Firebase Android：如何通过 RemoteMessage 访问嵌套在数据中的参数？

Question

via this shape:

{
  "to": "000",
  "priority": "high",
  "data": {
    "title": "A Title",
    "message": "A Message",
    "link": {
      "url": "http://www.espn.com",
      "text": "ESPN",
    }
  }
}

how can I access "url" and "text"?

String messageLink = remoteMessage.getData().get("link");

gets me:

{"text":"ESPN","url":"http://www.espn.com"}

but how do I drill deeper?

remoteMessage.getData().get("link").get("text");

doesnt quite work... I have also attempted JSONObject:

JSONObject json = new JSONObject(remoteMessage.getData());    
JSONObject link = json.getJSONObject("link");

but this gives me try catch errors...

Any help and direction as always is greatly appreciated!

Answer 1

I would use gson and define a model class. The remote message gives you a Map<String, String> and their is no matching constructor for creating a json object.

Add gson to your build.xml:

compile 'com.google.code.gson:gson:2.5'

Create a notification model:

import com.google.gson.annotations.SerializedName;

public class Notification {

    @SerializedName("title")
    String title;
    @SerializedName("message")
    String message;
    @SerializedName("link")
    private Link link;

    public String getTitle() {
        return title;
    }

    public String getMessage() {
        return message;
    }

    public Link getLink() {
        return link;
    }

    public class Link {

        @SerializedName("url")
        String url;
        @SerializedName("text")
        String text;

        public String getUrl() {
            return url;
        }

        public String getText() {
            return text;
        }

    }

}

Deserialize a notification object from the remote message.

If all your custom keys are at the top level:

Notification notification = gson.fromJson(gson.toJson(remoteMessage.getData()), Notification.class);

If your custom json data is nested in a single key for example "data" then use:

Notification notification = gson.fromJson(remoteMessage.getData().get("data"), Notification.class);

Note in this simple case the @SerializedName() annotations are unnecessary since the field names exactly match the keys in the json, but if you for example have a key name start_time but you want to name the java field startTime you would need the annotation.

Answer 2

Faced this issue when migrating from GCM to FCM.

The following is working for my use case, so perhaps it will work for you.

JsonObject jsonObject = new JsonObject(); // com.google.gson.JsonObject
JsonParser jsonParser = new JsonParser(); // com.google.gson.JsonParser
Map<String, String> map = remoteMessage.getData();
String val;

for (String key : map.keySet()) {
    val = map.get(key);
    try {
        jsonObject.add(key, jsonParser.parse(val));
    } catch (Exception e) {
        jsonObject.addProperty(key, val);
    }
}

// Now you can traverse jsonObject, or use to populate a custom object:
// MyObj o = new Gson().fromJson(jsonObject, MyObj.class)

Answer 3

As simple as that:

String linkData = remoteMessage.getData().get("link");
JSONObject linkObject = new JSONObject(linkData);

String url = linkObject.getString("url");
String text = linkObject.getString("text");

Of course, together with proper error handling.