嘿@Capitan Luzzatto，

• 在LOLLIPOP（API 21）之前，我们可以从ActivityManager获取正在运行的应用程序列表
• 但是从LOLLIPOP，我们应该只从UsageStatsManager获取

首先，您需要2个权限来读取任务

<uses-permission android:name="android.permission.GET_TASKS" />
<uses-permission android:name="android.permission.PACKAGE_USAGE_STATS" />

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您应该首先检查用户API级别是否为21或更高，如果是，您应该获得以下使用访问设置的访问权限

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP && !mIsChecked) {
        if (getUsageStatsList(getActivity()).isEmpty()) {
            Intent intent = new Intent(Settings.ACTION_USAGE_ACCESS_SETTINGS);
            startActivity(intent);
        }
 }

型
获取使用统计信息列表

public static List<UsageStats> getUsageStatsList(Context context){
    UsageStatsManager usm = (UsageStatsManager) context.getSystemService("usagestats");
    Calendar calendar = Calendar.getInstance();
    long endTime = calendar.getTimeInMillis();
    calendar.add(Calendar.DATE, -1);
    long startTime = calendar.getTimeInMillis();
    List<UsageStats> usageStatsList = usm.queryUsageStats(UsageStatsManager.INTERVAL_DAILY,startTime,endTime);
    return usageStatsList;
}

型
最后，您可以使用以下方法获得最新的前台应用程序

public String getRecentApps(Context context) {
    String topPackageName = "";
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        UsageStatsManager mUsageStatsManager = (UsageStatsManager) context.getSystemService(Context.USAGE_STATS_SERVICE);
        long time = System.currentTimeMillis();
        UsageEvents usageEvents = mUsageStatsManager.queryEvents(time - 1000 * 30, System.currentTimeMillis() + (10 * 1000));
        UsageEvents.Event event = new UsageEvents.Event();
        while (usageEvents.hasNextEvent()) {
            usageEvents.getNextEvent(event);
        }
        if (event != null && !TextUtils.isEmpty(event.getPackageName()) && event.getEventType() == UsageEvents.Event.MOVE_TO_FOREGROUND) {
            if (AndroidUtils.isRecentActivity(event.getClassName())) {
                return event.getClassName();
            }
            return event.getPackageName();
        } else {
            topPackageName = "";
        }
    } else {
        ActivityManager am = (ActivityManager) context.getSystemService(context.ACTIVITY_SERVICE);
        List<ActivityManager.RunningTaskInfo> taskInfo = am.getRunningTasks(1);
        ComponentName componentInfo = taskInfo.get(0).topActivity;
        if (AndroidUtils.isRecentActivity(componentInfo.getClassName())) {
            return componentInfo.getClassName();
        }
        topPackageName = componentInfo.getPackageName();
    }
    return topPackageName;
}

型
要获取前台活动，请使用以下方法

public String getRecentActivity(Context context) {
    String topActivityName = "";
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
        UsageStatsManager mUsageStatsManager = (UsageStatsManager) context.getSystemService(Context.USAGE_STATS_SERVICE);
        long time = System.currentTimeMillis();
        UsageEvents usageEvents = mUsageStatsManager.queryEvents(time - 1000 * 30, System.currentTimeMillis() + (10 * 1000));
        UsageEvents.Event event = new UsageEvents.Event();
        while (usageEvents.hasNextEvent()) {
            usageEvents.getNextEvent(event);
        }
        if (event != null && !TextUtils.isEmpty(event.getPackageName()) && event.getEventType() == UsageEvents.Event.MOVE_TO_FOREGROUND) {
            return event.getClassName();
        } else {
            topActivityName = "";
        }
    } else {
        ActivityManager am = (ActivityManager) context.getSystemService(context.ACTIVITY_SERVICE);
        List<ActivityManager.RunningTaskInfo> taskInfo = am.getRunningTasks(1);
        ComponentName componentInfo = taskInfo.get(0).topActivity;
        topActivityName = componentInfo.getClassName();
    }
    return topActivityName;
}

型
AndroidUtils.java要在哈克的方式获得设备最近的屏幕，也许我们应该对此进行更多的调查，不确定它会在所有设备上工作，但它几乎适用于所有设备

public class AndroidUtils {
    private static final String RECENT_ACTIVITY;
    static {
        if (Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP) {
            RECENT_ACTIVITY = "com.android.systemui.recents.RecentsActivity";
        } else if (Build.VERSION.SDK_INT > Build.VERSION_CODES.JELLY_BEAN_MR1) {
            RECENT_ACTIVITY = "com.android.systemui.recent.RecentsActivity";
        } else {
            RECENT_ACTIVITY = "com.android.internal.policy.impl.RecentApplicationDialog";
        }
    }
    /**
     * To get the Device recent screen activity
     *
     * @param className
     * @return activity
     */
    public static boolean isRecentActivity(String className) {
        if (RECENT_ACTIVITY.equalsIgnoreCase(className)) {
            return true;
        }
        return false;
    }
}

型

由于安全问题，您不应该这样做。您不希望其他应用知道您当前打开的活动。因此其他应用不希望您监视它们。这是操作系统的限制。