根据后台任务或服务确定当前的前台应用程序

我希望有一个在后台运行的应用程序，该应用程序知道何时运行任何内置应用程序（消息，联系人等）。

所以我的问题是：

1. 我应该如何在后台运行我的应用程序。

2. 我的后台应用程序如何知道当前在前台运行的应用程序是什么。

有经验的人们的回应将不胜感激。

关于“ 2.我的后台应用程序如何才能知道当前在前台运行的应用程序是什么”。

不要使用该getRunningAppProcesses()方法，因为根据我的经验，这会返回各种各样的系统垃圾，您将获得多个具有的结果RunningAppProcessInfo.IMPORTANCE_FOREGROUND。使用getRunningTasks()替代

这是我在服务中使用的代码，用于标识当前的前台应用程序，这非常容易：

ActivityManager am = (ActivityManager) AppService.this.getSystemService(ACTIVITY_SERVICE);
// The first in the list of RunningTasks is always the foreground task.
RunningTaskInfo foregroundTaskInfo = am.getRunningTasks(1).get(0);

就是这样，然后您可以轻松访问前台应用程序/活动的详细信息：

String foregroundTaskPackageName = foregroundTaskInfo .topActivity.getPackageName();
PackageManager pm = AppService.this.getPackageManager();
PackageInfo foregroundAppPackageInfo = pm.getPackageInfo(foregroundTaskPackageName, 0);
String foregroundTaskAppName = foregroundAppPackageInfo.applicationInfo.loadLabel(pm).toString();

这需要在活动清单中获得额外的许可，并且运行良好。

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

我不得不用困难的方式找出正确的解决方案。以下代码是cyanogenmod7的一部分（平板电脑进行了调整），并在android 2.3.3 / gingerbread上进行了测试。

方法：

• getForegroundApp-返回前台应用程序。
• getActivityForApp-返回找到的应用程序的活动。
• isStillActive-确定先前找到的应用是否仍然是活动应用。
• isRunningService-getForegroundApp的辅助功能

希望可以全面解决此问题（：

private RunningAppProcessInfo getForegroundApp() {
    RunningAppProcessInfo result=null, info=null;

    if(mActivityManager==null)
        mActivityManager = (ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
    List <RunningAppProcessInfo> l = mActivityManager.getRunningAppProcesses();
    Iterator <RunningAppProcessInfo> i = l.iterator();
    while(i.hasNext()){
        info = i.next();
        if(info.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND
                && !isRunningService(info.processName)){
            result=info;
            break;
        }
    }
    return result;
}

private ComponentName getActivityForApp(RunningAppProcessInfo target){
    ComponentName result=null;
    ActivityManager.RunningTaskInfo info;

    if(target==null)
        return null;

    if(mActivityManager==null)
        mActivityManager = (ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
    List <ActivityManager.RunningTaskInfo> l = mActivityManager.getRunningTasks(9999);
    Iterator <ActivityManager.RunningTaskInfo> i = l.iterator();

    while(i.hasNext()){
        info=i.next();
        if(info.baseActivity.getPackageName().equals(target.processName)){
            result=info.topActivity;
            break;
        }
    }

    return result;
}

private boolean isStillActive(RunningAppProcessInfo process, ComponentName activity)
{
    // activity can be null in cases, where one app starts another. for example, astro
    // starting rock player when a move file was clicked. we dont have an activity then,
    // but the package exits as soon as back is hit. so we can ignore the activity
    // in this case
    if(process==null)
        return false;

    RunningAppProcessInfo currentFg=getForegroundApp();
    ComponentName currentActivity=getActivityForApp(currentFg);

    if(currentFg!=null && currentFg.processName.equals(process.processName) &&
            (activity==null || currentActivity.compareTo(activity)==0))
        return true;

    Slog.i(TAG, "isStillActive returns false - CallerProcess: " + process.processName + " CurrentProcess: "
            + (currentFg==null ? "null" : currentFg.processName) + " CallerActivity:" + (activity==null ? "null" : activity.toString())
            + " CurrentActivity: " + (currentActivity==null ? "null" : currentActivity.toString()));
    return false;
}

private boolean isRunningService(String processname){
    if(processname==null || processname.isEmpty())
        return false;

    RunningServiceInfo service;

    if(mActivityManager==null)
        mActivityManager = (ActivityManager)mContext.getSystemService(Context.ACTIVITY_SERVICE);
    List <RunningServiceInfo> l = mActivityManager.getRunningServices(9999);
    Iterator <RunningServiceInfo> i = l.iterator();
    while(i.hasNext()){
        service = i.next();
        if(service.process.equals(processname))
            return true;
    }

    return false;
}

尝试以下代码：

ActivityManager activityManager = (ActivityManager) newContext.getSystemService( Context.ACTIVITY_SERVICE );
List<RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
for(RunningAppProcessInfo appProcess : appProcesses){
    if(appProcess.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND){
        Log.i("Foreground App", appProcess.processName);
    }
}

进程名称是在前台运行的应用程序的程序包名称。将其与应用程序的程序包名称进行比较。如果相同，则您的应用程序在前台运行。

我希望这回答了你的问题。

从棒棒糖开始，这种情况发生了变化。请先找到以下代码，然后该用户必须进入设置->安全->（向下滚动到最后）具有使用权限的应用->将权限授予我们的应用

private void printForegroundTask() {
    String currentApp = "NULL";
    if(android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP) {
        UsageStatsManager usm = (UsageStatsManager) this.getSystemService(Context.USAGE_STATS_SERVICE);
        long time = System.currentTimeMillis();
        List<UsageStats> appList = usm.queryUsageStats(UsageStatsManager.INTERVAL_DAILY,  time - 1000*1000, time);
        if (appList != null && appList.size() > 0) {
            SortedMap<Long, UsageStats> mySortedMap = new TreeMap<Long, UsageStats>();
            for (UsageStats usageStats : appList) {
                mySortedMap.put(usageStats.getLastTimeUsed(), usageStats);
            }
            if (mySortedMap != null && !mySortedMap.isEmpty()) {
                currentApp = mySortedMap.get(mySortedMap.lastKey()).getPackageName();
            }
        }
    } else {
        ActivityManager am = (ActivityManager)this.getSystemService(Context.ACTIVITY_SERVICE);
        List<ActivityManager.RunningAppProcessInfo> tasks = am.getRunningAppProcesses();
        currentApp = tasks.get(0).processName;
    }

    Log.e(TAG, "Current App in foreground is: " + currentApp);
}

对于需要从我们自己的服务/后台线程检查我们的应用程序是否在前台的情况。这是我实施的方式，对我来说很好用：

public class TestApplication extends Application implements Application.ActivityLifecycleCallbacks {

    public static WeakReference<Activity> foregroundActivityRef = null;

    @Override
    public void onActivityStarted(Activity activity) {
        foregroundActivityRef = new WeakReference<>(activity);
    }

    @Override
    public void onActivityStopped(Activity activity) {
        if (foregroundActivityRef != null && foregroundActivityRef.get() == activity) {
            foregroundActivityRef = null;
        }
    }

    // IMPLEMENT OTHER CALLBACK METHODS
}

现在要从其他类中检查应用是否在前台，只需调用：

if(TestApplication.foregroundActivityRef!=null){
    // APP IS IN FOREGROUND!
    // We can also get the activity that is currently visible!
}

更新（如SHS所指出）：

不要忘记在Application类的onCreate方法中注册回调。

@Override
public void onCreate() {
    ...
    registerActivityLifecycleCallbacks(this);
}

为了确定前台应用程序，可以使用来检测前台应用程序，可以使用https://github.com/ricvalerio/foregroundappchecker。根据设备的android版本，它使用不同的方法。

至于服务，存储库还提供您需要的代码。本质上，让android studio为您创建服务，然后onCreate添加使用appChecker的代码段。但是，您将需要请求许可。

考虑到getRunningTasks()过时和getRunningAppProcesses()不可靠，我决定组合使用StackOverflow中提到的2种方法：

   private boolean isAppInForeground(Context context)
    {
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP)
        {
            ActivityManager am = (ActivityManager) context.getSystemService(ACTIVITY_SERVICE);
            ActivityManager.RunningTaskInfo foregroundTaskInfo = am.getRunningTasks(1).get(0);
            String foregroundTaskPackageName = foregroundTaskInfo.topActivity.getPackageName();

            return foregroundTaskPackageName.toLowerCase().equals(context.getPackageName().toLowerCase());
        }
        else
        {
            ActivityManager.RunningAppProcessInfo appProcessInfo = new ActivityManager.RunningAppProcessInfo();
            ActivityManager.getMyMemoryState(appProcessInfo);
            if (appProcessInfo.importance == IMPORTANCE_FOREGROUND || appProcessInfo.importance == IMPORTANCE_VISIBLE)
            {
                return true;
            }

            KeyguardManager km = (KeyguardManager) context.getSystemService(Context.KEYGUARD_SERVICE);
            // App is foreground, but screen is locked, so show notification
            return km.inKeyguardRestrictedInputMode();
        }
    }

该ActivityManager类是适当的工具，看看哪些进程正在运行。

要在后台运行，通常需要使用Service。

这对我有用。但是它仅给出主菜单名称。就是说，如果用户打开了设置->蓝牙->设备名称屏幕，RunningAppProcessInfo便将其称为设置。无法深入研究

ActivityManager activityManager = (ActivityManager) context.getSystemService( Context.ACTIVITY_SERVICE );
                PackageManager pm = context.getPackageManager();
                List<RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
                for(RunningAppProcessInfo appProcess : appProcesses) {              
                    if(appProcess.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
                        CharSequence c = pm.getApplicationLabel(pm.getApplicationInfo(appProcess.processName, PackageManager.GET_META_DATA));
                        Log.i("Foreground App", "package: " + appProcess.processName + " App: " + c.toString());
                    }               
                }

做这样的事情：

int showLimit = 20;

/* Get all Tasks available (with limit set). */
ActivityManager mgr = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
List<ActivityManager.RunningTaskInfo> allTasks = mgr.getRunningTasks(showLimit);
/* Loop through all tasks returned. */
for (ActivityManager.RunningTaskInfo aTask : allTasks) 
{                  
    Log.i("MyApp", "Task: " + aTask.baseActivity.getClassName()); 
    if (aTask.baseActivity.getClassName().equals("com.android.email.activity.MessageList")) 
        running=true;
}

在棒棒糖及以上：

添加到mainfest：

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

并执行以下操作：

if( mTaskId < 0 )
{
    List<AppTask> tasks = mActivityManager.getAppTasks(); 
    if( tasks.size() > 0 )
        mTaskId = tasks.get( 0 ).getTaskInfo().id;
}

这就是我检查应用程序是否处于前台的方式。注意我按照官方Android文档的建议使用AsyncTask。

`

    private class CheckIfForeground extends AsyncTask<Void, Void, Void> {
    @Override
    protected Void doInBackground(Void... voids) {

        ActivityManager activityManager = (ActivityManager) mContext.getSystemService(Context.ACTIVITY_SERVICE);
        List<ActivityManager.RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
        for (ActivityManager.RunningAppProcessInfo appProcess : appProcesses) {
            if (appProcess.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
                Log.i("Foreground App", appProcess.processName);

                if (mContext.getPackageName().equalsIgnoreCase(appProcess.processName)) {
                    Log.i(Constants.TAG, "foreground true:" + appProcess.processName);
                    foreground = true;
                    // close_app();
                }
            }
        }
        Log.d(Constants.TAG, "foreground value:" + foreground);
        if (foreground) {
            foreground = false;
            close_app();
            Log.i(Constants.TAG, "Close App and start Activity:");

        } else {
            //if not foreground
            close_app();
            foreground = false;
            Log.i(Constants.TAG, "Close App");

        }

        return null;
    }
}

并像这样执行AsyncTask。 new CheckIfForeground().execute();

我用一种方法组合了两个解决方案，它对我来说适用于API 24和API21。其他我没有测试。

Kotlin中的代码：

private fun isAppInForeground(context: Context): Boolean {
    val appProcessInfo = ActivityManager.RunningAppProcessInfo()
    ActivityManager.getMyMemoryState(appProcessInfo)
    if (appProcessInfo.importance == IMPORTANCE_FOREGROUND ||
            appProcessInfo.importance == IMPORTANCE_VISIBLE) {
        return true
    } else if (appProcessInfo.importance == IMPORTANCE_TOP_SLEEPING ||
            appProcessInfo.importance == IMPORTANCE_BACKGROUND) {
        return false
    }

    val am = context.getSystemService(Context.ACTIVITY_SERVICE) as ActivityManager
    val foregroundTaskInfo = am.getRunningTasks(1)[0]
    val foregroundTaskPackageName = foregroundTaskInfo.topActivity.packageName
    return foregroundTaskPackageName.toLowerCase() == context.packageName.toLowerCase()
}

并在清单中

<!-- Check whether app in background or foreground -->
<uses-permission android:name="android.permission.GET_TASKS" />