我有一个包含RecyclerView和一个按钮的片段。按下上一个片段中的按钮（会添加一些数据）时，将显示该片段，然后回收站显示正确填充的内容，该按钮将起作用。然后，我回到上一个片段，再次按下按钮（添加更多数据），并且同一段代码显示相同的片段，但是RecyclerView未填充，并且该按钮不起作用。通过阅读此question，我的猜测是我正在片段管理中做某件事-因为一旦我改变方向并重新创建了片段，列表就可以很好地显示，并且按钮可以正常工作。
这就是我正在对片段进行的管理-我从互联网上的一个示例中获取了信息，但我担心它是不正确的
首先有一个我为片段制作的基类：
public class BaseFragment extends Fragment {
private AbstractFragmentCallback mCallback;
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mCallback = (AbstractFragmentCallback) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement " +
AbstractFragmentCallback.class.getCanonicalName());
}
}
/**
* This method replaces the currently shown fragment with a new
fragment of a particular class.
* If a fragment of the required class already shown - does
nothing.
* @param clazz the class of the fragment to show
* @param addToBackStack whether the replacement should be added
to back-stack
* @param args arguments for the newly created fragment (can be
null)
*/
public void replaceFragment(Class<? extends Fragment> clazz,
boolean addToBackStack,
Bundle args) {
mCallback.replaceFragment(clazz, addToBackStack, args);
}
public interface AbstractFragmentCallback {
/**
* Call to this method replaces the currently shown fragment
with a new one
*
* @param clazz the class of the new fragment
* @param addToBackStack whether the old fragment should be
added to the back stack
* @param args arguments to be set for the new fragment
*/
void replaceFragment(Class<? extends Fragment> clazz, boolean addToBackStack,
Bundle args);
}
}
因此，我的MainActivity然后实现了BaseFragment.AbstractfragmentCallback：
public class MainActivity extends AppCompatActivity implements BaseFragment.AbstractFragmentCallback {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(....);
if (null == savedInstanceState) {
replaceFragment(WelcomeFragment.class, false, null);
}
}
// ---------------------------------------------------------------------------------------------
//
// Fragments management
@Override
public void replaceFragment(Class<? extends Fragment> clazz, boolean addToBackStack,
Bundle args) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
Fragment newFragment;
try {
// Create new fragment
newFragment = clazz.newInstance();
if (args != null) newFragment.setArguments(args);
} catch (InstantiationException e) {
e.printStackTrace();
return;
} catch (IllegalAccessException e) {
e.printStackTrace();
return;
}
if (addToBackStack) {
ft.addToBackStack(null);
}
// Change to a new fragment
ft.replace(R.id.container, newFragment, clazz.getName());
ft.commit();
}
// End of fragments management
//
// ---------------------------------------------------------------------------------------------
}
当我的带有按钮的片段想要调出列表片段时，它将调用
replaceFragment(ListFragment.class, true, null);
所以-显然，ListFragemnt出现了，并且它的所有代码都触发了，包括重新获取RecyclerView并重新填充它-我什至看到适配器中的所有代码都针对每个项目被调用-但这些项目没有出现在列表
public class ListFragment extends BaseFragment implements ListFragmentMvc.ListViewMvcListener {
private List<MyStuff> stuffList;
@Override
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstance) {
stuffList = new ArrayList<>();
return inflater.inflate(R.layout.list_activity, container, true);
}
@Override
public void onResume() {
super.onResume();
recyclerView = mRootView.findViewById(R.id.recycler_view);
letsGoButton = mRootView.findViewById(R.id.lets_go_button);
letsGoButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Activity activity = getActivity();
if (activity != null) {
getActivity().onBackPressed();
}
}
});
recyclerView.setItemAnimator(new DefaultItemAnimator());
DividerItemDecoration itemDecor = new DividerItemDecoration(context, HORIZONTAL);
recyclerView.addItemDecoration(itemDecor);
RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(context);
recyclerView.setLayoutManager(mLayoutManager);
setData(MyApplication.getAllStuffItems());
}
public void setData(List<MyStuff> stuff) {
stuffList = stuff;
mAdapter = new StuffAdapter(stuffList);
recyclerView.setAdapter(mAdapter);
mAdapter.notifyDataSetChanged();
}
}
因此，有人知道为什么直到我重新输入listFragment改变方向后，这才起作用？
谢谢
答案 0 :(得分：0)
您是否可以尝试将设置/更新recyclerView和letGoButton的代码从 onResume 方法移动到 onViewCreated 方法，如下所示：
@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
recyclerView = view.findViewById(R.id.recycler_view);
letsGoButton = view.findViewById(R.id.lets_go_button);
letsGoButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Activity activity = getActivity();
if (activity != null) {
getActivity().onBackPressed();
}
}
});
recyclerView.setItemAnimator(new DefaultItemAnimator());
DividerItemDecoration itemDecor = new DividerItemDecoration(context, HORIZONTAL);
recyclerView.addItemDecoration(itemDecor);
RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(context);
recyclerView.setLayoutManager(mLayoutManager);
setData(MyApplication.getAllStuffItems());
}
答案 1 :(得分：0)
哇，那真是浪费一天。
最后，我遇到了两个错误，它们相互粘贴并相互隐藏。
这不起作用的真正真实原因，我想是因为我应该有
return inflater.inflate(R.layout.list_activity, container, false);
代替
return inflater.inflate(R.layout.list_activity, container, true);
我在代码中撒了些谎，因为我并没有真正直接返回inflater.inflate的结果。我正在调用它（使用错误的参数），然后返回null。
我想这会教会我在发布中更加诚实