So I am trying to pass data from the firebase Realtime database in String array at its every index but my Adapter class the get View methods show an attempt to read null array but I added the data in the array.
THIS IS THE ACTIVITY WHERE I INITIATED THE ARRAY mCost
public class Department extends AppCompatActivity {
ListView listView;
String[] mItem = {"Vehicle Dynamics", "Chassis", "Power Train", "Brakes", "Electronics","Miscellaneous"};
int[] mImage = {R.drawable.vehicledynamics, R.drawable.chassis, R.drawable.powertrain,R.drawable.brakes,
R.drawable.electronics, R.drawable.miscellaneous};
String[] mCost;
int sumofdcost=0;
String sumofdcostvalue;
private DatabaseReference vdDbcost,cDbcost,ptDbcost,bDbcost,eDbcost,mDbcost, dDb,nDb;
private FirebaseDatabase database;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_department);
listView = findViewById(R.id.listView);
Objects.requireNonNull(getSupportActionBar()).setDisplayHomeAsUpEnabled(true);
database=FirebaseDatabase.getInstance();
nDb=database.getReference().child("Navigation Activity").child("Cost");
dDb=database.getReference().child("Department");
vdDbcost=database.getReference().child("Department").child("Vehicle Dynamics").child("Cost");
cDbcost=database.getReference().child("Department").child("Chassis").child("Cost");
ptDbcost=database.getReference().child("Department").child("Brakes").child("Cost");
bDbcost=database.getReference().child("Department").child("Power Train").child("Cost");
eDbcost=database.getReference().child("Department").child("Electronics").child("Cost");
mDbcost=database.getReference().child("Department").child("Miscellaneous").child("Cost");
vdDbcost.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
Long cost=dataSnapshot.getValue(Long.class);
mCost[0]=String.valueOf(cost);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) { }
});
cDbcost.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
Long cost=dataSnapshot.getValue(Long.class);
mCost[1]=String.valueOf(cost);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) { }
});
ptDbcost.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
Long cost=dataSnapshot.getValue(Long.class);
mCost[2]=String.valueOf(cost);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) { }
});
bDbcost.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
Long cost=dataSnapshot.getValue(Long.class);
mCost[3]=String.valueOf(cost);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) { }
});
eDbcost.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
Long cost=dataSnapshot.getValue(Long.class);
mCost[4]=String.valueOf(cost);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) { }
});
mDbcost.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
Long cost=dataSnapshot.getValue(Long.class);
mCost[5]=String.valueOf(cost);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) { }
});
dDb.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot ds: dataSnapshot.getChildren()){
Map<String,Object> map=(Map<String,Object>) ds.getValue();
Object totalcost=map.get("Cost");
int totalcostvalue=Integer.parseInt(String.valueOf(totalcost));
sumofdcost+=totalcostvalue;
sumofdcostvalue=String.valueOf(sumofdcost);
}
nDb.setValue(sumofdcostvalue);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
//Creating ADAPTER class
MainAdapter adapter = new MainAdapter(this, mItem, mImage, mCost);
listView.setAdapter(adapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
if (position == 0) {
//A//
//sub department, vehicle dynamics//
Intent intent = new Intent(Department.this, VehicleDynamicsActivity.class);
startActivity(intent);
}
if (position == 1) {
//B//
//Sub department,chassis//
Intent intent = new Intent(Department.this, ChassisItemActivity.class);
startActivity(intent);
}
if (position == 2) {
//C//
//Sub department,power train//
Intent intent = new Intent(Department.this, PowerTrainActivity.class);
startActivity(intent);
}
if (position == 3) {
//D//
//Sub department, brakes//
Intent intent = new Intent(Department.this, BrakesItemActivity.class);
startActivity(intent);
}
if (position == 4) {
//E//
//sub department,electronics//
Intent intent = new Intent(Department.this, ElectronicsItemActivity.class);
startActivity(intent);
}
if (position == 5) {
//F//
//sub department, miscellaneous//
Intent intent = new Intent(Department.this, MiscellaneousItemActivity.class);
startActivity(intent);
}
}
});
}
}
ANd THIS IS THE ADAPTER getView method
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if(inflater==null){
inflater=(LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
if(convertView==null){
convertView = inflater.inflate(R.layout.row, null);
}
TextView itemName=convertView.findViewById(R.id.item_name);
itemName.setText(mItem[position]);
ImageView imageView = convertView.findViewById(R.id.d_image);
imageView.setImageResource(mImage[position]);
TextView cost1 = convertView.findViewById(R.id.cost_value);
cost1.setText(mCost[position]);
return convertView ;
AND THIS IS THE LOG CAT
2020-03-12 15:13:49.032 29730-29730/com.example.android.zfr E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.android.zfr, PID: 29730
java.lang.NullPointerException: Attempt to read from null array
at com.example.android.zfr.MainAdapter.getView(MainAdapter.java:56)
at android.widget.AbsListView.obtainView(AbsListView.java:2397)
at android.widget.ListView.makeAndAddView(ListView.java:2052)
at android.widget.ListView.fillDown(ListView.java:786)
at android.widget.ListView.fillFromTop(ListView.java:847)
at android.widget.ListView.layoutChildren(ListView.java:1826)
at android.widget.AbsListView.onLayout(AbsListView.java:2193)
at android.view.View.layout(View.java:19693)
at android.view.ViewGroup.layout(ViewGroup.java:6079)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1791)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1635)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1544)
at android.view.View.layout(View.java:19693)
at android.view.ViewGroup.layout(ViewGroup.java:6079)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:19693)
at android.view.ViewGroup.layout(ViewGroup.java:6079)
at androidx.appcompat.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:446)
at android.view.View.layout(View.java:19693)
at android.view.ViewGroup.layout(ViewGroup.java:6079)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at android.view.View.layout(View.java:19693)
at android.view.ViewGroup.layout(ViewGroup.java:6079)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1791)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1635)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1544)
at android.view.View.layout(View.java:19693)
at android.view.ViewGroup.layout(ViewGroup.java:6079)
at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
at com.android.internal.policy.DecorView.onLayout(DecorView.java:764)
at android.view.View.layout(View.java:19693)
at android.view.ViewGroup.layout(ViewGroup.java:6079)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2541)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2257)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1437)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6886)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1029)
at android.view.Choreographer.doCallbacks(Choreographer.java:841)
at android.view.Choreographer.doFrame(Choreographer.java:772)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1015)
at android.os.Handler.handleCallback(Handler.java:794)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:176)
at android.app.ActivityThread.main(ActivityThread.java:6651)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:824)
This error is because your string array is null and that is because it hasn't been initialized.
Try this on your Department class
String[] mCost = new String[5];
5 is the length of the string array