I cannot tell why my bitmap is null. Should it be initialized elsewhere?

Question

I am a little new to android app development, so forgive my rookie code. I am trying to program a game based on movement. As you rotate your phone, it slides an object (a bucket) right to left on the screen to catch falling objects. I have a Main Activity and a private SurfaceView within this class. I also have a custom thread in which this runs.

This is the error: FATAL EXCEPTION: main Process: course.examples.databaseanimation, PID: 17583 java.lang.NullPointerException: Attempt to invoke virtual method 'int android.graphics.Bitmap.getWidth()' on a null object reference at android.graphics.Bitmap.createBitmap(Bitmap.java:659) at course.examples.databaseanimation.BucketThread.(BucketThread.java:25) at course.examples.databaseanimation.MainActivity$BucketView.surfaceCreated(MainActivity.java:102) at android.view.SurfaceView.updateWindow(SurfaceView.java:582) at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:177) at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:944) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2067) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1119) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6060) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858) at android.view.Choreographer.doCallbacks(Choreographer.java:670) at android.view.Choreographer.doFrame(Choreographer.java:606) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844) at android.os.Handler.handleCallback(Handler.java:746) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5443) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)

This is my Thread:

public class BucketThread extends Thread {

private SurfaceHolder holder;
private boolean running = true;
private float shiftY;
private float vy;
private float x;
private Bitmap mBucket = Bitmap.createBitmap(BitmapFactory.decodeResource
        (Resources.getSystem(), R.mipmap.ic_launcher));

public BucketThread(SurfaceHolder holder){
    this.holder = holder;
    x = 0;

    }

public void run(){
    while(running){
        Canvas canvas = null;

        try{
            canvas = holder.lockCanvas();
            synchronized (holder){
                //update
                vy += shiftY * 0.1;
                x += vy;

                //draw

                Paint mPaint = new Paint();
                canvas.drawBitmap(mBucket, x, 0, mPaint);
            }

        }
        finally {
            if(canvas != null){
                holder.unlockCanvasAndPost(canvas);
            }
        }
    }
}

public void setRunning(boolean r){
    running = r;
}

public void setShift(float shiftY){
    this.shiftY = shiftY;
}

}

And this is my Main Activity:

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    RelativeLayout mainFrame = (RelativeLayout) findViewById
            (R.id.main_frame);
    BucketView bv = new BucketView(getApplicationContext());
    mainFrame.addView(bv);

}

private class BucketView extends SurfaceView implements SurfaceHolder.Callback,
        SensorEventListener {

    //private final Bitmap mBucket;
    //private DisplayMetrics mDisplay;
    private SurfaceHolder mSurfaceHolder;
    private BucketThread mBuckThread;
    //private int mDisplayWidth;
    //private float mY;


    public BucketView(Context context) {
        super(context);

        mSurfaceHolder = getHolder();
        mSurfaceHolder.addCallback(this);

        SensorManager manager = (SensorManager) context.getSystemService
                (Context.SENSOR_SERVICE);
        if (manager.getSensorList(Sensor.TYPE_ACCELEROMETER).size() != 0) {
            Sensor accelerometer = manager.getSensorList(Sensor
                    .TYPE_ACCELEROMETER).get(0);
            manager.registerListener(this, accelerometer, SensorManager
                    .SENSOR_DELAY_GAME);
        }


    }


    @Override
    public void onSensorChanged(SensorEvent event) {
        if (mBuckThread != null) {
            mBuckThread.setShift(event.values[1]);
            Log.i("Main Activity", getClass().getSimpleName() + "onSensorChanged");
        }

    }

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mBuckThread = new BucketThread(holder);
        mBuckThread.setRunning(true);
        mBuckThread.start();
    }


    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
                               int height) {
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        boolean retry = true;

        mBuckThread.setRunning(false);
        while (retry) {
            try {
                mBuckThread.join();
                retry = false;
            } catch (InterruptedException e) {
            }
        }
    }
}

}

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) — Daniele, Jun 14 '17 at 17:33

score 0 · Answer 1 · answered Jun 14 '17 at 18:15

0

Change

private Bitmap mBucket = Bitmap.createBitmap(BitmapFactory.decodeResource (Resources.getSystem(), R.mipmap.ic_launcher));

to

private Bitmap mBucket = Bitmap.createBitmap(BitmapFactory.decodeResource (getResources(), R.mipmap.ic_launcher));

Resources.getSystem() won't work because it is used to access System resources not application's resources. so use getResources() instead.

answered Jun 14 '17 at 18:15

Adithya

1,688
1
10
18

thank you so much for your prompt response. I had not done this because it tells me that getResources() cannot be resolved as a method. Could this be because it is in a Thread not an Activity? – fran Jun 16 '17 at 06:17
call it on the context like getApplicationContext().getResources() – Adithya Jun 16 '17 at 07:03

I cannot tell why my bitmap is null. Should it be initialized elsewhere?

1 Answers1