Question

我现在在一个项目上，正在尝试使用回收器视图和视图保持器从Firebase中获取数据，但是使用我的助手类，当应用启动时，我立即尝试通过助手类检索数据，它崩溃了，当我看起来通过我的logcat，它给了我这个错误E / RecyclerView：没有连接适配器；跳过布局...。我搜索了很多答案，我看到了一些答案，但它们与我的代码无关... 这是我的主要活动代码

package com.example.android.journalapp;


import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;


import com.example.android.journalapp.users.LogInActivity;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;


public class MainActivity extends AppCompatActivity {
    private static final String DATE_FORMAT = "dd/MM/yyy";
    private SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT, 
    Locale.getDefault());

    private FirebaseAuth mFirebaseAuth;
    private FirebaseUser mFirebaseUser;
    private DatabaseReference mDatabase;
    String mUserId;

    private RecyclerView mRecyclerView;


    private FirebaseHelper helper;

    Context context;

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

        mFirebaseAuth = FirebaseAuth.getInstance();
        mFirebaseUser = mFirebaseAuth.getCurrentUser();

        mRecyclerView = (RecyclerView) findViewById(R.id.journal_recycler);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        mRecyclerView.setHasFixedSize(true);


        if (mFirebaseUser == null) {
            // Not logged in, launch the Log In activity
            loadLogInView();
        } else {
            mDatabase = FirebaseDatabase.getInstance().getReference();
            mUserId = mFirebaseUser.getUid();
            helper = new FirebaseHelper(context, mDatabase, mRecyclerView, 
            mUserId);
            helper.refreshData();

        }

        FloatingActionButton fab = (FloatingActionButton) 
        findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent addJournalIntent = new Intent(MainActivity.this, 
                AddJournalActivity.class);
                addJournalIntent.putExtra("USER_ID", mUserId);
                startActivity(addJournalIntent);
            }
        });

    }

    private void loadLogInView() {
        Intent intent = new Intent(this, LogInActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
        startActivity(intent);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is         present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_logout) {
            mFirebaseAuth.signOut();
            loadLogInView();
        }

        return super.onOptionsItemSelected(item);
    }


}

这是我的Firebase助手类

    package com.example.android.journalapp;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v7.widget.RecyclerView;
import android.widget.Toast;

import com.example.android.journalapp.model.Journal;
import com.google.firebase.database.ChildEventListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.Locale;

public class FirebaseHelper {

    private String mUserId;
    private Context context;
    private DatabaseReference mDb;
    RecyclerView mRecyclerView;
    ArrayList<Journal> journals = new ArrayList<>();
    public JournalAdapter mJournalAdapter;
    private static final String DATE_FORMAT = "dd/MM/yyy";
private SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT,     Locale.getDefault());

    public FirebaseHelper(Context context, DatabaseReference mDb,     RecyclerView mRecyclerView, String mUserId) {
        this.context = context;
        this.mDb = mDb;
        this.mRecyclerView = mRecyclerView;
        this.mUserId = mUserId;


    }

    public void saveData(String journal, String date) {
        Journal journalEntry = new Journal(journal, date);
        mDb.child("users").child(mUserId).child("journals").push().setValue(journalEntry)    ;
//        .child("journal")
    }

    public void recieveData(DataSnapshot ds) {

        journals.clear();
        for (DataSnapshot dataSnapshot : ds.getChildren()) {
        Journal journal = dataSnapshot.getValue(Journal.class);

        journals.add(journal);
    }

        mJournalAdapter = new JournalAdapter(context, journals);
    mRecyclerView.setAdapter(mJournalAdapter);
//        if (journals.size() > 0) {
//
//            mJournalAdapter = new JournalAdapter(context, journals);
//            mRecyclerView.setAdapter(mJournalAdapter);
//        } else {
//            Toast.makeText(context, "No data", Toast.LENGTH_SHORT).show();
//        }
    }

    public void refreshData() {
        mDb.child("users").child(mUserId).child("journals").addChildEventListener(new     ChildEventListener() {
            @Override
            public void onChildAdded(@NonNull DataSnapshot dataSnapshot,     @Nullable String s) {
                recieveData(dataSnapshot);
            }

            @Override
            public void onChildChanged(@NonNull DataSnapshot dataSnapshot,     @Nullable String s) {
                recieveData(dataSnapshot);
            }

            @Override
            public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {

            }

            @Override
            public void onChildMoved(@NonNull DataSnapshot dataSnapshot,     @Nullable String s) {

            }

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

            }
        });
    }
}

这是我的模型课

    package com.example.android.journalapp.model;

import java.util.Date;

public class Journal {

    private String journalContent;
    private String date;

    public Journal(String journalContent, String date) {
        this.journalContent = journalContent;
        this.date = date;
    }

    public String getJournalContent() {
        return journalContent;
    }

    public void setJournalContent(String journalContent) {
        this.journalContent = journalContent;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }
}

/// 这是我的适配器类

    package com.example.android.journalapp;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.example.android.journalapp.model.Journal;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Locale;

public class JournalAdapter extends RecyclerView.Adapter<JournalHolder> {

    Context context;
    private ArrayList<Journal> journals;

    private static final String DATE_FORMAT = "dd/MM/yyy";
    private SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT,     Locale.getDefault());


    public JournalAdapter(Context context, ArrayList<Journal> journals) {
        this.context = context;
        this.journals = journals;
    }
    @NonNull
    @Override
    public JournalHolder onCreateViewHolder(@NonNull ViewGroup parent, int     viewType) {
        View view =     LayoutInflater.from(parent.getContext()).inflate(R.layout.journal_layout, parent,     false);
        JournalHolder holder = new JournalHolder(view);
        return holder;
    }

    @Override
    public void onBindViewHolder(@NonNull JournalHolder holder, int position)     {
        holder.mJournalTextView.setText(journals.get(position).getJournalContent());

        String date = journals.get(position).getDate();
        holder.mDateTextView.setText(date);
    }

    @Override
    public int getItemCount() {
        if (journals == null) {
            return 0;
        }

        return journals.size();
    }
}

// 这是我的观看者类

    package com.example.android.journalapp;

import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.TextView;

public class JournalHolder extends RecyclerView.ViewHolder {

    TextView mJournalTextView;
    TextView mDateTextView;

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

        mJournalTextView = itemView.findViewById(R.id.journal_text_view);
        mDateTextView = itemView.findViewById(R.id.journal_date_text_view);
    }
}

我能够推送到数据库，但是检索数据给我错误E / RecyclerView：未连接适配器；跳过布局

Answer 1

尝试此代码。 display_data.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">

<android.support.v7.widget.RecyclerView
    android:id="@+id/rvData"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

</android.support.v7.widget.RecyclerView>

<TextView
    android:id="@+id/dlTvEmpty"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="No Found"
    android:textSize="16dp"
    android:visibility="gone"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />
</android.support.constraint.ConstraintLayout>

DisplayActivity.java ..

public class DisplayActivity extends AppCompatActivity {
private RecyclerView mRvData;
private DisplayAllData allDataAdapter;
private DatabaseReference mDatabase;
private TextView mTvEmpty;
private FirebaseDatabase mFirebaseInstance;
private List<User> mUserList = new ArrayList<>();

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.display_data);
    initView();
}

private void initView() {
    mFirebaseInstance = FirebaseDatabase.getInstance();
    mDatabase = mFirebaseInstance.getReference("usersDb/UserTable");

    mRvData = findViewById(R.id.rvData);
    mTvEmpty = findViewById(R.id.dlTvEmpty);
    mRvData.setLayoutManager(new LinearLayoutManager(this));
    mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            mUserList.clear();
            for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                User user = dataSnapshot1.getValue(User.class);
                mUserList.add(user);
            }
            allDataAdapter = new DisplayAllData(DisplayActivity.this, mUserList);
            mRvData.setAdapter(allDataAdapter);
            allDataAdapter.notifyDataSetChanged();
            if (mUserList.isEmpty())
                mTvEmpty.setVisibility(View.VISIBLE);
            else
                mTvEmpty.setVisibility(View.GONE);
        }


        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

}
}

DisplayAdapter.java ..

public class DisplayAllData extends RecyclerView.Adapter<DisplayAllData.ItemViewHolder> {
private List<User> mUserLsit = new ArrayList<>();
private Context mContext;

@Override
public ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_layout, parent, false);
    return new ItemViewHolder(view);
}

public DisplayAllData(Context mContext, List<User> mUserLsit) {
    this.mContext = mContext;
    this.mUserLsit = mUserLsit;
}

@Override
public void onBindViewHolder(ItemViewHolder holder, int position) {
    User user = mUserLsit.get(position);
    holder.mTvName.setText(user.name);
    holder.mTvEmail.setText(user.email);
    holder.mTvPwd.setText(user.pwd);
}

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

public class ItemViewHolder extends RecyclerView.ViewHolder {
    TextView mTvName, mTvEmail, mTvPwd;

    public ItemViewHolder(View itemView) {
        super(itemView);
        mTvEmail = itemView.findViewById(R.id.rlTvEmail);
        mTvName = itemView.findViewById(R.id.rlTvName);
        mTvPwd = itemView.findViewById(R.id.rlTvPwd);

    }
}
}

row_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="10dp">

<TextView
    android:id="@+id/rlTvName"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Name"
    android:textSize="20dp" />

<TextView
    android:id="@+id/rlTvEmail"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Email"
    android:textSize="20dp"
    app:layout_constraintTop_toBottomOf="@+id/rlTvName" />

<TextView
    android:id="@+id/rlTvPwd"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Password"
    android:textSize="20dp"
    app:layout_constraintTop_toBottomOf="@+id/rlTvEmail" />


</android.support.constraint.ConstraintLayout>

我希望您将互联网许可添加到android清单文件中。

<uses-permission android:name="android.permission.INTERNET"/>

更多信息请参考此链接 https://www.simplifiedcoding.net/firebase-realtime-database-crud/

使用回收器视图从Firebase检索数据时出错：E / RecyclerView：未连接适配器；跳过布局

1 个答案: