Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.ar.sceneform.ArSceneView com.google.ar.sceneform.ux.ArFragment.getArSceneView()' on a null object reference at com.example.umair.dragfinal.MainActivity.onCreate(MainActivity.java:39)

[umairabbasi12]

package com.example.umair.dragfinal;

import android.net.Uri; import android.support.v7.app.AlertDialog; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.widget.ImageView; import android.widget.LinearLayout;

import com.google.ar.core.Anchor; import com.google.ar.core.Frame; import com.google.ar.core.HitResult; import com.google.ar.core.Plane; import com.google.ar.core.Trackable; import com.google.ar.core.TrackingState; import com.google.ar.sceneform.AnchorNode; import com.google.ar.sceneform.rendering.ModelRenderable; import com.google.ar.sceneform.rendering.Renderable; import com.google.ar.sceneform.ux.ArFragment; import com.google.ar.sceneform.ux.TransformableNode;

import java.util.List; import java.util.concurrent.CompletableFuture;

public class MainActivity extends AppCompatActivity { private ArFragment fragment; private PointerDrawable pointer = new PointerDrawable(); private boolean isTracking; private boolean isHitting;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    fragment = (ArFragment)
     getSupportFragmentManager().findFragmentById(R.id.sceneform_fragment);

    fragment.getArSceneView().getScene().addOnUpdateListener(frameTime -> {
        fragment.onUpdate(frameTime);
        onUpdate();
    });
    initializeGallery();

}

private void onUpdate() {
    boolean trackingChanged = updateTracking();
    View contentView = findViewById(android.R.id.content);
    if (trackingChanged) {
        if (isTracking) {
            contentView.getOverlay().add(pointer);
        } else {
            contentView.getOverlay().remove(pointer);
        }
        contentView.invalidate();
    }

    if (isTracking) {
        boolean hitTestChanged = updateHitTest();
        if (hitTestChanged) {
            pointer.setEnabled(isHitting);
            contentView.invalidate();
        }
    }
}
private boolean updateTracking() {
    Frame frame = fragment.getArSceneView().getArFrame();
    boolean wasTracking = isTracking;
    isTracking = frame != null &&
            frame.getCamera().getTrackingState() == TrackingState.TRACKING;
    return isTracking != wasTracking;
}
private boolean updateHitTest() {
    Frame frame = fragment.getArSceneView().getArFrame();
    android.graphics.Point pt = getScreenCenter();
    List<HitResult> hits;
    boolean wasHitting = isHitting;
    isHitting = false;
    if (frame != null) {
        hits = frame.hitTest(pt.x, pt.y);
        for (HitResult hit : hits) {
            Trackable trackable = hit.getTrackable();
            if (trackable instanceof Plane &&
                    ((Plane) trackable).isPoseInPolygon(hit.getHitPose())) {
                isHitting = true;
                break;
            }
        }
    }
    return wasHitting != isHitting;
}

private android.graphics.Point getScreenCenter() {
    View vw = findViewById(android.R.id.content);
    return new android.graphics.Point(vw.getWidth()/2, vw.getHeight()/2);
}
private void initializeGallery() {
    LinearLayout gallery = findViewById(R.id.gallery_layout);

    ImageView andy = new ImageView(this);
    andy.setImageResource(R.drawable.droid_thumb);
    andy.setContentDescription("andy");
    andy.setOnClickListener(view ->{addObject(Uri.parse("andy.sfb"));});
    gallery.addView(andy);

    ImageView cabin = new ImageView(this);
    cabin.setImageResource(R.drawable.cabin_thumb);
    cabin.setContentDescription("cabin");
    cabin.setOnClickListener(view ->{addObject(Uri.parse("Cabin.sfb"));});
    gallery.addView(cabin);

    ImageView house = new ImageView(this);
    house.setImageResource(R.drawable.house_thumb);
    house.setContentDescription("house");
    house.setOnClickListener(view ->{addObject(Uri.parse("House.sfb"));});
    gallery.addView(house);

    ImageView igloo = new ImageView(this);
    igloo.setImageResource(R.drawable.igloo_thumb);
    igloo.setContentDescription("igloo");
    igloo.setOnClickListener(view ->{addObject(Uri.parse("igloo.sfb"));});
    gallery.addView(igloo);
}
//Add the addObject method
private void addObject(Uri model) {
    Frame frame = fragment.getArSceneView().getArFrame();
    android.graphics.Point pt = getScreenCenter();
    List<HitResult> hits;
    if (frame != null) {
        hits = frame.hitTest(pt.x, pt.y);
        for (HitResult hit : hits) {
            Trackable trackable = hit.getTrackable();
            if (trackable instanceof Plane &&
                    ((Plane) trackable).isPoseInPolygon(hit.getHitPose())) {
                placeObject(fragment, hit.createAnchor(), model);
                break;

            }
        }
    }
}
//Add placeObject method
private void placeObject(ArFragment fragment, Anchor anchor, Uri model) {
    CompletableFuture<Void> renderableFuture =
            ModelRenderable.builder()
                    .setSource(fragment.getContext(), model)
                    .build()
                    .thenAccept(renderable -> addNodeToScene(fragment, anchor, renderable))
                    .exceptionally((throwable -> {
                        AlertDialog.Builder builder = new AlertDialog.Builder(this);
                        builder.setMessage(throwable.getMessage())
                                .setTitle("Codelab error!");
                        AlertDialog dialog = builder.create();
                        dialog.show();
                        return null;
                    }));
}
//add obj
private void addNodeToScene(ArFragment fragment, Anchor anchor, Renderable renderable) {
    AnchorNode anchorNode = new AnchorNode(anchor);
    TransformableNode node = new TransformableNode(fragment.getTransformationSystem());
    node.setRenderable(renderable);
    node.setParent(anchorNode);
    fragment.getArSceneView().getScene().addChild(anchorNode);
    node.select();
}

}