操作栏搜索视图（Android）空指针错误。

Question

我不确定为什么它会显示为空，如果与片段、片段标题或抽屉有关，因为它在这个片段被拉起的主要活动中。

这是我的菜单xml项：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto" >
    <item android:id="@+id/action_search"
        android:title="@string/action_search"
        android:icon="@drawable/ic_action_search"
        app:showAsAction="always"
        app:actionViewClass="android.support.v7.widget.SearchView" />
</menu>

这里是代码片段：

public class BrowseFragment extends Fragment {

    //action bar expands to search
    //search - keyword or tab search, title
    //include popular - same algorithm as home
    //show categories

    //category click takes you to grid activity
//adapter with custom model
    private CategoryViewerAdapter adapter;

    //list with custom model
    private List<CategoryItem> categoriesList;

    //List view
    private ListView categoryListView;

    //SearchView
    private SearchView search;

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        inflater.inflate(R.menu.browse, menu);

        //find the menu item and set search view at the same time
        search = (SearchView) menu.findItem(R.id.action_search).getActionView();


        //to always show the search view - to include this must implement it above
        search.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String s) {
                return false;
            }

            @Override
            public boolean onQueryTextChange(String s) {
                return false;
            }
        });
        search.setIconified(false);

        super.onCreateOptionsMenu(menu,inflater);
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_browse, container, false);

        //Allows menu options in fragment
        setHasOptionsMenu(true);


        //Set adapter for multi-select model and adapter
        adapter = new CategoryViewerAdapter(getActivity(), getSingleCategory());
        categoryListView = (ListView) rootView.findViewById(R.id.categoryListView);
        categoryListView.setAdapter(adapter);


        return rootView;
    }

    //call to retrieve list
    private List<CategoryItem> getSingleCategory() {
        //initiate new list
        categoriesList = new ArrayList<CategoryItem>();

        //called to get string array
        Resources res = getResources();
        String[] categories = res.getStringArray(R.array.categories);

        //loop through string array
        for (String category : categories) {
            categoriesList.add(get(category));
        }

        return categoriesList;
    }

    //call model to set names and methods for each item
    private CategoryItem get(String name) {
        return new CategoryItem(name);
    }


}

空指针错误指向这行代码：

search.setOnQueryTextListener(new SearchView.OnQueryTextListener() {

以下是错误日志：

03-03 02:50:33.590  15744-15744/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.app, PID: 15744
    java.lang.NullPointerException
            at com.example.app.BrowseFragment.onCreateOptionsMenu(BrowseFragment.java:64)
            at android.app.Fragment.performCreateOptionsMenu(Fragment.java:1780)
            at android.app.FragmentManagerImpl.dispatchCreateOptionsMenu(FragmentManager.java:1927)
            at android.app.Activity.onCreatePanelMenu(Activity.java:2539)
            at com.android.internal.policy.impl.PhoneWindow.preparePanel(PhoneWindow.java:436)
            at com.android.internal.policy.impl.PhoneWindow.doInvalidatePanelMenu(PhoneWindow.java:800)
            at com.android.internal.policy.impl.PhoneWindow$1.run(PhoneWindow.java:221)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
            at android.view.Choreographer.doCallbacks(Choreographer.java:574)
            at android.view.Choreographer.doFrame(Choreographer.java:543)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
            at android.os.Handler.handleCallback(Handler.java:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5017)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
            at dalvik.system.NativeStart.main(Native Method)

- Lion789

Answer 1

你是否在使用Proguard？如果是的话，请确保添加规则以保留android.support.v7.widget.SearchView类。

例如，要保留支持库的所有不同版本中的所有内容，请添加以下内容：

-keep class android.support.** { *; }
-keep interface android.support.** { *; }

将内容添加到你的proguard-rules.txt文件中。

- ashughes

---

谢谢！这对我有用。 - mogile_oli

请注意，对于这种情况，仅使用“-keep class android.support.v7.widget.SearchView { *; }”也可以，并且比保留所有支持库类更好。 - Benoit

这对我有效。第二行是干什么的，保持接口？ - Shahbaz Sheikh

通过保留-keep class android.support.v7.widget.SearchView { *; }对我很有效。谢谢伙计。 - Anish Kumar

Answer 2

我曾经遇到过同样的问题。我的解决方案在菜单中。

我有：

app:actionViewClass="android.support.v4.widget.SearchView"

我本应该有

app:actionViewClass="android.support.v7.widget.SearchView"

- easycheese

---

这两行代码看起来对我来说是一样的，我错过了什么？ - Brill Pappin

v7和v4之间的区别 - easycheese

Answer 3

我的错误是错误地初始化了MenuInflater。

MenuInflater inflater = getMenuInflater();

在纠正问题得到解决之后。

MenuInflater inflater = new MenuInflater(getApplicationContext());

- sasi kiran