Question

我对Android应用程序开发有点新，所以请原谅我的菜鸟代码。我正在尝试根据运动编写游戏。当您旋转手机时，它会在屏幕上从右向左滑动一个对象（一个水桶）以捕捉掉落的物体。我在这个类中有一个Main Activity和一个私有的SurfaceView。我也有一个自定义线程运行。

这是错误：致命异议：主要处理：course.examples.databaseanimation，PID：17583 java.lang.NullPointerException：尝试调用虚方法＆＃39; int android.graphics.Bitmap.getWidth（）＆＃39;在null对象引用上在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）在android.view.SurfaceView.updateWindow（SurfaceView.java:582）在android.view.SurfaceView $ 3.onPreDraw（SurfaceView.java:177）在android.view.ViewTreeObserver.dispatchOnPreDraw（ViewTreeObserver.java:944）在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:2067）在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1119）在android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:6060）在android.view.Choreographer $ CallbackRecord.run（Choreographer.java:858）在android.view.Choreographer.doCallbacks（Choreographer.java:670）在android.view.Choreographer.doFrame（Choreographer.java:606）在android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:844）在android.os.Handler.handleCallback（Handler.java:746）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:148）在android.app.ActivityThread.main（ActivityThread.java:5443） at java.lang.reflect.Method.invoke（Native Method）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:728）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:618）

这是我的主题：

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;
}

}

这是我的主要活动：

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) {
            }
        }
    }
}

}

Answer 1

更改

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

到

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

Resources.getSystem() 不会工作，因为它用于访问系统资源而不是应用程序的资源。所以请改用getResources()。

我不知道为什么我的位图为空。它应该在其他地方初始化吗？

1 个答案: