Question

我无法解决现在刚出现的这个问题......一切都运转良好......这就是错误：

com.google.firebase.database.DatabaseException：无法将java.lang.String类型的对象转换为com.example.nicco.wallpapersapp.GridItem类型在com.google.android.gms.internal.zzbtg.zze（未知来源）在com.google.android.gms.internal.zzbtg.zzb（未知来源）在com.google.android.gms.internal.zzbtg.zza（未知来源）在com.google.firebase.database.DataSnapshot.getValue（未知来源）在com.firebase.ui.database.FirebaseRecyclerAdapter.parseSnapshot（FirebaseRecyclerAdapter.java:151）在com.firebase.ui.database.FirebaseRecyclerAdapter.getItem（FirebaseRecyclerAdapter.java:140）在com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder（FirebaseRecyclerAdapter.java:183）在android.support.v7.widget.RecyclerView $ Adapter.onBindViewHolder（RecyclerView.java:6482）在android.support.v7.widget.RecyclerView $ Adapter.bindViewHolder（RecyclerView.java:6515）在android.support.v7.widget.RecyclerView $ Recycler.tryBindViewHolderByDeadline（RecyclerView.java:5458）在android.support.v7.widget.RecyclerView $ Recycler.tryGetViewHolderForPositionByDeadline（RecyclerView.java:5724）在android.support.v7.widget.RecyclerView $ Recycler.getViewForPosition（RecyclerView.java:5563）在android.support.v7.widget.RecyclerView $ Recycler.getViewForPosition（RecyclerView.java:5559）在android.support.v7.widget.LinearLayoutManager $ LayoutState.next（LinearLayoutManager.java:2229）在android.support.v7.widget.LinearLayoutManager.layoutChunk（LinearLayoutManager.java:1556）在android.support.v7.widget.LinearLayoutManager.fill（LinearLayoutManager.java:1516）在android.support.v7.widget.LinearLayoutManager.onLayoutChildren（LinearLayoutManager.java:608）在android.support.v7.widget.RecyclerView.dispatchLayoutStep2（RecyclerView.java:3693）在android.support.v7.widget.RecyclerView.dispatchLayout（RecyclerView.java:3410）在android.support.v7.widget.RecyclerView.consumePendingUpdateOperations（RecyclerView.java:1710）在android.support.v7.widget.RecyclerView $ 1.run（RecyclerView.java:346）在android.view.Choreographer $ CallbackRecord.run（Choreographer.java:874）在android.view.Choreographer.doCallbacks（Choreographer.java:686）在android.view.Choreographer.doFrame（Choreographer.java:618）在android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:860）在android.os.Handler.handleCallback（Handler.java:751）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:154）在android.app.ActivityThread.main（ActivityThread.java:6119） at java.lang.reflect.Method.invoke（Native Method）在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:886）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:776）申请已终止。

我的班级：

public class HomePage extends AppCompatActivity {

private DrawerLayout mDraw;
private android.support.v7.app.ActionBarDrawerToggle mToggle;

private DatabaseReference mDatabase;

private RecyclerView recycler;

private Toolbar mToolbar;

private NavigationView nView;


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

    mDatabase = FirebaseDatabase.getInstance().getReference("landscape");

    recycler = findViewById(R.id.recyclerView);
    recycler.setLayoutManager(new LinearLayoutManager(this));
    //layoutManager = new GridLayoutManager(this,2);
    //recycler.setLayoutManager(layoutManager);
    recycler.setHasFixedSize(true);

    mToolbar = findViewById(R.id.toolbarNature);
    setSupportActionBar(mToolbar);
    getSupportActionBar().setTitle("Landscape Wallpapers");
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    mDraw = findViewById(R.id.drawerLayout);
    mToggle = new android.support.v7.app.ActionBarDrawerToggle(this, mDraw, mToolbar, R.string.open, R.string.close);

    mDraw.addDrawerListener(mToggle);
    mToggle.syncState();

    nView = findViewById(R.id.navigViewNature);

    nView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {

            int id = item.getItemId();

            if(id == R.id.landscape_area){

                startActivity(getIntent());
            }

            if(id == R.id.wallMoment){

                startActivity(new Intent(HomePage.this, AppMoment.class));
            }

            if(id == R.id.minimal_area){

                //startActivity(new Intent(AppMoment.this, AppMoment.class));
            }

            if(id == R.id.city_area){

                //startActivity(new Intent(AppMoment.this, AppMoment.class));
            }

            if(id == R.id.mountain_area){

                //startActivity(new Intent(AppMoment.this, AppMoment.class));
            }

            if(id == R.id.beach_area){

                //startActivity(new Intent(AppMoment.this, AppMoment.class));
            }

            if(id == R.id.sea_area){

                //startActivity(new Intent(AppMoment.this, AppMoment.class));
            }

            if(id == R.id.cars_area){

                //startActivity(new Intent(AppMoment.this, AppMoment.class));
            }

            if(id == R.id.bikes_area){

                //startActivity(new Intent(AppMoment.this, AppMoment.class));
            }

            return false;
        }
    });

}

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

    FirebaseRecyclerAdapter<GridItem, MyViewHoler> firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<GridItem, MyViewHoler>(

            GridItem.class,
            R.layout.gridview_item_layout,
            MyViewHoler.class,
            mDatabase
    ) {
        @Override
        protected void populateViewHolder(MyViewHoler viewHolder, GridItem model, int position) {

            final String imageData = getRef(position).getKey();

            viewHolder.setImage(getApplicationContext(), model.getImage());


        }
    };

    recycler.setAdapter(firebaseRecyclerAdapter);
    recycler.setHasFixedSize(true);

    }


public static class MyViewHoler extends RecyclerView.ViewHolder {

    View mView;


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

        mView = itemView;
    }

    public void setImage(Context ctx, String image){

        ImageView mImage = mView.findViewById(R.id.item_image);
        //Picasso.with(ctx).load(image).into(mImage);
        Glide.with(ctx).load(image).into(mImage);
    }
  }
}

我的GridItem类：

public class GridItem  {

   private String image;

   public GridItem(){

   }

public GridItem(String image) {
    this.image = image;
   }

public String getImage() {
    return image;
   }

public void setImage(String image) {
    this.image = image;
   }
 }

这是数据库：

wallpapaersapp
-beach
-bikes
-cars
-city
-landscape
        image: "https://firebasestorage.googleapis.com/v0/b/wal..."
-minimal
-mountain
-sea
-wallmoment

Answer 1

FirebaseUI正在执行您的查询，以查找要显示的GridItem下的子项列表。您的代码假设每个子项都可以映射到-landscape - child1 - image: "https://firebasestorage.googleapis.com/v0/b/wal..." - child2 - image: "https://firebasestorage.googleapis.com/v0/b/wal..."类型。

但是，现在，您的位置只有一个子元素，其值为String。单个String无法映射到Java对象。这就是你的错误来自哪里。更改数据库的结构以添加可以映射到数据模型的额外级别的子对象，或将FirebaseUI类型映射更改为String。

如果您想使用GridItem，您的数据库应如下所示：

CREATE Table #tempTable
    (
        Place VARCHAR(2),
        First1 INT,
        Second1 INT
    )

INSERT INTO #tempTable (Place,First1,Second1)
values ('A1',1,8),('A2',2,5),('B1',4,6),('B2',3,7)

SELECT * from #tempTable

From this:
Place   First1  Second1
A1      1       8
A2      2       5
B1      4       6
B2      3       7

To this:
        A1      A2      B1      B2
First1  1       2       4       3
Second1 8       5       6       7

Answer 2

只需在此处添加toString()

即可

viewHolder.setImage(getApplicationContext(), model.getImage().toString());

或者您可以导入毕加索并添加此

compile 'com.squareup.picasso:picasso:2.5.2'

然后

  @Override
        protected void populateViewHolder(MyViewHoler viewHolder, GridItem model, int position) {

            final String imageData = getRef(position).getKey();

           // viewHolder.setImage(getApplicationContext(), model.getImage());


        }
    };
Picasso.with(viewHolder.imageView.getContext()).load(model.getUrl()).into(viewHolder.imageView);  //where imageView is where you want to put your firebase image
                    }
                };

无法将java.lang.String类型的对象转换为com.example

2 个答案: