【发布时间】：2019-11-08 16:06:59
【问题描述】：
我正在从 Firebase 获取数据并将其显示在回收站视图中。当我运行它时，什么都没有出现，我也没有收到任何错误。调试器显示我正在正确检索所有数据，但它显示 arraylist 一直返回零大小。
这是我的数据库结构：
{
"Classes" : {
"-LiGRe3e1YF_HFrHKMgi" : {
"Students" : {
"-LiId4URjJ8SWLAP4f4i" : "UhTQgJ4jugMqFtEZK8CsIkTqQl22",
"-LiIeT5t1T7JpcUee_MJ" : "UhTQgJ4jugMqFtEZK8CsIkTqQl22"
},
"class_info" : {
"date_clasname" : "mm",
"room_number" : "jjhh",
"subject" : "Science",
"teacher" : "mm",
"uid" : "-LiGRe3e1YF_HFrHKMgi"
}
}
},
"Users" : {
"UhTQgJ4jugMqFtEZK8CsIkTqQl22" : {
"Classes" : {
"-LiIeT5slTjC0B3lEqNJ" : "-LiGRe3e1YF_HFrHKMgi"
"-LiIeT5slTjC0B3lEqNJ" : "-LiGRe3e1YF_HFrHKMgi"
},
"User_info" : {
"email" : "samuelford48@gmail.com",
"grade" : "12",
"name" : "Samuel"
}
这是我的活动的代码：
public class home_fragment extends Fragment implements View.OnClickListener {
private Button button;
//DatabaseReference dref;
//ListView listview2;
//ArrayList<String> list=new ArrayList<>();
private FirebaseDatabase database;
private DatabaseReference myRef;
private List<Listdata> list;
private RecyclerView recyclerview;
public home_fragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.home_fragment, container, false);
//FirebaseUser fbUser = FirebaseAuth.getInstance().getCurrentUser();
//if(fbUser == null) { Intent intent = new Intent(getContext(), LoginActivity.class);
// startActivity(intent);}
button = (Button) view.findViewById(R.id.button);
button.setOnClickListener(this);
recyclerview = (RecyclerView) view.findViewById(R.id.rview);
database = FirebaseDatabase.getInstance();
myRef = database.getReference("Users")
.child(FirebaseAuth.getInstance().getCurrentUser().getUid()).child("Classes");
myRef.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(@NonNull DataSnapshot dataSnapshot, String s) {
list = new ArrayList<>();
String class_id = dataSnapshot.getValue(String.class);
myRef = database.getReference("Classes").child(class_id).child("class_info");
// StringBuffer stringbuffer = new StringBuffer();
myRef.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
Class_model new_class = dataSnapshot.getValue(Class_model.class);
assert new_class != null;
String nameofclass = new_class.getDate_clasname();
String teacherofclass = new_class.getTeacher();
String roomnumberofclass = new_class.getRoom_number();
String class_key = new_class.getUid();
Listdata listdata = new Listdata(nameofclass, teacherofclass, roomnumberofclass, class_key);
//String name = userdetails.getName();
//String email = userdetails.getEmail();
//String address = userdetails.getAddress();
listdata.setDate_class(nameofclass);
listdata.setTeacher(teacherofclass);
listdata.setRnumber(roomnumberofclass);
list.add(listdata);
// Toast.makeText(MainActivity.this,""+name,Toast.LENGTH_LONG).show();
}
@Override
public void onCancelled(DatabaseError error) {
AlertDialog alertDialog = new AlertDialog.Builder(getContext()).create();
alertDialog.setTitle("Error");
alertDialog.setMessage("Check your connection! If, problem persists please email svhsdev@vigoschools.org!");
alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
alertDialog.show();
}
});
RecyclerviewAdapter2 recycler = new RecyclerviewAdapter2(list);
RecyclerView.LayoutManager layoutmanager = new LinearLayoutManager(getContext());
recyclerview.setLayoutManager(layoutmanager);
recyclerview.setItemAnimator(new DefaultItemAnimator());
recyclerview.setAdapter(recycler);
}
@Override
public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
}
@Override
public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
}
@Override
public void onCancelled(DatabaseError error) {
AlertDialog alertDialog = new AlertDialog.Builder(getContext()).create();
alertDialog.setTitle("Error");
alertDialog.setMessage("Check your connection! If, problem persists please email svhsdev@vigoschools.org!");
alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
alertDialog.show();
}
});
return view;
}
@Override
public void onClick(View view) {
signout();
//startActivity(new Intent(home_fragment.this, LoginActivity.class));
}
public void signout(){
FirebaseAuth.getInstance().signOut();
Intent intent = new Intent(getContext(), LoginActivity.class);
startActivity(intent);
}
}
首先，Activity 获取类的 id，这些 id 存储在用户的类下，然后它获取类信息并将其显示在 recyclerview 中。 这是我的适配器的代码（这里应该没有问题）：
public class RecyclerviewAdapter2 extends RecyclerView.Adapter<RecyclerviewAdapter2.MyHolder>{
List<Listdata> listdata;
public RecyclerviewAdapter2(List<Listdata> listdata) {
this.listdata = listdata;
}
@Override
public RecyclerviewAdapter2.MyHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.cardview_class_model,parent,false);
RecyclerviewAdapter2.MyHolder myHolder = new RecyclerviewAdapter2.MyHolder(view);
return myHolder;
}
public void onBindViewHolder(RecyclerviewAdapter2.MyHolder holder, final int position) {
final Listdata data = listdata.get(position);
holder.vdate_class.setText(data.getDate_class());
holder.vteacher.setText(data.getTeacher());
holder.vrnumber.setText(data.getRnumber());
//System.out.println(data.getDate_class2());
holder.itemView.setOnClickListener(new View.OnClickListener()
{
@Override
public void onClick( final View view) {
Context context = view.getContext();
Intent intent = new Intent(context, Add_class_to_user.class);
intent.putExtra("date_class", listdata.get(position).getDate_class());
intent.putExtra("teacher", listdata.get(position).getTeacher());
intent.putExtra("room_number", listdata.get(position).getRnumber());
intent.putExtra("post_key", listdata.get(position).getUid());
context.startActivity(intent);
}
});
}
@Override
public int getItemCount() {
return listdata.size();
}
class MyHolder extends RecyclerView.ViewHolder{
TextView vdate_class , vteacher,vrnumber;
public MyHolder(View itemView) {
super(itemView);
vdate_class = (TextView) itemView.findViewById(R.id.date_class_name);
vteacher = (TextView) itemView.findViewById(R.id.teacher);
vrnumber = (TextView) itemView.findViewById(R.id.room_number);
}
}
}
谢谢您，如果您有任何问题，请告诉我！
【问题讨论】：
标签： android firebase android-fragments firebase-realtime-database android-recyclerview