate(View view) {
SQLHelper sqlHelper = new SQLHelper(this);
EditText addName = (EditText) findViewById(R.id.nameText);
sqlHelper.insert(addName.getText().toString(), 0);
Toast.makeText(this, "Your Account Details Have Been Saved", Toast.LENGTH_SHORT).show();
startActivity(new Intent(Register.this, MainMenu.class));
}}
Modify.java:
package my.example.com.mymedicare;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.EditText;
public class Modify extends AppCompatActivity {
static SQLiteDatabase db;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_modify);
EditText getName=(EditText)findViewById(R.id.nameText);
}
}

Follow this step.
put this method in SQLHelper.java file.
public ArrayList<String> fetch_Edittext() {
ArrayList<String> arr_ = new ArrayList<String>();
String selectQuery = "Select * FROM " + TABLE_SCANITEMS + " ORDER BY id";
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
if (cursor.moveToFirst()) {
do {
arr_.add(cursor.getString(0));
} while (cursor.moveToNext());
}
db.close();
return arr_;
}
put this class in your modify java class
private class GetEdittext extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
// dialog start
Log.e("Currency", "3");
}
#Override
protected Void doInBackground(Void... arg0) {
ArrayList<String> arr_ = new ArrayList<String>();
arr_ = db.fetch_Edittext();
return null;
}
#Override
protected void onPostExecute(Void resul) {
super.onPostExecute(resul);
// dialog dismiss
//hear set your edit text
}
}
then call this class at on create method like.
new GetEdittext().execute();

Android SQLite Update Query - What Am I Missing

package lab.ex1;
import java.util.ArrayList;
import java.util.List;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;
import lab.ex1.HospitalDatabase.Patient;
public class DisplayPatient extends HospitalActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.display);
displayData();
}
private void displayData()
{
final List<Integer> myList = new ArrayList<Integer>();
final Intent me = new Intent(DisplayPatient.this,UpdatePatient.class);
final Bundle b = new Bundle();
//Build new Patient
PatientData build = new PatientData();
final TableLayout viewData = (TableLayout)findViewById(R.id.tblDisplay);
SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
queryBuilder.setTables(Patient.patientTableName);
SQLiteDatabase db = mDatabase.getReadableDatabase();
String asColumnsToReturn[] = {Patient.patientTableName + "." + Patient.ID,
Patient.patientTableName + "." + Patient.firstName,
Patient.patientTableName + "." + Patient.lastName,
Patient.patientTableName + "." + Patient.room,
Patient.patientTableName + "." + Patient.department};
Cursor c = queryBuilder.query(db,asColumnsToReturn,null,null,null,null,Patient.DEFAULT_SORT_ORDER);
if (c.moveToFirst())
{
for (int i=0; i< c.getCount(); i++)
{
final TableRow newRow = new TableRow(this);
Button update = new Button(this);
TextView display = new TextView(this);
display.setTextSize(15);
update.setX(15);
update.setY(10);
update.setTextSize(10);
Button deleteButton = new Button(this);
deleteButton.setX(100);
deleteButton.setY(100);
deleteButton.setTextSize(10);
deleteButton.setText("Delete");
update.setText("Update");
deleteButton.setTag(c.getInt(c.getColumnIndex(Patient.ID)));
update.setTag(c.getInt(c.getColumnIndex(Patient.ID)));
newRow.setTag(c.getInt(c.getColumnIndex(Patient.ID))); // set the tag field on the TableRow view so we know which row to delete
myList.add(c.getInt(c.getColumnIndex(Patient.ID)));
build.setID(Integer.parseInt(c.getString(c.getColumnIndex((Patient.ID)))));
build.setFirstName((c.getString(c.getColumnIndex(Patient.firstName))));
build.setLastName(c.getString(c.getColumnIndex(Patient.lastName)));
build.setDepartment(c.getString(c.getColumnIndex(Patient.department)));
build.setRoom(Integer.parseInt(c.getString(c.getColumnIndex(Patient.room))));
deleteButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Integer id = (Integer) v.getTag();
deletePatient(id);
final TableLayout patientTable = (TableLayout) findViewById(R.id.tblDisplay);
View viewToDelete = patientTable.findViewWithTag(id);
viewData.removeView(viewToDelete);
}
});
update.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// TODO Auto-generated method stub
Integer id = (Integer)v.getTag();
final TableLayout patientRmv = (TableLayout)findViewById(R.id.tblDisplay);
for (Integer delete : myList )
{
View viewToDelete = patientRmv.findViewWithTag(delete);
viewData.removeView(viewToDelete);
}
b.putString("key", Integer.toString(id));
me.putExtras(b);
startActivity(me);
}
});
display.setText(build.toString());
newRow.addView(display);
newRow.addView(update);
//newRow.addView(deleteButton);
viewData.addView(newRow);
c.moveToNext();
}
}
else
{
TableRow newRow = new TableRow(this);
TextView noResults = new TextView(this);
noResults.setText("No results to show.");
newRow.addView(noResults);
viewData.addView(newRow);
}
c.close();
db.close();
}
public void deletePatient(Integer id)
{
SQLiteDatabase db = mDatabase.getWritableDatabase();
String astrArgs[] = { id.toString() };
db.delete(Patient.patientTableName, Patient.ID+ "=?",astrArgs );
db.close();
}
}
package lab.ex1;
import lab.ex1.HospitalDatabase.Patient;
import android.content.ContentValues;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
public class UpdatePatient extends HospitalActivity {
Spinner spinner;
TextView update;
String up;
Button check;
EditText entry;
String setPosition;
TextView updateID;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.updatepatient);
check = (Button)findViewById(R.id.btnUpdate);
entry = (EditText)findViewById(R.id.editUpdate);
updateID = (TextView)findViewById(R.id.txtIDUpdate);
Bundle accept = getIntent().getExtras();
up = accept.getString("key","0");
updateID.setText(null);
updateID.setText("ID: " + up);
update = (TextView)findViewById(R.id.txtUpdateMessage);
update.setText(null);
// update.setText(up);
spinner = (Spinner) findViewById(R.id.spnChoice);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.arrFields, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
spinner.setOnItemSelectedListener(new MyOnItemSelectedListener());
check.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
updateDB(entry.getText().toString(),setPosition,up);
}
});
}
public class MyOnItemSelectedListener implements OnItemSelectedListener {
public void onItemSelected(AdapterView<?> adapterView,
View view, int pos, long id) {
update.setText(null);
update.setText("I will update On " + adapterView.getItemAtPosition(pos).toString());
setPosition = adapterView.getItemAtPosition(pos).toString();
}
public void onNothingSelected(AdapterView parent) {
// Do nothing.
}
}
public void updateDB(String valuesToUpdate, String field,String ID)
{
SQLiteDatabase db = mDatabase.getWritableDatabase();
db.beginTransaction();
try
{
ContentValues updatePatient = new ContentValues();
if (field == "First Name")
{
updatePatient.put(Patient.firstName, valuesToUpdate);
String astrArgs[] = { up.toString() };
db.update(Patient.patientTableName,updatePatient, Patient.ID+"=?", astrArgs);
//
db.setTransactionSuccessful();
}
}
finally
{
db.endTransaction();
}
db.close();
Intent me = new Intent(UpdatePatient.this,DisplayPatient.class);
startActivity(me);
}
}
I am using Android SQLite Database. In my display class, it reads all the entries from the database and displays them along with an update button next to each entry. That entries update button's tag has entries Patient.ID. When the user clicks update, they are taken to the update class where they can select what they want to update, First Name, Last Name, Apartment, Room. Afterward they click update, to which they are taken back to the Display class and they should see there changes. However, when they are taken back, the previous value is still there, the changes do not show up, what am I missing?

Move your displaydata() call from onCreate to onResume.