Question

我正在开展这个大学项目，我必须在这里创建一个职位门户应用程序我已经使用了一个底部的导航视图，在其中一个菜单项中，我已经放置了一个标签布局，一旦我启动我的应用程序它工作正常，标签工作正常。但是，一旦我从一个菜单移动到另一个菜单并返回到菜单项，其中包含选项卡，则选项卡无法正常工作。我在选项卡中使用了回收器视图，并且首先显示列表但是一旦我移动到第三个底部菜单，列表就不再显示下面是我的标签布局和底部导航视图的代码

  private BottomNavigationView.OnNavigationItemSelectedListener 
  mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction transaction = 
   fragmentManager.beginTransaction();
        switch (item.getItemId()) {
            case R.id.navigation_home:

                transaction.replace(R.id.content,new 
    HomeFragment()).commit();
                return true;
            case R.id.navigation_JobBoard:

                transaction.replace(R.id.content,new 
   JobBoardFragment()).commit();
                return true;
            case R.id.navigation_notifications:

                transaction.replace(R.id.content,new 
    NotificationBoardFragment()).commit();

                return true;
        }
        return false;
    }

 };

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


    BottomNavigationView navigation = (BottomNavigationView) 
 findViewById(R.id.navigation);





 navigation.setOnNavigationItemSelectedListener
 (mOnNavigationItemSelectedListener);
    FragmentManager fragmentManager = getSupportFragmentManager();
    FragmentTransaction transaction = fragmentManager.beginTransaction();
    transaction.replace(R.id.content,new HomeFragment()).commit();
     }

}

JOBBoardFragment类

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view=  inflater.inflate(R.layout.fragment_jobs, container, false);

    TabLayout tabs = (TabLayout) view.findViewById(R.id.result_tabs);
    tabs.addTab(tabs.newTab().setText("saved"));
    tabs.addTab(tabs.newTab().setText("Inbox"));
    tabs.addTab(tabs.newTab().setText("sent"));
    ViewPager pager = (ViewPager) view.findViewById(R.id.viewpager);
    //       SimpleFragmentPagerAdapter adapter = new 
  SimpleFragmentPagerAdapter(this, getSupportFragmentManager());
    //       setContentView(R.layout.activity_main);
    TabsPagerAdapter adapter = new TabsPagerAdapter(getFragmentManager());
    pager.setAdapter(adapter);
    tabs.setupWithViewPager(pager);
    return view;


}

布局文件

 <RelativeLayout 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"
xmlns:app="http://schemas.android.com/apk/res-auto"

 tools:context="com.example.jimmy.workmen.
   DashboardFragment.JobBoardFragment">

<!-- TODO: Update blank fragment layout -->


<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:id="@+id/linearLayout2">

    <SearchView
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

<android.support.design.widget.CoordinatorLayout
    android:id="@+id/main_content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_alignParentStart="true"
    android:layout_below="@+id/linearLayout2">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:fitsSystemWindows="true"
        android:theme="@style/Theme.Design.NoActionBar"
        app:expanded="true">

        <android.support.design.widget.TabLayout
            android:id="@+id/result_tabs"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="@android:drawable/bottom_bar"

           android:theme="@style/Base.DialogWindowTitleBackground.AppCompat"
            app:tabGravity="fill"
            app:tabIndicatorColor="@android:color/holo_orange_dark"
            app:tabMaxWidth="0dp"
            app:tabMode="fixed"
            app:tabSelectedTextColor="?attr/colorBackgroundFloating" />
    </android.support.design.widget.AppBarLayout>


    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

</android.support.design.widget.CoordinatorLayout>


</RelativeLayout>

class tabspageradapter

 public class TabsPagerAdapter extends FragmentPagerAdapter {
private Context mContext ;
private String tabTitles[] = new String[]{"saved", "inbox", "sent"};

public TabsPagerAdapter( FragmentManager fm) {

    super(fm);
    //  mContext = context;

}

@Override
public Fragment getItem(int position) {
    // getItem is called to instantiate the fragment for the given page.

    if (position == 0) {
        return new InboxFragment();
    } else if (position == 1){
        return new SavedFragment();
    } else if (position == 2){
        return new SentFragment();
    } else {
        return null;
    }


}

@Override

public int getCount() {
    return 3;
}

public CharSequence getPageTitle(int position) {
    return tabTitles[position];
}






}

Answer 1

这个问题有两种解决方案。

第一个解决方案是TabsPagerAdapter扩展FragmentStatePagerAdapter。虽然我不确定为什么会这样，但它可能与FragmentStatePagerAdapter的内存有效方法有关，也就是说当你再次回来时它可能会从头开始创建片段。

第二个解决方案是将getChildFragmentManager()传递给TabsPagerAdapter，因为ViewPager会隐藏嵌套的片段结构：

TabsPagerAdapter adapter = new TabsPagerAdapter(getChildFragmentManager());

我认为第二种解决方案是可行的，可以找到更多信息here。

tablayout未正确显示BottomNavigation项目导航中的数据

1 个答案: