我有一個名為“Notification fragment”的片段，我想在其中使用 Tab layout 顯示另一個名為“Watching Fragment”的片段。當我運行應用程式時，選項卡布局欄可見，但片段不可見。
我的 Fragment 在其中顯示其他 Fragment（通知 Fragment）
public class NotificationsFragment extends Fragment{
GridView listv;
FragmentAdapter fragmentAdapter;
private NotificationsViewModel notificationsViewModel;
private FragmentNotificationsBinding binding;
public View onCreateView(@NonNull LayoutInflater inflater,
ViewGroup container, Bundle savedInstanceState) {
notificationsViewModel =
new ViewModelProvider(this).get(NotificationsViewModel.class);
binding = FragmentNotificationsBinding.inflate(inflater, container, false);
View root = binding.getRoot();
TabLayout tabLayout = root.findViewById(R.id.tabLayout);
ViewPager vp = root.findViewById(R.id.vp2);
fragmentAdapter = new FragmentAdapter(getChildFragmentManager() , tabLayout.getTabCount());
vp.setAdapter(fragmentAdapter);
tabLayout.addOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
vp.setCurrentItem(tab.getPosition());
if(tab.getPosition() == 0 || tab.getPosition() == 1 || tab.getPosition() == 2)
fragmentAdapter.notifyDataSetChanged();
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
vp.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
return root; }
我的第一個片段（看片段）
public class WatchingFragment extends Fragment {
ArrayList<String> list = new ArrayList<String>();
GridView gridv1;
private WatchingViewModel mViewModel;
public static WatchingFragment newInstance() {
return new WatchingFragment();
}
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
@Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.watching_fragment, container, false);
gridv1 = view.findViewById(R.id.gridv1);
Intent intent = getActivity().getIntent();
String animename = intent.getStringExtra("nameanime");
list.add(animename);
loadData2();
saveData2();
ListNewAdapter adapter = new ListNewAdapter(getContext(), R.layout.watch_list, list);
gridv1.setAdapter(adapter);
gridv1.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@Override
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
list.remove(position);
adapter.notifyDataSetChanged();
saveData2();
return true;
}
});
return view;
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mViewModel = new ViewModelProvider(this).get(WatchingViewModel.class);
// TODO: Use the ViewModel
}
private void saveData2() {
SharedPreferences sp = getActivity().getSharedPreferences("shared preferences", MODE_PRIVATE);
SharedPreferences.Editor ed = sp.edit();
Gson gson = new Gson();
String json = gson.toJson(list);
ed.putString("anime list", json);
ed.apply();
}
private void loadData2() {
SharedPreferences sp = getActivity().getSharedPreferences("shared preferences", MODE_PRIVATE);
Gson gson = new Gson();
String json = sp.getString("anime list", "");
Type type = new TypeToken<ArrayList<String>>() {}.getType();
list = gson.fromJson(json , type);
if (list == null) {
list = new ArrayList<String>();
}
}
}
我的視圖尋呼機配接器
public class FragmentAdapter extends FragmentPagerAdapter {
int tabcount;
public FragmentAdapter(@NonNull @NotNull FragmentManager fm, int behavior) {
super(fm, behavior);
tabcount = behavior;
}
@NonNull
@NotNull
@Override
public Fragment getItem(int position) {
switch (position){
case 0: return new WatchingFragment();
case 1: return new CompletedFragment();
case 2: return new WantToWatchFragment();
default: return null;
}
}
@Override
public int getCount() {
return 0;
}
}
通知片段布局
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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"
tools:context=".ui.notifications.NotificationsFragment">
<com.google.android.material.tabs.TabLayout
android:id="@ id/tabLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<com.google.android.material.tabs.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Watching" />
<com.google.android.material.tabs.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Completed" />
<com.google.android.material.tabs.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Want To Watch" />
</com.google.android.material.tabs.TabLayout>
<androidx.viewpager.widget.ViewPager
android:id="@ id/vp2"
android:name="com.example.animeguide.ui.notifications.NotificationsFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@id/tabLayout" />
</androidx.constraintlayout.widget.ConstraintLayout>
觀察片段布局
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
android:orientation="vertical"
tools:context=".ui.notifications.FragmentsInsideList.watching.WatchingFragment">
<TextView
android:id="@ id/textView4"
android:layout_width="184dp"
android:layout_height="58dp"
android:text="hello world"
android:textSize="34sp" />
<GridView
android:id="@ id/gridv1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:numColumns="2" />
</LinearLayout>
uj5u.com熱心網友回復：
為了讓配接器知道它有多少頁，您需要覆寫getCount方法。您確實覆寫了它，但使用 0 作為頁數，因此沒有頁。
在您的 FragmentAdapter 類中，嘗試更改此內容：
@Override
public int getCount() {
return 0;
}
對此：
@Override
public int getCount() {
return tabcount;
}
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