How to integrate two or more google-services.json file together for different google FCM service in same project

Question

I am making a project where I want to integrate different FCM google-service.json,how to integrate in same file different project key I tried 2 projects this like but not working we need to add in our project.

    {
          "project_info": {
            "project_number": "60554696754247",
            "firebase_url": "https://project-1fca7.firebaseio.com",
            "project_id": "project-1fca7",
            "storage_bucket": "project-1fca7.appspot.com"
          },
          "client": [
            {
              "client_info": {
                "mobilesdk_app_id": "xxxxxxxxxxxxx",
                "android_client_info": {
                  "package_name": "com.company.project1"
                }
              },
              "oauth_client": [
                {
                  "client_id": "xxxxxxxxxxxxxxxx",
                  "client_type": 3
                }
              ],
              "api_key": [
                {
                  "current_key": ""
                }
              ],
              "services": {
                "analytics_service": {
                  "status": 1
                },
                "appinvite_service": {
                  "status": 1,
                  "other_platform_oauth_client": []
                },
                "ads_service": {
                  "status": 2
                }
              }
            }
          ],
          "project_info": {
            "project_number": "13052496681",
            "firebase_url": "https://project-2ebf8.firebaseio.com",
            "project_id": "project-2ebf8",
            "storage_bucket": "project-2ebf8.appspot.com"
          },
          "client": [
            {
              "client_info": {
                "mobilesdk_app_id": "xxxxxxxxxxxxxxx",
                "android_client_info": {
                  "package_name": "com.company.project2"
                }
              },
              "oauth_client": [
                {
                  "client_id": "xxxxxxxxxxxxxx",
                  "client_type": 3
                }
              ],
              "api_key": [
                {
                  "current_key": "xxxxxxxxxxxxxxxx"
                }
              ],
              "services": {
                "analytics_service": {
                  "status": 1
                },
                "appinvite_service": {
                  "status": 1,
                  "other_platform_oauth_client": []
                },
                "ads_service": {
                  "status": 2
                }
              }
            }
          ],

          "configuration_version": "1"
        }

Answer 1

It's not clear exactly what your use case is, but it's worth noting that using the google-services.json file is totally optional and in your case you may want to skip it and configure your app manually.

The documentation here explains how the plugin processes the JSON file.

Basically the plugin creates a strings.xml file that looks like this:

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <! -- Present in all applications -->
    <string name="google_app_id" translatable="false">1:1035469437089:android:73a4fb8297b2cd4f</string>

    <! -- Present in applications with the appropriate services configured -->
    <string name="gcm_defaultSenderId" translatable="false">1035469437089</string>
    <string name="default_web_client_id" translatable="false">337894902146-e4uksm38sne0bqrj6uvkbo4oiu4hvigl.apps.googleusercontent.com</string>
    <string name="ga_trackingId" translatable="false">UA-65557217-3</string>
    <string name="firebase_database_url" translatable="false">https://example-url.firebaseio.com</string>
    <string name="google_api_key" translatable="false">AIzbSyCILMsOuUKwN3qhtxrPq7FFemDJUAXTyZ8</string>
    <string name="google_crash_reporting_api_key" translatable="false">AIzbSyCILMsOuUKwN3qhtxrPq7FFemDJUAXTyZ8</string>

</resources>

Since you're talking about FCM, the relevant pieces are google_app_id, gcm_defaultSenderId, and google_api_key. If you create strings with those names in your application, Firebase will auto-initialize correctly.

If you want to use multiple apps, as you said, you'll need to manually initialize FirebaseApp like this:

FirebaseApp customApp = FirebaseApp.initializeApp(this, 
       new FirebaseOptions.Builder()
           .setApplicationId(...)
           .setApiKey(...)
           .setGcmSenderId(...)
           .build(), 
       "custom-app-name");