I have the beginnings of a very basic app at the moment. It just has one main activity, which has a navigation drawer and one card. When I try and debug the app I get the following error:
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.support.v7.widget.RecyclerView$ViewHolder.shouldIgnore()' on a null object reference. Below is the code:
MainActivity:
public class MainActivity extends AppCompatActivity
{
private DrawerLayout mDrawerLayout;
private RecyclerView recyclerView;
private ScoreCardAdapter adapter;
private List<ScoreCard> scoreCardList;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Setting up the custom toolbar
Toolbar customToolbar = findViewById(R.id.custom_toolbar);
setSupportActionBar(customToolbar);
getSupportActionBar().setTitle(null);
customToolbar.setBackgroundColor(Color.TRANSPARENT);
//Creating the menu icon in the appbar
ActionBar actionBar = getSupportActionBar();
if (actionBar != null)
{
actionBar.setHomeAsUpIndicator(R.drawable.ic_menu_black_24dp);
actionBar.setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
}
mDrawerLayout = findViewById(R.id.drawer_layout);
// Initializing Drawer Layout and ActionBarToggle
ActionBarDrawerToggle actionBarDrawerToggle = new ActionBarDrawerToggle(this,mDrawerLayout,customToolbar,R.string.openDrawer, R.string.closeDrawer)
{
@Override
public void onDrawerClosed(View drawerView)
{
// Code here will be triggered once the drawer closes as we don't want anything to happen so we leave this blank
super.onDrawerClosed(drawerView);
}
@Override
public void onDrawerOpened(View drawerView) {
// Code here will be triggered once the drawer open as we don't want anything to happen so we leave this blank
super.onDrawerOpened(drawerView);
}
};
//Setting the actionbarToggle to drawer layout
mDrawerLayout.addDrawerListener(actionBarDrawerToggle);
//calling sync state is necessay or else your hamburger icon wont show up
actionBarDrawerToggle.syncState();
scoreCardList = new ArrayList<>();
recyclerView = findViewById(R.id.recycler_view);
adapter = new ScoreCardAdapter(this, scoreCardList);
RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(this);
recyclerView.setLayoutManager(mLayoutManager);
recyclerView.setHasFixedSize(true);
recyclerView.setAdapter(adapter);
scoreCardList.add(new ScoreCard("Sunday, 28th January 2018", R.drawable.launcher_logo, "3 -- 2", R.drawable.annan_athletic_fc_logo, "14:00, Forthbank Stadium"));
}
@Override
public boolean onOptionsItemSelected(MenuItem item)
{
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
//noinspection SimplifiableIfStatement
return super.onOptionsItemSelected(item);
}
@Override
public void onBackPressed()
{
if (mDrawerLayout.isDrawerOpen(GravityCompat.START))
{
mDrawerLayout.closeDrawer(GravityCompat.START);
}
else
{
super.onBackPressed();
}
}
}
Adapter:
public class ScoreCardAdapter extends RecyclerView.Adapter<ScoreCardAdapter.ScoreCardViewHolder>
{
private Context mCtx;
private List<ScoreCard> scoreCardList;
public class ScoreCardViewHolder extends RecyclerView.ViewHolder
{
public TextView dateTextView;
public ImageView homeTeamLogoImageView;
public TextView scoreTextView;
public ImageView enemyTeamLogoImageView;
public TextView timeAndLocationTextView;
public ScoreCardViewHolder(View view)
{
super(view);
dateTextView = itemView.findViewById(R.id.date_textview);
homeTeamLogoImageView = itemView.findViewById(R.id.home_team_logo_imageview);
scoreTextView = itemView.findViewById(R.id.score_textview);
enemyTeamLogoImageView = itemView.findViewById(R.id.enemy_team_logo_imageview);
timeAndLocationTextView = itemView.findViewById(R.id.time_and_location_textview);
}
}
public ScoreCardAdapter(Context mCtx, List<ScoreCard> scoreCardList)
{
this.mCtx = mCtx;
this.scoreCardList = scoreCardList;
}
@Override
public ScoreCardViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
{
View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.main_card_layout, parent, false);
return new ScoreCardViewHolder(itemView);
}
@Override
public void onBindViewHolder(final ScoreCardViewHolder holder, int position)
{
ScoreCard scoreCard = scoreCardList.get(position);
holder.dateTextView.setText(scoreCard.getDate());
holder.scoreTextView.setText(scoreCard.getScore());
holder.timeAndLocationTextView.setText(scoreCard.getTimeAndLocation());
holder.homeTeamLogoImageView.setImageDrawable(mCtx.getResources().getDrawable(scoreCard.getHomeTeamLogo(), null));
holder.enemyTeamLogoImageView.setImageDrawable(mCtx.getResources().getDrawable(scoreCard.getEnemyTeamLogo(), null));
}
@Override
public int getItemCount()
{
return scoreCardList.size();
}
}
Main XML:
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.application.andrewhaines.stirlingalbionfc.MainActivity">
<android.support.v7.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical"
app:layoutManager="android.support.v7.widget.LinearLayoutManager">
<android.support.v7.widget.Toolbar
android:id="@+id/custom_toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/SAFCRed"
android:elevation="4dp"
android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />
</android.support.v7.widget.RecyclerView>
<android.support.design.widget.NavigationView
android:id="@+id/nav_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
app:menu="@menu/nav_menu_list"
app:headerLayout="@layout/nav_drawer_layout"
android:theme="@style/NavigationDrawerStyle">
</android.support.design.widget.NavigationView>
</android.support.v4.widget.DrawerLayout>
CardXML:
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/score_card_overall_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.v7.widget.CardView
android:layout_width="match_parent"
android:layout_height="150dp"
android:layout_margin="5dp"
android:elevation="3dp">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<TextView
android:id="@+id/date_textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:fontFamily="sans-serif"
android:textAllCaps="true"
android:textSize="16sp"/>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<ImageView
android:id="@+id/home_team_logo_imageview"
android:layout_width="0dp"
android:layout_height="100dp"
android:layout_marginStart="10dp"
android:layout_weight="1"
android:contentDescription="home team logo"
android:scaleType="fitCenter"/>
<TextView
android:id="@+id/score_textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:layout_weight="1"
android:fontFamily="sans-serif"
android:gravity="center_horizontal"
android:textSize="20sp"/>
<ImageView
android:id="@+id/enemy_team_logo_imageview"
android:layout_width="0dp"
android:layout_height="100dp"
android:layout_marginEnd="10dp"
android:layout_weight="1"
android:contentDescription="enemy team logo"
android:scaleType="fitCenter"/>
</LinearLayout>
<TextView
android:id="@+id/time_and_location_textview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:fontFamily="sans-serif"
android:textAllCaps="true"
android:textSize="14sp"/>
</LinearLayout>
</android.support.v7.widget.CardView>
</LinearLayout>
Logcat:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.application.andrewhaines.stirlingalbionfc, PID: 16411
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.application.andrewhaines.stirlingalbionfc/com.application.andrewhaines.stirlingalbionfc.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.support.v7.widget.RecyclerView$ViewHolder.shouldIgnore()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.support.v7.widget.RecyclerView$ViewHolder.shouldIgnore()' on a null object reference
at android.support.v7.widget.RecyclerView$LayoutManager.removeAndRecycleAllViews(RecyclerView.java:9728)
at android.support.v7.widget.RecyclerView.setLayoutManager(RecyclerView.java:1220)
at com.application.andrewhaines.stirlingalbionfc.MainActivity.onCreate(MainActivity.java:79)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
I have looked at other NullPointerExcpetion threads, but they did not help!
