Issue
I am receiving the following error: error: java.lang.NullPointerException: Attempt to invoke virtual method 'void androidx.recyclerview.widget.RecyclerView.setAdapter(androidx.recyclerview.widget.RecyclerView$Adapter)' on a null object reference
Here is my code:
PropertyHome.java:
public class PropertyHome extends AppCompatActivity
{
private RecyclerView recyclerView;
private RecyclerView.Adapter recyclerAdapter;
private RecyclerView.LayoutManager recyclerLayoutManager;
...
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
try {
recyclerView = (RecyclerView)findViewById(R.id.get_property_entry_property_home);
String[] myRecycler = new String[5];
myRecycler[0] = "Recycler 1";
myRecycler[1] = "Recycler 2";
myRecycler[2] = "Recycler 3";
myRecycler[3] = "Recycler 4";
myRecycler[4] = "Recycler 5";
recyclerAdapter = new GetPropertyRecyclerViewAdapater(myRecycler);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(recyclerAdapter);
}
catch(Exception e)
{
Toast.makeText(PropertyHome.this, "Error: " + e.toString(), Toast.LENGTH_LONG).show();
}
}
...
}
activity_property_homr.xml:
<?xml version="1.0" encoding="utf-8"?>
<ScrollView 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="wrap_content"
tools:layout_editor_absoluteX="1dp"
tools:layout_editor_absoluteY="1dp"
tools:context=".MainActivity">
<LinearLayout
android:id="@+id/linear_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:onClick="AppLogout"
android:orientation="vertical"
android:textAlignment="gravity" >
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/get_property_entry_property_home"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:itemCount="0" />
</LinearLayout>
</ScrollView>
Layout for displaying each row of the RecyclerView:
GetPropertyRecyclerViewAdapter.java:
public class GetPropertyRecyclerViewAdapater extends RecyclerView.Adapter<GetPropertyRecyclerViewAdapater.ViewHolder>
{
private String[] dataSet;
public static class ViewHolder extends RecyclerView.ViewHolder
{
public final TextView mTextView;
public ViewHolder(View v)
{
super(v);
mTextView = (TextView)v.findViewById(R.id.location_property_home);
}
public TextView getTextView()
{
return mTextView;
}
}
public GetPropertyRecyclerViewAdapater(String[] myDataSet)
{
dataSet = myDataSet;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType)
{
View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.recycler_view_item, viewGroup, false);
return new ViewHolder(v);
}
@Override
public void onBindViewHolder(ViewHolder holder, final int position)
{
holder.getTextView().setText(dataSet[position]);
}
@Override
public int getItemCount()
{
return dataSet.length;
}
}
recycler_view_item.xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
android:padding="8dp">
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginTop="20dp"
android:text="Price:"
android:textColor="#000000"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/image_property_home" />
<TextView
android:id="@+id/price_property_home"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:text="0"
android:textColor="#000000"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="@+id/textView"
app:layout_constraintStart_toEndOf="@+id/textView"
app:layout_constraintTop_toTopOf="@+id/textView" />
<TextView
android:id="@+id/textView6"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="20dp"
android:layout_marginTop="10dp"
android:text="Location:"
android:textColor="#000000"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/textView" />
<TextView
android:id="@+id/location_property_home"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:text="N/A"
android:textColor="#000000"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="@+id/textView6"
app:layout_constraintStart_toEndOf="@+id/textView6"
app:layout_constraintTop_toTopOf="@+id/textView6" />
<ImageView
android:id="@+id/imageView"
android:layout_width="30dp"
android:layout_height="30dp"
android:layout_marginStart="20dp"
android:layout_marginTop="20dp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/location_property_home"
app:srcCompat="@drawable/bedroom" />
<TextView
android:id="@+id/bedrooms_property_home"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:text="0"
android:textColor="#000000"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="@+id/imageView"
app:layout_constraintStart_toEndOf="@+id/imageView"
app:layout_constraintTop_toTopOf="@+id/imageView" />
<ImageView
android:id="@+id/imageView2"
android:layout_width="30dp"
android:layout_height="30dp"
android:layout_marginStart="20dp"
android:layout_marginTop="20dp"
app:layout_constraintStart_toEndOf="@+id/bedrooms_property_home"
app:layout_constraintTop_toBottomOf="@+id/location_property_home"
app:srcCompat="@drawable/bathroom" />
<TextView
android:id="@+id/bathrooms_property_home"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:text="0"
android:textColor="#000000"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="@+id/imageView2"
app:layout_constraintStart_toEndOf="@+id/imageView2"
app:layout_constraintTop_toTopOf="@+id/imageView2" />
<ImageView
android:id="@+id/imageView3"
android:layout_width="30dp"
android:layout_height="30dp"
android:layout_marginStart="20dp"
android:layout_marginTop="20dp"
app:layout_constraintStart_toEndOf="@+id/bathrooms_property_home"
app:layout_constraintTop_toBottomOf="@+id/location_property_home"
app:srcCompat="@drawable/garage" />
<TextView
android:id="@+id/garages_property_home"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:text="0"
android:textColor="#000000"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="@+id/imageView3"
app:layout_constraintStart_toEndOf="@+id/imageView3"
app:layout_constraintTop_toTopOf="@+id/imageView3" />
<ImageView
android:id="@+id/imageView4"
android:layout_width="30dp"
android:layout_height="30dp"
android:layout_marginStart="20dp"
android:layout_marginTop="20dp"
app:layout_constraintStart_toEndOf="@+id/garages_property_home"
app:layout_constraintTop_toBottomOf="@+id/location_property_home"
app:srcCompat="@drawable/area" />
<TextView
android:id="@+id/area_property_home"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="10dp"
android:text="0"
android:textColor="#000000"
android:textSize="20sp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="@+id/imageView4"
app:layout_constraintStart_toEndOf="@+id/imageView4"
app:layout_constraintTop_toTopOf="@+id/imageView4" />
<ImageView
android:id="@+id/image_property_home"
android:layout_width="wrap_content"
android:layout_height="200dp"
android:layout_marginStart="20dp"
android:layout_marginTop="20dp"
android:layout_marginEnd="20dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/placeholder_image" />
<ImageButton
android:id="@+id/edit_property_home"
android:layout_width="48dp"
android:layout_height="48dp"
android:scaleType="center"
app:layout_constraintEnd_toEndOf="@+id/image_property_home"
app:layout_constraintTop_toTopOf="@+id/image_property_home"
app:srcCompat="@android:drawable/ic_menu_edit" />
<ImageButton
android:id="@+id/delete_property_home"
android:layout_width="48dp"
android:layout_height="48dp"
app:layout_constraintEnd_toStartOf="@+id/edit_property_home"
app:layout_constraintTop_toTopOf="@+id/image_property_home"
app:srcCompat="@android:drawable/ic_menu_delete" />
</androidx.constraintlayout.widget.ConstraintLayout>
I've tried my best to find where the error is, but cannot find it.
Solution
You missed an important part in your code, setContentView() add it in you onCreate() right after super() call Should be working then
public class PropertyHome extends AppCompatActivity
{
private RecyclerView recyclerView;
private RecyclerView.Adapter recyclerAdapter;
private RecyclerView.LayoutManager recyclerLayoutManager;
...
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_property_homr); // add setContentView here
try {
recyclerView = (RecyclerView)findViewById(R.id.get_property_entry_property_home);
String[] myRecycler = new String[5];
myRecycler[0] = "Recycler 1";
myRecycler[1] = "Recycler 2";
myRecycler[2] = "Recycler 3";
myRecycler[3] = "Recycler 4";
myRecycler[4] = "Recycler 5";
recyclerAdapter = new GetPropertyRecyclerViewAdapater(myRecycler);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
recyclerView.setAdapter(recyclerAdapter);
}
catch(Exception e)
{
Toast.makeText(PropertyHome.this, "Error: " + e.toString(), Toast.LENGTH_LONG).show();
}
}
...
}
Answered By - Sebastian
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