拖动button，不出边界
改进了一下网上查到的拖动button的代码。。。
不会出现超出屏幕的情况。
DisplayMetrics dm = getResources().getDisplayMetrics(); final int screenWidth = dm.widthPixels; final int screenHeight = dm.heightPixels - 50;setContentView(R.layout.main); btn = (Button) findViewById(R.id.btn); btn.setOnTouchListener(new View.OnTouchListener() { int[] temp = new int[]{0, 0}; public boolean onTouch(View v, MotionEvent event) { int eventaction = event.getAction(); //getRawX()-->屏幕的x坐标 int x = (int) event.getRawX(); //getRawY()-->屏幕的y坐标，需要加上标题跟最顶上栏的坐标(50)，也就是getRawY()最少就是50 int y = (int) event.getRawY(); switch (eventaction) { case MotionEvent.ACTION_DOWN: //getX()-->控件的x坐标，这里是指按钮的x坐标， // 如果是getY()，则需要减去标题栏和最顶上栏的高度(50左右)， temp[0] = (int) event.getX(); temp[1] = y - v.getTop(); Log.d(TAG, "x->" + x + ", y->" + y + ", v.getTop()->" + v.getTop()); Log.d(TAG, "temp[0]->" + temp[0] + ", temp[1]->" + temp[1]); break; case MotionEvent.ACTION_MOVE: int ll = x - temp[0]; int tt = y - temp[1]; int rr = x + v.getWidth() - temp[0]; int bb = y - temp[1] + v.getHeight(); Log.i(TAG, "ll->" + ll + ", rr->" + rr + ", tt->" + tt + ", bb->" + bb + ", temp[0]->" + temp[0] + ", temp[1]->" + temp[1]); if (ll < 0) { ll = 0; rr = v.getWidth(); } if (rr > screenWidth) { rr = screenWidth; ll = rr - v.getWidth(); } if (tt < 0) { tt = 0; bb = v.getHeight(); } if (bb > screenHeight) { bb = screenHeight; tt = bb - v.getHeight(); } v.layout(ll, tt, rr, bb); Log.d(TAG, "ll->" + ll + ", rr->" + rr + ", tt->" + tt + ", bb->" + bb + ", temp[0]->" + temp[0] + ", temp[1]->" + temp[1]); v.postInvalidate(); break; case MotionEvent.ACTION_UP: break; } return false; } });注释的地方注意一下