Question

因此，我的应用程序中有使用片段的导航抽屉，我想在其中一个片段中添加底部导航视图。问题是我的底部导航视图也应该有片段。如何将片段放入片段中？

下面的代码是我到目前为止尝试做的。而且我遇到了错误。

public class HskFragment extends Fragment {

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


        BottomNavigationView bottomNavigationView = getView().findViewById(R.id.bottom_navigation);
        bottomNavigationView.setOnNavigationItemSelectedListener(navListener);

        //I added this if statement to keep the selected fragment when rotating the device
        if (savedInstanceState == null) {
            getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,
                    new HskFragment()).commit();
        }


        return inflater.inflate(R.layout.fragment_hsk, container, false);
    }


    private BottomNavigationView.OnNavigationItemSelectedListener navListener =
            new BottomNavigationView.OnNavigationItemSelectedListener() {
                @Override
                public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                    Fragment selectedFragment = null;

                    switch (item.getItemId()) {
                        case R.id.nav_hsklist:
                            selectedFragment = new WordListFragment();
                            break;
                        case R.id.nav_favorites:
                            selectedFragment = new FavoriteFragment();
                            break;
                        case R.id.nav_search:
                            selectedFragment = new SearchFragment();
                            break;
                    }
                    return true;
                }
            };

}

错误：

    E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.kaymkassai.learnit, PID: 32324
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.kaymkassai.learnit/com.kaymkassai.learnit.MainMenuActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2723)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2784)
        at android.app.ActivityThread.-wrap12(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1523)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:163)
        at android.app.ActivityThread.main(ActivityThread.java:6238)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:933)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
        at com.kaymkassai.learnit.HskFragment.onCreateView(HskFragment.java:20)
        at android.support.v4.app.Fragment.performCreateView(Fragment.java:2439)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1460)
        at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1784)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1852)
        at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:802)
        at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2625)
        at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2411)
        at android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute(FragmentManager.java:2366)
        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2273)
        at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(FragmentManager.java:3273)
        at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:3229)
        at android.support.v4.app.FragmentController.dispatchActivityCreated(FragmentController.java:201)
        at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:620)
        at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:178)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1249)
        at android.app.Activity.performStart(Activity.java:6883)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2686)

Answer 1

使用getChildFragmentManager()代替getActivity().getSupportFragmentManager()

如何将片段放入片段中？

1 个答案: