布局错误 output:: RecyclerView: 未连接适配器； 跳过布局

Question

Upon trying to load a "log viewer" I'm building, the original pre-set layout doesn't show as output. I do get the appropriate output from my Firebase database, but the layout is all messed up/way too spaced. What am I doing wrong?

This is my LogActivity Class public class LogActivity extends AppCompatActivity {

List<Log> log;
RecyclerView recyclerView;
LogAdapter logAdapter;
DatabaseReference databaseReference;


DatabaseReference mbase; // Create object of the
// Firebase Realtime Database

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_log);
    recyclerView=findViewById(R.id.recyclerView);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    log=new ArrayList<>();

    databaseReference = FirebaseDatabase.getInstance().getReference("Logs");

    databaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {
            for(DataSnapshot ds: snapshot.getChildren())
            {
                Log data = new Log(ds.getValue(String.class));
                log.add(data);
            }
            logAdapter = new LogAdapter(log);
            recyclerView.setAdapter(logAdapter);

        }

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

        }
    });

My Adapter Class is as shown below: public class LogAdapter extends RecyclerView.Adapter {

List<Log> logList;

public LogAdapter(List<Log> logList) {
    this.logList = logList;
}

@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {

    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.log_layout, parent,false);
    ViewHolderClass viewHolderClass = new ViewHolderClass(view);

    return viewHolderClass;
}

@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {

    ViewHolderClass viewHolderClass=(ViewHolderClass)holder;
    Log log=logList.get(position);
    viewHolderClass.lockState.setText(log.getLockState());


}

@Override
public int getItemCount() {
    return logList.size();
}

public class ViewHolderClass extends RecyclerView.ViewHolder{

    TextView lockState;


    public ViewHolderClass(@NonNull View itemView) {
        super(itemView);
        lockState=itemView.findViewById(R.id.log_string);
    }
}

All of this interlocks with my " log" class which simply holds a string from my firebase DB

public class Log {

private String lockState;

public Log() {

}

public Log(String lockState) {
    this.lockState = lockState;
}

public String getLockState() {
    return lockState;
}

public void setLockState(String lockState) {
    this.lockState = lockState;
}

The following is the XML for my activity_log

<RelativeLayout
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:id="@+id/relativeLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/cardBackground"
tools:context=".LogActivity">

<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recyclerView"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginStart="4dp"
    android:layout_marginTop="4dp"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

XML for my log_layout file

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/log_layout"
android:orientation="vertical">


<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id="@+id/log_string"
    android:text="20sp"
    android:textColor="@android:color/black">

</TextView>

Lastly here are the simple strings I'm fetching and displaying successfully:

firebase-database

With my actual output here: (scroll down and the next output is there)

app-output

Answer 1

You are getting the following warning , as it's not an Error nor an Exception:

Error in layout output:: RecyclerView: No Adapter attached; Skipping Layout

Because you are trying to read "Log" objects that don't exist in the "Logs" location in your database. If Log objects existed there, your database schema would have been looking like this:

Firebase-root
  |
  --- Logs
       |
       --- -MW6C...tJ_2
             |
             --- lockState: "14h01 - Connected - Locker is NOT empty"

Meaning that under the Logs node, you have a pushed key under which exists an object of type "Log". In your schema, you only have pushed keys that only hold some Strings, hence that warning. There are two solutions. The first is to change the schema as explained above, or to use an adapter class of type String, and not Log .