java - 我正在尝试使用 getter 和 setter 从我的 firebase 数据库中检索数据，但收到错误消息说无法转换对象

Question

我正在尝试创建一个组 Activity ，其中用户连接的所有组都可以通过此 Activity 显示。我已经创建了组 Activity 并在其中插入了回收器 View ，并尝试从数据库中检索数据，但不幸的是，当我在 Android 手机上运行应用程序时遇到错误。应用程序崩溃，在 logcat 中，我收到消息“无法将 java.lang.String 类型的对象转换为 com.nanb.alpha.modelclass 类型”。如果您不介意，请帮助我，以便我完成我的 Activity 。

下面的代码是用户可以创建群组的代码。

      private void groupmethos(final String groupname) {
    DatabaseReference groupref = rootref.child("Group").push();
    final String grouppushid = groupref.getKey();
    Map groupmap = new HashMap<>();
    groupmap.put("GroupprofileName",groupname);
    groupmap.put("Creater",currentUser.getUid());
    groupmap.put("StatusGroup","");
    groupmap.put("profileimage","");
    groupmap.put("id",grouppushid);
    rootref.child("Group").child(grouppushid).updateChildren(groupmap).addOnCompleteListener(new OnCompleteListener() {
        @Override
        public void onComplete(@NonNull Task task) {
            rootref.child("GroupMessage").child(grouppushid).setValue("").addOnCompleteListener(new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    if (task.isSuccessful()){
                        rootref.child("userconnectedtogroup").child(currentUser.getUid()).child(grouppushid).setValue("Added").addOnCompleteListener(new OnCompleteListener<Void>() {
                            @Override
                            public void onComplete(@NonNull Task<Void> task) {
                                Toast.makeText(MainActivity.this,groupname + "group Created successfully",Toast.LENGTH_SHORT).show();
                            }
                        });

                    }
                }
            });

        }
    });
  }

在上面的代码中，用户请求创建一个组。下面给出的是使用 getter 和 setter 从数据库获取数据的代码。

  package com.nanb.alpha;

public class modelclass {
private String GroupprofileName,StatusGroup,profileimage;

public modelclass() {
}

public modelclass(String groupprofileName, String statusGroup, String profileimage) {
    this.GroupprofileName = groupprofileName;
    this.StatusGroup = statusGroup;
    this.profileimage = profileimage;
}

public String getGroupprofileName() {
    return GroupprofileName;
}

public void setGroupprofileName(String groupprofileName) {
    GroupprofileName = groupprofileName;
}

public String getStatusGroup() {
    return StatusGroup;
}

public void setStatusGroup(String statusGroup) {
    StatusGroup = statusGroup;
}

public String getProfileimage() {
    return profileimage;
}

public void setProfileimage(String profileimage) {
    this.profileimage = profileimage;
}
}

给定的代码是 recyclerview 将值设置为给定布局的代码。

     public class group extends AppCompatActivity {

     private RecyclerView recyclerView;
     private DatabaseReference conref,groupref;
     private FirebaseAuth mAuth;
     private String Currentuserid;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_group);

    intialiation();
    mAuth = FirebaseAuth.getInstance();
    Currentuserid = mAuth.getCurrentUser().getUid();
    conref = FirebaseDatabase.getInstance().getReference().child("userconnectedtogroup").child(Currentuserid);
    groupref = FirebaseDatabase.getInstance().getReference().child("Group");
    }

    private void intialiation() {
    recyclerView = findViewById(R.id.recyclerview);
    LinearLayoutManager layoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(layoutManager);
    }

     @Override
     protected void onStart() {
    super.onStart();
    FirebaseRecyclerOptions option = new FirebaseRecyclerOptions.Builder<modelclass>().setQuery(conref,modelclass.class).build();

    FirebaseRecyclerAdapter<modelclass,group_viewHolder> adapter = new FirebaseRecyclerAdapter<modelclass, group_viewHolder>(option) {
        @Override
        protected void onBindViewHolder(@NonNull final group_viewHolder group_viewHolder, int i, @NonNull modelclass modelclass) {
            String userid = getRef(i).getKey();
            groupref.child(userid).addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                  if(dataSnapshot.hasChild("profileimage")){
                      String profileimage = dataSnapshot.child("profileimage").getValue().toString();
                      String groupname = dataSnapshot.child("GroupprofileName").getValue().toString();
                      String groupStatus = dataSnapshot.child("StatusGroup").getValue().toString();

                      group_viewHolder.groupname.setText(groupname);
                      group_viewHolder.groupStatus.setText(groupStatus);
                      Picasso.get().load(profileimage).into(group_viewHolder.profileimage);
                  }else{
                      String groupname = dataSnapshot.child("GroupprofileName").getValue().toString();
                      String groupStatus = dataSnapshot.child("StatusGroup").getValue().toString();

                      group_viewHolder.groupname.setText(groupname);
                      group_viewHolder.groupStatus.setText(groupStatus);
                      Picasso.get().load(R.mipmap.groupicon).into(group_viewHolder.profileimage);
                  }
                }

                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) {

                }
            });
        }

        @NonNull
        @Override
        public group_viewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
           View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.grouplayout,parent,false);
           group_viewHolder groupholder = new group_viewHolder(view);
            return groupholder;
        }
    };
    recyclerView.setAdapter(adapter);
    adapter.startListening();
    }

    public static class group_viewHolder extends RecyclerView.ViewHolder{
    TextView groupname,groupStatus;
    CircleImageView profileimage;
    public group_viewHolder(@NonNull View itemView) {
        super(itemView);
        groupname = itemView.findViewById(R.id.Group_name);
        groupStatus = itemView.findViewById(R.id.Group_Status);
        profileimage = itemView.findViewById(R.id.group_profile_dp);
    }
    }
    }

下面给出的是我的 Firebase 数据库的图像。其中显示了与团体 Activity 相关的所有结构。

下面是应用程序崩溃后显示的 logcat 消息。

com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.nanb.alpha.modelclass at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(com.google.firebase:firebase-database@@19.1.0:418) at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(com.google.firebase:firebase-database@@19.1.0:214) at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(com.google.firebase:firebase-database@@19.1.0:79) at com.google.firebase.database.DataSnapshot.getValue(com.google.firebase:firebase-database@@19.1.0:203) at com.firebase.ui.database.ClassSnapshotParser.parseSnapshot(ClassSnapshotParser.java:29) at com.firebase.ui.database.ClassSnapshotParser.parseSnapshot(ClassSnapshotParser.java:15) at com.firebase.ui.common.BaseCachingSnapshotParser.parseSnapshot(BaseCachingSnapshotParser.java:35) at com.firebase.ui.common.BaseObservableSnapshotArray.get(BaseObservableSnapshotArray.java:52) at com.firebase.ui.database.FirebaseRecyclerAdapter.getItem(FirebaseRecyclerAdapter.java:106) at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:122) at androidx.recyclerview.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6781) at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6823) at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5752) at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6019) at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5858) at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5854) at androidx.recyclerview.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2230) at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1557) at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1517) at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:612) at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3924) at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3641) at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4194) at android.view.View.layout(View.java:15689) at android.view.ViewGroup.layout(ViewGroup.java:5048) at androidx.constraintlayout.widget.ConstraintLayout.onLayout(ConstraintLayout.java:1915) at android.view.View.layout(View.java:15689) at android.view.ViewGroup.layout(ViewGroup.java:5048) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579) at android.widget.FrameLayout.onLayout(FrameLayout.java:514) at android.view.View.layout(View.java:15689) at android.view.ViewGroup.layout(ViewGroup.java:5048) at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703) at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557) at android.widget.LinearLayout.onLayout(LinearLayout.java:1466) at android.view.View.layout(View.java:15689) at android.view.ViewGroup.layout(ViewGroup.java:5048) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579) at android.widget.FrameLayout.onLayout(FrameLayout.java:514) at android.view.View.layout(View.java:15689) at android.view.ViewGroup.layout(ViewGroup.java:5048) at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1703) at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1557) at android.widget.LinearLayout.onLayout(LinearLayout.java:1466) at android.view.View.layout(View.java:15689) at android.view.ViewGroup.layout(ViewGroup.java:5048) at android.widget.FrameLayout.layoutChildren(FrameLayout.java:579) at android.widget.FrameLayout.onLayout(FrameLayout.java:514) at android

Answer 1

在选项对象中使用 groupref 而不是 conref