我有一个Main Activity，它使用TabSelectedListener来显示AHBottomNavigation菜单的片段。该片段名为＆＃34; FirstFragment＆＃34;包含一个FragmentPagerAdapter，允许用户在两个选项卡之间滑动，每个选项卡都有自己的片段，名为FirstTabInFirstFragmentFragment和SecondTabInFirstFragmentFragment（为简单起见，重命名）。
我的问题是：
A）。当主要活动启动时，＆＃34; First＆＃34;选择了底部导航菜单项，但是＆＃34; FirstFragment＆＃34;没有发布。因此，它显示使用空白屏幕选择的正确项目。如果我再次点击菜单项，它只会启动First Fragment。
B）。一旦FirstFragment正确启动并显示在屏幕上（通过a中的临时修复），如果我选择不同的菜单项（即导航到SecondFragment），然后再次选择FirstFragment的菜单项，其中的两个标签是空白的。此外，两个标签的片段之间的滑动不起作用，并且卡住了＃34;所以你必须将它一直拉到一边或一直拉到另一边。
希望我已经清楚地解释了我的问题 - 如果我有什么遗漏，我可以提供更多细节。
请注意，我正在使用com.aurelhubert.ahbottomnavigation.AHBottomNavigation
以下是相关文件：
MainActivity.java ：
public class MainActivity extends AppCompatActivity{
private AHBottomNavigationAdapter navigationAdapter;
private AHBottomNavigationViewPager viewPager;
private AHBottomNavigation bottomNavigation;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Add menu items to bar
bottomNavigation = (AHBottomNavigation) findViewById(R.id.bottom_navigation);
this.createNavItems();
bottomNavigation.setOnTabSelectedListener(new AHBottomNavigation.OnTabSelectedListener() {
@Override
public boolean onTabSelected(int position, boolean wasSelected) {
//show fragment
if (position==0)
{
FirstFragment firstFragment=new FirstFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.content_id,firstFragment).commit();
}else if (position==1)
{
SecondFragment secondFragment=new SecondFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.content_id, secondFragment).commit();
}else if (position==2)
{
ThirdFragment thirdFragment=new ThirdFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.content_id,thirdFragment).commit();
}else{
FourthFragment fourthFragment=new FourthFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.content_id,fourthFragment).commit();
}
return true;
}
});
}
private void createNavItems(){
navigationAdapter = new AHBottomNavigationAdapter(this, R.menu.navigation);
navigationAdapter.setupWithBottomNavigation(bottomNavigation);
// set current item
bottomNavigation.setCurrentItem(0);
}
activity_main.xml中
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/content_id"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.aurelhubert.ahbottomnavigation.AHBottomNavigation
android:id="@+id/bottom_navigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"/>
</android.support.design.widget.CoordinatorLayout>
FirstFragment.java：
public class FirstFragment extends Fragment {
private FragmentActivity mContext;
public FirstFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_first, container, false);
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState){
super.onActivityCreated(savedInstanceState);
// Set the content of the activity to use the activity_main.xml layout file
//setContentView(R.layout.activity_first);
// Find the view pager that will allow the user to swipe between fragments
ViewPager viewPager = (ViewPager) getView().findViewById(R.id.viewpager);
// Create an adapter that knows which fragment should be shown on each page
// using getFragmentManager() will work too
FirstFragmentPagerAdapter adapter = new FirstFragmentPagerAdapter(mContext.getSupportFragmentManager(), mContext);
// Set the adapter onto the view pager
viewPager.setAdapter(adapter);
TabLayout tabLayout = (TabLayout) getView().findViewById(R.id.sliding_tabs);
tabLayout.setupWithViewPager(viewPager);
}
/**
* Override to set context. This context is used for getSupportFragmentManager in onCreateView
* @param activity
*/
@Override
public void onAttach(Activity activity) {
mContext=(FragmentActivity) activity;
super.onAttach(activity);
}
}
fragment_first.xml：
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<android.support.design.widget.TabLayout
android:id="@+id/sliding_tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabMode="fixed"
app:tabBackground="@color/firstTabBackground"
app:tabIndicatorColor="@color/firstTabIndicatorColor"/>
<android.support.v4.view.ViewPager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="0px"
android:layout_weight="1"/>
</LinearLayout>
</android.support.constraint.ConstraintLayout>
FirstFragmentPagerAdapter.java：
public class FirstFragmentPagerAdapter extends FragmentPagerAdapter {
private Context context;
public FirstFragmentPagerAdapter(FragmentManager fm, Context mContext){
super(fm);
context = mContext;
}
/**
* The ViewPager asks the adapter for the fragment at a given position,
* i.e. for the 1st fragment, the ViewPager asks for the fragment at
* position 1.
* @param position
* @return
*/
@Override
public Fragment getItem(int position){
if (position == 0){
return new FirstTabInFirstFragmentFragment();
}
else{
return new SecondTabInFirstFragmentFragment();
}
}
/**
* On launch, the ViewPager asks the adapter how many pages there will be.
* Here, our adapter returns how many pages there will be.
* @return
*/
@Override
public int getCount() {return 2;}
@Override
public CharSequence getPageTitle(int position) {
switch(position){
case 0:
return context.getResources().getString(R.string.first_tab_in_first_fragment_page_title);
case 1:
return context.getResources().getString(R.string.second_tab_in_first_fragment_page_title);
default:
return null;
}
}
}
答案 0 :(得分：3)
首先，为了在启动时初始加载frstfragment，你必须将frstfragments视图定义为mainactivitys视图的默认视图。
其次，在选择bottomnavigation菜单时，你需要有一个framelayout来加载每个片段的视图..在这里你只是替换了mainactivity的父布局，这是一个错误的概念，我相信。
因此，您需要创建子framelayout以加载每个bottomnavigation菜单项的片段视图。
编辑：
我的布局包含bottomnavigation，
"$(TargetDir)"和该活动的java类（仅包含bottomnavigation操作的方法）如下：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/content_home"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:showIn="@layout/app_bar_home"
android:keepScreenOn="false">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/ll_toolbar_home_search">
<android.support.v7.widget.Toolbar
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="?attr/colorPrimary">
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="30dp"
android:background="@drawable/btn_style_white"
android:layout_marginRight="10dp">
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_search"/>
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="10dp"
android:text="Search 18000+ products"
android:id="@+id/tv_search_home"/>
</LinearLayout>
</android.support.v7.widget.Toolbar>
</LinearLayout>
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@id/ll_toolbar_home_search"
android:layout_above="@+id/navigation"
android:id="@+id/frame_layout_fragment"
android:background="@color/white">
</FrameLayout>
<com.aurelhubert.ahbottomnavigation.AHBottomNavigation
android:id="@+id/navigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true" />
</RelativeLayout>
答案 1 :(得分：3)
我能够分两步解决这个问题。首先，在我的Main Activiy方法createNavItems中，除了执行bottomNavigation.setCurrentItem(0);之外，我还必须使用默认片段手动更新CoordinatorLayout（ID为content_id）：
getSupportFragmentManager().beginTransaction().replace(R.id.content_id, new FirstFragment()).commit();
接下来，要解决TabLayout问题，我必须更改此行：
FirstFragmentPagerAdapter adapter = new FirstFragmentPagerAdapter(mContext.getSupportFragmentManager(), mContext);
到
FirstFragmentPagerAdapter adapter = new FirstFragmentPagerAdapter(getChildFragmentManager(), mContext);
这样做的原因是，当使用ViewPager将片段嵌套在其他片段内时，getFragmentManager()用于管理片段中的片段，而mContext.getSupportFragmentManager()用于活动。