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16
17# Android Role for system developers
18
19This document targets system developers. App developers should refer to the [RoleManager
20documentation](https://developer.android.com/reference/android/app/role/RoleManager) and AndroidX
21[core-role](https://developer.android.com/reference/androidx/core/role/package-summary) library.
22
23## Definition
24
25A role is a unique name within the system for a purpose, associated with certain requirements and
26privileges if granted. For example, the SMS role requires the app to have certain declarations in
27its manifest that are central to SMS functionality, and grants the app privileges like reading and
28writing user's SMS.
29
30The list of available roles and their behavior can be updated via PermissionController upgrade, out
31of the platform release cycle. Since Android Q, all the default apps (e.g. default SMS app) are
32backed by a corresponding role implementation.
33
34The definition for all the roles can be found in [roles.xml](../../../../../res/xml/roles.xml) and
35associated [`RoleBehavior`](model/RoleBehavior.java) classes.
36
37## Defining a role
38
39A role is defined by a `<role>` tag in `roles.xml`.
40
41The following attributes are available for role:
42
43- `name`: The unique name to identify the role, e.g. `android.app.role.SMS`.
44- `behavior`: Optional name of a [`RoleBehavior`](model/RoleBehavior.java) class to control certain
45role behavior in Java code, e.g. `SmsRoleBehavior`. This can be useful when the XML syntax cannot
46express certain behavior specific to the role.
47- `defaultHolders`: Optional name of a system config resource that designates the default holders of
48the role, e.g. `config_defaultSms`. If the role is not exclusive, multiple package names can be
49specified by separating them with a semicolon (`;`). Each package name can also be optionally
50followed by a SHA-256 digest of the expected signing certificate to allow specifying non-system
51apps, separated by a colon (`:`) with the package name, for instance
52`com.example.normalapp:sha256;com.example.systemapp`.
53- `description`: The string resource for the description of the role, e.g.
54`@string/role_sms_description`, which says "Apps that allow you to use your phone number to send and
55receive short text messages, photos, videos, and more". For default apps, this string will appear in
56the default app detail page as a footer. This attribute is required if the role is `visible`.
57- `exclusive`: Whether the role is exclusive. If a role is exclusive, at most one application is
58allowed to be its holder.
59- `fallBackToDefaultHolder`: Whether the role should fall back to the default holder. This attribute
60is optional and defaults to `false`.
61- `label`: The string resource for the label of the role, e.g. `@string/role_sms_label`, which says
62"Default SMS app". For default apps, this string will appear in the default app detail page as the
63title. This attribute is required if the role is `visible`.
64- `minSdkVersion`: The minimum SDK version for the role to be available, e.g. `31` for Android S.
65This attribute is optional and defaults to `Build.VERSION_CODES.BASE`.
66- `requestDescription`: The string resource for the description in the request role dialog, e.g.
67`@string/role_sms_request_description`, which says "Gets access to contacts, SMS, phone". This
68description should describe to the user the privileges that are going to be granted, and should not
69be too long. This attribute is required if the role is both `visible` and `requestable`.
70- `requestTitle`: The string resource for the title of the request role dialog, e.g.
71`@string/role_sms_request_title`, which says "Set %1$s as your default SMS app?". This attribute is
72required if the role is both `visible` and `requestable`.
73- `requestable`: Whether the role will be requestable by apps. If a role isn't requestable but is
74still visible, apps cannot show the request role dialog to user, but user can still manage the role
75in Settings page. This attribute is optional and defaults to the value of `visible`.
76- `searchKeywords`: Optional string resource for additional search keywords for the role, e.g.
77`@string/role_sms_search_keywords` which says "text message, texting, messages, messaging". The role
78label is always implicitly included in search keywords.
79- `shortLabel`: The string resource for the short label of the role, e.g.
80`@string/role_sms_short_label`, which says "SMS app". For default apps, this string will appear in
81the default app list page as the title for the default app item. This attribute is required if the
82role is `visible`.
83- `showNone`: Whether this role will show a "None" option. This allows user to explicitly select
84none of the apps for a role. This attribute is optional, only applies to `exclusive` roles and
85defaults to `false`.
86- `static`: Whether this role is static, i.e. the role will always be assigned to its default
87holders. This attribute is optional and defaults to `false`.
88- `systemOnly`: Whether this role only allows system apps to hold it. This attribute is optional and
89defaults to `false.
90- `visible`: Whether this role is visible to users. If a role is invisible (a.k.a. hidden) to users,
91users won't be able to find it in Settings, and apps won't be able to request it. The role can still
92be managed by system APIs and shell command.
93
94The following tags can be specified inside a `<role>` tag:
95
96- `<required-components>`: Child tags like `<activity>`, `<service>`, `<provider>`, `<receiver>` and
97`<meta-data>` can be used to specified the app manifest requirements of the role, and an app is only
98qualified when it declares all these components. They follow a similar syntax as in typical
99`AndroidManifest.xml`.
100- `<permissions>`: Child tags like `<permission-set>` and `<permission>` can be used to specify the
101permissions that should be granted to the app when it has the role. Several `<permission-set>` are
102defined at the beginning of `roles.xml`.
103- `<app-op-permissions>`: The child tag `<app-op-permission>` can be used to specify the app op
104permissions whose app op should be granted to the app when it has the role.
105- `<app-ops>`: The child tag `<app-op>` can be used to specify the app ops that should be granted to
106the app when it has the role.
107- `<preferred-activities>`: The child tag `<preferred-activity>` can be used to specify the
108preferred activities that should be configured for the app when it gets the role. The first
109`<activity>` tag inside `<preferred-activity>` will identify the activity component inside the app,
110and the other `<intent-filter>` tags inside `<preferred-activity>` can be used to specify for which
111intent filters the identified activity component should be configured as preferred, i.e. the default
112handler for those intents.
113
114## Requesting a role
115
116Before requesting a role, an app should check whether it already has the role with
117`RoleManager.isRoleHeld()`. If it doesn't have the role, it should then check for the availability
118of the role with `RoleManager.isRoleAvailable()`.
119
120An app can request for a role by launching the intent returned by
121`RoleManager.createRequestRoleIntent()`. If the role is unavailable or the app isn't qualified for
122the role, the request role dialog won't show up and will return `RESULT_CANCELED` immediately. If
123the role is granted to the app, it will return `RESULT_OK`.
124
125The following is an example about how to request the SMS role:
126
127```kotlin
128val roleManager = getSystemService(RoleManager::class.java)
129if (roleManager.isRoleHeld(RoleManager.ROLE_SMS)) {
130    // We already have the role.
131} else if (roleManager.isRoleAvailable(RoleManager.ROLE_SMS)) {
132    startActivityForResult(roleManager.createRequestRoleIntent(RoleManager.ROLE_SMS), REQUEST_CODE)
133    // Check the result later in onActivityResult().
134} else {
135    // Role is unavailable.
136}
137```
138
139## Checking a role
140
141Role is not a replacement for permission, and if one needs to check a certain privilege for an
142action, they should typically check a permission instead, and introduce a new permission if there
143isn't an existing one.
144
145`RoleManager.isRoleHeld()` can be used to check whether an app itself has a role. For checking
146whether an arbitrary app has a certain role, `RoleManager.getRoleHoldersAsUser()` can be used to
147retrieve the list of role holders and check if the app is within the list. This is a system API and
148requires the `MANAGE_ROLE_HOLDERS` permission.
149
150## Managing a role
151
152Generally roles are managed by the role implementation and the user, so it's less likely one should
153manage them manually.
154
155In case the system does need to manage the holders of a role, `RoleManager.addRoleHolderAsUser()`,
156`RoleManager.removeRoleHolderAsUser()` and `RoleManager.clearRoleHoldersAsUser()` may be used. These
157are system APIs and require the `MANAGE_ROLE_HOLDERS` permission. These requests are asynchronous
158and the role might not be modified until the `callback` is notified. The role requirements and
159behavior will still apply even if managed via these APIs, so the request might fail and one need to
160check the result in `callback`. In the event that the role controller hanged or crashed, the
161`callback` will return with failure after a certain timeout.
162
163## Shell command
164
165The current list of roles and their holders can be checked with the following shell command on
166device:
167
168```bash
169dumpsys role
170```
171
172You can also manage the role holders with `cmd role`:
173
174```bash
175cmd role add-role-holder [--user USER_ID] ROLE PACKAGE [FLAGS]
176cmd role remove-role-holder [--user USER_ID] ROLE PACKAGE [FLAGS]
177cmd role clear-role-holders [--user USER_ID] ROLE [FLAGS]
178cmd role set-bypassing-role-qualification true|false
179```
180
181The command outputs nothing and exits with `0` on success. If there was an error, the error will be
182printed and the command will terminate with a non-zero exit code.
183