英文:
Firebase data won't load in my RecyclerView
问题
The screen launches but doesn't throw any errors or bugs. I just launch the blank recycler view as if it's not reading any of the Java codes, although they are in my manifest. I've tried bumping the Firebase path down to "Book," but then I receive a `can't convert object to java.lang.string` error.
**Main activity**
public class BarberView extends AppCompatActivity {
private ArrayList<Book> books;
private List<String> key;
private Context mContext;
private static final String TAG = "RealtimeDatabaseDemo";
private MyViewHolder adapter;
private TextView list_u, list_p, list_d, list_t, list_c;
DatabaseReference ref;
private FirebaseRecyclerOptions<Book> options;
RecyclerView recyclerView;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.barber_view);
recyclerView = findViewById(R.id.list_jobs);
recyclerView.setHasFixedSize(false);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
ref = FirebaseDatabase.getInstance().getReference();
Query query = ref.child("gregs-281717");
final FirebaseRecyclerOptions<Book> options = new FirebaseRecyclerOptions.Builder<Book>()
.setQuery(query, Book.class)
.setLifecycleOwner(this)
.build();
adapter = new MyViewHolder(options);
recyclerView.setAdapter(adapter);
query.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
for (DataSnapshot mdatasnapshot : snapshot.getChildren()) {
Book mbook = new Book();
mbook.setTime(mdatasnapshot.getValue().toString());
mbook.setDates(mdatasnapshot.getValue().toString());
mbook.setPayDone(mdatasnapshot.getValue().toString());
mbook.setCutDone(mdatasnapshot.getValue().toString());
mbook.setUser_id(mdatasnapshot.getValue().toString());
books.add(mbook);
}
adapter = new MyViewHolder(options);
adapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
}
@Override
public void onStart() {
super.onStart();
adapter.startListening();
adapter.notifyDataSetChanged();
}
@Override
protected void onStop() {
super.onStop();
adapter.startListening();
adapter.notifyDataSetChanged();
}
}
**ViewHolder**
public class MyViewHolder extends FirebaseRecyclerAdapter<Book, MyViewHolder.Holder> {
public MyViewHolder(@NonNull FirebaseRecyclerOptions<Book> options) {
super(options);
}
@Override
protected void onBindViewHolder(@NonNull Holder holder, int position, @NonNull Book book) {
holder.list_u.setText(book.getUser_id());
holder.list_c.setText(book.getCutDone());
holder.list_d.setText(book.getDates());
holder.list_t.setText(book.getTime());
holder.list_p.setText(book.getPayDone());
}
@NonNull
@Override
public Holder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext())
.inflate(R.layout.list_item, parent, false);
return new Holder(view);
}
class Holder extends RecyclerView.ViewHolder {
public TextView list_u, list_p, list_d, list_t, list_c;
public Holder(@NonNull View itemView) {
super(itemView);
list_u = itemView.findViewById(R.id.list_user);
list_p = itemView.findViewById(R.id.list_price);
list_d = itemView.findViewById(R.id.list_date);
list_t = itemView.findViewById(R.id.list_time);
list_c = itemView.findViewById(R.id.list_cut);
}
}
}
**Model**
import com.google.firebase.database.IgnoreExtraProperties;
import org.jetbrains.annotations.NotNull;
@IgnoreExtraProperties
public class Book {
public String time;
public String dates;
public String payDone;
public String cutDone;
public String user_id;
public Book() {
}
@NotNull
@Override
public String toString() {
return "Book{" +
"time='" + time + '\'' +
", dates='" + dates + '\'' +
", payDone='" + payDone + '\'' +
", cutDone='" + cutDone + '\'' +
", user_id='" + user_id + '\'' +
'}';
}
public Book(String time, String dates, String cutDone, String payDone, String user_id) {
this.time = time;
this.dates = dates;
this.payDone = payDone;
this.cutDone = cutDone;
this.user_id = user_id;
}
public String getTime() {
return time;
}
public void setTime(String time) {
this.time = time;
}
public String getDates() {
return dates;
}
public void setDates(String dates) {
this.dates = dates;
}
public String getPayDone() {
return payDone;
}
public void setPayDone(String payDone) {
this.payDone = payDone;
}
public String getCutDone() {
return cutDone;
}
public void setCutDone(String cutDone) {
this.cutDone = cutDone;
}
public String getUser_id() {
return user_id;
}
public void setUser_id(String user_id) {
this.user_id = user_id;
}
}
**RecyelerView.xml**
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BarberView">
<androidx.recyclerview.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/list_jobs"/>
</androidx.constraintlayout.widget.ConstraintLayout>
**List.XML**
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="16dp"
android:id="@+id/list_books">
<TextView
android:textColor="#000000"
android:id="@+id/list_cut"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/list_price"
android:layout_width="62dp"
android:layout_height="19dp"
android:text="TextView"
android:textSize="14sp"
android:textColor="#000000"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/list_date"
app:layout_constraintStart_toEndOf="@+id/list_cut"
app:layout_constraintTop_toTopOf="parent
<details>
<summary>英文:</summary>
The screen launches but doesn't throw any errors or bugs I just launch the blank recycler view as if it's not reading any of the java codes although they are in my manifest. I've tried bumping the firebase path down on to "Book" but then I receive a `can't convert object to java.lang.string` error.
**Main activity**
public class BarberView extends AppCompatActivity {
private ArrayList<Book> books ;
private List<String> key;
private Context mContext;
private static final String TAG = "RealtimeDatabaseDemo";
private MyViewHolder adapter;
private TextView list_u, list_p, list_d, list_t, list_c;
DatabaseReference ref;
private FirebaseRecyclerOptions<Book> options;
/**
* Get the last 50 chat messages.
*/
RecyclerView recyclerView;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate ( savedInstanceState );
setContentView ( R.layout.barber_view );
recyclerView =findViewById ( R.id.list_jobs );
recyclerView.setHasFixedSize ( false );
recyclerView.setLayoutManager ( new LinearLayoutManager ( this ) );
ref = FirebaseDatabase.getInstance ( ).getReference ( );
Query query = ref.child ( "gregs-281717" );
final FirebaseRecyclerOptions<Book> options=new FirebaseRecyclerOptions.Builder<Book> ( )
.setQuery ( query, Book.class )
.setLifecycleOwner ( this )
.build ( );
adapter = new MyViewHolder ( options );
recyclerView.setAdapter ( adapter );
query.addValueEventListener ( new ValueEventListener ( ) {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
for (DataSnapshot mdatasnapshot: snapshot.getChildren()) {
Book mbook =new Book();
mbook.setTime( mdatasnapshot.getValue ( ).toString () );
mbook.setDates( mdatasnapshot.getValue ( ).toString () );
mbook.setPayDone( mdatasnapshot.getValue ( ).toString () );
mbook.setCutDone( mdatasnapshot.getValue ( ).toString () );
mbook.setUser_id( mdatasnapshot.getValue ( ).toString () );
books.add(mbook);
}
adapter = new MyViewHolder (options );
adapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
}
@Override
public void onStart() {
super.onStart ( );
adapter.startListening ();
adapter.notifyDataSetChanged();
}
@Override
protected void onStop() {
super.onStop ( );
adapter.startListening ();
adapter.notifyDataSetChanged();
}
}
**ViewHolder**
public class MyViewHolder extends FirebaseRecyclerAdapter<Book, MyViewHolder.Holder> {
/**
* Initialize a {@link RecyclerView.Adapter} that listens to a Firebase query. See
* {@link FirebaseRecyclerOptions} for configuration options.
*
* @param options
*/
public MyViewHolder(@NonNull FirebaseRecyclerOptions<Book> options) {
super ( options );
}
@Override
protected void onBindViewHolder(@NonNull Holder holder, int position, @NonNull Book book) {
holder.list_u.setText ( book.getUser_id () );
holder.list_c.setText ( book.getCutDone () );
holder.list_d.setText ( book.getDates () );
holder.list_t.setText ( book.getTime () );
holder.list_p.setText ( book.getPayDone () );
}
@NonNull
@Override
public Holder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from ( parent.getContext ( ) )
.inflate ( R.layout.list_item, parent, false );
return new Holder ( view );
}
class Holder extends RecyclerView.ViewHolder{
public TextView list_u, list_p, list_d, list_t, list_c;
public Holder(@NonNull View itemView) {
super(itemView);
list_u = itemView.findViewById ( R.id.list_user );
list_p = itemView.findViewById ( R.id.list_price );
list_d = itemView.findViewById ( R.id.list_date );
list_t = itemView.findViewById ( R.id.list_time );
list_c = itemView.findViewById ( R.id.list_cut );
}}
}
**Model**
import com.google.firebase.database.IgnoreExtraProperties;
import org.jetbrains.annotations.NotNull;
@IgnoreExtraProperties
public class Book {
public String time;
public String dates;
public String payDone;
public String cutDone;
public String user_id;
public Book() {
}
@NotNull
@Override
public String toString() {
return "Book{" +
"time='" + time + '\'' +
", dates='" + dates + '\'' +
", payDone='" + payDone + '\'' +
", cutDone='" + cutDone + '\'' +
", user_id='" + user_id + '\'' +
'}';
}
public Book(String time, String dates, String cutDone, String payDone, String user_id) {
this.time = time;
this.dates = dates;
this.payDone = payDone;
this.cutDone = cutDone;
this.user_id = user_id;
}
public String getTime() {
return time;
}
public void setTime(String time) {
this.time = time;
}
public String getDates() {
return dates;
}
public void setDates(String dates) {
this.dates = dates;
}
public String getPayDone() {
return payDone;
}
public void setPayDone(String payDone) {
this.payDone = payDone;
}
public String getCutDone() {
return cutDone;
}
public void setCutDone(String cutDone) {
this.cutDone = cutDone;
}
public String getUser_id() {
return user_id;
}
public void setUser_id(String user_id) {
this.user_id = user_id;
}
}
**RecyelerView.xml**
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".BarberView">
<androidx.recyclerview.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/list_jobs"/>
</androidx.constraintlayout.widget.ConstraintLayout>
**List.XML**
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="16dp"
android:id="@+id/list_books">
<TextView
android:textColor="#000000"
android:id="@+id/list_cut"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/list_price"
android:layout_width="62dp"
android:layout_height="19dp"
android:text="TextView"
android:textSize="14sp"
android:textColor="#000000"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/list_date"
app:layout_constraintStart_toEndOf="@+id/list_cut"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/list_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
android:textColor="#000000"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:ignore="MissingConstraints" />
<TextView
android:id="@+id/list_date"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
android:textColor="#000000"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/list_user"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
android:textColor="#000000"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/list_time"
app:layout_constraintStart_toEndOf="@+id/list_date"
app:layout_constraintTop_toTopOf="parent" />
**gregs-281717.jason Firebase realtime database**
{
"Book" : {
"cutDone" : "cut1",
"dates" : "11/9/2020",
"payDone" : "20.00",
"time" : "03:36AM",
"user_id" : "notme@badcode.com"
}
}
</details>
# 答案1
**得分**: 0
你应该在从Firebase加载数据后，在你的主活动中设置适配器，就像这样：
```java
public class BarberView extends AppCompatActivity {
private ArrayList<Book> books;
private List<String> key;
private Context mContext;
private static final String TAG = "RealtimeDatabaseDemo";
private MyViewHolder adapter;
private TextView list_u, list_p, list_d, list_t, list_c;
DatabaseReference ref;
private FirebaseRecyclerOptions<Book> options;
RecyclerView recyclerView;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.barber_view);
recyclerView = findViewById(R.id.list_jobs);
recyclerView.setHasFixedSize(false);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
ref = FirebaseDatabase.getInstance().getReference();
Query query = ref.child("gregs-281717");
final FirebaseRecyclerOptions<Book> options = new FirebaseRecyclerOptions.Builder<Book>()
.setQuery(query, Book.class)
.setLifecycleOwner(this)
.build();
query.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
for (DataSnapshot mdatasnapshot : snapshot.getChildren()) {
Book mbook = new Book();
mbook.setTime(mdatasnapshot.child("Book").getValue(true).toString());
mbook.setDates(mdatasnapshot.getValue(true).toString());
mbook.setPayDone(mdatasnapshot.getValue(true).toString());
mbook.setCutDone(mdatasnapshot.getValue(true).toString());
mbook.setUser_id(mdatasnapshot.getValue(true).toString());
}
adapter = new MyViewHolder(options);
recyclerView.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
}
@Override
public void onStart() {
super.onStart();
recyclerView.setAdapter(adapter);
}
@Override
protected void onStop() {
super.onStop();
recyclerView.setAdapter(adapter);
}
}
英文:
You should set your adapter after loading data from firebase in your main activity
like this :-
public class BarberView extends AppCompatActivity {
private ArrayList<Book> books ;
private List<String> key;
private Context mContext;
private static final String TAG = "RealtimeDatabaseDemo";
private MyViewHolder adapter;
private TextView list_u, list_p, list_d, list_t, list_c;
DatabaseReference ref;
private FirebaseRecyclerOptions<Book> options;
/**
* Get the last 50 chat messages.
*/
RecyclerView recyclerView;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate ( savedInstanceState );
setContentView ( R.layout.barber_view );
recyclerView =findViewById ( R.id.list_jobs );
recyclerView.setHasFixedSize ( false );
recyclerView.setLayoutManager ( new LinearLayoutManager ( this ) );
ref = FirebaseDatabase.getInstance ( ).getReference ( );
Query query = ref.child ( "gregs-281717" );
final FirebaseRecyclerOptions<Book> options=new FirebaseRecyclerOptions.Builder<Book> ( )
.setQuery ( query, Book.class )
.setLifecycleOwner ( this )
.build ( );
query.addValueEventListener ( new ValueEventListener ( ) {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
for (DataSnapshot mdatasnapshot: snapshot.getChildren()) {
Book mbook =new Book();
mbook.setTime( mdatasnapshot.child ( "Book" ).getValue ( true).toString () );
mbook.setDates( mdatasnapshot.getValue (true ).toString () );
mbook.setPayDone( mdatasnapshot.getValue ( true).toString () );
mbook.setCutDone( mdatasnapshot.getValue (true ).toString () );
mbook.setUser_id( mdatasnapshot.getValue ( true).toString () );
}
adapter = new MyViewHolder (options );
recyclerView.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
}
@Override
public void onStart() {
super.onStart ( );
recyclerView.setAdapter(adapter);
}
@Override
protected void onStop() {
super.onStop ( );
recyclerView.setAdapter(adapter);
}
}
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