setAdapter() 上的 NullPointer 也会触发 InflateException

Question

所以，让我先解释一下场景。我有一个 activity 在其中获取一个字符串。我通过 intent extra 将该字符串传递给另一个 activity。第二个 activity 将承载一个使用该字符串执行搜索的片段，然后我在自定义 ListView 上显示我的结果。

问题：首先，当我尝试调用列表中的 setAdapter 时遇到 NullPointerException。我 google 解决了这个问题，但没有解决它。但同时我得到了一个 InflateException。如果我注释掉 setAdapter 调用，则不会发生崩溃。但是如果我离开它，这两个原因都会显示在日志中。

有人可以阐明问题所在吗？这是我的代码：

Activity 包含片段

它真的只有 onCreate 方法...

public class TracksContainerActivity extends AppCompatActivity {

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

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
}

这里是 activity_tracks_container 布局：

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

<include layout="@layout/toolbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/include" />

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/fragment_artist_results"
    android:name="com.spadatech.spotifystreamer.fragments.ArtistListFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.spadatech.spotifystreamer.fragments.ArtistListFragment"
    tools:layout="@android:layout/list_content" />

现在，片段：

public class ArtistListFragment extends Fragment {
private static final String LOG_TAG = ArtistListFragment.class.getSimpleName();

ListView albumsList;
ArrayList<ArtistResults> mArtistResults;
String query;
ArtistArrayAdapter adapter;

public ArtistListFragment() {
    // Required empty public constructor
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    query = getActivity().getIntent().getStringExtra("query");
    adapter = new ArtistArrayAdapter(getActivity(), mArtistResults);

    if (savedInstanceState == null || !savedInstanceState.containsKey("artistResults")) {
        mArtistResults = new ArrayList<>();
        performSearch(query);
    } else {
        mArtistResults = savedInstanceState.getParcelableArrayList("artistResults");
    }
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View v = getActivity().getLayoutInflater().inflate(R.layout.fragment_artist_list, null);
    albumsList = (ListView) v.findViewById(R.id.lvAlbums);
    albumsList.setAdapter(adapter);
    return v;
}

}

这里是片段的布局：

<FrameLayout 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"
tools:context="com.spadatech.spotifystreamer.fragments.ArtistListFragment">

<ListView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/lvAlbums"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />

我认为这可能有帮助，所以这是日志：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.spadatech.spotifystreamer/com.spadatech.spotifystreamer.activities.TracksContainerActivity}: android.view.InflateException: Binary XML file line #11: Error inflating class fragment
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access0(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: android.view.InflateException: Binary XML file line #11: Error inflating class fragment
            at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
            at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
            at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:249)
            at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:106)
            at com.spadatech.spotifystreamer.activities.TracksContainerActivity.onCreate(TracksContainerActivity.java:17)
            at android.app.Activity.performCreate(Activity.java:5990)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access0(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
            at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:330)
            at android.widget.ListView.setAdapter(ListView.java:487)
            at com.spadatech.spotifystreamer.fragments.ArtistListFragment.onCreateView(ArtistListFragment.java:72)
            at android.support.v4.app.Fragment.performCreateView(Fragment.java:1789)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:924)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1116)
            at android.support.v4.app.FragmentManagerImpl.addFragment(FragmentManager.java:1218)
            at android.support.v4.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2170)
            at android.support.v4.app.FragmentActivity.onCreateView(FragmentActivity.java:300)
            at android.support.v7.app.AppCompatDelegateImplV7.callActivityOnCreateView(AppCompatDelegateImplV7.java:838)
            at android.support.v7.app.AppCompatDelegateImplV11.callActivityOnCreateView(AppCompatDelegateImplV11.java:34)
            at android.support.v7.app.AppCompatDelegateImplV7.onCreateView(AppCompatDelegateImplV7.java:826)
            at android.support.v4.view.LayoutInflaterCompatHC$FactoryWrapperHC.onCreateView(LayoutInflaterCompatHC.java:44)
            at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:725)
            at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
            at android.support.v7.app.AppCompatDelegateImplV7.setContentView(AppCompatDelegateImplV7.java:249)
            at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:106)
            at com.spadatech.spotifystreamer.activities.TracksContainerActivity.onCreate(TracksContainerActivity.java:17)
            at android.app.Activity.performCreate(Activity.java:5990)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access0(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

Answer 1

您正在将一个空对象列表传递给您的适配器。

只需对您的代码进行以下更改。

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    query = getActivity().getIntent().getStringExtra("query");
    if (savedInstanceState == null || !savedInstanceState.containsKey("artistResults")) {
        mArtistResults = new ArrayList<>();
        performSearch(query);
    } else {
        mArtistResults = savedInstanceState.getParcelableArrayList("artistResults");
    }
    adapter = new ArtistArrayAdapter(getActivity(), mArtistResults);
}

setAdapter() 上的 NullPointer 也会触发 InflateException

NullPointer on setAdapter() also triggers InflateException

android

listview

android-fragments

layout-inflater

custom-adapter