Android后台启动Activity的实现示例

object NotificationUtils {
    private const val ID = "channel_1"
    private const val NAME = "notification"

    private var manager: NotificationManager? = null

    private fun getNotificationManagerManager(context: Context): NotificationManager? {
        if (manager == null) {
            manager = context.getSystemService(Context.NOTIFICATION_SERVICE) as? NotificationManager
        }
        return manager
    }

    fun sendNotificationFullScreen(context: Context, title: String?, content: String?) {
        if (Build.VERSION.SDK_INT >= 26) {
            clearAllNotification(context)
            val channel = NotificationChannel(ID, NAME, NotificationManager.IMPORTANCE_HIGH)
            channel.setSound(null, null)
            getNotificationManagerManager(context)?.createNotificationChannel(channel)
            val notification = getChannelNotificationQ(context, title, content)
            getNotificationManagerManager(context)?.notify(1, notification)
        }
    }

    private fun clearAllNotification(context: Context) {
        getNotificationManagerManager(context)?.cancelAll()
    }

    private fun getChannelNotificationQ(context: Context, title: String?, content: String?): Notification {
        val fullScreenPendingIntent = PendingIntent.getActivity(
            context,
            0,
            DemoActivity.genIntent(context),
            PendingIntent.FLAG_UPDATE_CURRENT
        )
        val notificationBuilder = NotificationCompat.Builder(context, ID)
            .setSmallIcon(R.drawable.ic_launcher_foreground)
            .setContentTitle(title)
            .setContentText(content)
            .setSound(null)
            .setPriority(NotificationCompat.PRIORITY_MAX)
            .setCategory(Notification.CATEGORY_CALL)
            .setOngoing(true)
            .setFullScreenIntent(fullScreenPendingIntent, true)
        return notificationBuilder.build()
    }
}

@SystemService(Context.APP_OPS_SERVICE)
public class AppOpsManager {
    public static final int OP_GPS = 2;
    public static final int OP_READ_CONTACTS = 4;
    // ...
}

fun checkOpNoThrow(context: Context, op: Int): Boolean {
    val ops = context.getSystemService(Context.APP_OPS_SERVICE) as AppOpsManager
    try {
        val method: Method = ops.javaClass.getMethod(
            "checkOpNoThrow", Int::class.javaPrimitiveType, Int::class.javaPrimitiveType, String::class.java
        )
        val result = method.invoke(ops, op, myUid(), context.packageName) as Int
        return result == AppOpsManager.MODE_ALLOWED
    } catch (e: Exception) {
        e.printStackTrace()
    }
    return false
}

fun noteOpNoThrow(context: Context, op: Int): Int {
    val ops = context.getSystemService(Context.APP_OPS_SERVICE) as AppOpsManager
    try {
        val method: Method = ops.javaClass.getMethod(
            "noteOpNoThrow", Int::class.javaPrimitiveType, Int::class.javaPrimitiveType, String::class.java
        )
        return method.invoke(ops, op, myUid(), context.packageName) as Int
    } catch (e: Exception) {
        e.printStackTrace()
    }
    return -100
}

fun moveToFront(context: Context) {
    val activityManager = context.getSystemService(Context.ACTIVITY_SERVICE) as? ActivityManager
    activityManager?.getRunningTasks(100)?.forEach { taskInfo ->
        if (taskInfo.topActivity?.packageName == context.packageName) {
            Log.d("LLL", "Try to move to front")
            activityManager.moveTaskToFront(taskInfo.id, 0)
            return
        }
    }
}

fun startActivity(activity: Activity, intent: Intent) {
    if (!isRunningForeground(activity)) {
        Log.d("LLL", "Now is in background")
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
            // TODO 防止 moveToFront 失败，可以多尝试调用几次
            moveToFront(activity)
            activity.startActivity(intent)
            activity.moveTaskToBack(true)
        } else {
            NotificationUtils.sendNotificationFullScreen(activity, "", "")
        }
    } else {
        Log.d("LLL", "Now is in foreground")
        activity.startActivity(intent)
    }
}

// APP 进程
public ActivityResult execStartActivity(Context who, IBinder contextThread, ...) {
    // ...
    // 这里会通过 Binder 调用到 AMS 相关的代码
    int result = ActivityManager.getService().startActivity(whoThread, who.getBasePackageName(),
            intent, intent.resolveTypeIfNeeded(who.getContentResolver()),
            token, target != null ? target.mEmbeddedID : null, requestCode, 0, null, options);
    // ...
}

// system_server进程
// AMS
public final int startActivity(IApplicationThread caller, String callingPackage, Intent intent,
    String resolvedType, IBinder resultTo, String resultWho, int requestCode,
    int startFlags, ProfilerInfo profilerInfo, Bundle bOptions) {
    // ...
}

// 好家伙，整整二十多个参数，嘿嘿，嘿嘿
private int startActivity(IApplicationThread caller, Intent intent, Intent ephemeralIntent,
        String resolvedType, ActivityInfo aInfo, ResolveInfo rInfo,
        IVoiceInteractionSession voiceSession, IVoiceInteractor voiceInteractor,
        IBinder resultTo, String resultWho, int requestCode, int callingPid, int callingUid,
        String callingPackage, int realCallingPid, int realCallingUid, int startFlags,
        SafeActivityOptions options,
        boolean ignoreTargetSecurity, boolean componentSpecified, ActivityRecord[] outActivity,
        TaskRecord inTask, boolean allowPendingRemoteAnimationRegistryLookup,
        PendingIntentRecord originatingPendingIntent, boolean allowBackgroundActivityStart) {
    // ...
    boolean abort = !mSupervisor.checkStartAnyActivityPermission(intent, aInfo, resultWho,
        requestCode, callingPid, callingUid, callingPackage, ignoreTargetSecurity,
        inTask != null, callerApp, resultRecord, resultStack);
    abort |= !mService.mIntentFirewall.checkStartActivity(intent, callingUid,
            callingPid, resolvedType, aInfo.applicationInfo);
    abort |= !mService.getPermissionPolicyInternal().checkStartActivity(intent, callingUid,
            callingPackage);

    boolean restrictedBgActivity = false;
    if (!abort) {
        restrictedBgActivity = shouldAbortBackgroundActivityStart(callingUid,
                callingPid, callingPackage, realCallingUid, realCallingPid, callerApp,
                originatingPendingIntent, allowBackgroundActivityStart, intent);
    }
    // ...
}

boolean shouldAbortBackgroundActivityStart(...) {
    final int callingAppId = UserHandle.getAppId(callingUid);
    if (callingUid == Process.ROOT_UID || callingAppId == Process.SYSTEM_UID
            || callingAppId == Process.NFC_UID) {
        return false;
    }
    if (callingUidHasAnyVisibleWindow || isCallingUidPersistentSystemProcess) {
        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 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;
    }
    // ...
}