在Android开发中，创建和切换用户是一个重要的功能，特别是在需要多用户支持的应用中，下面讲述一下用户切换的流程。
一、CarUserManager.java
准备创建新用户，可以减少真正创建用户的时间
@RequiresPermission(anyOf = {Manifest.permission.MANAGE_USERS,
Manifest.permission.CREATE_USERS})
public @NonNull UserInfo preCreateUser(@NonNull String userType)
throws UserOperationException {
try {
return mService.preCreateUserWithThrow(userType);
} catch (ServiceSpecificException e) {
throw UserOperationException.from(e);
} catch (RemoteException re) {
throw re.rethrowFromSystemServer();
}
}用户类型一般有车主、亲情、访客、临时还有一个system空间
51 @AddedIn(PlatformVersion.TIRAMISU_0)
52 public static final @UserIdInt int USER_SYSTEM = UserHandle.USER_SYSTEM;
55 @AddedIn(PlatformVersion.TIRAMISU_0)
56 public static final int FLAG_PRIMARY = UserInfo.FLAG_PRIMARY;
57 @AddedIn(PlatformVersion.TIRAMISU_0)
58 public static final int FLAG_ADMIN = UserInfo.FLAG_ADMIN;
59 @AddedIn(PlatformVersion.TIRAMISU_0)
60 public static final int FLAG_GUEST = UserInfo.FLAG_GUEST;
72 public static final int FLAG_EPHEMERAL = UserInfo.FLAG_EPHEMERAL;创建用户需要MANAGE_USERS跟Manifest.permission.CREATE_USERS权限，默认是会创建车主或者临时空间
@Deprecated
674 @AddedInOrBefore(majorVersion = 33, softRemovalVersion = 35, hardRemovalVersion = 37)
675 @RequiresPermission(anyOf = {android.Manifest.permission.MANAGE_USERS,
676 android.Manifest.permission.CREATE_USERS})
677 public AsyncFuture<UserCreationResult> createUser(@Nullable String name,
678 int flags) {
679 AndroidFuture<UserCreationResult> future = new AndroidFuture<>();
680 UserCreationRequest.Builder userCreationRequestBuilder = new UserCreationRequest.Builder();
681 if (name != null) {
682 userCreationRequestBuilder.setName(name);
683 }
684
685 if ((flags & UserManagerHelper.FLAG_ADMIN) == UserManagerHelper.FLAG_ADMIN) {
686 userCreationRequestBuilder.setAdmin();
687 }
688
689 if ((flags & UserManagerHelper.FLAG_EPHEMERAL) == UserManagerHelper.FLAG_EPHEMERAL) {
690 userCreationRequestBuilder.setEphemeral();
691 }
692
693 createUser(userCreationRequestBuilder.build(), Runnable::run, future::complete);
694 return new AndroidAsyncFuture<>(future);
695 }这里会调用CarUserService的createUser去创建用户
public void createUser(@NonNull UserCreationRequest userCreationRequest,
711 @NonNull @CallbackExecutor Executor executor,
712 @NonNull ResultCallback<UserCreationResult> callback) {
713 ...
742 mService.createUser(userCreationRequest, HAL_TIMEOUT_MS, resultCallbackImpl);
743 ...
751 }切换用户
@SystemApi
545 @RequiresPermission(anyOf = {android.Manifest.permission.MANAGE_USERS,
546 android.Manifest.permission.CREATE_USERS})
547 @ApiRequirements(minCarVersion = ApiRequirements.CarVersion.UPSIDE_DOWN_CAKE_0,
548 minPlatformVersion = ApiRequirements.PlatformVersion.TIRAMISU_0)
549 public void switchUser(@NonNull UserSwitchRequest userSwitchRequest,
550 @NonNull @CallbackExecutor Executor executor,
551 @NonNull ResultCallback<UserSwitchResult> callback) {
552 int uid = myUid();
553 int targetUserId = userSwitchRequest.getUserHandle().getIdentifier();
571 mService.switchUser(targetUserId, HAL_TIMEOUT_MS, resultCallbackImpl);
572
580 }退出用户
@RequiresPermission(anyOf = {android.Manifest.permission.MANAGE_USERS,
607 android.Manifest.permission.CREATE_USERS})
608 @AddedInOrBefore(majorVersion = 33)
609 public AsyncFuture<UserSwitchResult> logoutUser() {
610 int uid = myUid();
...
629 mService.logoutUser(HAL_TIMEOUT_MS, resultCallbackImpl);
...
638 }删除用户
public UserRemovalResult removeUser(@UserIdInt int userId) {
834 ...
836 removeUser(userRemovalRequest, Runnable::run, userRemovalResultCallback);
...
853 }
@SystemApi
781 @RequiresPermission(anyOf = {android.Manifest.permission.MANAGE_USERS,
782 android.Manifest.permission.CREATE_USERS})
783 @ApiRequirements(minCarVersion = ApiRequirements.CarVersion.UPSIDE_DOWN_CAKE_0,
784 minPlatformVersion = ApiRequirements.PlatformVersion.TIRAMISU_0)
785 public void removeUser(@NonNull UserRemovalRequest userRemovalRequest,
786 @NonNull @CallbackExecutor Executor executor,
787 @NonNull ResultCallback<UserRemovalResult> callback) {
788 ...
802 mService.removeUser(userRemovalRequest.getUserHandle().getIdentifier(),
803 resultCallbackImpl);
804 ...
812 }监听用户切换
@RequiresPermission(anyOf = {INTERACT_ACROSS_USERS, INTERACT_ACROSS_USERS_FULL})
864 @AddedInOrBefore(majorVersion = 33)
865 public void addListener(@NonNull @CallbackExecutor Executor executor,
866 @NonNull UserLifecycleListener listener) {
867 addListenerInternal(executor, /* filter= */null, listener);
868 }
public interface UserLifecycleListener {
1486 /**
1487 * Called to notify the given {@code event}.
1488 */1489 @AddedInOrBefore(majorVersion = 33)
1490 void onEvent(@NonNull UserLifecycleEvent event);
1491 }用户切换返回 UserLifecycleEvent的状态有，可以在返回的各个状态去做对应处理
/**
1371 * Gets the event type.
1372 *
1373 * @return either {@link CarUserManager#USER_LIFECYCLE_EVENT_TYPE_STARTING},
1374 * {@link CarUserManager#USER_LIFECYCLE_EVENT_TYPE_SWITCHING},
1375 * {@link CarUserManager#USER_LIFECYCLE_EVENT_TYPE_UNLOCKING},
1376 * {@link CarUserManager#USER_LIFECYCLE_EVENT_TYPE_UNLOCKED},
1377 * {@link CarUserManager#USER_LIFECYCLE_EVENT_TYPE_STOPPING} or
1378 * {@link CarUserManager#USER_LIFECYCLE_EVENT_TYPE_STOPPED} for all apps;
1379 * for apps {@link CarPackageManager#getTargetCarVersion() targeting car version}
1380 * {@link CarVersion.VERSION_CODES#TIRAMISU_1} or higher, it could be new types
1381 * added on later releases, such as
1382 * {@link CarUserManager#USER_LIFECYCLE_EVENT_TYPE_CREATED},
1383 * {@link CarUserManager#USER_LIFECYCLE_EVENT_TYPE_REMOVED} and possibly others.
1384 *
1385 */二、CarUserService
-
权限检查，每次会判断是否有ALLOWED_FLAGS_FOR_CREATE_USERS_PERMISSION中的权限，没有权限会直接抛异常，
2875 private static final int ALLOWED_FLAGS_FOR_CREATE_USERS_PERMISSION =
UserManagerHelper.FLAG_MANAGED_PROFILE2877
| UserManagerHelper.FLAG_PROFILE2878
| UserManagerHelper.FLAG_EPHEMERAL2879
| UserManagerHelper.FLAG_RESTRICTED2880
| UserManagerHelper.FLAG_GUEST2881
| UserManagerHelper.FLAG_DEMO2882
| UserManagerHelper.FLAG_FULL;
2898 private static void checkManageOrCreateUsersPermission(int creationFlags) {
2899 if ((creationFlags & ~ALLOWED_FLAGS_FOR_CREATE_USERS_PERMISSION) == 0) {
2900 if (!hasManageOrCreateUsersPermission()) {
2901 throw new SecurityException("You either need " + MANAGE_USERS + " or "2902 + CREATE_USERS + "permission to create a user with flags "2903 + creationFlags);
2904 }
2905 } else if (!hasManageUsersPermission()) {
2906 throw new SecurityException("You need " + MANAGE_USERS + " permission to create a user"
2907 + " with flags " + creationFlags);
2908 }
2909 }检查是否是系统应用跟是否有root权限
2911 private static boolean hasManageUsersPermission() {
2912 final int callingUid = Binder.getCallingUid();
2913 return isSameApp(callingUid, Process.SYSTEM_UID)
2914 || callingUid == Process.ROOT_UID2915
|| hasPermissionGranted(MANAGE_USERS, callingUid);
2916 }-
权限满足才会去创建用户，创建空间先生成NewUserResponse请求，里面有用户名、用户类型等，会先调用UserManager去创建用户，拿到UserHandler后会去判断是否支持User HAL,再调用UserHalService去创建用户，创建失败或者异常会调用removeCreatedUser去删除UserManager创建的newUser。
1299 @Override
1300 public void createUser(@NonNull UserCreationRequest userCreationRequest, int timeoutMs,1301 ResultCallbackImpl<UserCreationResult> callback) {
1302 String name = userCreationRequest.getName();
1303 String userType = userCreationRequest.isGuest() ? UserManager.USER_TYPE_FULL_GUEST1304 : UserManager.USER_TYPE_FULL_SECONDARY;
1305 int flags = 0;
1306 flags |= userCreationRequest.isAdmin() ? UserManagerHelper.FLAG_ADMIN : 0;
1307 flags |= userCreationRequest.isEphemeral() ? UserManagerHelper.FLAG_EPHEMERAL : 0;
1308
1309 createUser(name, userType, flags, timeoutMs, callback, /* hasCallerRestrictions= */ false);
1310 }
1311
1381 private void handleCreateUser(@Nullable String name, @NonNull String userType,
1382 int flags, int timeoutMs, @NonNull ResultCallbackImpl<UserCreationResult> callback,
1383 @NonNull UserHandle callingUser, boolean hasCallerRestrictions) {
//当前是访客没必要切换
1384 if (userType.equals(UserManager.USER_TYPE_FULL_GUEST) && flags != 0) {
1385 // Non-zero flags are not allowed when creating a guest user.
1386 String internalErroMessage = String
1387 .format(ERROR_TEMPLATE_INVALID_FLAGS_FOR_GUEST_CREATI
