一个控件在屏幕中拖拽到任意位置

最新推荐文章于 2024-05-05 11:59:49 发布

原创最新推荐文章于 2024-05-05 11:59:49 发布 · 428 阅读

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CC 4.0 BY-SA版权

本文介绍了一种实现视图在屏幕上拖动的方法，并通过边界检测确保视图不会移出屏幕范围。利用MotionEvent获取触摸位置，通过ACTION_DOWN、ACTION_MOVE等事件更新视图位置，并考虑了状态栏高度对屏幕可用区域的影响。

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b.setOnTouchListener(new OnTouchListener() {

int lastX, lastY;

@Override
public boolean onTouch(View v, MotionEvent event) {
// TODO Auto-generated method stub
int ea = event.getAction();

switch (ea) {
case MotionEvent.ACTION_DOWN:

lastX = (int) event.getRawX();// 获取触摸事件触摸位置的原始X坐标
lastY = (int) event.getRawY();
break;
case MotionEvent.ACTION_MOVE:
int dx = (int) event.getRawX() - lastX;
int dy = (int) event.getRawY() - lastY;

int r = v.getRight() + dx;
int l = v.getLeft() + dx;
int b = v.getBottom() + dy;
int t = v.getTop() + dy;

// 下面判断移动是否超出屏幕
if (l < 0) {
l = 0;
r = l + v.getWidth();
}
if (r > screenWidth) {
r = screenWidth;
l = r - v.getWidth();
}

if (t < 0) {
t = 0;
b = t + v.getHeight();
}
if (b > screenHeight) {
b = screenHeight;
t = b - v.getHeight();
}
v.layout(l, t, r, b);

lastX = (int) event.getRawX();
lastY = (int) event.getRawY();
/*
* Toast.makeText(MainActivity.this,
* "当前位置："+l+","+t+","+r+","+b, Toast.LENGTH_SHORT).show();
* v.postInvalidate();
*/
break;
case MotionEvent.ACTION_UP:

break;
}
return false;
}

});

屏幕长宽相关

DisplayMetrics dm = getResources().getDisplayMetrics();
final int screenWidth = dm.widthPixels;
final int screenHeight = dm.heightPixels - getStatusBarHeight();

状态栏高

private int getStatusBarHeight() {
Resources resources = this.getResources();
int resourceId = resources.getIdentifier("status_bar_height", "dimen",
"android");
int height = resources.getDimensionPixelSize(resourceId);

return height;
}