Firebase Unreal Plugin Demo

A project demonstrates how to integrate Firebase into Unreal Engine 4.

This is not a full integration

This repo is a personal note and also trying to help who implementing plugin in UE4.

Also demonstrates on how to fix a plist path bug in iOS by using iOS swizzling,
which I filed a Firebase issue here

Platform: iOS and Android
iOS Firebase Version: 7.5.0
Android Firebase Version: BOM 25.8.0
Unreal Engine 4 Version: 4.25.4

Firebase modules in this demo:
Analytic, Firebase Cloud Messaging.

Android build requirements:

• JDK 12.0.2
• NDK r21d

Plugin Implemetation Guide

Firebase config files google-services.json and GoogleService-Info.plist placed in /DemoPlugin/Source/DemoPlugin/Raw

iOS

Copying raw file in iOS

There are at least 3 methods to do so.

Method 1: Use DefaultGame.ini config file.

you add this path in DefaultGame.ini

[Staging]
+RemapDirectories=(From="UnrealPluginDemo/Plugins/DemoPlugin/Source/DemoPlugin/Raw", To="Raw")

and also in plugin Build.cs, you add

RuntimeDependencies.Add(Path.Combine(ModuleDirectory, "Raw/GoogleService-Info.plist"), StagedFileType.SystemNonUFS);

by default, the file will not be included as cooked file in UE4 System,
but you also need to move it out of cooked file folder which contain the project target name in the path.
that said, This config will copy files from cooked data folder to "Raw" folder
The disadvantage of doing so is you cannot move it root path of the app aka target.ipa/target.app/yourFile
here comes a problem, Firebase has a bug mentioned above cannot load plist file other than default location.
you will need that swizzling fix to use this method.

Method 2: Use "Cloud" folder.

UE4 will copy all files under Build/Cloud folder, tested from UE 4.23 onward.
add following code in Build.cs.

string cloudPath = ModuleDirectory+"/../../../../Build/IOS/Cloud";
string rawPath = Path.Combine(ModuleDirectory, "Raw");
if(Directory.Exists(cloudPath)==false){
    Directory.CreateDirectory(cloudPath);
}
File.Delete(cloudPath+"/GoogleService-Info.plist");//remove previous file if exists
File.Copy(rawPath +"/GoogleService-Info.plist",cloudPath+"/GoogleService-Info.plist");

this method can copy raw files under root folder of target.ipa/target.app/
The disadvantage of doing so is you must use Mac OS to build ipa.
This will not work when using PC to build ipa using UE4 remote build.

Method 3: Use IOS_UPL.xml

by looking at this repo by @nprudnikov
you can also use UPL copyFile command to copy raw files.

<iosPListUpdates>
  <if condition="bEnabled">
    <true>
      <copyFile src="$S(PluginDir)/../../../../$S(ConfigFile)" dst="$S(BuildDir)/GoogleService-Info.plist" force="false"/>
    </true>
  </if>
</iosPListUpdates>

Confront to FIRMessagingDelegate protocol

By default UE4 does not suport @import objective-C module,
you may encounter issue when you need to implement certain protocol in your class use NSObject conformsToProtocol method to implement, here is how to implement FIRMessagingDelegate.

+ (BOOL)conformsToProtocol:(Protocol *)protocol{
    if(protocol == NSProtocolFromString(@"FIRMessagingDelegate")){
        return YES;
    }
    return [super conformsToProtocol:protocol];
}

or you can find "Firebase.h" from cocoapod sources. use #import "Firebase.h" instead.

Android

Copy Raw files in Android

use Android_UPL.xml copyFile command to do so,
copy it to gradle build folder

<resourceCopies>
	<copyFile src="$S(PluginDir)/../Libs/Android/FirebaseUnrealWrapper-release.aar" dst="$S(BuildDir)/libs/FirebaseUnrealWrapper-release.aar" />
	<copyFile src="$S(PluginDir)/Raw/google-services.json" dst="$S(BuildDir)/gradle/app/google-services.json" />
</resourceCopies>

Support Google Services plugins

you will need to add plugins classpath in build.gradle,
and let Google firebase plugins to resolves google-services.json into strings.xml

again, in Android_UPL.xml

you add Google Services plugin in buildscriptGradleAdditions tag

<buildscriptGradleAdditions> 
<insert>
	dependencies {
		//firebase
		classpath 'com.google.gms:google-services:4.3.3'  // Google Services plugin
	}
</insert>
</buildscriptGradleAdditions>

and then add apply plugin in buildGradleAdditions tag

<buildGradleAdditions>
<insert>
	apply plugin: 'com.google.gms.google-services'  // Google Services plugin
</insert>
</buildGradleAdditions>

Support AndroidX

Swap UE4 support-library classes to AndroidX classes.
To do so you need you do that in UE4 Android_UPL.xml file,
use ant task to replace all "import" library package names.

task replaceImport {
	ant.replace(token:'import android.support.v13.app.FragmentCompat;', value:'import androidx.legacy.app.FragmentCompat;') {
		fileset(dir: '../permission_library/src/main/java/com/google/vr/sdk/samples/permission', includes: 'PermissionFragment.java')
	}
	ant.replace(token:'import android.support.v4.content.ContextCompat;', value:'import androidx.core.content.ContextCompat;') {
		fileset(dir: '../permission_library/src/main/java/com/google/vr/sdk/samples/permission', includes: 'PermissionHelper.java')
	}

	ant.replace(token:'import android.support.v4.app.NotificationCompat;', value:'import androidx.core.app.NotificationCompat;') {
		fileset(dir: 'src/main/java/com/google/android/vending/expansion/downloader/impl', includes: 'DownloadNotification.java')
	}

	ant.replace(token:'import android.support.v4.app.NotificationCompat;', value:'import androidx.core.app.NotificationCompat;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4', includes: 'LocalNotificationReceiver.java')
	}

	ant.replace(token:'import android.support.annotation.NonNull;', value:'import androidx.annotation.NonNull;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4/network', includes: 'NetworkChangedManager.java')
	}
	ant.replace(token:'import android.support.annotation.Nullable;', value:'import androidx.annotation.Nullable;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4/network', includes: 'NetworkChangedManager.java')
	}
	ant.replace(token:'import android.support.annotation.NonNull;', value:'import androidx.annotation.NonNull;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4/network', includes: 'NetworkConnectivityClient.java')
	}

	ant.replace(token:'import android.support.v4.app.NotificationManagerCompat;', value:'import androidx.core.app.NotificationManagerCompat;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4', includes: 'GameActivity.java')
	}

	ant.replace(token:'import android.support.v4.app.ActivityCompat;', value:'import androidx.core.app.ActivityCompat;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4', includes: 'SplashActivity.java')
	}
	ant.replace(token:'import android.support.v4.content.ContextCompat;', value:'import androidx.core.content.ContextCompat;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4', includes: 'SplashActivity.java')
	}

	ant.replace(token:'import android.support.v4.content.FileProvider;', value:'import androidx.core.content.FileProvider;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4', includes: 'GameActivity.java')
	}

	ant.replace(token:'import android.arch.lifecycle.Lifecycle;', value:'import androidx.lifecycle.Lifecycle;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4', includes: 'GameApplication.java')
	}
	ant.replace(token:'import android.arch.lifecycle.LifecycleObserver;', value:'import androidx.lifecycle.LifecycleObserver;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4', includes: 'GameApplication.java')
	}
	ant.replace(token:'import android.arch.lifecycle.OnLifecycleEvent;', value:'import androidx.lifecycle.OnLifecycleEvent;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4', includes: 'GameApplication.java')
	}
	ant.replace(token:'import android.arch.lifecycle.ProcessLifecycleOwner;', value:'import androidx.lifecycle.ProcessLifecycleOwner;') {
		fileset(dir: 'src/main/java/com/epicgames/ue4', includes: 'GameApplication.java')
	}

}

also add android.useAndroidX=true & android.enableJetifier=true in gradle.properties file

<gradleProperties>
  <insert>
    android.useAndroidX=true
    android.enableJetifier=true
  </insert>
</gradleProperties>

Thread handling of JNI Callback from java

Be aware which thread you are using when performing task in Java side,
normally the best practice is using UI Thread of Android system and use Game Thread
when picking up callback in JNI.

In UE4, use AsyncTask to run callback code in UE4 engine.

extern "C"
{
    
    /*
    * Class:
    * Method:    nativeOnManualFcmTokenSuccess
    * Signature: (Ljava/lang/String;)V
    */
    JNIEXPORT void JNICALL Java_com_epicgames_ue4_GameActivity_nativeOnReceiveFcmToken
    (JNIEnv * env, jclass _class, jstring jtoken){
        std::string ctoken = jstring2string(jtoken);
        AsyncTask(ENamedThreads::GameThread, [=]()
		    { 
            DemoPluginWrapper::getInstance()->onReceiveFcmToken(ctoken);
        });
    }
    
}

C++ implementation in UE4

Callback handling

in this demo, use C++11 feature to bind delegate methods.
where CPP_CALLBACK_0 = zero method parameter
CPP_CALLBACK_2 = two method parameters

#define CPP_CALLBACK_0(__selector__,__target__, ...) std::bind(&__selector__,__target__, ##__VA_ARGS__)
#define CPP_CALLBACK_1(__selector__,__target__, ...) std::bind(&__selector__,__target__, std::placeholders::_1, ##__VA_ARGS__)
#define CPP_CALLBACK_2(__selector__,__target__, ...) std::bind(&__selector__,__target__, std::placeholders::_1, std::placeholders::_2, ##__VA_ARGS__)
#define CPP_CALLBACK_3(__selector__,__target__, ...) std::bind(&__selector__,__target__, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3, ##__VA_ARGS__)

assign delegate in DemoPluginListenerComponet.cpp:

DemoPluginWrapper::getInstance()->m_onReceiveFcmToken = CPP_CALLBACK_1(UDemoPluginListenerComponent::onReceiveFcmToken, this);

DemoPluginListenerComponent extends UActorComponent which can be added in you Map.
DemoPluginListenerComponent use Multicast Delegate to boardcast callback to other UE4 receiver.
This callback support both c++ and blueprint.

DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FonReceiveFcmTokenEvent,FString, token);

Others

Using Visual Studio Code with UE4

if you use VSCode and have problem with UE 4.25, you can read my gist as well.