PopupWindow(4)半透明的popupwindow

public class CustomActionProvider extends ActionProvider implements
        OnMenuItemClickListener, OnClickListener, OnTouchListener, OnKeyListener {

    private final Context context;// 上下文
    private View actionView;//action view

    private PopupWindow mPopupWindow;//popup window 里有个view,view显示的像个menu
    private View mMenu;                //popup window 里的显示控件
    

    private void initPopupMenu(){
        
        LayoutInflater lif = LayoutInflater.from(context);

        mMenu = lif.inflate(R.layout.custom_popup_window, null);
        mMenu.setAlpha(0.5f);

        
        mPopupWindow = new PopupWindow(mMenu,
                WindowManager.LayoutParams.WRAP_CONTENT,
                WindowManager.LayoutParams.WRAP_CONTENT);
        
        
        /*
         * setBackgroundDrawable很重要,没有这个函数 back键和menu键关闭popwindow 很麻烦,
         * 有了它以后,就不用为popwindow内的控件分别设置setOnKeyListener和setOnTouchListener了
         * 可以同时支持back返回和点popwindow外面关闭popwindow,
         */
        mPopupWindow.setBackgroundDrawable(new ColorDrawable(0x00000));

    }
　　//...
}