android 视图（view）置顶

在很多音乐播放器中都会出现歌词的置顶，这种置顶是对于整个系统而言的。

实现方式

WindowManager wm = (WindowManager)getApplicationContext().getSystemService(WINDOW_SERVICE);//获得WindowManager  
        WindowManager.LayoutParams params = new WindowManager.LayoutParams();  //布局参数对象
        params.type = WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY;  //system overlay windows, which need to be displayed on top of everything else.
          
        params.width = WindowManager.LayoutParams.WRAP_CONTENT;  
        params.height = WindowManager.LayoutParams.WRAP_CONTENT;  
        params.flags = LayoutParams.FLAG_NOT_TOUCH_MODAL | LayoutParams.FLAG_NOT_FOCUSABLE; //可选的。使得这个view失去焦点，后面的view可获得焦点。

        TextView tv = new TextView(this);  
        wm.addView(tv, params);

记得要在Manifest添加权限

    <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>