如何使用java中的FirebaseListAdapter从firebase数据库读取儿童？

问题描述

我在Firebase中很新。所以，我有这样的数据库结构：




$ $ $ $ $ $ c $ databaseReference = FirebaseDatabase.getInstance（）。getReference（）。child（Firebase）。child 用户）;
firebaseListAdapter = new FirebaseListAdapter< String>（this，String.class，android.R.layout.simple_list_item_1，databaseReference）{
@Override
protected void populateView（View v，String string，int位置）{
TextView textView =（TextView）v.findViewById（android.R.id.text1）;
textView.setText（string）;
}
};
listView =（ListView）findViewById（R.id.listView）;
listView.setAdapter（firebaseListAdapter）;

这是我的User类：

  class User {
 private String userName; 
私人字符串电子邮件; 
 
 void setUserName（String userName）{this.userName = userName;} 
 String getUserName（）{return userName;} 
 $ b $ void setEmail（String email）{ this.email = email;} 
 String getEmail（）{return email;} 
} 
  

当我复制这个，我得到这个错误： com.google.firebase.database.DatabaseException：无法将类型java.util.HashMap的值转换为字符串

如何解决这个问题？

将 populateView 方法实现更改为

<$ p $ FirebaseListAdapter = new FirebaseListAdapter< User>（this，User.class，android.R.layout.simple_list_item_1，databaseReference）{
@Override
protected void populateView（View v，用户用户，int位置）{
TextView textView =（TextView）v.findViewById（android.R.id.text1）;
字符串userKey = this.getRef（position）.getKey（）;
textView.setText（userKey）;
}
};

I am very new in Firebase. So, i have a database structure like this:

and want to display those generated id's into a listview. I'm using FirebaseListAdapter. Here is my code:

    databaseReference = FirebaseDatabase.getInstance().getReference().child("Firebase").child("Users");
    firebaseListAdapter = new FirebaseListAdapter<String>(this, String.class, android.R.layout.simple_list_item_1, databaseReference) {
        @Override
        protected void populateView(View v, String string, int position) {
            TextView textView = (TextView) v.findViewById(android.R.id.text1);
            textView.setText(string);
        }
    };
    listView = (ListView) findViewById(R.id.listView);
    listView.setAdapter(firebaseListAdapter);

This is my User class:

class User {
private String userName;
private String email;

    void setUserName(String userName) {this.userName = userName;}
    String getUserName() {return userName;}

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

When i copile this, i get this error: com.google.firebase.database.DatabaseException: Failed to convert value of type java.util.HashMap to String

How can i fix this?

Thanks in advance!

解决方案

Change the populateView method implementation to

firebaseListAdapter = new FirebaseListAdapter<User>(this, User.class, android.R.layout.simple_list_item_1, databaseReference) {
    @Override
    protected void populateView(View v, User user, int position) {
        TextView textView = (TextView) v.findViewById(android.R.id.text1);
        String userKey = this.getRef(position).getKey();
        textView.setText(userKey);
    }
};

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