安卓实现拖动功能~整理~亲测可用

private int screenWidth; 
private int screenHeight; 
private ImageView img1; 
private ImageView img2;
img1 = (ImageView) findViewById(R.id.imageView1); 
img2 = (ImageView) findViewById(R.id.imageView2);
DisplayMetrics dm = getResources().getDisplayMetrics(); 
screenWidth = dm.widthPixels; 
screenHeight = dm.heightPixels - 50;
img1.setOnTouchListener(movingEventListener); 
img2.setOnTouchListener(movingEventListener);
private OnTouchListener movingEventListener = new OnTouchListener() { 
int lastX, lastY; 
@Override 
public boolean onTouch(View v, MotionEvent event) { 
    switch (event.getAction()) { 
    case MotionEvent.ACTION_DOWN: 
        lastX = (int) event.getRawX(); 
        lastY = (int) event.getRawY(); 
        break; 
    case MotionEvent.ACTION_MOVE: 
        int dx = (int) event.getRawX() - lastX; 
        int dy = (int) event.getRawY() - lastY;
        int left = v.getLeft() + dx; 
        int top = v.getTop() + dy; 
        int right = v.getRight() + dx; 
        int bottom = v.getBottom() + dy; 
        // ÉèÖò»Äܳö½ç 
        if (left < 0) { 
            left = 0; 
            right = left + v.getWidth(); 
        }
        if (right > screenWidth) { 
            right = screenWidth; 
            left = right - v.getWidth(); 
        }
        if (top < 0) { 
            top = 0; 
            bottom = top + v.getHeight(); 
        }
        if (bottom > screenHeight) { 
            bottom = screenHeight; 
            top = bottom - v.getHeight(); 
        }
        v.layout(left, top, right, bottom);
        lastX = (int) event.getRawX(); 
        lastY = (int) event.getRawY();
        break; 
    case MotionEvent.ACTION_UP: 
        break; 
    } 
    return true; 
} 
};