android 如何判断程序是否在前台运行

protected static boolean isTopActivity(Activity activity){

        String packageName = "xxxxx";

        ActivityManager activityManager = (ActivityManager) activity.getSystemService(Context.ACTIVITY_SERVICE);

        List<RunningTaskInfo>  tasksInfo = activityManager.getRunningTasks(1);  

        if(tasksInfo.size() > 0){  

            System.out.println("---------------包名-----------"+tasksInfo.get(0).topActivity.getPackageName());

            //应用程序位于堆栈的顶层  

            if(packageName.equals(tasksInfo.get(0).topActivity.getPackageName())){  

                return true;  

            }  

        }  

        return false;

    }