在Custom Object Firebase Android中获取参考和密钥 [英] Obtaining the reference and key in Custom Object Firebase Android

问题描述

我希望将每个特定对象的dataSnapshot和key的引用传递给自定义的Message对象。

I'm looking to pass the reference of the dataSnapshot and key of each specific object into a custom 'Message' object.

我尝试过使用密钥Message.class中的'String key'但它似乎返回null。

I've tried using the key 'String key' within the Message.class but it appears to come back null.

以下是我的Message对象的当前状态：

Here is how my Message object currently is:

public class Message {

    private String key;
    private String sender_id;
    private String sender_username;
    private String receiver_username;
    private String receiver_id;
    private String chat_id;
    private String message;
    private Firebase ref;
    private double createdAt;
    private boolean read;

    public Message() {
        // empty default constructor, necessary for Firebase to be able to deserialize messages
    }

    public String getKey() { return key; }
    public String getSender_id() { return sender_id; }
    public String getSender_username() { return sender_username; }
    public String getReceiver_username() { return receiver_username; }
    public String getReceiver_id() { return receiver_id; }
    public String getChat_id() { return chat_id; }
    public String getMessage() { return message; }
    public Firebase getRef() { return ref; }
    public double getCreatedAt() { return createdAt; }
    public boolean getRead() { return read; }

}

任何想法，我如何正确传递dataSnapshot.getKey （）自定义对象的字符串？我没有在Firebase文档中看到一个示例，并且在更新之前要清楚我正在使用旧版Firebase。

Any ideas, how I properly pass the dataSnapshot.getKey() String to the custom object? I don't see an example on the Firebase docs, and to be clear I'm using the "legacy Firebase", before they updated.

推荐答案

当您从 DataSnapshot 获得消息实例时，您可能会这样做：

When you get a Message instance from a DataSnapshot, you are likely doing:

Message message = snapshot.getValue(Message.class)

由于这是从 getValue（）开始的，因此该消息将不包含 DataSnapshot的密钥。

Since this is starting from getValue(), the message will not contain the key of the DataSnapshot.

您可以做的是在阅读消息后自己设置密钥：

Message message = snapshot.getValue(Message.class);
message.setKey(snapshot.getKey());

您需要标记 getKey（） as @JsonIgnore 在这种情况下，确保Jackson尝试自动填充或序列化它。

You'll want to mark the getKey() as @JsonIgnore in that case, to ensure that Jackson tries to auto-populate or serialize it.

这篇关于在Custom Object Firebase Android中获取参考和密钥的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！