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

意思：當前activity的控制元件未渲染完畢，pop.showAtLocation(parent, Gravity.TOP,0, 0)這句不能執行

解決：判斷當前activity獲得焦點之後，activity是載入完畢的，即可設定popupwindow

//解決popupwindow在onCreate方法中控制元件未渲染完畢出現的錯誤
@Override
 
public void onWindowFocusChanged(boolean hasFocus) {
    super.onWindowFocusChanged(hasFocus);
    if (hasFocus){
        if (popupWindow==null){
           //彈窗建立操作}
    }
}