我正在使用自定义的recyclelerview来填充我的firebase数据库中的数据。我已经能够成功地做到这一点，但现在我正在努力在点击项目时开始一项新活动。当我点击一个项目时，我收到一个空指针错误。我正在尝试检索项目的pushID并使用它来开始其详细活动。这是我的代码
我的适配器
public class SearchResultsAdapter extends RecyclerView.Adapter<SearchResultsAdapter.SearchViewHolder> {
Context context;
String downloadUrl;
String post_key;
ArrayList<Search1> mSearchList = new ArrayList<Search1>();
private ItemClickListener mItemClickListener;
private DatabaseReference databaseReference15;
//Constructor of this class
public SearchResultsAdapter(ArrayList<Search1> mSearchList,Context context) {
this.context = context;
//Getting all superheroes
this.mSearchList = mSearchList;
}
@Override
public SearchViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext())
.inflate(R.layout.searchrow, parent, false);
SearchViewHolder searchViewHolder = new SearchViewHolder(itemView, mItemClickListener);
return searchViewHolder;
}
@Override
public void onBindViewHolder(SearchViewHolder viewHolder, final int position) {
final Context context = viewHolder.downloadUrls.getContext();
//Showing data on the views
final Search1 c = mSearchList.get(position);
post_key = c.getKey();
viewHolder.uzername.setText(c.getUsername());
Picasso.with(context).load(c.downloadUrl).into(viewHolder.downloadUrls);
databaseReference15 = FirebaseDatabase.getInstance().getReference().child("UG").child("UzersAll");
viewHolder.setItemClickListener(new ItemClickListener() {
@Override
public void onClick(View view, int position) {
databaseReference15.child(post_key).addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String searched = (String) dataSnapshot.child("username").getValue();
String halls = (String) dataSnapshot.child("halls").getValue();
Intent SearchIntent = new Intent(context, SearchView1.class);
SearchIntent.putExtra("key", post_key);
SearchIntent.putExtra("username", searched);
SearchIntent.putExtra("halls", halls);
context.startActivity(SearchIntent);
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(context, "Check Connection", Toast.LENGTH_LONG).show();
}
});
}
});
}
@Override
public int getItemCount() {
return mSearchList.size();
}
public class SearchViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
//Views
public TextView uzername;
public CircularImageView downloadUrls;
private ItemClickListener mItemClickListener;
Context context;
// ArrayList<Search1> mSearchList = new ArrayList<Search1> ();
//Initializing Views
public SearchViewHolder(View itemView,ItemClickListener itemClickListener ) {
super(itemView);
context = itemView.getContext();
this.mItemClickListener = itemClickListener;
// this.context = context;
//this.mSearchList = mSearchList;
uzername = (TextView) itemView.findViewById(R.id.uzername);
downloadUrls = (CircularImageView) itemView.findViewById(R.id.downloadUrls);
// itemView.setClickable(true);
itemView.setOnClickListener(this);
}
public void setItemClickListener(ItemClickListener itemClickListener){
this.mItemClickListener = itemClickListener ;
}
@Override
public void onClick(View v) {
// int position = getAdapterPosition();
//Search1 mSearchList = this.mSearchList.get(position);
// post_key = mSearchList.getKey();
if(mItemClickListener != null){
mItemClickListener.onClick(v,getAdapterPosition());
}
}
}
}
我的活动
public class SearchResultsTest extends AppCompatActivity {
private RecyclerView mSearchlist;
private DatabaseReference databaseReference1, databaseReference2;
private FirebaseAuth firebaseAuth;
private ProgressDialog mProgressDialog;
Query query;
String user_key;
String halls;
String lastKnownKey;
private ArrayList<Search1> searchList = new ArrayList<>();
private LinearLayoutManager mlinearLayout;
private SearchResultsAdapter mAdapter;
private SwipeRefreshLayout mRefreshLayout;
private static final int TOTAL_ITEMS_TO_LOAD = 2;
private int mCurrentPage = 1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.searchlist);
Intent SearchIntent = getIntent();
halls = SearchIntent.getStringExtra("halls");
// final String sex = SearchIntent.getStringExtra("sex");
mProgressDialog = new ProgressDialog(this);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar3);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
getSupportActionBar().setTitle(halls);
mAdapter = new SearchResultsAdapter(searchList,this);
mSearchlist = (RecyclerView) findViewById(R.id.searchlist);
mlinearLayout = new LinearLayoutManager(this);
mRefreshLayout = (SwipeRefreshLayout) findViewById(R.id.swipe);
mSearchlist.setHasFixedSize(true);
mSearchlist.setLayoutManager(mlinearLayout);
// mSearchlist.setAdapter(mAdapter);
mSearchlist.swapAdapter(mAdapter, true);
//setAdapter(adapter)
databaseReference1 = FirebaseDatabase.getInstance().getReference().child("UG").child("UzersH");
databaseReference2 = FirebaseDatabase.getInstance().getReference().child("UG").child("Users1");
firebaseAuth = FirebaseAuth.getInstance();
final String user_id = firebaseAuth.getCurrentUser().getUid();
loadResults();
/* mSearchlist.addOnScrollListener(new EndlessRecyclerOnScrollListener(mlinearLayout) {
@Override
public void onLoadMore(int current_page) {
mCurrentPage++;
searchList.clear();// when we have reached end of RecyclerView this event fired
loadResults();
}
});*/
mProgressDialog.setMessage("Loading Please Wait...");
mProgressDialog.show();
/* mRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener(){
@Override
public void onRefresh() {
mCurrentPage++;
searchList.clear();// when we have reached end of RecyclerView this event fired
loadResults();
}
});*/
mRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
@Override
public void onRefresh() {
mCurrentPage++;
searchList.clear();// when we have reached end of RecyclerView this event fired
mAdapter.notifyDataSetChanged();// when we have reached end of RecyclerView this event fired
loadResults();
}
});
}
private void loadResults() {
// Query query = databaseReference1.child(halls);
/* Query query = databaseReference1.child(halls).orderByChild("ts").limitToFirst(mCurrentPage * TOTAL_ITEMS_TO_LOAD);
query.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if(!dataSnapshot.hasChildren()){
mCurrentPage--;
}
for (DataSnapshot data : dataSnapshot.getChildren()) {
Search1 search = data.getValue(Search1.class);
searchList.add(search);
mAdapter.notifyDataSetChanged();
mProgressDialog.dismiss();
}
*//* Search1 search = dataSnapshot.getValue(Search1.class);
searchList.add(search);
mAdapter.notifyDataSetChanged();
mProgressDialog.dismiss();*//*
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});*/
// .startAt(mCurrentPage*TOTAL_ITEMS_TO_LOAD);;
//.startAt(2).orderByChild("ts");
//.limitToFirst(TOTAL_ITEMS_TO_LOAD);
//.startAt(mCurrentPage*TOTAL_ITEMS_TO_LOAD);
Query query = databaseReference1.child(halls).orderByChild("ts").limitToFirst(mCurrentPage * TOTAL_ITEMS_TO_LOAD);
query.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
if (!dataSnapshot.hasChildren()){
mProgressDialog.dismiss();
}
Search1 search = dataSnapshot.getValue(Search1.class);
searchList.add(search);
mAdapter.notifyDataSetChanged();
mSearchlist.scrollToPosition(searchList.size()-1);
mRefreshLayout.setRefreshing(false);
mProgressDialog.dismiss();
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// todo: goto back activity from here
/*Intent intent = new Intent(ViewProfile.this, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);*/
finish();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
}
LOG CAT ERROR
E/AndroidRuntime: FATAL EXCEPTION: main
Process: dev.mintz.minzter, PID: 4703
java.lang.NullPointerException: Can't pass null for argument 'pathString' in child()
at com.google.firebase.database.DatabaseReference.child(Unknown Source)
at dev.mintz.minzter.SearchResultsAdapter$1.onClick(SearchResultsAdapter.java:73)
at dev.mintz.minzter.SearchResultsAdapter$SearchViewHolder.onClick(SearchResultsAdapter.java:158)
at android.view.View.performClick(View.java:4780)
at android.view.View$PerformClick.run(View.java:19866)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
答案 0 :(得分：0)
此行post_key = c.getKey();指定空值
然后，当您致电databaseReference15.child(post_key)时，它表示null不是允许的值。
查看变量mSearchList中的值，了解其发生的原因。