Android可以支持多个用户使用系统，通常第一个在系统中注册的用户将默认成为系统管理员。
不同用户的设置各不相同，并且不同用户安装的应用及应用数据也不相同。但是系统中和硬件相关的设置则是共用的，如网络设置等。
用户切换后前面用户运行的后台进程还可以继续运行，这样进行用户切换时无须中断一些后台进行的耗时操作（如下载）。
管理用户的系统服务–UserManagerService
UserManagerService的主要功能是创建和删除用户，以及查询用户信息。
1.在PackageManagerService中进行初始化
final ArrayMap<String, PackageParser.Package> mPackages =
new ArrayMap<String, PackageParser.Package>();
public PackageManagerService(Context context, Installer installer,
boolean factoryTest, boolean onlyCore) {
...
synchronized (mInstallLock) {
// writer
synchronized (mPackages) {
...
sUserManager = new UserManagerService(context, this, mPackages);
...
} // synchronized (mPackages)
} // synchronized (mInstallLock)
...
}
@Override
public void systemReady() {
...
sUserManager.systemReady();
...
}UserManagerService的构造方法如下：
UserManagerService(Context context, PackageManagerService pm, Object packagesLock) {
this(context, pm, packagesLock, Environment.getDataDirectory());
}调用了另一个构造方法，并多传递了一个参数：/data目录
private static final String USER_INFO_DIR = "system" + File.separator + "users";
private UserManagerService(Context context, PackageManagerService pm,
Object packagesLock, File dataDir) {
mContext = context;
mPm = pm;
mPackagesLock = packagesLock;
mHandler = new MainHandler();
synchronized (mPackagesLock) {
// /data/system/users
mUsersDir = new File(dataDir, USER_INFO_DIR);
mUsersDir.mkdirs();
// Make zeroth user directory, for services to migrate their files to that location
File userZeroDir = new File(mUsersDir, String.valueOf(UserHandle.USER_SYSTEM));
// 创建第一个用户目录：/data/system/users/0
userZeroDir.mkdirs();
// 设置访问文件的权限
FileUtils.setPermissions(mUsersDir.toString(),
FileUtils.S_IRWXU | FileUtils.S_IRWXG | FileUtils.S_IROTH | FileUtils.S_IXOTH,
-1, -1);
// /data/system/users/userlist.xml
mUserListFile = new File(mUsersDir, USER_LIST_FILENAME);
// 初始化来宾账户的默认限制条件
initDefaultGuestRestrictions();
// 从/data/system/users/userlist.xml文件读取用户信息
readUserListLP();
sInstance = this;
}
mLocalService = new LocalService();
LocalServices.addService(UserManagerInternal.class, mLocalService);
mLockPatternUtils = new LockPatternUtils(mContext);
mUserStates.put(UserHandle.USER_SYSTEM, UserState.STATE_BOOTING);
}
private final Bundle mGuestRestrictions = new Bundle();
// 初始化来宾账户的默认限制条件
private void initDefaultGuestRestrictions() {
synchronized (mGuestRestrictions) {
if (mGuestRestrictions.isEmpty()) {
// "no_config_wifi"，不允许配置WiFi
mGuestRestrictions.putBoolean(UserManager.DISALLOW_CONFIG_WIFI, true);
// "no_install_unknown_sources"，不允许安装未知来源的应用
mGuestRestrictions.putBoolean(UserManager.DISALLOW_INSTALL_UNKNOWN_SOURCES, true);
// "no_outgoing_calls"，不允许呼叫电话
mGuestRestrictions.putBoolean(UserManager.DISALLOW_OUTGOING_CALLS, true);
// "no_sms"，不允许收发短信
mGuestRestrictions.putBoolean(UserManager.DISALLOW_SMS, true);
}
}
}先看下/data/system/users/userlist.xml文件的内容，再分析读取过程，文件内容如下：
<?xml version='1.0' encoding='utf-8' standalone='yes' ?>
<users nextSerialNumber="10" version="5">
<guestRestrictions>
<restrictions no_config_wifi="true" no_outgoing_calls="true" no_sms="true" />
</guestRestrictions>
<user id="0" />
</users>// 从/data/system/users/userlist.xml文件读取用户信息
private final SparseArray<UserData> mUsers = new SparseArray<>();
private void readUserListLP() {
// 如果文件不存在，则创建管理员用户并返回
if (!mUserListFile.exists()) {
fallbackToSingleUserLP();
return;
}
FileInputStream fis = null;
AtomicFile userListFile = new AtomicFile(mUserListFile);
try {
fis = userListFile.openRead();
XmlPullParser parser = Xml.newPullParser();
parser.setInput(fis, StandardCharsets.UTF_8.name());
int type;
while ((type = parser.next()) != XmlPullParser.START_TAG
&& type != XmlPullParser.END_DOCUMENT) {
// Skip
}
if (type != XmlPullParser.START_TAG) {
Slog.e(LOG_TAG, "Unable to read user list");
// 如果文件异常，则创建管理员用户并返回
fallbackToSingleUserLP();
return;
}
mNextSerialNumber = -1;
// 解析文件
if (parser.getName().equals(TAG_USERS)) {
String lastSerialNumber = parser.getAttributeValue(null, ATTR_NEXT_SERIAL_NO);
if (lastSerialNumber != null) {
mNextSerialNumber = Integer.parseInt(lastSerialNumber);
}
String versionNumber = parser.getAttributeValue(null, ATTR_USER_VERSION);
if (versionNumber != null) {
mUserVersion = Integer.parseInt(versionNumber);
}
}
final Bundle newDevicePolicyGlobalUserRestrictions = new Bundle();
while ((type = parser.next()) != XmlPullParser.END_DOCUMENT) {
if (type == XmlPullParser.START_TAG) {
final String name = parser.getName();
if (name.equals(TAG_USER)) {
String id = parser.getAttributeValue(null, ATTR_ID);
// 初始化UserData对象保存从 /data/system/users/${id}.xml 文件中读取到的用户信息
UserData userData = readUserLP(Integer.parseInt(id));
if (userData != null) {
synchronized (mUsersLock) {
// 把解析到的用户信息保存到mUsers中
mUsers.put(userData.info.id, userData);
if (mNextSerialNumber < 0
|| mNextSerialNumber <= userData.info.id) {
mNextSerialNumber = userData.info.id + 1;
}
}
}
} else if (name.equals(TAG_GUEST_RESTRICTIONS)) {
while ((type = parser.next()) != XmlPullParser.END_DOCUMENT
&& type != XmlPullParser.END_TAG) {
if (type == XmlPullParser.START_TAG) {
if (parser.getName().equals(TAG_RESTRICTIONS)) {
synchronized (mGuestRestrictions) {
UserRestrictionsUtils
.readRestrictions(parser, mGuestRestrictions);
}
} else if (parser.getName().equals(TAG_DEVICE_POLICY_RESTRICTIONS)
) {
UserRestrictionsUtils.readRestrictions(parser,
newDevicePolicyGlobalUserRestrictions);
}
break;
}
}
} else if (name.equals(TAG_GLOBAL_RESTRICTION_OWNER_ID)) {
String ownerUserId = parser.getAttributeValue(null, ATTR_ID);
if (ownerUserId != null) {
mGlobalRestrictionOwnerUserId = Integer.parseInt(ownerUserId);
}
}
}
}
synchronized (mRestrictionsLock) {
mDevicePolicyGlobalUserRestrictions = newDevicePolicyGlobalUserRestrictions;
}
// 解析完文件后，更新用户ID
updateUserIds();
// 如果有必要，则升级Version
upgradeIfNecessaryLP();
} catch (IOException | XmlPullParserException e) {
fallbackToSingleUserLP();
} finally {
IoUtils.closeQuietly(fis);
}
}
// 创建管理员用户
private void fallbackToSingleUserLP() {
int flags = UserInfo.FLAG_INITIALIZED;
// In split system user mode, the admin and primary flags are assigned to the first human
// user.
if (!UserManager.isSplitSystemUser()) {
flags |= UserInfo.FLAG_ADMIN | UserInfo.FLAG_PRIMARY;
}
// Create the system user
UserInfo system = new UserInfo(UserHandle.USER_SYSTEM, null, null, flags);
UserData userData = new UserData();
userData.info = system;
synchronized (mUsersLock) {
mUsers.put(system.id, userData);
}
mNextSerialNumber = MIN_USER_ID;
mUserVersion = USER_VERSION;
Bundle restrictions = new Bundle();
synchronized (mRestrictionsLock) {
mBaseUserRestrictions.append(UserHandle.USER_SYSTEM, restrictions);
}
// 更新用户ID
updateUserIds();
// 初始化来宾账户的默认限制条件
initDefaultGuestRestrictions();
/*
* 把用户信息写到 /data/system/users/${id}.xml文件中，简单的写文件，不再看源码
* Writes the user file in this format:
*
* <user flags="20039023" id="0">
* <name>Primary</name>
* </user>
*/
writeUserLP(userData);
/*
* 把用户信息写到 /data/system/users/userlist.xml文件中
* Writes the user list file in this format:
*
* <users nextSerialNumber="3">
* <user id="0"></user>
* <user id="2"></user>
* </users>
*/
writeUserListLP();
}这样UserManagerService的初始化工作就完成了，主要的工作就是解析userlist.xml文件，并创建了mUsers列表中的UserData对象。
2.UserData的定义
private static class UserData {
// Basic user information and properties
UserInfo info;
// Account name used when there is a strong association between a user and an account
String account;
// Account information for seeding into a newly created user. This could also be
// used for login validation for an existing user, for updating their credentials.
// In the latter case, data may not need to be persisted as it is only valid for the
// current login session.
String seedAccountName;
String seedAccountType;
PersistableBundle seedAccountOptions;
// Whether to perist the seed account information to be available after a boot
boolean persistSeedData;
void clearSeedAccountData() {
seedAccountName = null;
seedAccountType = null;
seedAccountOptions = null;
persistSeedData = false;
}
}
public class UserInfo implements Parcelable {
/** 8 bits for user type 用户类型*/
public static final int FLAG_MASK_USER_TYPE = 0x000000FF;
/**
* *************************** NOTE ***************************
* These flag values CAN NOT CHANGE because they are written
* directly to storage.
*/
/**
* Primary user. Only one user can have this flag set. It identifies the first human user
* on a device.主用户标志，通常是第一个ID为0的用户
*/
public static final int FLAG_PRIMARY = 0x00000001;
/**
* User with administrative privileges. Such a user can create and
* delete users.admin用户标志，有此标志才有创建和删除用户的权限
*/
public static final int FLAG_ADMIN = 0x00000002;
/**
* Indicates a guest user that may be transient.guest用户标志
*/
public static final int FLAG_GUEST = 0x00000004;
/**
* Indicates the user has restrictions in privileges, in addition to those for normal users.
* Exact meaning TBD. For instance, maybe they can't install apps or administer WiFi access pts.
* 标志权限受限的用户，具体受限功能未定
*/
public static final int FLAG_RESTRICTED = 0x00000008;
/**
* Indicates that this user has gone through its first-time initialization.
* 标志该用户是否已经初始化
*/
public static final int FLAG_INITIALIZED = 0x00000010;
/**
* Indicates that this user is a profile of another user, for example holding a users
* corporate data.标志该UserInfo是另一个用户的profile
*/
public static final int FLAG_MANAGED_PROFILE = 0x00000020;
/**
* Indicates that this user is disabled.标志该用户已被禁止
*
* <p>Note: If an ephemeral user is disabled, it shouldn't be later re-enabled. Ephemeral users
* are disabled as their removal is in progress to indicate that they shouldn't be re-entered.
*/
public static final int FLAG_DISABLED = 0x00000040;
public static final int FLAG_QUIET_MODE = 0x00000080;
/**
* Indicates that this user is ephemeral. I.e. the user will be removed after leaving
* the foreground.
*/
public static final int FLAG_EPHEMERAL = 0x00000100;
public static final int NO_PROFILE_GROUP_ID = UserHandle.USER_NULL;
public int id; // 用户ID
public int serialNumber; // 用户的序列号，不会重复
public String name; // 用户名称
public String iconPath; // 用户头像路径
public int flags; // 用户标志
public long creationTime; // 创建用户的时间
public long lastLoggedInTime; // 最后一次登录的时间
public String lastLoggedInFingerprint; // 最后一次用指纹登录的时间
public int profileGroupId; // 用户profile的group ID
public int restrictedProfileParentId;
/** User is only partially created. */
public boolean partial; // true表示该用户没有创建完成
public boolean guestToRemove;
...
}3.添加用户
UserManagerService中添加用户的方法是createUser()：
@Override
public UserInfo createUser(String name, int flags) {
if (DBG) Slog.i(LOG_TAG, "createUser name " + name);
// 检查添加用户的权限
checkManageOrCreateUsersPermission(flags);
return createUserInternal(name, flags, UserHandle.USER_NULL);
}
private UserInfo createUserInternal(String name, int flags, int parentId) {
// 如果没有添加用户的权限则返回null
if (hasUserRestriction(UserManager.DISALLOW_ADD_USER, UserHandle.getCallingUserId())) {
Log.w(LOG_TAG, "Cannot add user. DISALLOW_ADD_USER is enabled.");
return null;
}
return createUserInternalUnchecked(name, flags, parentId);
}
private UserInfo createUserInternalUnchecked(String name, int flags, int parentId) {
// 如果是一个低内存设备，则返回null
if (ActivityManager.isLowRamDeviceStatic()) {
return null;
}
final boolean isGuest = (flags & UserInfo.FLAG_GUEST) != 0;
final boolean isManagedProfile = (flags & UserInfo.FLAG_MANAGED_PROFILE) != 0;
final boolean isRestricted = (flags & UserInfo.FLAG_RESTRICTED) != 0;
final long ident = Binder.clearCallingIdentity();
UserInfo userInfo;
UserData userData;
final int userId;
try {
synchronized (mPackagesLock) {
UserData parent = null;
if (parentId != UserHandle.USER_NULL) {
synchronized (mUsersLock) {
// 根据userId获取UserData信息
parent = getUserDataLU(parentId);
}
if (parent == null) return null;
}
// 判断是否可以添加更多profile
if (isManagedProfile && !canAddMoreManagedProfiles(parentId, false)) {
Log.e(LOG_TAG, "Cannot add more managed profiles for user " + parentId);
return null;
}
// 判断是否达到用户上限
if (!isGuest && !isManagedProfile && isUserLimitReached()) {
// If we're not adding a guest user or a managed profile and the limit has
// been reached, cannot add a user.
return null;
}
// If we're adding a guest and there already exists one, bail.
// 如果创建的是guest用户且guest用户已经存在则返回
if (isGuest && findCurrentGuestUser() != null) {
return null;
}
// In legacy mode, restricted profile's parent can only be the owner user
if (isRestricted && !UserManager.isSplitSystemUser()
&& (parentId != UserHandle.USER_SYSTEM)) {
Log.w(LOG_TAG, "Cannot add restricted profile - parent user must be owner");
return null;
}
if (isRestricted && UserManager.isSplitSystemUser()) {
if (parent == null) {
Log.w(LOG_TAG, "Cannot add restricted profile - parent user must be "
+ "specified");
return null;
}
if (!parent.info.canHaveProfile()) {
Log.w(LOG_TAG, "Cannot add restricted profile - profiles cannot be "
+ "created for the specified parent user id " + parentId);
return null;
}
}
if (!UserManager.isSplitSystemUser() && (flags & UserInfo.FLAG_EPHEMERAL) != 0) {
Log.e(LOG_TAG,
"Ephemeral users are supported on split-system-user systems only.");
return null;
}
// In split system user mode, we assign the first human user the primary flag.
// And if there is no device owner, we also assign the admin flag to primary user.
if (UserManager.isSplitSystemUser()
&& !isGuest && !isManagedProfile && getPrimaryUser() == null) {
flags |= UserInfo.FLAG_PRIMARY;
synchronized (mUsersLock) {
if (!mIsDeviceManaged) {
flags |= UserInfo.FLAG_ADMIN;
}
}
}
// 获取下一个可用的userId
userId = getNextAvailableId();
// 创建/data/system/users/userId文件夹
Environment.getUserSystemDirectory(userId).mkdirs();
boolean ephemeralGuests = Resources.getSystem()
.getBoolean(com.android.internal.R.bool.config_guestUserEphemeral);
synchronized (mUsersLock) {
// Add ephemeral flag to guests/users if required. Also inherit it from parent.
if ((isGuest && ephemeralGuests) || mForceEphemeralUsers
|| (parent != null && parent.info.isEphemeral())) {
flags |= UserInfo.FLAG_EPHEMERAL;
}
// 初始化新用户
userInfo = new UserInfo(userId, name, null, flags);
userInfo.serialNumber = mNextSerialNumber++;
long now = System.currentTimeMillis();
userInfo.creationTime = (now > EPOCH_PLUS_30_YEARS) ? now : 0;
// 设置partial变量为true，表示用户还没有创建完成
userInfo.partial = true;
userInfo.lastLoggedInFingerprint = Build.FINGERPRINT;
userData = new UserData();
userData.info = userInfo;
mUsers.put(userId, userData);
}
// 保存用户信息
writeUserLP(userData);
writeUserListLP();
if (parent != null) {
if (isManagedProfile) {
if (parent.info.profileGroupId == UserInfo.NO_PROFILE_GROUP_ID) {
parent.info.profileGroupId = parent.info.id;
writeUserLP(parent);
}
userInfo.profileGroupId = parent.info.profileGroupId;
} else if (isRestricted) {
if (parent.info.restrictedProfileParentId == UserInfo.NO_PROFILE_GROUP_ID) {
parent.info.restrictedProfileParentId = parent.info.id;
writeUserLP(parent);
}
userInfo.restrictedProfileParentId = parent.info.restrictedProfileParentId;
}
}
}
// 为新建用户准备存储区域
final StorageManager storage = mContext.getSystemService(StorageManager.class);
storage.createUserKey(userId, userInfo.serialNumber, userInfo.isEphemeral());
mPm.prepareUserData(userId, userInfo.serialNumber,
StorageManager.FLAG_STORAGE_DE | StorageManager.FLAG_STORAGE_CE);
// 保存所有安装应用在新建用户目录下的安装状态
mPm.createNewUser(userId);
// 创建完新用户后修改partial变量为false，表示用户创建完成，并重新保存用户信息
userInfo.partial = false;
synchronized (mPackagesLock) {
writeUserLP(userData);
}
updateUserIds();
Bundle restrictions = new Bundle();
if (isGuest) {
synchronized (mGuestRestrictions) {
restrictions.putAll(mGuestRestrictions);
}
}
synchronized (mRestrictionsLock) {
mBaseUserRestrictions.append(userId, restrictions);
}
// 发送成功添加新用户的广播
Intent addedIntent = new Intent(Intent.ACTION_USER_ADDED);
addedIntent.putExtra(Intent.EXTRA_USER_HANDLE, userId);
mContext.sendBroadcastAsUser(addedIntent, UserHandle.ALL,
android.Manifest.permission.MANAGE_USERS);
MetricsLogger.count(mContext, isGuest ? TRON_GUEST_CREATED : TRON_USER_CREATED, 1);
} finally {
Binder.restoreCallingIdentity(ident);
}
return userInfo;
}
// 根据userId获取UserData信息
private UserData getUserDataLU(int userId) {
final UserData userData = mUsers.get(userId);
// If it is partial and not in the process of being removed, return as unknown user.
if (userData != null && userData.info.partial && !mRemovingUserIds.get(userId)) {
return null;
}
return userData;
}
final Settings mSettings;
/** Called by UserManagerService */
// 保存所有安装应用在新建用户目录下的安装状态
void createNewUser(int userId) {
synchronized (mInstallLock) {
// 把所有已安装的应用数据拷贝到新建用户对应目录（/data/user/0/）下
mSettings.createNewUserLI(this, mInstaller, userId);
}
synchronized (mPackages) {
// 在/data/system/users/0/package-restrictions.xml文件中保存应用的限制信息
scheduleWritePackageRestrictionsLocked(userId);
// 更新/data/system/packages.list文件
scheduleWritePackageListLocked(userId);
// 保存默认浏览器应用，并更新/data/system/users/0/package-restrictions.xml文件
applyFactoryDefaultBrowserLPw(userId);
// 主要域名验证
primeDomainVerificationsLPw(userId);
}
}
/** Map from package name to settings 每个包名对应一个PackageSetting*/
final ArrayMap<String, PackageSetting> mPackages = new ArrayMap<>();
// 把所有已安装的系统应用数据拷贝到新建用户对应目录下
void createNewUserLI(@NonNull PackageManagerService service, @NonNull Installer installer,
int userHandle) {
String[] volumeUuids;
String[] names;
int[] appIds;
String[] seinfos;
int[] targetSdkVersions;
int packagesCount;
synchronized (mPackages) {
// 从map中获取出所有的settings
Collection<PackageSetting> packages = mPackages.values();
packagesCount = packages.size();
volumeUuids = new String[packagesCount];
names = new String[packagesCount];
appIds = new int[packagesCount];
seinfos = new String[packagesCount];
targetSdkVersions = new int[packagesCount];
Iterator<PackageSetting> packagesIterator = packages.iterator();
// 遍历所有的PackageSetting
for (int i = 0; i < packagesCount; i++) {
PackageSetting ps = packagesIterator.next();
if (ps.pkg == null || ps.pkg.applicationInfo == null) {
continue;
}
// Only system apps are initially installed.初始化时只安装系统应用
/** M: [Operator] Operator package should also be installed @{ */
boolean curInstalledStatus = ps.isSystem()
|| (ps.pkgFlagsEx & ApplicationInfo.FLAG_EX_OPERATOR) != 0;
// 设置每一个应用在新创建用户下的安装状态，系统应用为true
ps.setInstalled(curInstalledStatus, userHandle);
/** @} */
// Need to create a data directory for all apps under this user. Accumulate all
// required args and call the installer after mPackages lock has been released
volumeUuids[i] = ps.volumeUuid;
names[i] = ps.name;
appIds[i] = ps.appId;
seinfos[i] = ps.pkg.applicationInfo.seinfo;
targetSdkVersions[i] = ps.pkg.applicationInfo.targetSdkVersion;
}
}
for (int i = 0; i < packagesCount; i++) {
if (names[i] == null) {
continue;
}
// TODO: triage flags!
final int flags = StorageManager.FLAG_STORAGE_CE | StorageManager.FLAG_STORAGE_DE;
try {
// 在新建用户目录（/data/user/0/）下创建每个应用的数据目录（包名命名的文件夹）
installer.createAppData(volumeUuids[i], names[i], userHandle, flags, appIds[i],
seinfos[i], targetSdkVersions[i]);
} catch (InstallerException e) {
Slog.w(TAG, "Failed to prepare app data", e);
}
}
synchronized (mPackages) {
// 解析"etc/preferred-apps"目录下所有XML文件，XML文件中保存的是设备使用者指定的响应某个Intent
// 的最合适的组件信息
applyDefaultPreferredAppsLPw(service, userHandle);
}
}4.删除用户
/**
* Removes a user and all data directories created for that user. This method should be called
* after the user's processes have been terminated.
* @param userHandle the user's id
*/
@Override
public boolean removeUser(int userHandle) {
// 检查调用者是否有删除用户的权限
checkManageOrCreateUsersPermission("Only the system can remove users");
if (getUserRestrictions(UserHandle.getCallingUserId()).getBoolean(
UserManager.DISALLOW_REMOVE_USER, false)) {
Log.w(LOG_TAG, "Cannot remove user. DISALLOW_REMOVE_USER is enabled.");
return false;
}
long ident = Binder.clearCallingIdentity();
try {
final UserData userData;
int currentUser = ActivityManager.getCurrentUser();
if (currentUser == userHandle) {
Log.w(LOG_TAG, "Current user cannot be removed");
return false;
}
synchronized (mPackagesLock) {
synchronized (mUsersLock) {
userData = mUsers.get(userHandle);
if (userHandle == 0 || userData == null || mRemovingUserIds.get(userHandle)) {
return false;
}
// We remember deleted user IDs to prevent them from being
// reused during the current boot; they can still be reused
// after a reboot.保存要删除的userId，防止重复删除
mRemovingUserIds.put(userHandle, true);
}
try {
mAppOpsService.removeUser(userHandle);
} catch (RemoteException e) {
Log.w(LOG_TAG, "Unable to notify AppOpsService of removing user", e);
}
// Set this to a partially created user, so that the user will be purged
// on next startup, in case the runtime stops now before stopping and
// removing the user completely.
// 删除用户并没有删除相关用户文件，只是把partial变量修改为true，
// 开机后如果该变量还是true会删除相关文件
userData.info.partial = true;
// Mark it as disabled, so that it isn't returned any more when
// profiles are queried.
userData.info.flags |= UserInfo.FLAG_DISABLED;
// 更新/data/system/users/${id}.xml文件
writeUserLP(userData);
}
if (userData.info.profileGroupId != UserInfo.NO_PROFILE_GROUP_ID
&& userData.info.isManagedProfile()) {
// Send broadcast to notify system that the user removed was a
// managed user.发送删除用户的广播
sendProfileRemovedBroadcast(userData.info.profileGroupId, userData.info.id);
}
if (DBG) Slog.i(LOG_TAG, "Stopping user " + userHandle);
int res;
try {
// 停止正在运行的用户
res = ActivityManagerNative.getDefault().stopUser(userHandle, /* force= */ true,
new IStopUserCallback.Stub() {
@Override
public void userStopped(int userId) {
// 删除用户相关应用信息
finishRemoveUser(userId);
}
@Override
public void userStopAborted(int userId) {
}
});
} catch (RemoteException e) {
return false;
}
return res == ActivityManager.USER_OP_SUCCESS;
} finally {
Binder.restoreCallingIdentity(ident);
}
}5.多用户管理
UserManagerService主要管理用户的账号信息，运行中的用户管理由ActivityManagerService来负责。
用户的状态有5种，定义在UserState类中：
public final class UserState {
// User is first coming up.启动中
public final static int STATE_BOOTING = 0;
// User is in the locked state.锁定
public final static int STATE_RUNNING_LOCKED = 1;
// User is in the unlocking state.未锁定
public final static int STATE_RUNNING_UNLOCKING = 2;
// User is in the running state.运行中
public final static int STATE_RUNNING_UNLOCKED = 3;
// User is in the initial process of being stopped.停止的初始过程中
public final static int STATE_STOPPING = 4;
// User is in the final phase of stopping, sending Intent.ACTION_SHUTDOWN.停止的最后阶段
public final static int STATE_SHUTDOWN = 5;
...
}
@Override
public boolean switchUser(final int targetUserId) {
// 检查调用者是否有切换用户的权限
enforceShellRestriction(UserManager.DISALLOW_DEBUGGING_FEATURES, targetUserId);
UserInfo currentUserInfo;
UserInfo targetUserInfo;
synchronized (this) {
// 获取当用用户的相关信息
int currentUserId = mUserController.getCurrentUserIdLocked();
currentUserInfo = mUserController.getUserInfo(currentUserId);
// 获取切换目标用户的相关信息
targetUserInfo = mUserController.getUserInfo(targetUserId);
if (targetUserInfo == null) {
Slog.w(TAG, "No user info for user #" + targetUserId);
return false;
}
// 如果目标用户不支持切换，则返回
if (!targetUserInfo.supportsSwitchTo()) {
Slog.w(TAG, "Cannot switch to User #" + targetUserId + ": not supported");
return false;
}
// 如果目标用户是另一个用户的profile，则返回
if (targetUserInfo.isManagedProfile()) {
Slog.w(TAG, "Cannot switch to User #" + targetUserId + ": not a full user");
return false;
}
mUserController.setTargetUserIdLocked(targetUserId);
}
// 发送切换用户的消息
Pair<UserInfo, UserInfo> userNames = new Pair<>(currentUserInfo, targetUserInfo);
mUiHandler.removeMessages(START_USER_SWITCH_UI_MSG);
mUiHandler.sendMessage(mUiHandler.obtainMessage(START_USER_SWITCH_UI_MSG, userNames));
return true;
}
final class UiHandler extends Handler {
public UiHandler() {
super(com.android.server.UiThread.get().getLooper(), null, true);
}
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
...
case START_USER_SWITCH_UI_MSG: {
mUserController.showUserSwitchDialog((Pair<UserInfo, UserInfo>) msg.obj);
break;
}
...
}
}
}
void showUserSwitchDialog(Pair<UserInfo, UserInfo> fromToUserPair) {
// The dialog will show and then initiate the user switch by calling startUserInForeground
Dialog d = new UserSwitchingDialog(mService, mService.mContext, fromToUserPair.first,
fromToUserPair.second, true /* above system */);
d.show();
}
@Override
public void show() {
// Slog.v(TAG, "show called");
super.show();
final View decorView = getWindow().getDecorView();
if (decorView != null) {
decorView.getViewTreeObserver().addOnWindowShownListener(this);
}
// Add a timeout as a safeguard, in case a race in screen on/off causes the window
// callback to never come.
mHandler.sendMessageDelayed(mHandler.obtainMessage(MSG_START_USER),
WINDOW_SHOWN_TIMEOUT_MS);
}
private final Handler mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_START_USER:
// 调用startUser()方法
startUser();
break;
}
}
};
void startUser() {
synchronized (this) {
if (!mStartedUser) {
// 调用startUserInForeground方法
mService.mUserController.startUserInForeground(mUserId, this);
mStartedUser = true;
final View decorView = getWindow().getDecorView();
if (decorView != null) {
decorView.getViewTreeObserver().removeOnWindowShownListener(this);
}
mHandler.removeMessages(MSG_START_USER);
}
}
}
/**
* Start user, if its not already running, and bring it to foreground.
* 开启用户，如果用户没有在运行，则开启它
*/
boolean startUserInForeground(final int userId, Dialog dlg) {
boolean result = startUser(userId, /* foreground */ true);
dlg.dismiss();
return result;
}
/**
* Start user, if its not already running.
* <p>The user will be brought to the foreground, if {@code foreground} parameter is set.
* When starting the user, multiple intents will be broadcast in the following order:</p>
* <ul>
* <li>{@link Intent#ACTION_USER_STARTED} - sent to registered receivers of the new user
* <li>{@link Intent#ACTION_USER_BACKGROUND} - sent to registered receivers of the outgoing
* user and all profiles of this user. Sent only if {@code foreground} parameter is true
* <li>{@link Intent#ACTION_USER_FOREGROUND} - sent to registered receivers of the new
* user and all profiles of this user. Sent only if {@code foreground} parameter is true
* <li>{@link Intent#ACTION_USER_SWITCHED} - sent to registered receivers of the new user.
* Sent only if {@code foreground} parameter is true
* <li>{@link Intent#ACTION_USER_STARTING} - ordered broadcast sent to registered receivers
* of the new fg user
* <li>{@link Intent#ACTION_LOCKED_BOOT_COMPLETED} - ordered broadcast sent to receivers of
* the new user
* <li>{@link Intent#ACTION_USER_UNLOCKED} - sent to registered receivers of the new user
* <li>{@link Intent#ACTION_PRE_BOOT_COMPLETED} - ordered broadcast sent to receivers of the
* new user. Sent only when the user is booting after a system update.
* <li>{@link Intent#ACTION_USER_INITIALIZE} - ordered broadcast sent to receivers of the
* new user. Sent only the first time a user is starting.
* <li>{@link Intent#ACTION_BOOT_COMPLETED} - ordered broadcast sent to receivers of the new
* user. Indicates that the user has finished booting.
* </ul>
*
* @param userId ID of the user to start
* @param foreground true if user should be brought to the foreground
* @return true if the user has been successfully started
*/
boolean startUser(final int userId, final boolean foreground) {
// 检查调用者权限
if (mService.checkCallingPermission(INTERACT_ACROSS_USERS_FULL)
!= PackageManager.PERMISSION_GRANTED) {
String msg = "Permission Denial: switchUser() from pid="
+ Binder.getCallingPid()
+ ", uid=" + Binder.getCallingUid()
+ " requires " + INTERACT_ACROSS_USERS_FULL;
Slog.w(TAG, msg);
throw new SecurityException(msg);
}
Slog.i(TAG, "Starting userid:" + userId + " fg:" + foreground);
final long ident = Binder.clearCallingIdentity();
try {
synchronized (mService) {
final int oldUserId = mCurrentUserId;
// 如果要开启的用户已经存在，则直接返回true
if (oldUserId == userId) {
return true;
}
mService.mStackSupervisor.setLockTaskModeLocked(null,
ActivityManager.LOCK_TASK_MODE_NONE, "startUser", false);
// 获取目标用户的相关信息
final UserInfo userInfo = getUserInfo(userId);
if (userInfo == null) {
Slog.w(TAG, "No user info for user #" + userId);
return false;
}
if (foreground && userInfo.isManagedProfile()) {
Slog.w(TAG, "Cannot switch to User #" + userId + ": not a full user");
return false;
}
// 如果要把用户切到前台，则播放动画
if (foreground) {
mService.mWindowManager.startFreezingScreen(
R.anim.screen_user_exit, R.anim.screen_user_enter);
}
boolean needStart = false;
// If the user we are switching to is not currently started, then
// we need to start it now.如果目标用户不存在，则修改用户状态为正在开启
// UserState的状态默认值是STATE_BOOTING
if (mStartedUsers.get(userId) == null) {
UserState userState = new UserState(UserHandle.of(userId));
mStartedUsers.put(userId, userState);
getUserManagerInternal().setUserState(userId, userState.state);
// 根据用户状态更新已经开启的用户列表
updateStartedUserArrayLocked();
needStart = true;
}
final UserState uss = mStartedUsers.get(userId);
final Integer userIdInt = userId;
mUserLru.remove(userIdInt);
// 调整用户在mUserLru中的位置，当前用户位于末尾
mUserLru.add(userIdInt);
if (foreground) {
// 修改当前用户的Id
mCurrentUserId = userId;
// 更新用户配置信息
mService.updateUserConfigurationLocked();
mTargetUserId = UserHandle.USER_NULL; // reset, mCurrentUserId has caught up
// 更新与当前用户相关的用户列表
updateCurrentProfileIdsLocked();
mService.mWindowManager.setCurrentUser(userId, mCurrentProfileIds);
// Once the internal notion of the active user has switched, we lock the device
// with the option to show the user switcher on the keyguard.
mService.mWindowManager.lockNow(null);
} else {
final Integer currentUserIdInt = mCurrentUserId;
// 更新与当前用户相关的用户列表
updateCurrentProfileIdsLocked();
mService.mWindowManager.setCurrentProfileIds(mCurrentProfileIds);
mUserLru.remove(currentUserIdInt);
mUserLru.add(currentUserIdInt);
}
// Make sure user is in the started state. If it is currently
// stopping, we need to knock that off.确保用户处于启动状态，如果处于
// 停止的初始阶段，则中止它。如果已经发送过停止运行的广播，则重新设置用户的状态
if (uss.state == UserState.STATE_STOPPING) {
// If we are stopping, we haven't sent ACTION_SHUTDOWN,
// so we can just fairly silently bring the user back from
// the almost-dead.
uss.setState(uss.lastState);
getUserManagerInternal().setUserState(userId, uss.state);
// 根据用户状态更新已经开启的用户列表
updateStartedUserArrayLocked();
needStart = true;
} else if (uss.state == UserState.STATE_SHUTDOWN) {
// This means ACTION_SHUTDOWN has been sent, so we will
// need to treat this as a new boot of the user.
uss.setState(UserState.STATE_BOOTING);
getUserManagerInternal().setUserState(userId, uss.state);
// 根据用户状态更新已经开启的用户列表
updateStartedUserArrayLocked();
needStart = true;
}
if (uss.state == UserState.STATE_BOOTING) {
// Give user manager a chance to propagate user restrictions
// to other services and prepare app storage
// 在用户启动之前，先准备相关用户的限制及存储
getUserManager().onBeforeStartUser(userId);
// Booting up a new user, need to tell system services about it.
// Note that this is on the same handler as scheduling of broadcasts,
// which is important because it needs to go first.
mHandler.sendMessage(mHandler.obtainMessage(SYSTEM_USER_START_MSG, userId, 0));
}
if (foreground) {
// 发送相关消息
mHandler.sendMessage(mHandler.obtainMessage(SYSTEM_USER_CURRENT_MSG, userId,
oldUserId));
mHandler.removeMessages(REPORT_USER_SWITCH_MSG);
mHandler.removeMessages(USER_SWITCH_TIMEOUT_MSG);
mHandler.sendMessage(mHandler.obtainMessage(REPORT_USER_SWITCH_MSG,
oldUserId, userId, uss));
mHandler.sendMessageDelayed(mHandler.obtainMessage(USER_SWITCH_TIMEOUT_MSG,
oldUserId, userId, uss), USER_SWITCH_TIMEOUT);
}
if (needStart) {
// Send USER_STARTED broadcast 如果需要开启用户，则发送相应广播
// 用户切换牵扯到很多模块，如壁纸管理、输入法、账号管理等，都需要收到通知
Intent intent = new Intent(Intent.ACTION_USER_STARTED);
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY
| Intent.FLAG_RECEIVER_FOREGROUND);
intent.putExtra(Intent.EXTRA_USER_HANDLE, userId);
mService.broadcastIntentLocked(null, null, intent,
null, null, 0, null, null, null, AppOpsManager.OP_NONE,
null, false, false, MY_PID, SYSTEM_UID, userId);
}
if (foreground) {
// 把开启的用户设为前台用户
moveUserToForegroundLocked(uss, oldUserId, userId);
} else {
// 用户启动结束，则切换用户到STATE_RUNNING_LOCKED状态
mService.mUserController.finishUserBoot(uss);
}
if (needStart) {
// 如果需要开启用户，则发送相应广播
Intent intent = new Intent(Intent.ACTION_USER_STARTING);
intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY);
intent.putExtra(Intent.EXTRA_USER_HANDLE, userId);
mService.broadcastIntentLocked(null, null, intent,
null, new IIntentReceiver.Stub() {
@Override
public void performReceive(Intent intent, int resultCode,
String data, Bundle extras, boolean ordered, boolean sticky,
int sendingUser) throws RemoteException {
}
}, 0, null, null,
new String[] {INTERACT_ACROSS_USERS}, AppOpsManager.OP_NONE,
null, true, false, MY_PID, SYSTEM_UID, UserHandle.USER_ALL);
}
}
} finally {
Binder.restoreCallingIdentity(ident);
}
return true;
}
// 根据用户状态更新已经开启的用户列表mStartedUserArray
private void updateStartedUserArrayLocked() {
int num = 0;
for (int i = 0; i < mStartedUsers.size(); i++) {
UserState uss = mStartedUsers.valueAt(i);
// This list does not include stopping users.
if (uss.state != UserState.STATE_STOPPING
&& uss.state != UserState.STATE_SHUTDOWN) {
num++;
}
}
mStartedUserArray = new int[num];
num = 0;
for (int i = 0; i < mStartedUsers.size(); i++) {
UserState uss = mStartedUsers.valueAt(i);
if (uss.state != UserState.STATE_STOPPING
&& uss.state != UserState.STATE_SHUTDOWN) {
mStartedUserArray[num++] = mStartedUsers.keyAt(i);
}
}
}
发送的msg消息是在ActivityManagerService中处理的：
final class UiHandler extends Handler {
public UiHandler() {
super(com.android.server.UiThread.get().getLooper(), null, true);
}
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
...
case SYSTEM_USER_START_MSG: {
mBatteryStatsService.noteEvent(BatteryStats.HistoryItem.EVENT_USER_RUNNING_START,
Integer.toString(msg.arg1), msg.arg1);
// 新建用户时调用
mSystemServiceManager.startUser(msg.arg1);
break;
}
case SYSTEM_USER_CURRENT_MSG: {
mBatteryStatsService.noteEvent(
BatteryStats.HistoryItem.EVENT_USER_FOREGROUND_FINISH,
Integer.toString(msg.arg2), msg.arg2);
mBatteryStatsService.noteEvent(
BatteryStats.HistoryItem.EVENT_USER_FOREGROUND_START,
Integer.toString(msg.arg1), msg.arg1);
// 切换用户时调用
mSystemServiceManager.switchUser(msg.arg1);
break;
}
case REPORT_USER_SWITCH_MSG: {
mUserController.dispatchUserSwitch((UserState) msg.obj, msg.arg1, msg.arg2);
break;
}
case CONTINUE_USER_SWITCH_MSG: {
mUserController.continueUserSwitch((UserState) msg.obj, msg.arg1, msg.arg2);
break;
}
case USER_SWITCH_TIMEOUT_MSG: {
mUserController.timeoutUserSwitch((UserState) msg.obj, msg.arg1, msg.arg2);
break;
}
case REPORT_USER_SWITCH_COMPLETE_MSG: {
mUserController.dispatchUserSwitchComplete(msg.arg1);
break;
}
...
}
};
// 该方法主要是调用mUserSwitchObservers列表中的IUserSwitchObserver对象的onUserSwitching方法
// 如果想知道用户切换，可以调用AMS的registerUserSwitchObserver()方法来注册一个观察者对象
void dispatchUserSwitch(final UserState uss, final int oldUserId, final int newUserId) {
Slog.d(TAG, "Dispatch onUserSwitching oldUser #" + oldUserId + " newUser #" + newUserId);
// 获取所有注册回调方法的总数
final int observerCount = mUserSwitchObservers.beginBroadcast();
if (observerCount > 0) {
final IRemoteCallback callback = new IRemoteCallback.Stub() {
int mCount = 0;
@Override
public void sendResult(Bundle data) throws RemoteException {
synchronized (mService) {
if (mCurUserSwitchCallback == this) {
// 收到一条回调，就加一
mCount++;
// 所有注册的回调方法都执行了，发送继续处理的消息
if (mCount == observerCount) {
sendContinueUserSwitchLocked(uss, oldUserId, newUserId);
}
}
}
}
};
synchronized (mService) {
uss.switching = true;
mCurUserSwitchCallback = callback;
}
// 遍历调用所有注册回调对象的onUserSwitching方法
for (int i = 0; i < observerCount; i++) {
try {
mUserSwitchObservers.getBroadcastItem(i).onUserSwitching(
newUserId, callback);
} catch (RemoteException e) {
}
}
} else {
synchronized (mService) {
// 如果没有注册回调方法的，直接调用继续执行用户切换的方法
sendContinueUserSwitchLocked(uss, oldUserId, newUserId);
}
}
mUserSwitchObservers.finishBroadcast();
}
void sendContinueUserSwitchLocked(UserState uss, int oldUserId, int newUserId) {
mCurUserSwitchCallback = null;
mHandler.removeMessages(USER_SWITCH_TIMEOUT_MSG);
mHandler.sendMessage(mHandler.obtainMessage(ActivityManagerService.CONTINUE_USER_SWITCH_MSG,
oldUserId, newUserId, uss));
}
void continueUserSwitch(UserState uss, int oldUserId, int newUserId) {
Slog.d(TAG, "Continue user switch oldUser #" + oldUserId + ", newUser #" + newUserId);
synchronized (mService) {
mService.mWindowManager.stopFreezingScreen();
}
uss.switching = false;
// 发送完成切换用户的消息
mHandler.removeMessages(REPORT_USER_SWITCH_COMPLETE_MSG);
mHandler.sendMessage(mHandler.obtainMessage(REPORT_USER_SWITCH_COMPLETE_MSG,
newUserId, 0));
// 停止切换到后台的Guest或临时用户
stopGuestOrEphemeralUserIfBackground();
// 强制停止后台用户
stopBackgroundUsersIfEnforced(oldUserId);
}
/** Called on handler thread */
void dispatchUserSwitchComplete(int userId) {
final int observerCount = mUserSwitchObservers.beginBroadcast();
for (int i = 0; i < observerCount; i++) {
try {
// 遍历调用所有观察者的onUserSwitchComplete方法
mUserSwitchObservers.getBroadcastItem(i).onUserSwitchComplete(userId);
} catch (RemoteException e) {
}
}
mUserSwitchObservers.finishBroadcast();
}
/**
* Stops the guest or ephemeral user if it has gone to the background.
* 停止切换到后台的Guest或临时用户
*/
private void stopGuestOrEphemeralUserIfBackground() {
synchronized (mService) {
final int num = mUserLru.size();
for (int i = 0; i < num; i++) {
Integer oldUserId = mUserLru.get(i);
UserState oldUss = mStartedUsers.get(oldUserId);
if (oldUserId == UserHandle.USER_SYSTEM || oldUserId == mCurrentUserId
|| oldUss.state == UserState.STATE_STOPPING
|| oldUss.state == UserState.STATE_SHUTDOWN) {
continue;
}
UserInfo userInfo = getUserInfo(oldUserId);
if (userInfo.isEphemeral()) {
LocalServices.getService(UserManagerInternal.class)
.onEphemeralUserStop(oldUserId);
}
if (userInfo.isGuest() || userInfo.isEphemeral()) {
// This is a user to be stopped.
stopUsersLocked(oldUserId, true, null);
break;
}
}
}
}
// 强制停止后台用户
private void stopBackgroundUsersIfEnforced(int oldUserId) {
// Never stop system user
if (oldUserId == UserHandle.USER_SYSTEM) {
return;
}
// For now, only check for user restriction. Additional checks can be added here
boolean disallowRunInBg = hasUserRestriction(UserManager.DISALLOW_RUN_IN_BACKGROUND,
oldUserId);
if (!disallowRunInBg) {
return;
}
synchronized (mService) {
if (DEBUG_MU) Slog.i(TAG, "stopBackgroundUsersIfEnforced stopping " + oldUserId
+ " and related users");
stopUsersLocked(oldUserId, false, null);
}
}
void timeoutUserSwitch(UserState uss, int oldUserId, int newUserId) {
synchronized (mService) {
/// M: Change Slog.wtf to Slog.w to avoid having WTF easily after adding new user
Slog.w(TAG, "User switch timeout: from " + oldUserId + " to " + newUserId);
sendContinueUserSwitchLocked(uss, oldUserId, newUserId);
}
}Activity进入Idle状态时会调用activityIdleInternalLocked方法，该方法中会修改用户的状态到STATE_RUNNING_LOCKED状态
