Develop Reference

How to showing text inside recycleview without restarting the app?

My problem is I can not add text inside of recycleview after pressing the OK button unless i restart the app , every time I am writing a word inside of dialog box then press OK but the word does not appear inside of recycleview only after restart the app ,I want to type the word and then press the OK button Then the word appears directly inside the recycleview
// class Tab1 :
import android.content.Context;
import android.content.DialogInterface;
import android.graphics.drawable.AnimationDrawable;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AlertDialog;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.RelativeLayout;
import android.widget.Toast;
import com.raizlabs.android.dbflow.sql.language.SQLite;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import javax.inject.Inject;
import static android.R.attr.fragment;
import static com.example.chirag.slidingtabsusingviewpager.R.id.parent;
/**
* A simple {#link Fragment} subclass.
* Activities that contain this fragment must implement the
* {#link Tab1.OnFragmentInteractionListener} interface
* to handle interaction events.
* Use the {#link Tab1#newInstance} factory method to
* create an instance of this fragment.
*/
public class Tab1 extends Fragment {
#Inject
Context mContext_;
View rootView;
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
Context context;
SimpleAdapter adapter;// = new SimpleAdapter(generateSimpleList());
RecyclerView recyclerView ;//= (RecyclerView) view.findViewById(R.id.simple_recyclerview);
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private List<Organization>organizationList;
private OnFragmentInteractionListener mListener;
private static Context mContext;
LayoutInflater inflater2;
ViewGroup Container = null;
View vr;
public Tab1(){
// Required empty public constructor
// test ();
//context = getContext();
Organization organization = new Organization();
organizationList = SQLite.select().from(Organization.class).queryList();
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment Tab1.
*/
// TODO: Rename and change types and number of parameters
public static Tab1 newInstance(String param1, String param2) {
Tab1 fragment = new Tab1();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
View view = inflater.inflate(R.layout.fragment_tab1, container,false);
vr = view;//inflater.inflate(R.layout.fragment_tab1, container,false);
initViews();
showInputDialog();
return view;
}
private void initViews(){
adapter = new SimpleAdapter(generateSimpleList());
recyclerView = (RecyclerView)vr.findViewById(R.id.simple_recyclerview);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
recyclerView.setAdapter(adapter);
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString() + "must implement OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
private List<SimpleViewModel> generateSimpleList(){
List<SimpleViewModel>simpleViewModelList = new ArrayList<>();
for(int i=0; i<organizationList.size(); i++){
simpleViewModelList.add(new SimpleViewModel(String.format(Locale.US,organizationList.get(i).getName().toString(),""+organizationList.get(i).getName().toString())));
// Toast.makeText(MainActivity.this,"as"+ organizationList.get(i).getName(), Toast.LENGTH_LONG).show();
}
return simpleViewModelList;
}
protected void showInputDialog(){
LayoutInflater layoutInflater = LayoutInflater.from(getActivity());
//LayoutInflater layoutInflater = LayoutInflater.from(getContext().getApplicationContext());
final View promptView = layoutInflater.inflate(R.layout.input_dialog, null);
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(getActivity());
alertDialogBuilder.setView(promptView);
final EditText editText = (EditText) promptView.findViewById(R.id.edittext);
// final EditText editText = (EditText) promptView.findViewById(R.id.edittext);
// setup a dialog window
alertDialogBuilder.setCancelable(false).setPositiveButton("OK",new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int id){
Organization organization = new Organization();
organization.setId(organizationList.size()+1);
organization.setName(editText.getText().toString());
organization.save();
//initViews();
}}).setNegativeButton("Cancel",new DialogInterface.OnClickListener(){
public void onClick(DialogInterface dialog, int id) {
dialog.cancel();
}
});
//create an alert dialog
AlertDialog alert = alertDialogBuilder.create();
alert.show();
/*
AlertDialog alert = alertDialogBuilder.create();
alert.show();
*/
}
}
/
/Organization class :
import com.raizlabs.android.dbflow.annotation.Column;
import com.raizlabs.android.dbflow.annotation.PrimaryKey;
import com.raizlabs.android.dbflow.annotation.Table;
import com.raizlabs.android.dbflow.structure.BaseModel;
// **Note:** Your class must extend from BaseModel
#Table(database = MyDatabase.class)
public class Organization extends BaseModel {
#Column
#PrimaryKey
int id;
#Column
String name;
private Organization organization;
public String getName() {
return name;
}
public void setId(int id) {
this.id = id;
}
public void setOrganization(Organization organization) {
this.organization = organization;
}
public void setName(String name) {
this.name = name;
}
}
// input_dialog.xml :
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="10dp">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:text="Enter Name"
android:id="#+id/textView"/>
<EditText
android:id="#+id/edittext"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:hint="Enter text here.."
android:padding="10dp"/>
</LinearLayout>

After you have changed the data you need to call notifyDataSetChanged() on your Adapter in order to update the data in your RecycleView.
Set this wherever you make changes to the source data:
adapter.notifyDataSetChanged()
Note: As a precaution you might want to check that "adapter" is not null.

Add these two lines, inside your onClick of setPositiveButton
(Just after organization.save())
.......
organization.save();
organizationList.add(organization);
adapter.notifyDataSetChanged();

How to programmatically Next and Prev buttons for Master / Detail flow

I have created a sample app using the "Master / Detail flow" activity. I have added two buttons, Next and Prev to the detail activity. How to I set programmatically the buttons actions instead having to go back and forth between the List and detail?
item_detail.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingStart="30dp"
android:paddingEnd="30dp"
android:weightSum="4"
android:gravity="end"
android:orientation="horizontal">
<Button
android:id="#+id/button_prev"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="Prev"/>
<Button
android:id="#+id/button_next"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="Next"/>
</LinearLayout>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/item_detail"
style="?android:attr/textAppearanceLarge"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="16dp"
android:textIsSelectable="true"
tools:context="co.test.app.sample.itemapplication.ItemDetailFragment"/>
</LinearLayout>
activity_item_detail.xml
<android.support.design.widget.CoordinatorLayout 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:fitsSystemWindows="true"
tools:context="co.test.app.sample.itemapplication.ItemDetailActivity"
tools:ignore="MergeRootFrame">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="#dimen/app_bar_height"
android:fitsSystemWindows="true"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/toolbar_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed"
app:toolbarId="#+id/toolbar">
<android.support.v7.widget.Toolbar
android:id="#+id/detail_toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:layout_collapseMode="pin"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light"/>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<android.support.v4.widget.NestedScrollView
android:id="#+id/item_detail_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
</android.support.v4.widget.NestedScrollView>
</android.support.design.widget.CoordinatorLayout>
DummyContent.java
package co.test.app.sample.itemapplication.dummy;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* Helper class for providing sample content for user interfaces created by
* Android template wizards.
* <p>
* TODO: Replace all uses of this class before publishing your app.
*/
public class DummyContent {
/**
* An array of sample (dummy) items.
*/
public static final List<DummyItem> ITEMS = new ArrayList<DummyItem>();
/**
* A map of sample (dummy) items, by ID.
*/
public static final Map<String, DummyItem> ITEM_MAP = new HashMap<String, DummyItem>();
private static final int COUNT = 25;
static {
// Add some sample items.
for (int i = 1; i <= COUNT; i++) {
addItem(createDummyItem(i));
}
}
private static void addItem(DummyItem item) {
ITEMS.add(item);
ITEM_MAP.put(item.id, item);
}
private static DummyItem createDummyItem(int position) {
return new DummyItem(String.valueOf(position), "Item " + position, makeDetails(position));
}
private static String makeDetails(int position) {
StringBuilder builder = new StringBuilder();
builder.append("Details about Item: ").append(position);
for (int i = 0; i < position; i++) {
builder.append("\nMore details information here.");
}
return builder.toString();
}
/**
* A dummy item representing a piece of content.
*/
public static class DummyItem {
public final String id;
public final String content;
public final String details;
public DummyItem(String id, String content, String details) {
this.id = id;
this.content = content;
this.details = details;
}
#Override
public String toString() {
return content;
}
}
}
ItemDetailActivity.java
package co.test.app.sample.itemapplication;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.app.ActionBar;
import android.view.MenuItem;
/**
* An activity representing a single Item detail screen. This
* activity is only used narrow width devices. On tablet-size devices,
* item details are presented side-by-side with a list of items
* in a {#link ItemListActivity}.
*/
public class ItemDetailActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_item_detail);
Toolbar toolbar = (Toolbar) findViewById(R.id.detail_toolbar);
setSupportActionBar(toolbar);
// Show the Up button in the action bar.
ActionBar actionBar = getSupportActionBar();
if (actionBar != null) {
actionBar.setDisplayHomeAsUpEnabled(true);
}
// savedInstanceState is non-null when there is fragment state
// saved from previous configurations of this activity
// (e.g. when rotating the screen from portrait to landscape).
// In this case, the fragment will automatically be re-added
// to its container so we don't need to manually add it.
// For more information, see the Fragments API guide at:
//
// http://developer.android.com/guide/components/fragments.html
//
if (savedInstanceState == null) {
// Create the detail fragment and add it to the activity
// using a fragment transaction.
Bundle arguments = new Bundle();
arguments.putString(ItemDetailFragment.ARG_ITEM_ID,
getIntent().getStringExtra(ItemDetailFragment.ARG_ITEM_ID));
ItemDetailFragment fragment = new ItemDetailFragment();
fragment.setArguments(arguments);
getSupportFragmentManager().beginTransaction()
.add(R.id.item_detail_container, fragment)
.commit();
}
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == android.R.id.home) {
// This ID represents the Home or Up button. In the case of this
// activity, the Up button is shown. For
// more details, see the Navigation pattern on Android Design:
//
// http://developer.android.com/design/patterns/navigation.html#up-vs-back
//
navigateUpTo(new Intent(this, ItemListActivity.class));
return true;
}
return super.onOptionsItemSelected(item);
}
}
ItemListActivity.java
package co.test.app.sample.itemapplication;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import co.test.app.sample.itemapplication.dummy.DummyContent;
import java.util.List;
/**
* An activity representing a list of Items. This activity
* has different presentations for handset and tablet-size devices. On
* handsets, the activity presents a list of items, which when touched,
* lead to a {#link ItemDetailActivity} representing
* item details. On tablets, the activity presents the list of items and
* item details side-by-side using two vertical panes.
*/
public class ItemListActivity extends AppCompatActivity {
/**
* Whether or not the activity is in two-pane mode, i.e. running on a tablet
* device.
*/
private boolean mTwoPane;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_item_list);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
toolbar.setTitle(getTitle());
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
View recyclerView = findViewById(R.id.item_list);
assert recyclerView != null;
setupRecyclerView((RecyclerView) recyclerView);
if (findViewById(R.id.item_detail_container) != null) {
// The detail container view will be present only in the
// large-screen layouts (res/values-w900dp).
// If this view is present, then the
// activity should be in two-pane mode.
mTwoPane = true;
}
}
private void setupRecyclerView(#NonNull RecyclerView recyclerView) {
recyclerView.setAdapter(new SimpleItemRecyclerViewAdapter(DummyContent.ITEMS));
}
public class SimpleItemRecyclerViewAdapter
extends RecyclerView.Adapter<SimpleItemRecyclerViewAdapter.ViewHolder> {
private final List<DummyContent.DummyItem> mValues;
public SimpleItemRecyclerViewAdapter(List<DummyContent.DummyItem> items) {
mValues = items;
}
#Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.item_list_content, parent, false);
return new ViewHolder(view);
}
#Override
public void onBindViewHolder(final ViewHolder holder, int position) {
holder.mItem = mValues.get(position);
holder.mIdView.setText(mValues.get(position).id);
holder.mContentView.setText(mValues.get(position).content);
holder.mView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (mTwoPane) {
Bundle arguments = new Bundle();
arguments.putString(ItemDetailFragment.ARG_ITEM_ID, holder.mItem.id);
ItemDetailFragment fragment = new ItemDetailFragment();
fragment.setArguments(arguments);
getSupportFragmentManager().beginTransaction()
.replace(R.id.item_detail_container, fragment)
.commit();
} else {
Context context = v.getContext();
Intent intent = new Intent(context, ItemDetailActivity.class);
intent.putExtra(ItemDetailFragment.ARG_ITEM_ID, holder.mItem.id);
context.startActivity(intent);
}
}
});
}
#Override
public int getItemCount() {
return mValues.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
public final View mView;
public final TextView mIdView;
public final TextView mContentView;
public DummyContent.DummyItem mItem;
public ViewHolder(View view) {
super(view);
mView = view;
mIdView = (TextView) view.findViewById(R.id.id);
mContentView = (TextView) view.findViewById(R.id.content);
}
#Override
public String toString() {
return super.toString() + " '" + mContentView.getText() + "'";
}
}
}
}

This is the code snippet used to forward to the detail page.
if (mTwoPane) {
Bundle arguments = new Bundle();
arguments.putString(ItemDetailFragment.ARG_ITEM_ID, holder.mItem.id);
ItemDetailFragment fragment = new ItemDetailFragment();
fragment.setArguments(arguments);
getSupportFragmentManager().beginTransaction()
.replace(R.id.item_detail_container, fragment)
.commit();
} else {
Context context = v.getContext();
Intent intent = new Intent(context, ItemDetailActivity.class);
intent.putExtra(ItemDetailFragment.ARG_ITEM_ID, holder.mItem.id);
context.startActivity(intent);
}
You can forward to any page by changing the value of arguments.putString(ItemDetailFragment.ARG_ITEM_ID, holder.mItem.id);
Use the above snippets in the onClick events of next and prev buttons. cheers :)

App crashed after adding navigation menu in Android Studio

Please take a look at my source code, my app crashed after I added the navigation Menu. Can you please tell what is wrong I have been searching all on Google and could not arrive at a solution to this issue? Thank You.
My MainActivity looks like:
package com.example.rssreader;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.SearchManager;
import android.content.Intent;
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.support.v7.app.ActionBar;
import android.view.LayoutInflater;
import android.view.MenuInflater;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.Toast;
import java.util.Locale;
public class MainActivity extends AppCompatActivity {
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private android.support.v4.app.ActionBarDrawerToggle mDrawerToggle;
private CharSequence mDrawerTitle;
private CharSequence mTitle;
private String[] mPlanetTitles;
RecyclerView recyclerView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = (RecyclerView) findViewById(R.id.recyclerview);
ReadRss readRss = new ReadRss(this, recyclerView);
readRss.execute();
mTitle = mDrawerTitle = getTitle();
mPlanetTitles = getResources().getStringArray(R.array.contents);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
// set a custom shadow that overlays the main content when the drawer opens
mDrawerLayout.setDrawerShadow(R.drawable.drawer_shadow, GravityCompat.START);
// set up the drawer's list view with items and click listener
mDrawerList.setAdapter(new ArrayAdapter<String>(this,
R.layout.drawer_list_item, mPlanetTitles));
mDrawerList.setOnItemClickListener(new DrawerItemClickListener());
// enable ActionBar app icon to behave as action to toggle nav drawer
// ActionBarDrawerToggle ties together the the proper interactions
// between the sliding drawer and the action bar app icon
mDrawerToggle = new android.support.v4.app.ActionBarDrawerToggle(
this, /* host Activity */
mDrawerLayout, /* DrawerLayout object */
R.drawable.ic_drawer, /* nav drawer image to replace 'Up' caret */
R.string.drawer_open, /* "open drawer" description for accessibility */
R.string.drawer_close /* "close drawer" description for accessibility */
) {
public void onDrawerClosed(View view) {
getActionBar().setTitle(mTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
public void onDrawerOpened(View drawerView) {
getActionBar().setTitle(mDrawerTitle);
invalidateOptionsMenu(); // creates call to onPrepareOptionsMenu()
}
};
mDrawerLayout.setDrawerListener(mDrawerToggle);
if (savedInstanceState == null) {
selectItem(0);
}
getWindow().setNavigationBarColor(getResources().getColor(R.color.colorPrimary));
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.layout.main, menu);
return super.onCreateOptionsMenu(menu);
}
/* Called whenever we call invalidateOptionsMenu() */
#Override
public boolean onPrepareOptionsMenu(Menu menu) {
// If the nav drawer is open, hide action items related to the content view
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_websearch).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// The action bar home/up action should open or close the drawer.
// ActionBarDrawerToggle will take care of this.
if (mDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
// Handle action buttons
switch(item.getItemId()) {
case R.id.action_websearch:
// create intent to perform web search for this planet
Intent intent = new Intent(Intent.ACTION_WEB_SEARCH);
// catch event that there's no activity to handle intent
if (intent.resolveActivity(getPackageManager()) != null) {
startActivity(intent);
} else {
Toast.makeText(this, R.string.app_not_available, Toast.LENGTH_LONG).show();
}
return true;
default:
return super.onOptionsItemSelected(item);
}
}
/* The click listner for ListView in the navigation drawer */
private class DrawerItemClickListener implements ListView.OnItemClickListener {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
selectItem(position);
}
}
private void selectItem(int position) {
// update the main content by replacing fragments
Fragment fragment = new PlanetFragment();
Bundle args = new Bundle();
args.putInt(PlanetFragment.ARG_CONTENT_NUMBER, position);
fragment.setArguments(args);
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.content_frame, fragment).commit();
// update selected item and title, then close the drawer
mDrawerList.setItemChecked(position, true);
setTitle(mPlanetTitles[position]);
mDrawerLayout.closeDrawer(mDrawerList);
}
#Override
public void setTitle(CharSequence title) {
mTitle = title;
getActionBar().setTitle(mTitle);
}
/**
* When using the ActionBarDrawerToggle, you must call it during
* onPostCreate() and onConfigurationChanged()...
*/
#Override
protected void onPostCreate(Bundle savedInstanceState) {
super.onPostCreate(savedInstanceState);
// Sync the toggle state after onRestoreInstanceState has occurred.
mDrawerToggle.syncState();
}
#Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Pass any configuration change to the drawer toggls
mDrawerToggle.onConfigurationChanged(newConfig);
}
/**
* Fragment that appears in the "content_frame", shows a planet
*/
public static class PlanetFragment extends Fragment {
public static final String ARG_CONTENT_NUMBER = "planet_number";
public PlanetFragment() {
// Empty constructor required for fragment subclasses
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_content, container, false);
int i = getArguments().getInt(ARG_CONTENT_NUMBER);
String planet = getResources().getStringArray(R.array.contents)[i];
int imageId = getResources().getIdentifier(planet.toLowerCase(Locale.getDefault()),
"drawable", getActivity().getPackageName());
((ImageView) rootView.findViewById(R.id.image)).setImageResource(imageId);
getActivity().setTitle(planet);
return rootView;
}
}
}
My Activity_main.xml looks like:
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<FrameLayout
android:id="#+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<ListView
android:id="#+id/left_drawer"
android:layout_width="240dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:choiceMode="singleChoice"
android:divider="#android:color/transparent"
android:dividerHeight="0dp"
android:background="#ccc"/>
</android.support.v4.widget.DrawerLayout>
Drawer_list_item.xml looks like:
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#android:id/text1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceListItemSmall"
android:gravity="center_vertical"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:textColor="#113d5e"
android:background="?android:attr/activatedBackgroundIndicator"
android:minHeight="?android:attr/listPreferredItemHeightSmall"/>
Fragment_content.xml looks like:
<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/image"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#000000"
android:gravity="center"
android:padding="32dp" />
Main.xml looks like:
<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/image"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#000000"
android:gravity="center"
android:padding="32dp" />
Thank You

I was able to fix that issue by creating a separate class for the navigation drawer. However, I am facing another issue with the RssFeeds.
public class ReadRss extends AsyncTask and recyclerView.setLayoutManager(new LinearLayoutManager(context) is where the error is pointing to when the app crashed when running the debug.
Here is the ReadRss.java:
package tk.mattercast.myapplication;
import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
public class ReadRss extends AsyncTask<Void, Void, Void> {
Context context;
String address = "http://www.oecd.org/corruption/index.xml";
ProgressDialog progressDialog;
ArrayList<FeedItem>feedItems;
RecyclerView recyclerView;
URL url;
public ReadRss(Context context,RecyclerView recyclerView) {
this.recyclerView=recyclerView;
this.context = context;
progressDialog = new ProgressDialog(context);
progressDialog.setMessage("Fetching Data...");
}
#Override
protected void onPreExecute() {
progressDialog.show();
super.onPreExecute();
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
progressDialog.dismiss();
MyAdapter adapter=new MyAdapter(context,feedItems);
recyclerView.setLayoutManager(new LinearLayoutManager(context) {
#Override
public RecyclerView.LayoutParams generateDefaultLayoutParams() {
return null;
}
});
recyclerView.addItemDecoration(new VerticalSpace(50));
recyclerView.setAdapter(adapter);
}
#Override
protected Void doInBackground(Void... params) {
ProcessXml(Getdata());
return null;
}
private void ProcessXml(Document data) {
if (data != null) {
feedItems=new ArrayList<>();
Element root = data.getDocumentElement();
Node channel = root.getChildNodes().item(1);
NodeList items = channel.getChildNodes();
for (int i = 0; i < items.getLength(); i++) {
Node cureentchild = items.item(i);
if (cureentchild.getNodeName().equalsIgnoreCase("item")) {
FeedItem item=new FeedItem();
NodeList itemchilds = cureentchild.getChildNodes();
for (int j = 0; j < itemchilds.getLength(); j++) {
Node cureent = itemchilds.item(j);
if (cureent.getNodeName().equalsIgnoreCase("title")){
item.setTitle(cureent.getTextContent());
}else if (cureent.getNodeName().equalsIgnoreCase("description")){
item.setDescription(cureent.getTextContent());
}else if (cureent.getNodeName().equalsIgnoreCase("pubDate")){
item.setPubDate(cureent.getTextContent());
}else if (cureent.getNodeName().equalsIgnoreCase("link")){
item.setLink(cureent.getTextContent());
}
}
feedItems.add(item);
}
}
}
}
public Document Getdata() {
try {
url = new URL(address);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
InputStream inputStream = connection.getInputStream();
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = builderFactory.newDocumentBuilder();
Document xmlDoc = builder.parse(inputStream);
return xmlDoc;
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
}

java.lang.NullPointerException: Android Studio

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
I am getting a NullPointerException at line 67 while trying to set a listView with a chat adapter. Here is the class:
I have placed ** around the line I am getting the NullPointerException on. I'm not really understading why its returning as null when I'm setting messageAdapter to a new object of an inner class called ChatAdapter(this).
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class MessageListActivity extends AppCompatActivity {
/**
* Whether or not the activity is in two-pane mode, i.e. running on a tablet
* device.
*/
ListView listView;
Button sendButton;
ArrayList<String> arrayList = new ArrayList<String>();
ChatDatabaseHelper Cdb;
private boolean mTwoPane;
ChatAdapter messageAdapter = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_message_list);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
toolbar.setTitle(getTitle());
listView = (ListView)findViewById(R.id.chatListView);
final EditText editText = (EditText)findViewById(R.id.messageText);
sendButton = (Button)findViewById(R.id.sendButton);
messageAdapter = new ChatAdapter(this); // chatAdapter is a built in adapater
**listView.setAdapter(messageAdapter);**
Cdb = new ChatDatabaseHelper(this);
Cursor cursor = Cdb.getMessages(); // get messages method is of type Cursor from database helper class
// cursor will move through the database to find the next text if there is any.
while (cursor.moveToNext()) { arrayList.add(cursor.getString(cursor.getColumnIndex(Cdb.KEY_MESSAGE))); }
sendButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) { // on click listener for the send button
String chatText = editText.getText().toString(); // changing editText to String
arrayList.add(chatText); // adding the string from EditTest to arrayList
boolean isInserted = Cdb.insertData(chatText); // inserting the message text into the database
if(isInserted = true)
{ Toast.makeText(MessageListActivity.this,"Message Sent",Toast.LENGTH_SHORT).show(); } // if the message inserts into the database this toast will show
else {
Toast.makeText(MessageListActivity.this,"Message not Sent",Toast.LENGTH_SHORT).show(); } // if message does not nter the database this toast will show
messageAdapter.notifyDataSetChanged(); // notifying the adapter that a message has been sent, changing from incoming to outgoing
editText.setText(" "); // set the text on the send button to blank.
} // end of onClick view
}); // end of onClickListener
if (findViewById(R.id.message_detail_container) != null) {
// The detail container view will be present only in the
// large-screen layouts (res/values-w900dp).
// If this view is present, then the
// activity should be in two-pane mode.
mTwoPane = true;
}
}
class ChatAdapter extends ArrayAdapter<String> { // custom adapter class // when youc all the adapter it forms the for loop for you.
public ChatAdapter(MessageListActivity ctx) {
super(ctx, 0);
} // default constructor
// method to return the number of rows that will be in your array
// will tell how many times to run a for loop
public int getCount(){ return arrayList.size(); } // will return the size of the array
public String getItem(int position){ return arrayList.get(position); } // will return the item at position
// getview method
#Override
public View getView(int position, final View convertView, ViewGroup parent) {// inner class
LayoutInflater Inflater = MessageListActivity.this.getLayoutInflater(); // an inflater inflates the xml layout into a view.
View result = null;
if(position%2 == 0){ // if position number in the array is odd do this, if number is even, do this.
result = Inflater.inflate(R.layout.chat_row_incoming, null); // depending on the position, show layout incoming
} else {
result = Inflater.inflate(R.layout.chat_row_outgoing,null); // depending on the position, show layout outgoing
}
TextView message = (TextView)result.findViewById(R.id.messageText); // creating a message of type TextView connected to messageText
final String messageText = getItem(position) ;
message.setText(messageText);
result.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (mTwoPane) {
Bundle arguments = new Bundle();
arguments.putString(MessageDetailFragment.ARG_ITEM_ID,messageText );
MessageDetailFragment fragment = new MessageDetailFragment();
fragment.setArguments(arguments);
getSupportFragmentManager().beginTransaction()
.replace(R.id.message_detail_container, fragment)
.commit();
} else {
Context context = v.getContext();
Intent intent = new Intent(context, MessageDetailActivity.class);
intent.putExtra(MessageDetailFragment.ARG_ITEM_ID,messageText );
context.startActivity(intent);
}
}
});
return result; // return the view which is the Inflater.
}
} // end of chat adapter class
private void setupRecyclerView(#NonNull RecyclerView recyclerView) {
recyclerView.setAdapter(new SimpleItemRecyclerViewAdapter(DummyContent.ITEMS));
}
public class SimpleItemRecyclerViewAdapter
extends RecyclerView.Adapter<SimpleItemRecyclerViewAdapter.ViewHolder> {
private final List<DummyContent.DummyItem> mValues;
public SimpleItemRecyclerViewAdapter(List<DummyContent.DummyItem> items) {
mValues = items;
}
#Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.message_list_content, parent, false);
return new ViewHolder(view);
}
#Override
public void onBindViewHolder(final ViewHolder holder, int position) {
holder.mItem = mValues.get(position);
holder.mIdView.setText(mValues.get(position).id);
holder.mContentView.setText(mValues.get(position).content);
holder.mView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if (mTwoPane) {
Bundle arguments = new Bundle();
arguments.putString(MessageDetailFragment.ARG_ITEM_ID, holder.mItem.id);
MessageDetailFragment fragment = new MessageDetailFragment();
fragment.setArguments(arguments);
getSupportFragmentManager().beginTransaction()
.replace(R.id.message_detail_container, fragment)
.commit();
} else {
Context context = v.getContext();
Intent intent = new Intent(context, MessageDetailActivity.class);
intent.putExtra(MessageDetailFragment.ARG_ITEM_ID, holder.mItem.id);
context.startActivity(intent);
}
}
});
}
#Override
public int getItemCount() {
return mValues.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
public final View mView;
public final TextView mIdView;
public final TextView mContentView;
public DummyContent.DummyItem mItem;
public ViewHolder(View view) {
super(view);
mView = view;
mIdView = (TextView) view.findViewById(R.id.id);
mContentView = (TextView) view.findViewById(R.id.content);
}
#Override
public String toString() {
return super.toString() + " '" + mContentView.getText() + "'";
}
}
}
xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.example.ChatWindow">
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/chatListView"
android:layout_alignParentStart="true"
android:layout_alignParentEnd="true"
android:layout_alignParentTop="true"
android:layout_alignParentBottom="false"
android:layout_alignWithParentIfMissing="false"
android:layout_above="#+id/sendButton" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/sendButton"
android:id="#+id/sendButton"
android:layout_alignParentBottom="true"
android:layout_alignParentEnd="true"
android:layout_alignParentRight="true"
android:singleLine="true" />
<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/messageText"
android:layout_toStartOf="#id/sendButton"
android:layout_alignParentStart="true"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:enabled="true"
/>
</RelativeLayout>

just try
messageAdapter = new ChatAdapter(MessageListActivity .this);

Issue with TabLayout in fragment (android/java)

i've tried to add tabLayout in my application. When I open the fragment (where there is my tablayout) for the first time it works fine, but if I close the fragment and I try to re-open it, the tab indicator doesn't follow my swipe and all viewPager became blank... how can I resolve this problem?
my fragment:
package com.gabrielemarcozzi.mycal;
import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.app.Fragment;
import android.support.design.widget.TabLayout;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class PercentageFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private OnFragmentInteractionListener mListener;
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* #param param1 Parameter 1.
* #param param2 Parameter 2.
* #return A new instance of fragment PercentageFragment.
*/
// TODO: Rename and change types and number of parameters
public static PercentageFragment newInstance(String param1, String param2) {
PercentageFragment fragment = new PercentageFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
public PercentageFragment() {
// Required empty public constructor
}
private FragmentActivity context;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_percentage, container, false);
Toolbar mToolbar = (Toolbar)getActivity().findViewById(R.id.toolbar);
mToolbar.setTitle(R.string.percentage);
ViewPager percentagePager = (ViewPager)view.findViewById(R.id.percentage_pager);
percentagePager.setAdapter(new PercentagePagerAdapter(context.getSupportFragmentManager()));
TabLayout percentageTab = (TabLayout)view.findViewById(R.id.percentage_tabs);
percentageTab.setupWithViewPager(percentagePager);
return view;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
MainActivity main = (MainActivity) activity;
mListener = main;
context = (FragmentActivity) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p/>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
public void onFragmentInteraction(Uri uri);
}
class PercentagePagerAdapter extends FragmentPagerAdapter {
String[] pergentageTabsArray;
public PercentagePagerAdapter(FragmentManager fm) {
super(fm);
pergentageTabsArray = getResources().getStringArray(R.array.percentage_tabs);
}
#Override
public android.support.v4.app.Fragment getItem(int position) {
TabsPercentageFragment TabsPercFrag = TabsPercentageFragment.getIstance(position);
return TabsPercFrag;
}
#Override
public CharSequence getPageTitle(int position) {
return pergentageTabsArray[position];
}
#Override
public int getCount() {
return 3;
}
}
public static class TabsPercentageFragment extends android.support.v4.app.Fragment {
public static TabsPercentageFragment getIstance(int position) {
TabsPercentageFragment increaseFrag = new TabsPercentageFragment();
Bundle args = new Bundle();
args.putInt("position", position);
increaseFrag.setArguments(args);
return increaseFrag;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view;
Bundle bundle = getArguments();
switch(bundle.getInt("position")) {
case 1:
view = inflater.inflate(R.layout.fragment_discount, container, false);
break;
case 2:
view = inflater.inflate(R.layout.fragment_xofy, container, false);
break;
default:
view =inflater.inflate(R.layout.fragment_increase, container, false);
break;
}
return view;
}
}
}
my fragment xml file:
<LinearLayout
android:id="#+id/percentage_fragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.gabrielemarcozzi.mycal.PercentageFragment">
<android.support.design.widget.TabLayout
android:id="#+id/percentage_tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/colorPrimary"
app:tabMode="fixed"
app:tabIndicatorColor="#color/colorUp"
app:tabTextColor="#android:color/white"
app:tabSelectedTextColor="#color/colorUp"/>
<android.support.v4.view.ViewPager
android:id="#+id/percentage_pager"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"/>
<!-- TODO: Update blank fragment layout -->
</LinearLayout>

Try to user getChildFragmentManager() instead of getSupportFragmentManager() at:
percentagePager.setAdapter(new PercentagePagerAdapter(context.getSupportFragmentManager()));
and change your import from:
import android.app.Fragment;
to
import android.support.v4.app.Fragment;