java - ListPopupWindow getListView 创建后返回 nullpointerException

Question

我正在使用ListPopupWindow:

@NonNull
private ListPopupWindow createListPopupWindow() {
    ListPopupWindow listPopupWindow = new ListPopupWindow(mContext);
    listPopupWindow.setBackgroundDrawable(mContext.getDrawable(R.drawable.custom_dropdown));
    listPopupWindow.setDropDownGravity(Gravity.CENTER);
    listPopupWindow.setWidth(ListPopupWindow.WRAP_CONTENT);
    listPopupWindow.setHeight(ListPopupWindow.WRAP_CONTENT);
    listPopupWindow.setModal(true);
    return listPopupWindow;
}

当我尝试打电话时:

listPopupWindow.setAdapter(new DropDownlistAdapter(mContext,
                armAwayItems));
View container = (View) listPopupWindow.getListView().getParent();

它总是返回NPE，但该方法已经存在于ListPopupWindow中:

 Attempt to invoke virtual method 'android.view.ViewParent android.widget.ListView.getParent()' on a null object reference

当我尝试打电话时也是如此

listPopupWindow.getListView().setDividerHeight(1);

和

listPopupWindow.getListView().setDivider(...);

所以listPopupWindow.getListView()总是返回NULL。

Answer 1

试试这个

if(listPopupWindow != null){
listPopupWindow.setAdapter(new DropDownlistAdapter(mContext,
            armAwayItems));
View container = (View) listPopupWindow.getListView().getParent();

What is a Null Pointer Exception, and how do I fix it?