我的带有 FirebaseRecyclerAdapter 的 RecyclerView 没有在屏幕上显示任何内容
My RecyclerView with FirebaseRecyclerAdapter does not show anything on screen
我不确定为什么 RecyclerView 没有在 UI 上显示任何图像或数据。
JSON Structure of Firebase database
这是我的 Firebase 数据库的结构图 table
CategoryFragment.java
这是我使用 FirebaseRecyclerAdapter 配置 RecyclerView 的片段。在这里我想那个错误在哪里，但我找不到它。
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.example.abdullah.livewallpapers.Interface.ItemClickListener;
import com.example.abdullah.livewallpapers.Model.CategoryItem;
import com.example.abdullah.livewallpapers.R;
import com.example.abdullah.livewallpapers.Viewholder.CategoryViewholder;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.firebase.ui.database.FirebaseRecyclerOptions;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.squareup.picasso.Callback;
import com.squareup.picasso.NetworkPolicy;
import com.squareup.picasso.Picasso;
import java.util.List;
/**
* A simple {@link Fragment} subclass.
*/
public class CategoryFragment extends Fragment {
private static final String STR_CATEGORY_BACKGROUND = "CategoryBackground";
DatabaseReference categoryBackground;
FirebaseDatabase database;
FirebaseRecyclerOptions<CategoryItem> options;
FirebaseRecyclerAdapter<CategoryItem,CategoryViewholder> adapter;
RecyclerView recyclerView;
private static CategoryFragment INSTANCE = null;
public CategoryFragment() {
database = FirebaseDatabase.getInstance();
categoryBackground = database.getReference(STR_CATEGORY_BACKGROUND);
options = new FirebaseRecyclerOptions.Builder<CategoryItem>()
.setQuery(categoryBackground,CategoryItem.class)
.build();
adapter = new FirebaseRecyclerAdapter<CategoryItem, CategoryViewholder>(options) {
@Override
protected void onBindViewHolder(@NonNull final CategoryViewholder holder, int position, @NonNull final CategoryItem model) {
Picasso.with(getActivity())
.load(model.getImageLink())
.networkPolicy(NetworkPolicy.OFFLINE)
.into(holder.backgroud_image, new Callback(){
@Override
public void onSuccess() {
}
@Override
public void onError() {
Picasso.with(getActivity())
.load(model.getImageLink())
.error(R.drawable.ic_terrain_black_24dp)
.into(holder.backgroud_image, new Callback() {
@Override
public void onSuccess() {
}
@Override
public void onError() {
Log.i("category_error","error comes");
}
});
}
} );
holder.category_name.setText(model.getName());
holder.setItemClickListener(new ItemClickListener() {
@Override
public void onClick(View view, int postion) {
}
});
}
@NonNull
@Override
public CategoryViewholder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
View itemView = LayoutInflater.from(viewGroup.getContext())
.inflate(R.layout.layout_category_item,viewGroup,false);
return new CategoryViewholder(itemView);
}
};
}
private void setCategory() {
adapter.startListening();
recyclerView.setAdapter(adapter);
}
@Override
public void onStart() {
super.onStart();
if (adapter!=null)
adapter.startListening();
}
@Override
public void onStop() {
super.onStop();
if (adapter!=null)
adapter.stopListening();
}
@Override
public void onResume() {
super.onResume();
if (adapter!=null)
adapter.startListening();
}
public static CategoryFragment getInstance() {
if (INSTANCE == null)
INSTANCE = new CategoryFragment();
return INSTANCE;
}
@Override
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_category, container, false);
recyclerView = (RecyclerView)view.findViewById(R.id.category_recyclerview);
recyclerView.setHasFixedSize(true);
GridLayoutManager gridLayoutManager = new GridLayoutManager(getActivity(),2);
recyclerView.setLayoutManager(gridLayoutManager);
setCategory();
return view;
}
}
类别项目
public class CategoryItem {
public String Name;
public String ImageLink;
public CategoryItem() {
}
public CategoryItem(String name, String imageLink) {
Name = name;
ImageLink = imageLink;
}
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
public String getImageLink() {
return ImageLink;
}
public void setImageLink(String imageLink) {
ImageLink = imageLink;
}
}
来自 Logcat
的错误
这些是 logcat 中出现的错误。
com.google.firebase.database.DatabaseException: Found two getters or fields with conflicting case sensitivity for property: imagelink
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper$BeanMapper.addProperty(com.google.firebase:firebase-database@@16.0.6:545)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper$BeanMapper.<init>(com.google.firebase:firebase-database@@16.0.6:476)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.loadOrCreateBeanMapperForClass(com.google.firebase:firebase-database@@16.0.6:317)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(com.google.firebase:firebase-database@@16.0.6:418)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(com.google.firebase:firebase-database@@16.0.6:214)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(com.google.firebase:firebase-database@@16.0.6:79)
at com.google.firebase.database.DataSnapshot.getValue(com.google.firebase:firebase-database@@16.0.6:212)
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 android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6781)
at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6823)
at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5752)
at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6019)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5858)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5854)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2230)
at android.support.v7.widget.GridLayoutManager.layoutChunk(GridLayoutManager.java:557)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1517)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:612)
at android.support.v7.widget.GridLayoutManager.onLayoutChildren(GridLayoutManager.java:171)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3924)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3641)
at android.support.v7.widget.RecyclerView.consumePendingUpdateOperations(RecyclerView.java:1888)
at android.support.v7.widget.RecyclerView.run(RecyclerView.java:407)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
at android.view.Choreographer.doCallbacks(Choreographer.java:555)
at android.view.Choreographer.doFrame(Choreographer.java:524)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4960)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
at dalvik.system.NativeStart.main(Native Method)
V/FA: Activity resumed, time: 5548276
I/Process: Sending signal. PID: 8700 SIG: 9
Application terminated.
您的 POJO 混淆了 Firebase SDK public仅公开了具有相同名称的 属性 和 getter：imageLink
public class CategoryItem {
public String ImageLink;
// ...
public String getImageLink() {
return ImageLink;
}
// ...
}
不知道使用哪一个，因为它们具有相同的名称。您应该做的是将字段设为私有，并保留访问器 public，因此不会有两个 public 同名的东西：
public class CategoryItem {
private String Name;
private String ImageLink;
// ...
}
这是创建 POJO 类型对象的标准方法。
我不确定为什么 RecyclerView 没有在 UI 上显示任何图像或数据。
JSON Structure of Firebase database
这是我的 Firebase 数据库的结构图 table
CategoryFragment.java
这是我使用 FirebaseRecyclerAdapter 配置 RecyclerView 的片段。在这里我想那个错误在哪里，但我找不到它。
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.example.abdullah.livewallpapers.Interface.ItemClickListener;
import com.example.abdullah.livewallpapers.Model.CategoryItem;
import com.example.abdullah.livewallpapers.R;
import com.example.abdullah.livewallpapers.Viewholder.CategoryViewholder;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.firebase.ui.database.FirebaseRecyclerOptions;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.squareup.picasso.Callback;
import com.squareup.picasso.NetworkPolicy;
import com.squareup.picasso.Picasso;
import java.util.List;
/**
* A simple {@link Fragment} subclass.
*/
public class CategoryFragment extends Fragment {
private static final String STR_CATEGORY_BACKGROUND = "CategoryBackground";
DatabaseReference categoryBackground;
FirebaseDatabase database;
FirebaseRecyclerOptions<CategoryItem> options;
FirebaseRecyclerAdapter<CategoryItem,CategoryViewholder> adapter;
RecyclerView recyclerView;
private static CategoryFragment INSTANCE = null;
public CategoryFragment() {
database = FirebaseDatabase.getInstance();
categoryBackground = database.getReference(STR_CATEGORY_BACKGROUND);
options = new FirebaseRecyclerOptions.Builder<CategoryItem>()
.setQuery(categoryBackground,CategoryItem.class)
.build();
adapter = new FirebaseRecyclerAdapter<CategoryItem, CategoryViewholder>(options) {
@Override
protected void onBindViewHolder(@NonNull final CategoryViewholder holder, int position, @NonNull final CategoryItem model) {
Picasso.with(getActivity())
.load(model.getImageLink())
.networkPolicy(NetworkPolicy.OFFLINE)
.into(holder.backgroud_image, new Callback(){
@Override
public void onSuccess() {
}
@Override
public void onError() {
Picasso.with(getActivity())
.load(model.getImageLink())
.error(R.drawable.ic_terrain_black_24dp)
.into(holder.backgroud_image, new Callback() {
@Override
public void onSuccess() {
}
@Override
public void onError() {
Log.i("category_error","error comes");
}
});
}
} );
holder.category_name.setText(model.getName());
holder.setItemClickListener(new ItemClickListener() {
@Override
public void onClick(View view, int postion) {
}
});
}
@NonNull
@Override
public CategoryViewholder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
View itemView = LayoutInflater.from(viewGroup.getContext())
.inflate(R.layout.layout_category_item,viewGroup,false);
return new CategoryViewholder(itemView);
}
};
}
private void setCategory() {
adapter.startListening();
recyclerView.setAdapter(adapter);
}
@Override
public void onStart() {
super.onStart();
if (adapter!=null)
adapter.startListening();
}
@Override
public void onStop() {
super.onStop();
if (adapter!=null)
adapter.stopListening();
}
@Override
public void onResume() {
super.onResume();
if (adapter!=null)
adapter.startListening();
}
public static CategoryFragment getInstance() {
if (INSTANCE == null)
INSTANCE = new CategoryFragment();
return INSTANCE;
}
@Override
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_category, container, false);
recyclerView = (RecyclerView)view.findViewById(R.id.category_recyclerview);
recyclerView.setHasFixedSize(true);
GridLayoutManager gridLayoutManager = new GridLayoutManager(getActivity(),2);
recyclerView.setLayoutManager(gridLayoutManager);
setCategory();
return view;
}
}
类别项目
public class CategoryItem {
public String Name;
public String ImageLink;
public CategoryItem() {
}
public CategoryItem(String name, String imageLink) {
Name = name;
ImageLink = imageLink;
}
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
public String getImageLink() {
return ImageLink;
}
public void setImageLink(String imageLink) {
ImageLink = imageLink;
}
}
来自 Logcat
的错误这些是 logcat 中出现的错误。
com.google.firebase.database.DatabaseException: Found two getters or fields with conflicting case sensitivity for property: imagelink
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper$BeanMapper.addProperty(com.google.firebase:firebase-database@@16.0.6:545)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper$BeanMapper.<init>(com.google.firebase:firebase-database@@16.0.6:476)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.loadOrCreateBeanMapperForClass(com.google.firebase:firebase-database@@16.0.6:317)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(com.google.firebase:firebase-database@@16.0.6:418)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(com.google.firebase:firebase-database@@16.0.6:214)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(com.google.firebase:firebase-database@@16.0.6:79)
at com.google.firebase.database.DataSnapshot.getValue(com.google.firebase:firebase-database@@16.0.6:212)
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 android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6781)
at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6823)
at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5752)
at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6019)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5858)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5854)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2230)
at android.support.v7.widget.GridLayoutManager.layoutChunk(GridLayoutManager.java:557)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1517)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:612)
at android.support.v7.widget.GridLayoutManager.onLayoutChildren(GridLayoutManager.java:171)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3924)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3641)
at android.support.v7.widget.RecyclerView.consumePendingUpdateOperations(RecyclerView.java:1888)
at android.support.v7.widget.RecyclerView.run(RecyclerView.java:407)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
at android.view.Choreographer.doCallbacks(Choreographer.java:555)
at android.view.Choreographer.doFrame(Choreographer.java:524)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4960)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
at dalvik.system.NativeStart.main(Native Method)
V/FA: Activity resumed, time: 5548276
I/Process: Sending signal. PID: 8700 SIG: 9
Application terminated.
您的 POJO 混淆了 Firebase SDK public仅公开了具有相同名称的 属性 和 getter：imageLink
public class CategoryItem {
public String ImageLink;
// ...
public String getImageLink() {
return ImageLink;
}
// ...
}
不知道使用哪一个，因为它们具有相同的名称。您应该做的是将字段设为私有，并保留访问器 public，因此不会有两个 public 同名的东西：
public class CategoryItem {
private String Name;
private String ImageLink;
// ...
}
这是创建 POJO 类型对象的标准方法。