尝试使用自定义适配器在片段内部实现recycleview并收到以下错误。
java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference。在StoreAdapter.getItemCount(StoreAdapter.java:xx)
我环顾四周，但没有看到任何导致解决方案的事情。任何帮助，将不胜感激。
和其他几个人
public class StoreAdapter extends RecyclerView.Adapter<StoreAdapter.StoreHolder>{
private LayoutInflater mInflator;
private List<Store> mStore= Collections.emptyList();
private Context mContext;
public StoreAdapter(Context mContext, List<Store> mStore){
mInflator = LayoutInflater.from(mContext);
this.mStore = mStore;
this.mContext = mContext;
}
// Simple nested class that holds the various view components for the adapter
// and as specified in *layout.xml .
public class StoreHolder extends RecyclerView.ViewHolder{
TextView mStoreTitle, mStoreDetails, mStoreCategory;
public StoreHolder (View itemView){
super(itemView);
mStoreTitle = (TextView) itemView.findViewById(R.id.title);
mStoreDetails = (TextView) itemView.findViewById(R.id.details);
mStoreCategory = (TextView) itemView.findViewById(R.id.category);
}
}
// Called when the RecyclerView needs a new RecyclerView.ViewHolder (*Holder)
// to represent an item. We inflate the XML layout and return our view (*Holder)
@Override
public StoreHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = mInflator.inflate(R.layout.todo_list_row, parent,false);
return new StoreHolder(view);
}
// Called by RecyclerView to display the data at the specified position.
// This method needs to update the contents of the view to reflect the item at the
// given position e.g. we are updating the view here with the data
@Override
public void onBindViewHolder(StoreAdapter.StoreHolder holder, int position) {
holder.mStoreTitle.setText(mStore.get(position).getStoreTitle());
holder.mStoreDetails.setText(mStore.get(position).getStoreDetails());
holder.mStoreCategory.setText(mStore.get(position).getStoreCategory());
}
public void setData(List<Store> store){
this.mStore = store;
}
public void delete(int position){
mStore.remove(position);
notifyItemRemoved(position);
}
@Override
public int getItemCount() {
return mStore.size();
}
}
public class StoreSectionLoader extends AsyncTaskLoader<List<Store>> {
private static final String LOG_TAG = StoreSectionLoader.class.getSimpleName();
private List<Store> mStore;
private ContentResolver mContentResolver;
private Cursor mCursor;
public StoreSectionLoader(Context context, Uri uri, ContentResolver contentResolver){
super(context);
mContentResolver = contentResolver;
}
@Override
public List<Store> loadInBackground() {
String[] projection = {BaseColumns._ID,
RetailFinderContract.RetailFinderColumns.STORE_COMPLETE,
RetailFinderContract.RetailFinderColumns.STORE_CREATED,
RetailFinderContract.RetailFinderColumns.STORE_TITLE,
RetailFinderContract.RetailFinderColumns.STORE_DETAILS,
RetailFinderContract.RetailFinderColumns.STORE_CATEGRORY};
List<Store> entry = new ArrayList<>();
Uri uri = RetailFinderContract.URI_LOCATION_TABLE;
mCursor = mContentResolver.query(uri, projection, null, null, null);
if(mCursor != null){
if(mCursor.moveToFirst()){
do {
int _id = mCursor.getInt(mCursor.getColumnIndex(BaseColumns._ID));
String store_title = mCursor.getString(
mCursor.getColumnIndex(RetailFinderContract.RetailFinderColumns.STORE_TITLE));
String store_details = mCursor.getString(
mCursor.getColumnIndex(RetailFinderContract.RetailFinderColumns.STORE_DETAILS));
String store_category = mCursor.getString(
mCursor.getColumnIndex(RetailFinderContract.RetailFinderColumns.STORE_CATEGRORY));
Store store = new Store(_id,store_title,store_details,store_category);
entry.add(store);
} while (mCursor.moveToNext());
}
}
return entry;
}
@Override
public void deliverResult(List<Store> store) {
if(isReset()){
if (mStore != null){
mCursor.close();
}
}
List<Store> oldStoreList = mStore;
if(mStore == null || mStore.size() == 0 ){
Log.d(LOG_TAG, "+++++++++++++++ No Data returned");
}
mStore = store;
if(isStarted()){
super.deliverResult(store);
}
if(oldStoreList != null && oldStoreList != store){
mCursor.close();
}
}
@Override
protected void onStartLoading() {
if(mStore != null){
deliverResult(mStore);
}
if(takeContentChanged() || mStore == null){
forceLoad();
}
}
@Override
protected void onStopLoading() {
cancelLoad();
}
@Override
protected void onReset() {
onStopLoading();
if(mCursor != null){
mCursor.close();
}
mStore = null;
}
@Override
public void onCanceled(List<Store> store) {
super.onCanceled(store);
if(mCursor != null){
mCursor.close();
}
}
@Override
public void forceLoad() {
super.forceLoad();
}
}
public class StoreFragment extends Fragment implements
LoaderManager.LoaderCallbacks<List<Store>> {
private static final String LOG_TAG = StoreListFragment.class.getSimpleName();
private StoreAdapter mAdapter;
private static final int LOADER_ID = 1;
private ContentResolver mContentReslover;
private List<Store> mStore;
private Context mContext;
protected RecyclerView mRecyclerView;
private static final String TAG = "RecyclerViewFragment";
private static final String KEY_LAYOUT_MANAGER = "layoutManager";
private enum LayoutManagerType {
GRID_LAYOUT_MANAGER,
LINEAR_LAYOUT_MANAGER
}
protected LayoutManagerType mCurrentLayoutManagerType;
protected RecyclerView.LayoutManager mLayoutManager;
// end added
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setHasOptionsMenu(true);
mContentReslover = getActivity().getContentResolver();
getLoaderManager().initLoader(LOADER_ID, null, this);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.store_list_row, container, false);
rootView.setTag(TAG);
mRecyclerView = (RecyclerView) rootView.findViewById(R.id.t_recycler);
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
if (savedInstanceState != null) {
// Restore saved layout manager type.
mCurrentLayoutManagerType = (LayoutManagerType) savedInstanceState
.getSerializable(KEY_LAYOUT_MANAGER);
}
setRecyclerViewLayoutManager(mCurrentLayoutManagerType);
mAdapter = StoreAdapter(getContext(), mStore); //issue
mRecyclerView.setAdapter(mAdapter);
return rootView;
}
public void setRecyclerViewLayoutManager(LayoutManagerType layoutManagerType) {
int scrollPosition = 0;
// If a layout manager has already been set, get current scroll position.
if (mRecyclerView.getLayoutManager() != null) {
scrollPosition = ((LinearLayoutManager) mRecyclerView.getLayoutManager())
.findFirstCompletelyVisibleItemPosition();
}
switch (layoutManagerType) {
case LINEAR_LAYOUT_MANAGER:
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
break;
default:
mLayoutManager = new LinearLayoutManager(getActivity());
mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
}
mRecyclerView.setLayoutManager(mLayoutManager);
mRecyclerView.scrollToPosition(scrollPosition);
}
@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
// Save currently selected layout manager.
savedInstanceState.putSerializable(KEY_LAYOUT_MANAGER, mCurrentLayoutManagerType);
super.onSaveInstanceState(savedInstanceState);
}
@Override
public Loader<List<Store>> onCreateLoader(int id, Bundle args) {
mContentReslover = getActivity().getContentResolver();
return new StoreSectionLoader(getActivity(), RetailFinderContract.URI_STORES_TABLE, mContentReslover);
}
@Override
public void onLoadFinished(Loader<List<Store>> loader, List<Store> store) {
mAdapter.setData(store);
mStore = store;
}
@Override
public void onLoaderReset(Loader<List<Store>> loader) {
mAdapter.setData(null);
}
}