How to Create Unity Android Plugins?

Disclaimer: This is based on FastEgg’s Tutorial http://fastegggames.com/blog/2013/3/30/tutorial-admob

Sometimes we need to create Plugins to easily use external frameworks such as Ad Networks in Unity.

Android

1. Create new Android Application Project

* Application Name, Project Name should refer to the specific plugin (admob for a plugin for AdMob)

2. Add Additional Libraries

• right click on Project and select “Properties”
• navigate to “Java Build Path”
• select “Libraries” tab
• click on “Add External JARs”
• add Unity’s “classes.jar” (located at <UnityInstallPath>\Editor\Data\PlaybackEngines\AndroidPlayer\bin\classes.jar)
• add other JARs that are required by the plugin (such as AdMob’s jar)

Unity’s classes.jar

• it is found in the installation folder
• C:\Program Files\Unity\Editor\Data\PlaybackEngines\AndroidPlayer\bin on Windows
• /Applications/Unity/PlaybackEngines/AndroidPlayer/bin on Mac

• select “Order and Export”
• tick all external JARs to make sure that they will be exported together with the new JAR file

3. Code the Plugin

• create new class with the same name as the project (such as AdMob.java)
• make sure to give it the package name of your plugins package
• create a Constructor
• can refer to activity using UnityPlayer.currentActivity

package com.example.AdMob
public class AdMob
{ private Activity activity; //Store the android main activity

  //Constructor
  public AdMob()
  { activity =UnityPlayer.currentActivity;
  }
}

4. Export Plugin

• right click on project and select “Export”
• in the Export Window, select “Java/JAR file”
• in Jar Export Window, make sure current project is ticked
• set export location to our Unity Project’s “Assets\Plugins\Android folder”
• name plugin (such as AdMob.jar)
• the wizard will pack the jar file, making it available for Unity

* sometimes plugins require additional JARs to be included our Unity Project’s “Assets\Plugins\Android folder” (such as the AdMob SDK)

5. Call Plugin From Unity

• create a new MonoBehaviour script in Unity, and name it closely to your plugin (such as AdMobController)

#pragma strict
public class AdMobController extends MonoBehaviour
{ function Awake()
  {
  }
}

• to activate our new plugin, we need to create a new AndroidJavaObject, and by using our package name, we can have it cast to the type we created in our JAR file:

#pragma strict
public class AdMobController extends MonoBehaviour
{ private static var jo:AndroidJavaObject;
  function Awake()
  { 
   #if UNITY_ANDROID
   jo =newAndroidJavaObject("com.example.admob.AdMob");
   #endif
  }
}

6. Modifying the Manifest

• Unity will usually create it’s own AndroidManifest.xml file when packaging your project, but also allows for you to override the one it creates with one you define inside of the Assets/Plugins/Android folder
• you can either create one from scratch, or copy over the default one that Unity has created for your project
• to get the default, make a build in Unity, and let it complete and save. Then look in your projects temp/stagingarea folder. There should be a AndroidManifest.xml file generated for you. Copy that to your projects Assets/Plugins/Android folder, and edit it using MonoDevelop
• modify the Manifest file to include things required by your plugin (such as requires Internet): <uses-permission android:name=”android.permission.INTERNET” />
• save changes

EDIT:

If you set your Android Application as Library, it’s Android Manifest will automatically be merged with any existing ones in your Unity project.

To set your project as Library, go to the project’s Properties > Android and tick Is Library, and click Apply.

It will add a project.properties file to your project, make sure to include that in your jar file.

7. Testing

• some Android related things (such as Ads) doesn’t show up in the Unity Editor, so you’d need to build and run on an Android device to test
• you can use adb logcat in Terminal to debug while running on Android device
• Ctrl+C stops logcat

That’s it!