android - 返回存储在 Firebase Android 中的值

Question

我看了几个关于这个问题的答案，但是我在 Firebase Android App 的答案中仍然有 null 。其中之一是:

Firebase retrieve/read returns null values - Android

我的问题:

我可以写入 Firebase，但无法读取值。

我尝试:

1 更改 Firebase 规则的值:

{
  "rules": {
    ".read": "auth != null",
    ".write": "auth != null"
  }
} 

到:

{
  "rules": {
    ".read": true,
    ".write": true
  }
}

但没有用，我可以写但不能读值。

我的代码:

 private void postComment() {
        //final String uid = getUid();
        FirebaseDatabase.getInstance().getReference().child("users")/*.child("KU1y_SLZGLZpJB2j_Pc")*/
                .addListenerForSingleValueEvent(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        // Get user information
                        UserClassGu user = dataSnapshot.getValue(UserClassGu.class);
                        String authorName = user.name;
                        Log.d(TAG,"name read into postCopmment = "+authorName);


                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {

                    }
                });
    }

这是我在 getValue(UserClassGu.class) 中使用的类

/** * 由 Cliente 创建于 14/10/2016。 */

public class UserClassGu {

    public String userUid;
    public   String email;
    public String name;
    public String telephone;

    public UserClassGu() {

    }

    public String getUserUid() {
        return userUid;
    }

    public UserClassGu(String userUid, String email, String name, String telephone) {
        userUid = userUid;
        this.email = email;
        this.name = name;
        this.telephone = telephone;
    }

    public void setUserUid(String userUid) {
        userUid = userUid;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getTelephone() {
        return telephone;
    }

    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }


}

我的数据库:

{
  "messages" : {
    "-KU87z9hSXew-Li37xgF" : {
      "destinatario" : "ad@g.com",
      "name" : "app app",
      "photoUrl" : "https://lh5.googleusercontent.com/-jjv4PSa0NzA/AAAAAAAAAAI/AAAAAAAAAAA/APaXHhQm8WxqRupmfbe87U11m9pfn9C9ag/s96-c/photo.jpg",
      "text" : "hello"
    },
    "-KU88ciYGXz39PZGZW98" : {
      "destinatario" : "rere",
      "name" : "app app",
      "photoUrl" : "https://lh5.googleusercontent.com/-jjv4PSa0NzA/AAAAAAAAAAI/AAAAAAAAAAA/APaXHhQm8WxqRupmfbe87U11m9pfn9C9ag/s96-c/photo.jpg",
      "text" : "adafa"
    }
  },
  "messages_private" : {
    "rere" : {
      "553xVAMEVcQZPKNVqfal8S9tOM03" : {
        "-KU88ciZUNQkCskad6Xc" : {
          "destinatario" : "rere",
          "name" : "app app",
          "photoUrl" : "https://lh5.googleusercontent.com/-jjv4PSa0NzA/AAAAAAAAAAI/AAAAAAAAAAA/APaXHhQm8WxqRupmfbe87U11m9pfn9C9ag/s96-c/photo.jpg",
          "text" : "adafa"
        }
      }
    }
  },
  "users" : {
    "-KU3ZlBN-gmHZOhg74-M" : {
      "email" : "app@gmail.com",
      "name" : "app app",
      "telephone" : ""
    },
    "-KU3_ZjTHJHprd36xT1u" : {
      "email" : "appa@gmail.com",
      "name" : "app app",
      "telephone" : ""
    }
  }
}

Answer 1

我解决了将数据路径更改为 Firebase 的问题:

进入 UserGu 类:

1. 我忘了写getter getUserUid()

   公共(public)字符串 getUserUid() { 返回用户名；

2.我要读取的数据的数据库Firebase路径不对:我改为: mFirebaseDatabaseReference.child("users").child(mUserUid).setValue(userClassGu);

UserClassGu userClassGu = UserClassGu(mUserUid,mUserEmail,mUsername,"");   



            mFirebaseDatabaseReference.child("users").child(mUserUid).setValue(userClassGu);


            //Write data of users
            mFirebaseDatabaseReference.child("users").child(mUserUid).setValue(userClassGu);


            //Reading the data


mFirebaseDatabaseReference.child("users").child(mUserUid).addValueEventListener(
                new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        // Get user value
                        UserClassGu userClassgu = dataSnapshot.getValue(UserClassGu.class);
                        Log.d(TAG,"reading data  :userClassgu.email = "+userClassgu.email);
                        Log.d(TAG,"reading data  :userClassgu.name: = "+userClassgu.name);
                        Log.d(TAG,"reading data  :userClassgu.telephone: = "+userClassgu.telephone);
                        Log.d(TAG,"reading data  :userClassgu.userUid: = "+userClassgu.userUid);
                        // ...
                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {
                        Log.w(TAG, "getUser:onCancelled", databaseError.toException());
                        // ...
                    }
                });

在 userClassGu 类中，我放置了方法:

@Exclude
public Map<String, Object> toMap() {
    HashMap<String, Object> result = new HashMap<>();
    result.put("uid", userUid);
    result.put("email", email);
    result.put("name", name);
    result.put("telephone", telephone);
    return result;
}

我将 int 类 UserClassGuthe 文本:@IgnoreExtraProperties

userClassGu类的代码变成了:

package com.sciencesoftware.friends;

import com.google.firebase.database.Exclude;
import com.google.firebase.database.IgnoreExtraProperties;

import java.util.HashMap;
import java.util.Map;

/**
 * Created by Cliente on 14/10/2016.
 */
@IgnoreExtraProperties
public class UserClassGu {
    public String userUid;
    public   String email;
    public String name;
    public String telephone;

    public UserClassGu() {
// Default constructor required for calls to DataSnapshot.getValue(UserClassGu.class)

    }

    public UserClassGu(String userUid, String email, String name, String telephone) {
        this.userUid = userUid;
        this.email = email;
        this.name = name;
        this.telephone = telephone;
    }


    public String getUserUid() {
        return userUid;
    }





    public void setUserUid(String userUid) {
        this.userUid = userUid;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getTelephone() {
        return telephone;
    }

    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }


    @Exclude
    public Map<String, Object> toMap() {
        HashMap<String, Object> result = new HashMap<>();
        result.put("uid", userUid);
        result.put("email", email);
        result.put("name", name);
        result.put("telephone", telephone);
        return result;
    }



}

3。这是 Firebase 的 JSON:

{
  "users" : {
    "Bl0AiMMUXsV2H58lqoj0rO8457j1" : {
      "email" : "myEmail@gmail.com",
      "name" : "my name",
      "telephone" : "",
      "userUid" : "Bl0AiMMUXsV2H58lqoj0rO8457j1"
    }
  }
}

研究文档:将数据放入数据库的类必须:1 有一个空的构造函数:2 有一个包含变量所有参数的构造函数 -(我对此并不完全正确)该类的变量必须是公共(public)的，或者必须将所有 getter 都公开(我对此并不完全正确)。3 拥有所有 setter/getter 。4 不需要二传手。

如果我对以上这 4 件事说错了，如果有人纠正我，我会很高兴。