最近项目中遇到一个问题：一个客户应用从后台启动Activity，有如下打印

Slog.w(TAG, "Background activity start [callingPackage: " + callingPackage
                + "; callingUid: " + callingUid
                + "; isCallingUidForeground: " + isCallingUidForeground
                + "; isCallingUidPersistentSystemProcess: " + isCallingUidPersistentSystemProcess
                + "; realCallingUid: " + realCallingUid
                + "; isRealCallingUidForeground: " + isRealCallingUidForeground
                + "; isRealCallingUidPersistentSystemProcess: "
                + isRealCallingUidPersistentSystemProcess
                + "; originatingPendingIntent: " + originatingPendingIntent
                + "; isBgStartWhitelisted: " + allowBackgroundActivityStart
                + "; intent: " + intent
                + "; callerApp: " + callerApp
                + "]");

通过在源代码里面搜索，找到对应的文件是

frameworks/base/services/core/java/com/android/server/wm/ActivityStarter.java

在shouldAbortBackgroundActivityStart方法里面会判断是否拦截，方法如下：

   boolean shouldAbortBackgroundActivityStart(int callingUid, int callingPid,
            final String callingPackage, int realCallingUid, int realCallingPid,
            WindowProcessController callerApp, PendingIntentRecord originatingPendingIntent,
            boolean allowBackgroundActivityStart, Intent intent) {
        // don't abort for the most important UIDs
        final int callingAppId = UserHandle.getAppId(callingUid);
        if (callingUid == Process.ROOT_UID || callingAppId == Process.SYSTEM_UID
                || callingAppId == Process.NFC_UID) {
            return false;
        }
        // don't abort if the callingUid has a visible window or is a persistent system process
        final int callingUidProcState = mService.getUidState(callingUid);
        final boolean callingUidHasAnyVisibleWindow =
                mService.mWindowManager.mRoot.isAnyNonToastWindowVisibleForUid(callingUid);
        final boolean isCallingUidForeground = callingUidHasAnyVisibleWindow
                || callingUidProcState == ActivityManager.PROCESS_STATE_TOP
                || callingUidProcState == ActivityManager.PROCESS_STATE_BOUND_TOP;
        final boolean isCallingUidPersistentSystemProcess =
                callingUidProcState <= ActivityManager.PROCESS_STATE_PERSISTENT_UI;
        if (callingUidHasAnyVisibleWindow || isCallingUidPersistentSystemProcess) {
            return false;
        }
        // take realCallingUid into consideration
        final int realCallingUidProcState = (callingUid == realCallingUid)
                ? callingUidProcState
                : mService.getUidState(realCallingUid);
        final boolean realCallingUidHasAnyVisibleWindow = (callingUid == realCallingUid)
                ? callingUidHasAnyVisibleWindow
                : mService.mWindowManager.mRoot.isAnyNonToastWindowVisibleForUid(realCallingUid);
        final boolean isRealCallingUidForeground = (callingUid == realCallingUid)
                ? isCallingUidForeground
                : realCallingUidHasAnyVisibleWindow
                        || realCallingUidProcState == ActivityManager.PROCESS_STATE_TOP;
        final int realCallingAppId = UserHandle.getAppId(realCallingUid);
        final boolean isRealCallingUidPersistentSystemProcess = (callingUid == realCallingUid)
                ? isCallingUidPersistentSystemProcess
                : (realCallingAppId == Process.SYSTEM_UID)
                        || realCallingUidProcState <= ActivityManager.PROCESS_STATE_PERSISTENT_UI;
        if (realCallingUid != callingUid) {
            // don't abort if the realCallingUid has a visible window
            if (realCallingUidHasAnyVisibleWindow) {
                return false;
            }
            // if the realCallingUid is a persistent system process, abort if the IntentSender
            // wasn't whitelisted to start an activity
            if (isRealCallingUidPersistentSystemProcess && allowBackgroundActivityStart) {
                return false;
            }
            // don't abort if the realCallingUid is an associated companion app
            if (mService.isAssociatedCompanionApp(UserHandle.getUserId(realCallingUid),
                    realCallingUid)) {
                return false;
            }
        }
        // don't abort if the callingUid has START_ACTIVITIES_FROM_BACKGROUND permission
        if (mService.checkPermission(START_ACTIVITIES_FROM_BACKGROUND, callingPid, callingUid)
                == PERMISSION_GRANTED) {
            return false;
        }
        // don't abort if the caller has the same uid as the recents component
        if (mSupervisor.mRecentTasks.isCallerRecents(callingUid)) {
            return false;
        }
        // don't abort if the callingUid is the device owner
        if (mService.isDeviceOwner(callingUid)) {
            return false;
        }
        // don't abort if the callingUid has companion device
        final int callingUserId = UserHandle.getUserId(callingUid);
        if (mService.isAssociatedCompanionApp(callingUserId, callingUid)) {
            return false;
        }
        // If we don't have callerApp at this point, no caller was provided to startActivity().
        // That's the case for PendingIntent-based starts, since the creator's process might not be
        // up and alive. If that's the case, we retrieve the WindowProcessController for the send()
        // caller, so that we can make the decision based on its foreground/whitelisted state.
        int callerAppUid = callingUid;
        if (callerApp == null) {
            callerApp = mService.getProcessController(realCallingPid, realCallingUid);
            callerAppUid = realCallingUid;
        }
        // don't abort if the callerApp or other processes of that uid are whitelisted in any way
        if (callerApp != null) {
            // first check the original calling process
            if (callerApp.areBackgroundActivityStartsAllowed()) {
                return false;
            }
            // only if that one wasn't whitelisted, check the other ones
            final ArraySet<WindowProcessController> uidProcesses =
                    mService.mProcessMap.getProcesses(callerAppUid);
            if (uidProcesses != null) {
                for (int i = uidProcesses.size() - 1; i >= 0; i--) {
                    final WindowProcessController proc = uidProcesses.valueAt(i);
                    if (proc != callerApp && proc.areBackgroundActivityStartsAllowed()) {
                        return false;
                    }
                }
            }
        }
        // don't abort if the callingUid has SYSTEM_ALERT_WINDOW permission
        if (mService.hasSystemAlertWindowPermission(callingUid, callingPid, callingPackage)) {
            Slog.w(TAG, "Background activity start for " + callingPackage
                    + " allowed because SYSTEM_ALERT_WINDOW permission is granted.");
            return false;
        }
        // anything that has fallen through would currently be aborted
        Slog.w(TAG, "Background activity start [callingPackage: " + callingPackage
                + "; callingUid: " + callingUid
                + "; isCallingUidForeground: " + isCallingUidForeground
                + "; isCallingUidPersistentSystemProcess: " + isCallingUidPersistentSystemProcess
                + "; realCallingUid: " + realCallingUid
                + "; isRealCallingUidForeground: " + isRealCallingUidForeground
                + "; isRealCallingUidPersistentSystemProcess: "
                + isRealCallingUidPersistentSystemProcess
                + "; originatingPendingIntent: " + originatingPendingIntent
                + "; isBgStartWhitelisted: " + allowBackgroundActivityStart
                + "; intent: " + intent
                + "; callerApp: " + callerApp
                + "]");
        // log aborted activity start to TRON
        if (mService.isActivityStartsLoggingEnabled()) {
            mSupervisor.getActivityMetricsLogger().logAbortedBgActivityStart(intent, callerApp,
                    callingUid, callingPackage, callingUidProcState, callingUidHasAnyVisibleWindow,
                    realCallingUid, realCallingUidProcState, realCallingUidHasAnyVisibleWindow,
                    (originatingPendingIntent != null));
        }
        return true;
    }

从此方法可以看出，有如下打印，就是此方法返回true,拦截启动

Slog.w(TAG, "Background activity start [callingPackage: " + callingPackage

查看官方文档，在android q版本上增加了对后台启动Activity的限制
https://developer.android.google.cn/guide/components/activities/background-starts

新增加了一个权限定义在

frameworks/base/core/res/AndroidManifest.xml

具体定义如下：

<permission android:name="android.permission.START_ACTIVITIES_FROM_BACKGROUND"
        android:protectionLevel="signature|privileged|vendorPrivileged|oem|verifier" />

应用预制在system/app下是不满足条件的，修改到system/priv-app/目录下，满足privileged这个条件，不会拦截