[Android]几句代码实现轻量级可拖动button

有的时候的悬浮按钮并不需要一直在后台运行,而且写service的悬浮按钮的demo也很多,最近碰到一个需求,只要在一个界面出现悬浮按钮,本着代码越少越好的原则,摸索了好几个方法来写这样需求,最后将最简单的和大家分享出来,代码量不多,主要就是重写view的setOnTouchListener,先看效果:

GIF.gif

代码比较简单,其实就是一个button,下面上代码:

 DisplayMetrics dm = getResources().getDisplayMetrics();
        final Button btn = (Button) findViewById(R.id.btn);

        final int screenWidth = dm.widthPixels;
        final int screenHeight = dm.heightPixels-dip2px(this,60);
        
        btn.setOnTouchListener(new View.OnTouchListener() {
            int lastX, lastY;
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch (event.getAction()) {
                    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 l = v.getLeft() + dx;
                        int b = v.getBottom() + dy;
                        int r = v.getRight() + dx;
                        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 (t < 0) {
                            t = 0;
                            b = t + v.getHeight();
                        }
                        if (r > screenWidth) {
                            r = screenWidth;
                            l = r - v.getWidth();
                        }
                        if (b > screenHeight) {
                            b = screenHeight;
                            t = b - v.getHeight();
                        }
                        v.layout(l, t, r, b);
                        lastX = (int) event.getRawX();
                        lastY = (int) event.getRawY();
                        v.postInvalidate();
                        break;
                    case MotionEvent.ACTION_UP:
                        break;
                }
                return false;
            }
        });

这个就不解释了吧

public static int dip2px(Context context, float dpValue) {
        final float scale = context.getResources().getDisplayMetrics().density;
        return (int) (dpValue * scale + 0.5f);
    }

写的不好多有指教,邮箱[email protected]