无法将java.lang.String类型的对象转换为类型 - Firebase错误

Question

它的firebase错误我无法得到它请帮助我解决并告诉我它发生的原因。对不起英语并尝试解决它

    E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.example.kunalgharate.weedon, PID: 16793
              com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.example.kunalgharate.weedon.Friends
                  at com.google.android.gms.internal.zg.zzb(Unknown Source)
                  at com.google.android.gms.internal.zg.zza(Unknown Source)
                  at com.google.firebase.database.DataSnapshot.getValue(Unknown Source)
                  at com.firebase.ui.database.ClassSnapshotParser.parseSnapshot(ClassSnapshotParser.java:22)
                  at com.firebase.ui.database.ObservableSnapshotArray.getObject(ObservableSnapshotArray.java:160)
                  at com.firebase.ui.database.CachingObservableSnapshotArray.getObject(CachingObservableSnapshotArray.java:40)
                  at com.firebase.ui.database.FirebaseRecyclerAdapter.getItem(FirebaseRecyclerAdapter.java:180)
                  at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:217)
                  at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6482)
                  at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6515)
                  at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5458)
                  at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5724)
                  at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5563)
                  at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5559)
                  at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2229)
                  at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1556)
                  at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1516)
                  at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:608)
                  at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3693)
                  at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3410)
                  at android.support.v7.widget.RecyclerView.consumePendingUpdateOperations(RecyclerView.java:1710)
                  at android.support.v7.widget.RecyclerView$1.run(RecyclerView.java:346)
                  at android.view.Choreographer$CallbackRecord.run(Choreographer.java:871)
                  at android.view.Choreographer.doCallbacks(Choreographer.java:683)
                  at android.view.Choreographer.doFrame(Choreographer.java:616)
                  at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:857)
                  at android.os.Handler.handleCallback(Handler.java:751)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:154)
                  at android.app.ActivityThread.main(ActivityThread.java:6123)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:757)

申请终止。

活动主要

import android.content.Context;
import android.content.Intent;
import android.os.Build;
import android.support.design.widget.TabLayout;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.squareup.picasso.Picasso;

import de.hdodenhof.circleimageview.CircleImageView;

public class MainActivity extends AppCompatActivity {
    private FirebaseAuth mAuth;
    RecyclerView mSubsList;
    DatabaseReference mFriendsDatabase;
    DatabaseReference mUsersDatabase;
    private String mCurrent_user_id;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Toolbar toolbar = findViewById(R.id.main_page_toolbar);
        setSupportActionBar(toolbar);
         getSupportActionBar().setTitle("WeedON");
        mAuth = FirebaseAuth.getInstance();
        mCurrent_user_id = mAuth.getCurrentUser().getUid();
        mSubsList =findViewById(R.id.subscribes_list);
        mSubsList.setHasFixedSize(true);
        mSubsList.setLayoutManager(new LinearLayoutManager(this));


        mFriendsDatabase = FirebaseDatabase.getInstance().getReference().child("subscribers").child(mCurrent_user_id);
        mFriendsDatabase.keepSynced(true);
        mUsersDatabase = FirebaseDatabase.getInstance().getReference().child("Users");
        mUsersDatabase.keepSynced(true);




    }

    private void signOut() {
        mAuth.signOut();
    }


    @Override
    protected void onStart() {
        super.onStart();

        FirebaseRecyclerAdapter<Friends,MainViewHolder> firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Friends,MainViewHolder>(


                Friends.class,
                R.layout.single_service_layout,
                MainViewHolder.class,
                mFriendsDatabase
                )
        {
            @Override
            protected void populateViewHolder(MainViewHolder viewHolder, Friends model, int position) {



            }
        };

       mSubsList.setAdapter(firebaseRecyclerAdapter);
        }





    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);

        getMenuInflater().inflate(R.menu.main_menu, menu);

        return true;
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        super.onOptionsItemSelected(item);

        if(item.getItemId() == R.id.main_logout_btn){

          //  mUserRef.child("online").setValue(ServerValue.TIMESTAMP);

            signOut();
            Intent intent = new Intent(this, LoginActivity.class);
            startActivity(intent);
            finish();
         //   sendToStart();

        }

        if(item.getItemId() == R.id.main_settings_btn){

            Intent settingsIntent = new Intent(MainActivity.this, SettingsActivity.class);
            startActivity(settingsIntent);

        }

        if(item.getItemId() == R.id.main_all_btn){

            Intent settingsIntent = new Intent(MainActivity.this, AllServicesActivity.class);
            startActivity(settingsIntent);

        }

        return true;
    }

    public static class MainViewHolder extends RecyclerView.ViewHolder{

        View mView;

        public MainViewHolder(View itemView) {
            super(itemView);

            mView =itemView;
        }


    }



}

数据库截图

enter image description here

它没有显示布局错误或代码错误我该怎么办？

Answer 1

通过查看您的数据库，我可以看到您的mFriendsDatabase DatabseReference指向某些'String'值，并且您告诉您的firebaseRecyclerAdapter那些类型为'Friends，这就是抛出异常的原因。大多数情况下您可能在保存时出错了数据库的值，而不是保存您保存一些字符串值的Friends对象。但如果不是这样，您可以将firebaseRecyclerAdapter更改为此...

FirebaseRecyclerAdapter<String,MainViewHolder> firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<String,MainViewHolder>(


            String.class,
            R.layout.single_service_layout,
            MainViewHolder.class,
            mFriendsDatabase
            )
    {
        @Override
        protected void populateViewHolder(MainViewHolder viewHolder, String mString, int position) {
          Log.d("TAG",mString);
        }
    };

   mSubsList.setAdapter(firebaseRecyclerAdapter);

Answer 2

要显示这些消息，请使用以下代码：

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference uidRef = rootRef.child("subscribers").child(mCurrent_user_id);
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String message = ds.getValue(String.class);
            Log.d("TAG", message);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
uidRef.addListenerForSingleValueEvent(eventListener);