Android plugin thread error

I am trying to alter the brightness in a android plugin but i am getting the following error.

AndroidJavaException: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

my unity code

public void Dim()
    	{
    		AndroidJNI.AttachCurrentThread ();
    		AndroidJavaClass unity = new AndroidJavaClass ("com.unity3d.player.UnityPlayer");
    		AndroidJavaObject currentActivity = unity.GetStatic<AndroidJavaObject> ("currentActivity");
    		currentActivity.Call("Dim");
    	}

android code

 public void Dim()
    {
    	WindowManager.LayoutParams WMLP = getWindow().getAttributes();
    	WMLP.screenBrightness = 0.1f;
    	getWindow().setAttributes(WMLP);
     }

Any help will be appreciated.

Fixed

UnityPlayer.currentActivity.runOnUiThread(new Runnable()
    	{
    		public void run()
    		{
    			WindowManager.LayoutParams WMLP = getWindow().getAttributes();
    	    	WMLP.screenBrightness = 0.1f;
    	    	getWindow().setAttributes(WMLP);
    	}
    	});