Unity3D for Android: Using a Native Java Plugin to Grab the Android Device ID

The java code returns an MEID (Android Device ID) on CDMA phones (Verizon, Sprint), an IMEI on GSM phones (AT&T, T Mobile) and an Android ID on WIFI-only devices (no cellular network).

This code is based on Android Java Plugin for Unity example project in the Unity manual.

Why bother with a plugin?

I tried using Unity 3.5’s built-in SystemInfo.deviceUniqueIdentifier getter for obtaining a unique device ID but it didn’t meet our ad network’s requirements.

The set up in Unity 3.5

  • Drag the AndroidJava.jar file inside /Assets/Plugins/Android/. /Assets/Plugins/Android/bin/ worked too. This .jar file is created via Eclipse or command line javac based on the Java source code
  • Drag the example libjni.so file inside /Assets/Plugins/Android/. Make sure it’s inside /Plugins/Android or you’ll get a “DllNotFoundException: jni” error when you test on device with adb.
  • Drag JNI.cs into /Assets/Plugins/
  • Drag JavaVM.cs into /Assets/Plugins/
  • Make sure your project has an AndroidManifest.xml file inside /Assets/Plugins/Android/ with android.permission.READ_PHONE_STATE permission set. android.permission.READ_PHONE_STATE is needed to access an Android phone/tablet’s Android ID, IMEI or MEID. If you’re making HTTP calls you’ll also need additional permissions, etc.

Code that worked:

...
	private static IntPtr	JavaClass; 
	private static int		GetDeviceId;
...

	///if you're calling the plugin from a static method, you still have to make sure an instance of this script is attached to 
	///an empty GameObject in Hierarchy so Start() method runs & the below code initializes:	
	void Start() {
		
		#if UNITY_ANDROID 		
		
			// attach our thread to the java vm; obviously the main thread is already attached but this is good practice..
			JavaVM.AttachCurrentThread();
			
			// first we try to find our main activity..
			IntPtr cls_Activity		= JNI.FindClass("com/unity3d/player/UnityPlayer");
			int fid_Activity		= JNI.GetStaticFieldID(cls_Activity, "currentActivity", "Landroid/app/Activity;");
			IntPtr obj_Activity		= JNI.GetStaticObjectField(cls_Activity, fid_Activity);
			Debug.Log("obj_Activity = " + obj_Activity);		
			
			// create a JavaClass object...
               //"com/yourCompany/yourProjectName" should be your Bundle ID in Unity's Player Settings & should be the package name in your Java class
			IntPtr cls_JavaClass	= JNI.FindClass("com/yourCompany/yourProjectName/JavaClass"); 	
			int mid_JavaClass		= JNI.GetMethodID(cls_JavaClass, "<init>", "(Landroid/app/Activity;)V");
			IntPtr obj_JavaClass	= JNI.NewObject(cls_JavaClass, mid_JavaClass, obj_Activity);
			Debug.Log("java Helper object = " + obj_JavaClass);		
			
			// create a global reference to the JavaClass object and fetch method id(s)..
			JavaClass					= JNI.NewGlobalRef(obj_JavaClass);
			GetDeviceId					= JNI.GetMethodID(cls_JavaClass, "GetDeviceId", "()Ljava/lang/String;");
			Debug.Log("JavaClass global ref = " + JavaClass);
			Debug.Log("JavaClass GetDeviceId method id = " + GetDeviceId);						
		
		#endif			
	}	
...

	/// <summary>
	/// Gets the unique device for Android devices (IMEI, MEID or Android ID).
	/// </summary>
	/// <returns>
	/// Returns the id as a string.
	/// </returns>
	private string GetTheDeviceID()
	{		
		//didn't work... supposed to return IMEI but didn't 
		//return SystemInfo.deviceUniqueIdentifier;
		
		String dID = "";
		
		#if UNITY_ANDROID 
	
			// again, make sure the thread is attached..
			JavaVM.AttachCurrentThread();
						
			// get the Java String object from the Helper java object
			IntPtr str_cacheDir 	= JNI.CallObjectMethod(JavaClass, GetDeviceId);
			Debug.Log("str_cacheDir = " + str_cacheDir);		
			
			// convert the Java String into a Mono string
			IntPtr stringPtr = JNI.GetStringUTFChars(str_cacheDir, 0);
			Debug.Log("stringPtr = " +stringPtr);
			dID = Marshal.PtrToStringAnsi(stringPtr);
			JNI.ReleaseStringUTFChars(str_cacheDir, stringPtr); 		
					
		#endif

		Debug.Log(" Device ID value is = " + dID);
		
		return devID;		
	}		

/// call GetTheDeviceID() when you need to use it
...

The Java Code

The below code is based on requirements by ad networks that need to use a specific device ID for metrics like conversion tracking. It’s the main source file for generating the AndroidJava.jar you need to import into Unity’s Plugins folder.

The Device ID & hashing methods implementations come directly from Millennial Media‘s public wiki.

package com.yourCompany.yourProjectName;

import android.app.Activity;
import android.content.Context;
import android.provider.Settings.Secure;
import android.telephony.TelephonyManager;
import android.util.Log;
import java.io.File;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class JavaClass
{
	private Activity mActivity;
	
	public JavaClass(Activity currentActivity)
	{
		Log.i("JavaClass", "Constructor called with currentActivity = " + currentActivity);
		mActivity = currentActivity;
	}
	
	public String GetDeviceId()
	{		
		// Get the device ID
        String auid = android.provider.Settings.Secure.ANDROID_ID + "android_id";
        
        Context context = mActivity.getApplicationContext();
        
        TelephonyManager tm = (TelephonyManager)context.getSystemService(Context.TELEPHONY_SERVICE);
        if(tm != null)
        {
             try{
             auid = tm.getDeviceId();
             }
             catch (SecurityException e){
                  e.printStackTrace();
             }
             tm = null;
        }
        if(((auid == null) || (auid.length() == 0)) && (context != null))
             auid = Secure.getString(context.getContentResolver(), Secure.ANDROID_ID);
        if((auid == null) || (auid.length() == 0))
             auid = null;
        
        return auid;	
	}
	
	public String GetHashedDeviceIdSHA1()
	{
		String deviceId = GetDeviceId();
		
		String hashedDeviceId = hashInputSHA1(deviceId);
		
		return hashedDeviceId;
	}
	
	public String GetHashedDeviceIdMD5()
	{
		String deviceId = GetDeviceId();
		
		String hashedDeviceId = hashInputMD5(deviceId);
		
		return hashedDeviceId;
	}

	
	/**
     * <p>
     * Hashes the given plain text using the MD5 algorithm.
     * </p>
     * 
     * <p>
     * Example:
     * </p>
     * 
     * <p>
     * 098f6bcd4621d373cade4e832627b4f6
     * </p>
     * 
     * @param input
     *            The raw input which must be hashed.
     * @return A String representing the MD5 hashed output.
     */
    public static String hashInputMD5(String input)
    {
        String rv = null;
          
        if (input != null)
        {
            try
            {
                // Hash the user ID
                byte[] hashBytes = null;
                MessageDigest md = MessageDigest.getInstance("MD5");
                  
                synchronized (md)
                {
                    hashBytes = md.digest(input.getBytes());
                }
                 
                // Convert the hashed bytes into a properly formatted String
                if (hashBytes != null)
                {
                    StringBuilder sb = new StringBuilder();
                    
                    for (byte b : hashBytes)
                    {
                        String hexString = Integer.toHexString(0x00FF & b);
                        sb.append((hexString.length() == 1) ? "0" + hexString
                                                           : hexString);
                    }
                         
                    rv = sb.toString();
                }
            }
            catch (NoSuchAlgorithmException exception)
            {
                // This exception should never occur
            }
        }
         
        return rv;
    }
    
    /**
     * <p>
     * Hashes the given plain text using the SHA-1 algorithm.
     * </p>
     *
     * <p>
     * Example:
     * </p>
     *
     * <p>
     * a94a8fe5ccb19ba61c4c0873d391e987982fbbd3
     * </p>
     *
     * @param userId
     *            The raw input which must be hashed.
     * @return A String representing the SHA-1 hashed input.
     */
    public static String hashInputSHA1(String input)
    {
        String rv = null;
          
        if (input != null)
        {
            try
            {
                // Hash the user ID
                byte[] hashBytes = null;
                MessageDigest md = MessageDigest.getInstance("SHA1");
             
                synchronized (md)
                {
                    hashBytes = md.digest(input.getBytes());
                }
              
                // Convert the hashed bytes into a properly formatted String
                if (hashBytes != null)
                {
                    StringBuilder sb = new StringBuilder();
              
                    for (byte b : hashBytes)
                    {
                        String hexString = Integer.toHexString(0x00FF & b);
                        sb.append((hexString.length() == 1) ? "0" + hexString
                                                           : hexString);
                    }
                 
                    rv = sb.toString();
                }
            }
            catch (NoSuchAlgorithmException exception)
            {
                // This exception should never occur
            }
        }
             
        return rv;
    }
}

AndroidManifest.xml

If you don’t specify the correct permissions for your app and try to do things like make an HTTP request or grab the Device ID, you’ll get an error, like this:

10-02 15:06:49.223  7776  7784 W System.err: java.lang.SecurityException: Requires READ_PHONE_STATE: Neither user 10109 nor current process has android.permission.READ_PHONE_STATE.
10-02 15:06:49.223  7776  7784 W System.err: 	at android.os.Parcel.readException(Parcel.java:1322)
10-02 15:06:49.223  7776  7784 W System.err: 	at android.os.Parcel.readException(Parcel.java:1276)
10-02 15:06:49.223  7776  7784 W System.err: 	at com.android.internal.telephony.IPhoneSubInfo$Stub$Proxy.getDeviceId(IPhoneSubInfo.java:150)
10-02 15:06:49.231  7776  7784 W System.err: 	at android.telephony.TelephonyManager.getDeviceId(TelephonyManager.java:216)
10-02 15:06:49.231  7776  7784 W System.err: 	at com.yourCompany.yourProjectName.JavaClass.GetDeviceId(JavaClass.java:44)
10-02 15:06:49.231  7776  7784 W System.err: 	at com.unity3d.player.UnityPlayer.nativeRender(Native Method)
10-02 15:06:49.231  7776  7784 W System.err: 	at com.unity3d.player.UnityPlayer.onDrawFrame(Unknown Source)
10-02 15:06:49.231  7776  7784 W System.err: 	at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1363)
10-02 15:06:49.231  7776  7784 W System.err: 	at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1118)

I grabbed the default one from inside Unity.app on my Mac:

/Applications/Unity/Unity.app/Contents/PlaybackEngines/AndroidDevelopmentPlayer/AndroidManifest.xml

Kept all as is, just added my permissions and it worked:

<?xml version="1.0" encoding="utf-8"?>
<manifest
    xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.unity3d.player"
	android:installLocation="preferExternal"
    android:versionCode="1"
    android:versionName="1.0">
    <supports-screens
        android:smallScreens="true"
        android:normalScreens="true"
        android:largeScreens="true"
        android:xlargeScreens="true"
        android:anyDensity="true"/>

    <application
		android:icon="@drawable/app_icon"
        android:label="@string/app_name"
        android:debuggable="true">

        //...

    </application>

	
	<!-- PERMISSIONS -->
		<uses-permission android:name="android.permission.INTERNET"/>
		<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
		<uses-permission android:name="android.permission.READ_PHONE_STATE"/>
	
</manifest>

Some Other Possible Errors

Here’s a fun one, based on a dumb mistake I made. I put the libjni.so into the wrong folder, /Assets/Plugins/, instead of /Assets/Plugins/Android/:

10-02 14:43:17.147  7587  7596 E Unity   : Unable to find jni
10-02 14:43:17.147  7587  7596 E Unity   : Unable to find jni
10-02 14:43:17.155  7587  7596 E Unity   : Unable to find jni
10-02 14:43:17.163  7587  7596 E Unity   : Unable to find jni
10-02 14:43:17.171  7587  7596 E Unity   : Unable to find jni
10-02 14:43:17.171  7587  7596 E Unity   : Unable to find jni
10-02 14:43:17.179  7587  7596 E Unity   : Unable to find jni
10-02 14:43:17.186  7587  7596 E Unity   : Unable to find jni
10-02 14:43:17.897  1410  1410 I wpa_supplicant: WPS-AP-AVAILABLE 
10-02 14:43:17.905  1320  1411 V WifiMonitor: Event [WPS-AP-AVAILABLE ]
10-02 14:43:17.905  1320  1411 D WifiMonitor: WPS Event: WPS-AP-AVAILABLE 
10-02 14:43:18.264  1391  1391 D RadioSignalLevel: evdo dbmLevel: 4, snrLevel: 3
10-02 14:43:18.522  7587  7596 I Unity   : DllNotFoundException: jni
10-02 14:43:18.522  7587  7596 I Unity   :   at (wrapper managed-to-native) JavaVM:AttachCurrentThread ()
10-02 14:43:18.522  7587  7596 I Unity   :   at MyUnityDeviceIdScript.Start () [0x00000] in <filename unknown>:0 
10-02 14:43:18.522  7587  7596 I Unity   :  
10-02 14:43:18.522  7587  7596 I Unity   : (Filename:  Line: -1)
10-02 14:43:18.522  7587  7596 I Unity   : 
10-02 14:43:21.561  7587  7596 I Unity   : checkDeviceID() called
10-02 14:43:21.561  7587  7596 I Unity   :  
10-02 14:43:21.561  7587  7596 I Unity   : (Filename: ./Runtime/ExportGenerated/AndroidManaged/UnityEngineDebug.cpp Line: 43)
10-02 14:43:21.561  7587  7596 I Unity   : 
10-02 14:43:21.671  7587  7596 E Unity   : Unable to find jni
10-02 14:43:21.679  7587  7596 E Unity   : Unable to find jni
10-02 14:43:21.679  7587  7596 E Unity   : Unable to find jni
10-02 14:43:21.679  7587  7596 E Unity   : Unable to find jni
10-02 14:43:21.694  7587  7596 I Unity   : DllNotFoundException: jni
10-02 14:43:21.694  7587  7596 I Unity   :   at (wrapper managed-to-native) JavaVM:AttachCurrentThread ()
10-02 14:43:21.694  7587  7596 I Unity   :   at MyUnityDeviceIdScript.GetUniqueDeviceID () [0x00000] in <filename unknown>:0 
10-02 14:43:21.694  7587  7596 I Unity   :   at MyUnityDeviceIdScript.callTheUrlWithDeviceIDParam () [0x00000] in <filename unknown>:0 
10-02 14:43:21.694  7587  7596 I Unity   :   at GameManager.checkDeviceID () [0x00000] in <filename unknown>:0 
10-02 14:43:21.694  7587  7596 I Unity   :  

As far as I’ve seen, this code only works on a device. If you try to test inside Unity, you’ll get a similar error:

DllNotFoundException: jni
MyUnityDeviceIdScript.Start () (at Assets/Scripts/MyUnityDeviceIdScript.cs:21)

Once you test on a device, if all else if good, this error should go away.

NOTE: looks like this code requires some time to load up the JNI .so file. Not absolutely sure yet, but it appears if I have a fairly complex project and I try to call a JNI related method very soon after app loading, the app crashes with weird mystery output in adb logcat. Need to look into this more to be sure about the details.

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One thought on “Unity3D for Android: Using a Native Java Plugin to Grab the Android Device ID

  1. Hi,
    First of all, thanks for sharing. I got that error therefore I put following line beginning of Start and Update methods.

    if (Application.platform != RuntimePlatform.Android) return;

    It seems work well now but I wonder if I use an other library such as android.telephony.SmsManager.

    How can I reach SmsManager’s methods?

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