android - 为什么我的应用会抛出 PopupWindow BadTokenException 错误？

Question

当我的应用程序正在运行时，出现此错误:

android.view.WindowManager$BadTokenException: Unable to add window -- token null is not valid; is your activity running?

我的代码是:

LayoutInflater layoutInflater = (LayoutInflater)getBaseContext().getSystemService(LAYOUT_INFLATER_SERVICE);
View popupView = layoutInflater.inflate(R.layout.nextround_popup, parent, false);
final PopupWindow popupWindow = new PopupWindow(popupView,(int) (width * .6), (int) (height * .8));  
Button btnDismiss = (Button)popupView.findViewById(R.id.dismiss);
popupWindow.setBackgroundDrawable(getResources().getDrawable(R.drawable.black_gradient));
new Handler().postDelayed(new Runnable(){
    public void run() {
        popupWindow.showAtLocation(parent, Gravity.CENTER, 0, 0);
    }
}, 100L);        

我在 SO 上找到了一些有用的解决方案，但我没有设法解决它。

Answer 1

此错误的原因是 PopupWindow 显示需要一个 token ，但 View 在 Activity 渲染完成之前不会有 token 。即使你让它延迟。以及 100ms 很短，但如果让它变长，就显得很愚蠢。您可以在方法onWindowFocusChanged 中显示PopupWindow，当Activity 渲染完成时，将调用此方法。如下所示:

class MyActivity extends Activity{
    //...
    @Override
    public void onWindowFocusChanged(boolean hasFocus){
        if(hasFocus){
            //show your PopupWindow
            popupWindow.showAtLocation(parent, Gravity.CENTER, 0, 0);
        }
    }
    
    //...
}