android - 在 ViewStub 中使用 ListView 时出现 NullPointerException

Question

我正在尝试在 ViewStub 中创建一个 ListView，但我一直收到 NullPointerException。我的按钮在 ViewStub 中按预期工作。失败的代码如下:

else if(v.getId() == R.id.comments_button_series_view){
    if(stubUsed == false){

        stub = (ViewStub) findViewById(R.id.stub);
        View inflatedStub = stub.inflate();

        String[] comments = new String[]{"comment1", "comment2"}; 
        commentsAdapter = new ArrayAdapter<String>(this, 
                                  R.layout.patient_list_element,
                                  R.id.comments_list_comments_view, comments);
        commentsList = (ListView)findViewById(R.id.comments_list_comments_view); 
        commentsList.setAdapter(commentsAdapter);

我认为它在 commentsList.setAdapter(commentsAdapter) 处失败了。

这个包含 ListView 的 ViewStub 内容的 XML 文件如下:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/comment_stub"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/settings_background" >

    <Button
        android:id="@+id/comments_button_comment_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_marginRight="10dp"
        android:layout_marginTop="62dp"
        android:text="Add comment" />


    <ListView
        android:id="@+id/comments_list_comments_view"
        android:layout_width="match_parent"
        android:layout_height="470dp"
        android:layout_alignLeft="@+id/pin_button_comments_view"
        android:layout_below="@+id/comments_button_comment_view" >

    </ListView>

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_alignRight="@+id/comments_button_comment_view"
        android:layout_marginRight="119dp"
        android:text="COMMENTS"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <Button
        android:id="@+id/pin_button_comments_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/comments_button_comment_view"
        android:layout_alignBottom="@+id/comments_button_comment_view"
        android:layout_marginRight="30dp"
        android:layout_toLeftOf="@+id/comments_button_comment_view"
        android:text="Add Pin" />

    <Button
        android:id="@+id/hide_button_comments_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/pin_button_comments_view"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="10dp"
        android:text="Hide" />

</RelativeLayout>

我已经在不使用 viewstub 的情况下测试了 ListView 的代码，它工作得很好。

我想我明白了吗？任何帮助表示赞赏! :)

编辑:

感谢快速回复!

contentView 设置在 ViewStub 膨胀的 View 上。但正如所提到的，它与按钮一起工作得很好，但我不明白为什么我用 ListView 得到一个空指针! :(

这是 LogCat 的结果:

04-11 10:37:55.400: W/dalvikvm(971):        threadid=1: thread exiting with uncaught exception (group=0x40014760)
04-11 10:37:55.450: E/AndroidRuntime(971):  FATAL EXCEPTION: main
04-11 10:37:55.450: E/AndroidRuntime(971):  java.lang.NullPointerException
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:396)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.ArrayAdapter.getView(ArrayAdapter.java:366)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.AbsListView.obtainView(AbsListView.java:1964)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.ListView.makeAndAddView(ListView.java:1756)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.ListView.fillDown(ListView.java:656)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.ListView.fillFromTop(ListView.java:716)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.ListView.layoutChildren(ListView.java:1609)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.AbsListView.onLayout(AbsListView.java:1794)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.View.layout(View.java:9330)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.ViewGroup.layout(ViewGroup.java:3795)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.RelativeLayout.onLayout(RelativeLayout.java:912)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.View.layout(View.java:9330)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.ViewGroup.layout(ViewGroup.java:3795)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.RelativeLayout.onLayout(RelativeLayout.java:912)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.View.layout(View.java:9330)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.ViewGroup.layout(ViewGroup.java:3795)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.FrameLayout.onLayout(FrameLayout.java:400)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.View.layout(View.java:9330)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.ViewGroup.layout(ViewGroup.java:3795)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1542)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1403)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.LinearLayout.onLayout(LinearLayout.java:1314)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.View.layout(View.java:9330)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.ViewGroup.layout(ViewGroup.java:3795)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.widget.FrameLayout.onLayout(FrameLayout.java:400)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.View.layout(View.java:9330)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.ViewGroup.layout(ViewGroup.java:3795)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.ViewRoot.performTraversals(ViewRoot.java:1201)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1944)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.os.Handler.dispatchMessage(Handler.java:99)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.os.Looper.loop(Looper.java:126)
04-11 10:37:55.450: E/AndroidRuntime(971):  at android.app.ActivityThread.main(ActivityThread.java:3997)
04-11 10:37:55.450: E/AndroidRuntime(971):  at java.lang.reflect.Method.invokeNative(Native Method)
04-11 10:37:55.450: E/AndroidRuntime(971):  at java.lang.reflect.Method.invoke(Method.java:491)
04-11 10:37:55.450: E/AndroidRuntime(971):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
04-11 10:37:55.450: E/AndroidRuntime(971):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
04-11 10:37:55.450: E/AndroidRuntime(971):  at dalvik.system.NativeStart.main(Native Method)

再次感谢:)

Answer 1

创建 ArrayAdapter 对象时似乎有错误。构造函数中的第三个参数 (textViewResourceId) 应该是 TextView 而不是 ListView。

改变它，它应该可以工作。