获取屏幕上正在显示的activity

参考文章 http://chroya.iteye.com/blog/754608

ActivityManager am = 
			(ActivityManager) context.getSystemService(Activity.ACTIVITY_SERVICE);
		ComponentName cn = am.getRunningTasks(1).get(0).topActivity;
		
		Log.d("", "pkg:"+cn.getPackageName());
		Log.d("", "cls:"+cn.getClassName());