Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

Question

Trying learn googleSceneform for AR and my app crashes every time,any thougts?

My error from logcat and application crahses not on emulator and on the phone too.

    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ar/com.example.ar.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at com.example.ar.MainActivity.SetClickListener(MainActivity.java:213)
        at com.example.ar.MainActivity.onCreate(MainActivity.java:63)
        at android.app.Activity.performCreate(Activity.java:7009)
        at android.app.Activity.performCreate(Activity.java:7000)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6494) 
        at java.lang.reflect.Method.invoke(Native Method)

This is my MainActivty.java application crashes imediately and it is even not open

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    ArFragment arFragment;
    private ModelRenderable bearRenderable;

    ImageView bear, cat, cow, dog, elephant, ferret, hippopotamus, horse, koala, lion, reindeer, wolverine;

    View arrayView[];
    ViewRenderable name_animal;
    int selected = 1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        arFragment = (ArFragment) getSupportFragmentManager().findFragmentById(R.id.sceneform_ux_fragment);
        //View
        bear = (ImageView) findViewById(R.id.bear);
        cat = (ImageView) findViewById(R.id.cat);

        SetArrayView();
        SetClickListener();
        setupModel();
        arFragment.setOnTapArPlaneListener(new BaseArFragment.OnTapArPlaneListener() {
            @Override
            public void onTapPlane(HitResult hitResult, Plane plane, MotionEvent motionEvent) {          
                if (selected == 1) {
                    Anchor anchor = hitResult.createAnchor();
                    AnchorNode anchorNode = new AnchorNode(anchor);
                anchorNode.setParent(arFragment.getArSceneView().getScene());
                    createModel(anchorNode, selected);
                }
            }
        });
    }
    private void setupModel() {
        ModelRenderable.builder()
                .setSource(this, R.raw.bear)
                .build().thenAccept(renderable -> bearRenderable = renderable)
                .exceptionally(
                        throwable -> {
                            Toast.makeText(this, "Unnable to load bear model", Toast.LENGTH_SHORT).show();
                            return null;
                        }
                );
    private void createModel(AnchorNode anchorNode, int selected) {
        if (selected == 1) {
            TransformableNode bear = new TransformableNode(arFragment.getTransformationSystem());
            bear.setParent(anchorNode);
            bear.setRenderable(bearRenderable);
            bear.select();
        }
    }
    private void SetClickListener() {
        for (int i=0;i<arrayView.length;i++)
            arrayView[i].setOnClickListener(this);
    }

    private void SetArrayView() {
        arrayView = new View[]{
                bear,cat,cow,dog,elephant,ferret,hippopotamus,horse,koala,lion,reindeer,wolverine
        };
    }
    @Override
    public void onClick(View v) {

    }
}

I am a beginner so i just try to find my mistakes. I thinks it is about View and something about ClickListener

Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Tamir Abutbul, Apr 01 '19 at 14:14
Most of your `ImageView` objects are `null` (e.g cow, dog, elephant..), and you are calling `setOnClickListener` on them, so it crashes . — Arnaud, Apr 01 '19 at 14:14

score 0 · Answer 1 · answered Apr 01 '19 at 14:17

To prevent null pointer exception you can do this in your SetClickListener method :

 private void SetClickListener() {
        for (int i=0;i<arrayView.length;i++)
        {
           if( arrayView[i] != null ) 
            arrayView[i].setOnClickListener(this);
        }    
    }

score 0 · Accepted Answer · answered Apr 01 '19 at 14:19

In your code only bear and cat aren't null, so you can either bind other image views either you apply a click listener on the not null objects like this

private void SetClickListener() {
    for (int i=0;i<arrayView.length;i++)
      if (arrayView[i] != null)
        arrayView[i].setOnClickListener(this);
}

score 0 · Answer 3 · edited Apr 01 '19 at 15:03

In your onCreate method, you are initializing only 2 ImageView components, bear and cat. The others, cow, dog, elephant... are null. To manage this, you should find all other ImageView components.

cow = (ImageView) findViewById(R.id.cow);
dog = (ImageView) findViewById(R.id.dog);

or test the null value in setOnClickListener

 private void SetClickListener() {
        for (int i=0;i<arrayView.length;i++)
          if (arrayView[i] != null)
            arrayView[i].setOnClickListener(this);
    }

Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

3 Answers3