getRunningTask似乎无法在Android4.4.2中运行

Question

我想知道我的手机是否在带有isDesktop（）的桌面页面上，而logcat给出了false，如下所示。我想知道我的代码有什么问题。它在我的模拟器API 21中运行良好，但在我的手机Android 4.4.2中保持错误。

public boolean isDesktop() {
    Log.e("KOST", "Check");
    String[] activePackages;
    if (Build.VERSION.SDK_INT > Build.VERSION_CODES.KITKAT) {
        activePackages = getActivePackages();
    } else {
        activePackages = getActivePackagesCompat();
    }
    Log.e("KOST", Arrays.toString(activePackages));
    if (activePackages != null) {
        for (String activePackage : activePackages) {
            if (activePackage.equals("com.android.launcher")) {
                Log.e("isDesktop", "true");
                return true;
            }
        }
    }
    Log.e("isDesktop", "false");
    return false;

}

String[] getActivePackagesCompat() {
    final List<ActivityManager.RunningTaskInfo> taskInfo = am
            .getRunningTasks(1);
    final ComponentName componentName = taskInfo.get(0).topActivity;
    final String[] activePackages = new String[1];
    activePackages[0] = componentName.getPackageName();
    return activePackages;
}

String[] getActivePackages() {
    final Set<String> activePackages = new HashSet<String>();
    final List<ActivityManager.RunningAppProcessInfo> processInfos = am
            .getRunningAppProcesses();
    for (ActivityManager.RunningAppProcessInfo processInfo : processInfos) {
        if (processInfo.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
            activePackages.addAll(Arrays.asList(processInfo.pkgList));
        }
    }
    return activePackages.toArray(new String[activePackages.size()]);
}

下面是logcat输出：

    03-31 18:17:14.256  13148-13194/com.example.jackey.trafficmaster E/KOST﹕ Check

    03-31 18:17:14.261  13148-13194/com.example.jackey.trafficmaster E/KOST﹕ [com.sec.android.app.launcher]

    03-31 18:17:14.261  13148-13194/com.example.jackey.trafficmaster E/isDesktop﹕ false

    03-31 18:17:14.261  13148-13194/com.example.jackey.trafficmaster E/KOST﹕ Check

    03-31 18:17:14.271  13148-13194/com.example.jackey.trafficmaster E/KOST﹕ [com.sec.android.app.launcher]

    03-31 18:17:14.271  13148-13194/com.example.jackey.trafficmaster E/isDesktop﹕ false

    03-31 18:17:14.271  13148-13194/com.example.jackey.trafficmaster E/KOST﹕ Check

    03-31 18:17:14.271  13148-13194/com.example.jackey.trafficmaster E/KOST﹕ [com.sec.android.app.launcher]

    03-31 18:17:14.276  13148-13194/com.example.jackey.trafficmaster E/isDesktop﹕ false