Android PopupWindow 實現遮罩層效果

此篇博客實現的功能是：點擊界面中的圖片，跳出一個PopupWindow，PopupWindow中含有相應的文字和圖標，並且在顯示PopupWindow的時候，背景爲半透明。

看圖描述：點擊加號，跳出PopupWindow，其中包含三個圖片，點擊叉號PopupWindow消失；當PopupWindow顯示的時候，背景爲半透明


顯示PopupWindow的代碼

private void showPopupWindow() {
  View view = (LinearLayout) getLayoutInflater().inflate(R.layout.popup_window_layout, null);
  ImageView ivP = (ImageView) view.findViewById(R.id.ivP);
  ImageView ivX = (ImageView) view.findViewById(R.id.ivX);
  ImageView ivClose = (ImageView) view.findViewById(R.id.ivClose);
  LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT,
    LayoutParams.WRAP_CONTENT);
  ivP.setLayoutParams(params);
  ivX.setLayoutParams(params);
  ivClose.setLayoutParams(params);
  ivClose.setOnClickListener(this);
  popupWindow = new PopupWindow(WindowManager.LayoutParams.WRAP_CONTENT, WindowManager.LayoutParams.WRAP_CONTENT);
  popupWindow.setContentView(view);
  popupWindow.setFocusable(true);
  popupWindow.setTouchable(true);
  popupWindow.setOutsideTouchable(false);
  popupWindow.showAsDropDown(ivAdd, 0, 0);
  backgroundAlpha(0.4f);
 }

private void backgroundAlpha(float f) {
  WindowManager.LayoutParams lp =getWindow().getAttributes(); 
  lp.alpha = f; 
  getWindow().setAttributes(lp);
 }

backgroundAlpha()方法用於設置PopupWindow顯示後的背景半透明，參數 f 的範圍是0.0~1.0，數值越大透明度越高。