修改

Question

我通过扩展View定义了一个简单的自定义LinearLayout。关键是它包含ExpandableListView并添加了标题视图：

public class MyView extends LinearLayout {
private View mHeaderView;
private ExpandableListView mListView;

@SuppressWarnings("UnusedDeclaration")
public MyView(Context context) {
    super(context);
    init(context);
}

@SuppressWarnings("UnusedDeclaration")
public MyView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context);
}

private void init(Context context) {
    setOrientation(LinearLayout.VERTICAL);
    setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
    LayoutInflater inflater = LayoutInflater.from(context);

    //Inflate custom view into LinearLayout
    inflater.inflate(
            R.layout.merge_myview, this);

    //Inflate header with no parent so we can set it as the ListView header in onFinishInflate()
    mHeaderView = inflater.inflate(R.layout.header_bundles_list, null);
}

@Override
protected void onFinishInflate() {
    super.onFinishInflate();

    mListView = (ExpandableListView) (findViewById(R.id.lv_expandable));

    Log.d("MyView", "Almost done...");

    //Commenting out this line makes it work
    mListView.addHeaderView(mHeaderView, null, false);
}
}

这是merge_myview.xml：

<merge xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ExpandableListView
        android:id="@+id/lv_expandable"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />    
</merge>

这是标题：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
     >

    <TextView
        android:id="@+id/tv_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:background="#EFEEFF"
        android:clickable="true"
        android:gravity="center"
        android:minHeight="96dp"
        android:onClick="openPane"
        android:paddingBottom="24dp"
        android:paddingTop="24dp"
        android:text="HELLO!"
        android:textColor="#333333"
        android:textIsSelectable="true"
        android:textSize="48sp" />

</RelativeLayout>

在我的活动中使用简单onCreate：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_myview);
}

activity_myview.xml仅包含我的自定义视图：

<com.example.app.MyView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:orientation="vertical"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"/>

然而，当我运行此应用程序时，我收到以下错误：

java.lang.NullPointerException   at
 android.widget.ListView.clearRecycledState(ListView.java:507)   at
 android.widget.ListView.resetList(ListView.java:493)   at
 android.widget.ListView.layoutChildren(ListView.java:1431)   at
 android.widget.AbsListView.onLayout(AbsListView.java:1147)   at
 android.view.View.layout(View.java:7035)   at
 android.widget.LinearLayout.setChildFrame(LinearLayout.java:1252)   at
 android.widget.LinearLayout.layoutVertical(LinearLayout.java:1128)   at
 android.widget.LinearLayout.onLayout(LinearLayout.java:1045)   at
 android.view.View.layout(View.java:7035)   at
 android.widget.FrameLayout.onLayout(FrameLayout.java:333)   at
 android.view.View.layout(View.java:7035)   at
 android.widget.LinearLayout.setChildFrame(LinearLayout.java:1252)   at
 android.widget.LinearLayout.layoutVertical(LinearLayout.java:1128)   at 
 android.widget.LinearLayout.onLayout(LinearLayout.java:1045)   at
 android.view.View.layout(View.java:7035)   at
 android.widget.LinearLayout.setChildFrame(LinearLayout.java:1252)   at
 android.widget.LinearLayout.layoutVertical(LinearLayout.java:1128)   at
 android.widget.LinearLayout.onLayout(LinearLayout.java:1045)   at
 android.view.View.layout(View.java:7035)

我认为这是一个在Android 2.3.7和4.1.1之间修复的错误，因为我在使用前者测试时只会收到错误。 ~~我在bug tracker找不到它。~~ 那么为什么会出现这种错误呢？有没有解决办法？

修改

我认为this是错误，已于2013年6月修复。

Answer 1

尝试不使用合并。

private void init(Context context) {
    setOrientation(LinearLayout.VERTICAL);
    setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
    LayoutInflater inflater = LayoutInflater.from(context);

    inflater.inflate(R.layout.expandablelistview, this, true);
    inflater.inflate(R.layout.textview, this, true);
    mHeaderView = inflater.inflate(R.layout.header_bundles_list, null);
}

expandablelistview.xml

<ExpandableListView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/lv_expandable"
    android:layout_width="match_parent"
    android:background="#ffffd467"
    android:layout_weight="2"
    android:layout_height="0dp"/>

textview.xml

<TextView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/textview"
    android:text="HELLO"
    android:background="#AA4242"
    android:layout_width="match_parent"
    android:layout_weight="1"
    android:layout_height="0dp"/>

示例onCreate()：

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_myview);
    MyView myView = (MyView) findViewById(R.id.myview);

    //Set up adapter
    int groupnum=2;
    int childnum=3;
    List<Map<String, String>> groupData=new ArrayList<Map<String, String>>(groupnum);
    List<List<Map<String,String>>> childData=new ArrayList<List<Map<String, String>>>(groupnum);
    for(int i=0;i<groupnum;i++){
        HashMap<String, String> map = new HashMap<String, String>(1);
        map.put("title","I'm a group");
        groupData.add(map);

        List<Map<String, String>> thisChildData = new ArrayList<Map<String, String>>(childnum);
        for(int j=0;j<childnum;j++){
        HashMap<String, String> childmap = new HashMap<String, String>(1);
            childmap .put("title","I'm a child");
            thisChildData.add(childmap );
        }
        childData.add(thisChildData);
    }

    ExpandableListAdapter adapter=new SimpleExpandableListAdapter(
            this,
            groupData,
            android.R.layout.simple_expandable_list_item_1,
            new String[] {"title"},
            new int[] {android.R.id.text1},
            childData,
            android.R.layout.simple_list_item_1,
            new String[] {"title"},
            new int[] {android.R.id.text1}
    );

    //Set adapter
    myView.mListView.setAdapter(adapter);
}

Answer 2

替换

mListView = (ExpandableListView) (findViewById(R.id.lv_expandable));

带

mListView = (ExpandableListView) (mHeaderView.findViewById(R.id.lv_expandable));

扩展LinearLayout中带有标头的ExpandableListView：NullPointerException

修改

2 个答案: