Android实现拖动效果的两种方法

2019-10-22 18:12:23

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因为最近项目的需要，需要实现一个拖动效果，看了一下网上刚好有这种拖动效果的demo,代码大概如下：

private void initListener(){    screenWidth = getScreenWidth(this);//获取屏幕宽度    screenHeight = getScreenHeight(this) - getStatusHeight(MainActivity.this);//屏幕高度-状态栏    testTv.setOnTouchListener(new View.OnTouchListener() {      @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 top = v.getTop() + dy;            int left = v.getLeft() + dx;            if (top <= 0) {              top = 0;            }            if (top >= screenHeight - testTv.getHeight() ) {              top = screenHeight - testTv.getHeight();            }            if (left >= screenWidth - testTv.getWidth()) {              left = screenWidth - testTv.getWidth();            }            if (left <= 0) {              left = 0;            }            v.layout(left, top, left+v.getWidth(), top+v.getHeight());            v.postInvalidate();            lastX = (int) event.getRawX();            lastY = (int) event.getRawY();        break;        case MotionEvent.ACTION_UP:        break;        }        return true;//这里根据项目需要选择false与true      }    });  }

可是我的项目本身是有涂鸦的界面，还有很多复杂的事件，发现会有很奇怪的效果，抖动很厉害，而且时不时回到原来的位置，后来发现这个v.layout(left, top, left+v.getWidth(), top+v.getHeight());可能不适合项目的需求，所以我想了另一种解法。代码如下：

 private void initListener(){    screenWidth = getScreenWidth(this);//获取屏幕宽度    screenHeight = getScreenHeight(this) - getStatusHeight(MainActivity.this);//屏幕高度-状态栏    testTv.setOnTouchListener(new View.OnTouchListener() {      @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 top = v.getTop() + dy;            int left = v.getLeft() + dx;            if (top <= 0) {              top = 0;            }            if (top >= screenHeight - testTv.getHeight() ) {              top = screenHeight - testTv.getHeight();            }            if (left >= screenWidth - testTv.getWidth()) {              left = screenWidth - testTv.getWidth();            }            if (left <= 0) {              left = 0;            }            RelativeLayout.LayoutParams param = new RelativeLayout.LayoutParams(v.getWidth(), v.getHeight());            param.leftMargin = left;            param.topMargin = top;            v.setLayoutParams(param);//            v.layout(left, top, left+v.getWidth(), top+v.getHeight());            v.postInvalidate();            lastX = (int) event.getRawX();            lastY = (int) event.getRawY();        break;        case MotionEvent.ACTION_UP:        break;        }        return true;      }    });  }

效果如下图：

Android,拖动