我有一个带有 3 个选项卡的 ViewPager，每个选项卡加载一个片段，同一片段类的新实例，但带有一个额外的参数。
您可以在下面找到片段类，我在该片段中有一个回收器视图，当用户长按回收器视图中的项目时，我正在尝试打开上下文菜单。
我能够显示上下文菜单并获取片段单个实例的选定项目的位置，当我滑动到下一个片段时，我得到相同的索引位置，当我进一步调试时，我发现我在上一个片段上获得了相同的适配器用于 RecyclerView。当我记录该回收器视图的适配器大小时，可以看到这一点。
任何人都可以帮助我理解为什么当我在 ViewPager 中滑动到该片段的完全不同的实例时，即使我可以在片段中看到正确的数据并在onBindViewHolder方法中获取正确的值，为什么我会获得以前的适配器数据。
您可以在下面找到片段类的简化代码
public class HistoryFragment extends Fragment{
private static final String LOG_TAG = HistoryFragment.class.getSimpleName();
private RecyclerView mRecyclerView;
private HistoryAdapter mHistoryAdapter;
private List<Group> mGroups;
private String mGroupType;
/**
* tried using a static int value to track which context menu was opened and on which fragment
* refer post https://caughtinthemobileweb.wordpress.com/2013/10/22/android-viewpager-holds-reference-to-old-fragments/
* BUG LOGGED AT https://code.google.com/p/android/issues/detail?id=19211
* does not work :(
*/
/*private static int selectedContextMenu;*/ // returns valid index as int is static, but adapter still has old data
/**
* The fragment argument for this fragment.
*/
private static final String ARG_GROUP_TYPE = "group_type";
public HistoryFragment() { }
/**
* Returns a new instance of this fragment
*/
public static HistoryFragment newInstance(String groupType) {
HistoryFragment fragment = new HistoryFragment();
Bundle args = new Bundle();
args.putString(ARG_GROUP_TYPE, groupType);
fragment.setArguments(args);
return fragment;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_history, container, false);
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerViewHistoryItem);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false);
mRecyclerView.setLayoutManager(layoutManager);
mGroups = new ArrayList<>();
mHistoryAdapter = new HistoryAdapter(getActivity(), mGroups);
mRecyclerView.setAdapter(mHistoryAdapter);
Bundle bundle = getArguments();
mGroupType = bundle.getString(ARG_GROUP_TYPE);
if(mGroupType != null && !mGroupType.equals("")){
loadDataFromDb();
} else {
if(IS_DEBUG_ON) Log.d(LOG_TAG, "invalid fragment arguments");
getActivity().finish();
}
return rootView;
}
@Override
public boolean onContextItemSelected(MenuItem item){
// int id = item.getItemId();
Log.d(LOG_TAG, "position2: " + mHistoryAdapter.getSelectedItemPosition() +
" " + mGroups.get(mHistoryAdapter.getSelectedItemPosition()).getName()); // returns old data
Log.d(LOG_TAG, "size2: " + mHistoryAdapter.getItemCount()); // returns old data
// Log.d(LOG_TAG, "position3: " + selectedContextMenu); // returns correct index, but cant use as adapter still has old data
Log.d(LOG_TAG, "position4: " + ((HistoryAdapter) mRecyclerView.getAdapter()).getSelectedItemPosition()); // returns old data
return true;
}
private void loadDataFromDb(){
new LoadGroups().execute();
}
class HistoryAdapter extends RecyclerView.Adapter<HistoryFragment.HistoryAdapter.ViewHolder> {
private Context mContext;
private List<Group> mList;
private int mSelectedItemPosition;
HistoryAdapter(Context mContext, List<Group> mList) {
this.mContext = mContext;
this.mList = mList;
}
class ViewHolder extends RecyclerView.ViewHolder implements View.OnCreateContextMenuListener {
View mView;
TextView mTextViewName;
TextView mTextViewDescription;
ImageView mImageViewProfile;
ImageView mImageCheck;
public ViewHolder(View itemView) {
super(itemView);
this.mView = itemView;
this.mTextViewName = (TextView) itemView.findViewById(R.id.textViewGroupName);
this.mTextViewDescription = (TextView) itemView.findViewById(R.id.textViewGroupDescription);
this.mImageViewProfile = (ImageView) itemView.findViewById(R.id.groupImage);
this.mImageCheck = (ImageView) itemView.findViewById(R.id.imageCheck);
this.mView.setOnCreateContextMenuListener(this); // registering listener
}
@Override
public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
if(mGroupType.equals(GroupContract.GroupEntry.GROUP_TYPE_HISTORY_GROUP)){
menu.add(Menu.NONE, R.id.action_resubscribed_group, Menu.NONE, R.string.action_resubscribed_group);
} else if(mGroupType.equals(GroupContract.GroupEntry.GROUP_TYPE_SUBSCRIBED_GROUP)){
if(!mList.get(getAdapterPosition()).isDefault()){
menu.add(Menu.NONE, R.id.action_unsubscribe_group, Menu.NONE, R.string.action_unsubscribe_group);
}
menu.add(Menu.NONE, R.id.action_mute, Menu.NONE, R.string.action_mute);
menu.add(Menu.NONE, R.id.action_view_group_info, Menu.NONE, R.string.action_view_group_info);
}
}
}
@Override
public HistoryAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(mContext).inflate(R.layout.recycler_view_history, parent, false);
return new HistoryAdapter.ViewHolder(view);
}
@Override
public void onBindViewHolder(final HistoryAdapter.ViewHolder holder, final int position) {
if(mGroupType.equals(GroupContract.GroupEntry.GROUP_TYPE_SUBSCRIBED_GROUP)){
holder.mImageCheck.setVisibility(View.VISIBLE);
} else {
holder.mImageCheck.setVisibility(View.GONE);
}
holder.mTextViewName.setText(mList.get(position).getName());
holder.mTextViewDescription.setText(mList.get(position).getDescription());
holder.mView.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
// mSelectedItemPosition = position; // tried this, returns correct
// selectedContextMenu = position; // also tried this, returns correct
mSelectedItemPosition = holder.getAdapterPosition(); // this also returns correct
Log.d(LOG_TAG, "position1 - onBind: " + mSelectedItemPosition + " "+ mList.get(mSelectedItemPosition).getName()); // returns correct data
return false;
}
});
}
@Override
public void onViewRecycled(ViewHolder holder) {
holder.mView.setOnLongClickListener(null); // clearing listener to avoid collision between list items
super.onViewRecycled(holder);
}
@Override
public int getItemViewType(int position) {
return 0;
}
@Override
public int getItemCount() {
return mList.size();
}
int getSelectedItemPosition() {
Log.d(LOG_TAG, "getter: " + mSelectedItemPosition); // this returns wrong data, shows that fragment is referring old adapter data
return mSelectedItemPosition;
}
}
// get data from db
class LoadGroups extends AsyncTask<Void, Void, Void>{
@Override
protected Void doInBackground(Void... voids) {
mGroups = GroupContract.getGroupEntriesFromDB(getActivity(), mGroupType);
return null;
}
@Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
mHistoryAdapter = new HistoryAdapter(getActivity(), mGroups);
mRecyclerView.setAdapter(mHistoryAdapter);
}
}
}
您可以在下面找到 ViewPager 适配器类
public class HomeTabsPagerAdapter extends FragmentPagerAdapter {
private Context mContext;
HomeTabsPagerAdapter(Context context, FragmentManager fm) {
super(fm);
mContext = context;
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return HistoryFragment.newInstance("TYPE_1");
case 1:
return HistoryFragment.newInstance("TYPE_2");
case 2:
return HistoryFragment.newInstance("TYPE_3");
}
return null;
}
@Override
public int getCount() {
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return mContext.getString(R.string.text_type_1);
case 1:
return mContext.getString(R.string.text_type_2);
case 2:
return mContext.getString(R.string.text_type_3);
}
return null;
}
// Doesn't work even when I use this or not
/*@Override
public int getItemPosition(Object object) {
// try http://stackoverflow.com/a/8024557
// return super.getItemPosition(object);
return POSITION_NONE;
}*/
}
我怀疑使用RecyclerView.LayoutManager可能是一个问题，因为你有一个静态类，前两个创建的片段将具有相同的内容(第二个)。下一个片段也是如此.此外，getItemPosition(Object object) -> return POSITION_NONE 只能与 FragmentStatePagerAdapter 一起使用。一旦创建，您永远不会更改片段的片段适配器。 所以，我建议而不是：
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity()， LinearLayoutManager.VERTICAL， false); mRecyclerView.setLayoutManager(layoutManager);
使用
mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
//或设置一个网格布局管理器
如果您计划更新片段的内容，请使用 FragmentStatePagerAdapter。
我遇到了类似的问题，并通过将其放在我的片段上来修复它：
@Override
public void onDetach() {
super.onDetach();
recyclerView.getRecycledViewPool().clear();
}
在您的情况下，您可以在更改选项卡时调用getRecycledViewPool。