Why am I getting that error? It's causing my app to crash. Every time I test my app on my device the logcat puts out that error and I don't know why. I have a reasonable understanding of what a null pointer exception is and I have search thoroughly for an issue similar to mine. I have tried to reformat the click listener in several ways, made sure I have the correct view ID etc. Here is my code.
public class GridActivity extends AppCompatActivity {
Button dijkstra;
Button astar;
GridView grid;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_grid);
dijkstra = findViewById(R.id.dijkstra);
astar = astar.findViewById(R.id.astar);
grid = astar.findViewById(R.id.grid);
dijkstra.setOnClickListener(new View.OnClickListener( ) {
@Override
public void onClick(View v) {
GridViewe geoView = new GridViewe(GridActivity.this);
geoView.Dijkstra( );
}
});
astar.setOnClickListener(new View.OnClickListener( ) {
@Override
public void onClick(View v) {
GridViewe geoView = new GridViewe(GridActivity.this);
geoView.Astar( );
}
});
}
public void setContentView(int activity_grid) {
}
@Override
public void onStop() {
GridViewe geoView = new GridViewe(GridActivity.this);
if(geoView.dijkstrathread.getStatus()== AsyncTask.Status.RUNNING)
geoView.dijkstrathread.cancel(true);
if(geoView.astarthread.getStatus()==AsyncTask.Status.RUNNING){
geoView.astarthread.cancel(true);
}
super.onStop();
}
}
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".GridActivity">
<GridView
android:id="@+id/grid"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
<Button
android:id="@+id/dijkstra"
android:layout_width="63dp"
android:layout_height="35dp"
android:layout_weight="1"
android:text="DIJKSTRA"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/astar"
android:layout_width="106dp"
android:layout_height="27dp"
android:layout_weight="1"
android:text="A* (A star)"
tools:layout_editor_absoluteX="168dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
