Question

我收到一些错误，我不知道为什么。我用片段中的字符串填充了ListView和数组适配器。我使用此片段作为主屏幕显示在主要活动中这是我的代码

public class HomePage extends Fragment {

private ListView lvHomePage;
private String[] items;

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

    items = getActivity().getResources().getStringArray(R.array.test);
    lvHomePage = (ListView) getActivity().findViewById(R.id.lvHomePage);

    lvHomePage.setAdapter(new ArrayAdapter<String>(getActivity().getApplicationContext(),
    android.R.layout.simple_list_item_1 , items));

    return view;
}
}

我收到此输出错误：

09-18 21:07:27.315: E/AndroidRuntime(3839): FATAL EXCEPTION: main
09-18 21:07:27.315: E/AndroidRuntime(3839): Process: com.kiko.bmgu.crnobelo, PID: 3839
09-18 21:07:27.315: E/AndroidRuntime(3839): java.lang.RuntimeException: Unable to start activity ComponentInfo     com.kiko.bmgu.crnobelo/com.kiko.bmgu.crnobelo.activities.MainActivity}: java.lang.NullPointerException
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)\
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.os.Handler.dispatchMessage(Handler.java:102)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.os.Looper.loop(Looper.java:136)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.ActivityThread.main(ActivityThread.java:5017)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at java.lang.reflect.Method.invokeNative(Native Method)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at java.lang.reflect.Method.invoke(Method.java:515)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at dalvik.system.NativeStart.main(Naive Method)
09-18 21:07:27.315: E/AndroidRuntime(3839): Caused by: java.lang.NullPointerException
09-18 21:07:27.315: E/AndroidRuntime(3839):     at com.kiko.bmgu.fragments.HomePage.onCreateView(HomePage.java:25)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.Fragment.performCreateView(Fragment.java:1700)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:890)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.BackStackRecord.run(BackStackRecord.java:684)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.Activity.performStart(Activity.java:5240)
09-18 21:07:27.315: E/AndroidRuntime(3839):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2168)
09-18 21:07:27.315: E/AndroidRuntime(3839):     ... 11 more

Answer 1

lvHomePage必须为null。请改用lvHomePage = (ListView) view.findViewById(R.id.lvHomePage);。

Answer 2

试试这种方式

 private ListView lvHomePage;
    private String[] items;
    private View view;

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

    return view;
}

@Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

    items = view.getResources().getStringArray(R.array.test);
    lvHomePage = (ListView) view.findViewById(R.id.lvHomePage);

    lvHomePage.setAdapter(new ArrayAdapter<String>(view.getContext(),
    android.R.layout.simple_list_item_1 , items));
   ...
}

Answer 3

问题出在lvHomePage = (ListView) getActivity().findViewById(R.id.lvHomePage);之内你应该获得根视图的错误是view而不是活动所以它应该是这样的

lvHomePage = (ListView) view.findViewById(R.id.lvHomePage);

片段中的ArrayAdapter - Android

3 个答案: