android中如何实现图像视图的缩放效果

Android中如何实现图像视图的缩放效果？

java
public class ImageZoomActivity extends AppCompatActivity implements OnScaleGestureListener {
    private ImageView imageView;
    private GestureDetector gestureDetector;
    private ScaleGestureDetector scaleGestureDetector;
    private Matrix matrix;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_image_zoom);
        imageView = findViewById(R.id.imageView);
        gestureDetector = new GestureDetector(this, new GestureDetector.SimpleOnGestureListener());
        scaleGestureDetector = new ScaleGestureDetector(this, this);
        matrix = new Matrix();
        imageView.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                gestureDetector.onTouchEvent(event);
                scaleGestureDetector.onTouchEvent(event);
                return true;
            }
        });
    }
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        float scaleFactor = detector.getScaleFactor();
        matrix.postScale(scaleFactor, scaleFactor);
        imageView.setImageMatrix(matrix);
        return true;
    }
    @Override
    public boolean onScaleBegin(ScaleGestureDetector detector) {
        return true;
    }
    @Override
    public void onScaleEnd(ScaleGestureDetector detector) {
    }
}