Question

我一直在关注一个教程，但我认为它已经过时了，我已经设置了我认为listView可以使用的所有内容，但是当我运行它时，它会说 -

 java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
                                                   at youknow.smscontrol.jason.testexpandiblelistview.CoustmListViewSettup.getView(CoustmListViewSettup.java:29)

这是我的XML：

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:text="Medium Text"
    android:textColor="@android:color/white"
    android:id="@+id/CMDnameItem"
    android:padding="10dp"
    android:layout_alignParentTop="true"
    android:layout_alignParentStart="true"/>

<ImageView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/item_launch"
    android:id="@+id/LaunchArrow"
    android:layout_alignBottom="@+id/CMDnameItem"
    android:layout_alignParentEnd="true"
    android:layout_alignTop="@+id/CMDnameItem"/>

这是我的主要代码：

   public void SettupIds(){
    listView = (ListView) findViewById(R.id.listView);
}

public void SetupAndDisplayListView(){
    String[] CMDlist = {"Launch App Settings", "Alarm Settings", "Lock Screen Settings", "Display Message Settings", "Take Picture Settings"};
    ListAdapter CMDlistAdapter = new CustomListViewSetup(getApplicationContext(), CMDlist);
    listView.setAdapter(CMDlistAdapter);
}

这是我的customListViewSetup类：

 class CustomListViewSetup extends ArrayAdapter<String>{

public CustomListViewSetup(Context context, String[] CMDList){
    super(context,R.layout.coustom_list_item ,CMDList);
}

@Override
public View getView(int position, View convertView, ViewGroup parent){

    LayoutInflater CMDlistInflater = LayoutInflater.from(getContext());
    View coustomView = CMDlistInflater.inflate(R.layout.coustom_list_item, parent, false);

    String CurrentCMDlistitem = getItem(position);
       LINE 29>> TextView CMDlist = (TextView) convertView.findViewById(R.id.CMDnameItem);
    ImageView CMDLaunchArrow = (ImageView) convertView.findViewById(R.id.LaunchArrow);

    CMDlist.setText(CurrentCMDlistitem);
    CMDLaunchArrow.setBackgroundResource(R.drawable.item_launch);




    return coustomView;
}
 }

提前谢谢你！

Answer 1

替换

行

 TextView CMDlist = (TextView) convertView.findViewById(R.id.CMDnameItem);
ImageView CMDLaunchArrow = (ImageView) convertView.findViewById(R.id.LaunchArrow);

通过

 TextView CMDlist = (TextView) coustomView.findViewById(R.id.CMDnameItem);
    ImageView CMDLaunchArrow = (ImageView) coustomView.findViewById(R.id.LaunchArrow);

Answer 2

LayoutInflater CMDlistInflater = LayoutInflater.from(getContext());
View coustomView = CMDlistInflater.inflate(R.layout.coustom_list_item, parent, false);

删除此行

如何在android中设置customListView？

2 个答案: