Android操作系统服务（Context.getSystemService() ）

getSystemService是Android很重要的一个API，它是Activity的一个方法，根据传入的NAME来取得对应的Object，然后转换成相应的服务对象。下面介绍系统相应的服务：

代码示例，使用判断网络连接是否可用，并判断是否是wifi：

    protected int checkNetworkInfo() {
        ConnectivityManager con = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkinfo = con.getActiveNetworkInfo();
        if (networkinfo == null || !networkinfo.isAvailable()) {
            // 当前网络不可用
            return 1;
        }
        boolean wifi = con.getNetworkInfo(ConnectivityManager.TYPE_WIFI)
                .isConnectedOrConnecting();
        if (wifi) {
            // 使用wifi上网
            return 2;
        }
        return 3;
    }

转载：获取Android正在运行的任务和服务

检测某ActivityUpdate是否在当前Task的栈顶

public static boolean isTopActivy(String cmdName, Context context)
    {
        ActivityManager manager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
        List<RunningTaskInfo> runningTaskInfos = manager.getRunningTasks(Integer.MAX_VALUE);
        String cmpNameTemp = null;
        if (null != runningTaskInfos)
        {
            cmpNameTemp = (runningTaskInfos.get(0).topActivity).toString();
        }        if (null == cmpNameTemp)
        {
            return false;
        }        return cmpNameTemp.equals(cmdName);    }

判断Android应用是否在前台

public static boolean isAppOnForeground(Context context)
    {
        ActivityManager activityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
        String packageName = context.getPackageName();
        List<RecentTaskInfo> appTask = activityManager.getRecentTasks(Integer.MAX_VALUE, 1);        if (appTask == null)
        {
            return false;
        }        if (appTask.get(0).baseIntent.toString().contains(packageName))
        {
            return true;
        }
        return false;
    }

获取Android手机内安装的所有桌面

private static List<String> getAllTheLauncher(Context context)
    {
        List<String> names = null;
        PackageManager pkgMgt = context.getPackageManager();
        Intent it = new Intent(Intent.ACTION_MAIN);
        it.addCategory(Intent.CATEGORY_HOME);
        List<ResolveInfo> ra = pkgMgt.queryIntentActivities(it, 0);
        if (ra.size() != 0)
        {
            names = new ArrayList<String>();
        }
        for (int i = 0; i < ra.size(); i++)
        {
            String packageName = ra.get(i).activityInfo.packageName;
            names.add(packageName);
        }
        return names;
    }

Android 判断程序前后台状态

public static boolean isLauncherRunnig(Context context)
    {
        boolean result = false;
        List<String> names = getAllTheLauncher(context);
        ActivityManager mActivityManager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
        List<ActivityManager.RunningAppProcessInfo> appList = mActivityManager.getRunningAppProcesses();
        for (RunningAppProcessInfo running : appList)
        {
            if (running.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND)
            {
                for (int i = 0; i < names.size(); i++)
                {
                    if (names.get(i).equals(running.processName))
                    {
                        result = true;
                        break;
                    }
                }
            }
        }
        return result;
    }