行为变更：以 Android 17 或更高版本为目标平台的应用

与之前的版本一样，Android 17 包含一些可能会影响应用的行为变更。以下行为变更仅影响以 Android 17 或更高版本为目标平台的应用。如果应用以 Android 17 或更高版本为目标平台，则应根据情况修改应用，以支持这些行为。

无论应用的 targetSdkVersion 为何，都请务必查看对 Android 17 上运行的所有应用都有影响的行为变更列表。

核心功能

Android 17 包含以下变更，这些变更会修改或扩展 Android 系统的各种核心功能。

MessageQueue 的新无锁实现

Beginning with Android 17, apps targeting Android 17 (API level 37) or higher receive a new lock-free implementation of android.os.MessageQueue. The new implementation improves performance and reduces missed frames, but may break clients that reflect on MessageQueue private fields and methods.

For more information, including mitigation strategies, see MessageQueue behavior change guidance.

静态 final 字段现在不可修改

Apps running on Android 17 or higher that target Android 17 (API level 37) or higher cannot change static final fields. If an app attempts to change a static final field by using reflection, it will cause an IllegalAccessException. Attempting to modify one of these fields through JNI APIs (such as SetStaticLongField()) will cause the app to crash.

无障碍

Android 17 进行了以下变更，以改进无障碍功能。

This feature introduces new AccessibilityEvent and TextAttribute APIs to enhance screen reader spoken feedback for CJKV language input. CJKV IME apps can now signal whether a text conversion candidate has been selected during text composition. Apps with edit fields can specify text change types when sending text changed accessibility events. For example, apps can specify that a text change occurred during text composition, or that a text change resulted from a commit. Doing this enables accessibility services such as screen readers to deliver more precise feedback based on the nature of the text modification.

App adoption

IME Apps: When setting composing text in edit fields, IMEs can use TextAttribute.Builder.setTextSuggestionSelected() to indicate whether a specific conversion candidate was selected.
Apps with Edit Fields: Apps that maintain a custom InputConnection can retrieve candidate selection data by calling TextAttribute.isTextSuggestionSelected(). These apps should then call AccessibilityEvent.setTextChangeTypes() when dispatching TYPE_VIEW_TEXT_CHANGED events. Apps targeting Android 17 (API level 37) that use the standard TextView will have this feature enabled by default. (That is, TextView will handle retrieving data from the IME and setting text change types when sending events to accessibility services).
Accessibility Services: Accessibility services that process TYPE_VIEW_TEXT_CHANGED events can call AccessibilityEvent.getTextChangeTypes() to identify the nature of the modification and adjust their feedback strategies accordingly.

隐私权

Android 17 包含以下变更，以改进用户隐私保护。

机会性启用 ECH（加密客户端 Hello）

Android 17 引入了对加密 Client Hello (ECH) 的平台支持。ECH 是一项 TLS 扩展，可通过加密 TLS 握手中的服务器名称指示 (SNI) 来增强用户隐私保护。这种加密有助于防止网络观察者轻松识别应用所连接的特定网域。

对于以 Android 17（API 级别 37）或更高版本为目标平台的应用，ECH 会机会性地用于 TLS 连接。只有当应用使用的网络库（例如 HttpEngine、WebView 或 OkHttp）已集成 ECH 支持，并且远程服务器也支持 ECH 协议时，ECH 才会处于有效状态。如果无法协商 ECH，连接会自动回退到不含 SNI 加密的标准 TLS 握手。

为了允许应用自定义此行为，Android 17 向网络安全配置文件添加了一个新的 <domainEncryption> 元素。开发者可以在 <base-config> 或 <domain-config> 标记中使用 <domainEncryption> 来全局或按网域选择 ECH 模式（例如 "opportunistic"、"enabled" 或 "disabled"）。

如需了解详情，请参阅加密的客户端 Hello 文档。

以 Android 17 为目标平台的应用需要本地网络权限

Android 17 introduces the ACCESS_LOCAL_NETWORK runtime permission to protect users from unauthorized local network access. Because this falls under the existing NEARBY_DEVICES permission group, users who have already granted other NEARBY_DEVICES permissions aren't prompted again. This new requirement prevents malicious apps from exploiting unrestricted local network access for covert user tracking and fingerprinting. By declaring and requesting this permission, your app can discover and connect to devices on the local area network (LAN), such as smart home devices or casting receivers.

Apps targeting Android 17 (API level 37) or higher now have two paths to maintain communication with LAN devices: Adopt system-mediated, privacy-preserving device pickers to skip the permission prompt, or explicitly request this new permission at runtime to maintain local network communication.

For more information, see the Local network permission documentation.

在实体设备上隐藏密码

If an app targets Android 17 (API level 37) or higher and the user is using a physical input device (for example, an external keyboard), the Android operating system applies the new show_passwords_physical setting to all characters in the password field. By default, that setting hides all password characters.

The Android system shows the last-typed password character to help the user see if they mistyped the password. However, this is much less necessary with larger external keyboards. In addition, devices with external keyboards often have larger displays, which increases the danger of someone seeing the typed password.

If the user is using the device's touchscreen, the system applies the new show_passwords_touch setting.

安全

Android 17 对设备和应用安全性进行了以下改进。

Activity 安全性

在 Android 17 中，平台继续向“默认安全”架构转变，引入了一系列旨在缓解严重程度较高的漏洞利用（例如网络钓鱼、交互劫持和混淆代理攻击）的增强功能。此更新要求开发者明确选择启用新的安全标准，以保持应用兼容性和用户保护。

对开发者的主要影响包括：

BAL 强化和改进的选择启用机制：我们正在通过将保护范围扩展到 IntentSender 来完善后台 activity 启动 (BAL) 限制。开发者必须弃用旧版 MODE_BACKGROUND_ACTIVITY_START_ALLOWED 常量。相反，您应采用精细的控制措施，例如 MODE_BACKGROUND_ACTIVITY_START_ALLOW_IF_VISIBLE，该措施会将 activity 启动限制在调用应用可见的场景中，从而显著减小攻击面。
采用工具：开发者应利用严格模式和更新后的 lint 检查来识别旧版模式，并确保做好准备，以满足未来的目标 SDK 要求。

默认启用 CT

如果应用以 Android 17（API 级别 37）或更高版本为目标平台，证书透明度 (CT) 默认处于启用状态。（在 Android 16 上，CT 可用，但应用必须选择启用。）

更安全的原生 DCL-C

如果您的应用以 Android 17（API 级别 37）或更高版本为目标平台，则 Android 14 中针对 DEX 和 JAR 文件引入的更安全的动态代码加载 (DCL) 保护功能现在也适用于原生库。

使用 System.load() 加载的所有原生文件都必须标记为只读。否则，系统会抛出 UnsatisfiedLinkError。

我们建议应用尽可能避免动态加载代码，因为这样做会大大增加应用因代码注入或代码篡改而遭到入侵的风险。

限制 CP2 数据视图中的 PII 字段

For apps targeting Android 17 (API level Android 17 (API level 37)) and higher, Contacts Provider 2 (CP2) restricts certain columns containing Personally Identifiable Information (PII) from the data view. When this change is enabled, these columns are removed from the data view to enhance user privacy. The restricted columns include:

Apps that are using these columns from ContactsContract.Data can extract them from ContactsContract.RawContacts instead, by joining with RAW_CONTACT_ID.

在 CP2 中强制执行严格的 SQL 检查

For apps targeting Android 17 (API level Android 17 (API level 37)) and higher, Contacts Provider 2 (CP2) enforces strict SQL query validation when the ContactsContract.Data table is accessed without READ_CONTACTS permission.

With this change, if an app doesn't have READ_CONTACTS permission, StrictColumns and StrictGrammar options are set when querying the ContactsContract.Data table. If a query uses a pattern that isn't compatible with these, it will be rejected and cause an exception to be thrown.

设备类型

Android 17 包含以下变更，以改进各种尺寸和类型的设备的用户体验。

平台 API 变更，以忽略大屏设备 (sw>=600dp) 上的屏幕方向、尺寸调整能力和宽高比限制

我们在 Android 16 中引入了平台 API 变更，以忽略屏幕方向、宽高比和尺寸调整能力限制（针对大型屏幕，sw >= 600dp），适用于面向 API 级别 36 或更高级别的应用。开发者可以选择使用 SDK 36 退出这些变更，但对于面向 Android 17（API 级别 37）或更高级别的应用，此退出选项将不再可用。

如需了解详情，请参阅忽略屏幕方向和尺寸调整能力限制。