Question

标题有点令人困惑，但我不知道该写些什么。

我正在使用库来展示我的应用程序启动的滑动教程（SlidingTutorial）。问题是我需要在findViewById中找到片段中的视图，但是我需要从片段的视图中派生出这个调用。我应该使用onCreateView方法，但正如我在标题中所说，我的片段需要从TutorialSupportFragment扩展（尽管有Fragment），所以如果我重写onCreateView方法，那么库中的某些组件无法加载。

有没有办法在不破坏扩展方法的情况下使用onCreateView？

public class CustomTutorialFragment extends TutorialSupportFragment implements OnTutorialPageChangeListener, CustomTutorialMvpView {

...

我需要运行这个：

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

        btNext = (Button) view.findViewById(R.id.btNext);
        btSkip = (Button) view.findViewById(R.id.btSkip);

        btNext.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                nextPage();
            }
        });

        btSkip.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                skipTutorial();
            }
        });

        return view;
    }

这是错误，我认为问题在于我可以在不破坏库创建的前一个方法的情况下覆盖该方法。

FATAL EXCEPTION: main
   Process: com.dummy.carrefour.mvp, PID: 24342
   java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dummy.carrefour.mvp/com.dummy.carrefour.mvp.ui.tutorial.TutorialActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.view.ViewPager.setAdapter(android.support.v4.view.PagerAdapter)' on a null object reference
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2666)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2727)
       at android.app.ActivityThread.-wrap12(ActivityThread.java)
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1478)
       at android.os.Handler.dispatchMessage(Handler.java:102)
       at android.os.Looper.loop(Looper.java:154)
       at android.app.ActivityThread.main(ActivityThread.java:6121)
       at java.lang.reflect.Method.invoke(Native Method)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)
    Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.view.ViewPager.setAdapter(android.support.v4.view.PagerAdapter)' on a null object reference
       at com.cleveroad.slidingtutorial.TutorialImpl.onViewCreated(TutorialImpl.java:97)
       at com.cleveroad.slidingtutorial.TutorialSupportFragment.onViewCreated(TutorialSupportFragment.java:146)
       at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1314)
       at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1528)
       at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1595)
       at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:758)
       at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2363)
       at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2149)
       at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2103)
       at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2013)
       at android.support.v4.app.FragmentController.execPendingActions(FragmentController.java:388)
       at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:607)
       at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:178)
       at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1248)
       at android.app.Activity.performStart(Activity.java:6699)
       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2629)
       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2727) 
       at android.app.ActivityThread.-wrap12(ActivityThread.java) 
       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1478) 
       at android.os.Handler.dispatchMessage(Handler.java:102) 
       at android.os.Looper.loop(Looper.java:154) 
       at android.app.ActivityThread.main(ActivityThread.java:6121) 
       at java.lang.reflect.Method.invoke(Native Method) 
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:889) 
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:779)

Answer 1

您有两种选择。

首先是调用super.onCreateView()并使用返回的View执行操作：

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View view = super.onCreateView(inflater, container, savedInstanceState);
    // Perform necessary actions
    Button button = view.findViewById(R.id.button);
    return view;
}

第二个选项是覆盖onViewCreated()。

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    // Perform necessary actions
    Button button = view.findViewById(R.id.button);
}

如何使用另一个类扩展片段的视图？

1 个答案: