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我使用以下代码在我的应用程序中获取当前的前台应用程序包名称。我有一个运行 android 5 的用户，它总是返回 null （我有其他运行 android 5 的用户确认我的代码正在运行！）。用户安装我的应用程序，授予权限（我检查了它们，我的应用程序具有使用权限USAGE_STATS_SERVICE，然后我调用getCurrentForegroundPackage它并返回 null。应用程序在大约一分钟之前运行......它正在许多其他设备上运行......在哪里可能是问题吗？有什么想法吗？

代码 - 获取前台应用程序包

public static String getCurrentForegroundPackage(Context context)
{
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP)
    {
        String foregroundPackage = getCurrentForegroundPackage(context, Constants.CHECK_INTERVAL_SECOND);
        if (foregroundPackage == null)
            foregroundPackage = getCurrentForegroundPackage(context, Constants.CHECK_INTERVAL_MINUTE);
        if (foregroundPackage == null)
            foregroundPackage = getCurrentForegroundPackage(context, Constants.CHECK_INTERVAL_HOUR);
        return foregroundPackage;
    }
    else
    {
        ActivityManager am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
        List<ActivityManager.RunningTaskInfo> taskInfo = am.getRunningTasks(1);
        ComponentName componentInfo = taskInfo.get(0).topActivity;
        return componentInfo.getPackageName();
    }
}

@TargetApi(Build.VERSION_CODES.LOLLIPOP)
private static String getCurrentForegroundPackage(Context context, long interval)
{
    long to = System.currentTimeMillis();
    long from = to - interval;
    UsageStatsManager manager = (UsageStatsManager) context.getSystemService(Context.USAGE_STATS_SERVICE);
    UsageEvents usageEvents = manager.queryEvents(from, to);
    return getForeGroundPackage(usageEvents);
}

@TargetApi(Build.VERSION_CODES.LOLLIPOP)
private static String getForeGroundPackage(UsageEvents usageEvents)
{
    String packageName = null;
    long highestMoveToForegroundTimeStamp = 0;
    while (usageEvents.hasNextEvent())
    {
        UsageEvents.Event event = new UsageEvents.Event();
        usageEvents.getNextEvent(event);
        if (event.getEventType() == UsageEvents.Event.MOVE_TO_FOREGROUND)
        {
            long timeStamp = event.getTimeStamp();
            if (timeStamp > highestMoveToForegroundTimeStamp)
            {
                packageName = event.getPackageName();
                highestMoveToForegroundTimeStamp = timeStamp;
            }
        }
    }
    return packageName;
}

代码 - 检查我的应用程序是否有权限

@TargetApi(Build.VERSION_CODES.KITKAT)
public static boolean hasUsageAccess()
{
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP)
    {
        try
        {
            PackageManager packageManager = MainApp.get().getPackageManager();
            ApplicationInfo applicationInfo = packageManager.getApplicationInfo(MainApp.get().getPackageName(), 0);
            AppOpsManager appOpsManager = (AppOpsManager) MainApp.get().getSystemService(Context.APP_OPS_SERVICE);
            int mode = appOpsManager.checkOpNoThrow(AppOpsManager.OPSTR_GET_USAGE_STATS, applicationInfo.uid, applicationInfo.packageName);
            return mode == AppOpsManager.MODE_ALLOWED;
        }
        catch (Exception e)
        {
            L.e(PermissionUtil.class, e);
        }
        return false;
    }
    return true;
}
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