功能和 API

Android 16 面向开发者引入了一些出色的新功能和 API。以下各部分总结了这些功能，可帮助您开始使用相关 API。

有关新增、修改和移除的 API 的详细列表，请参阅 API 差异报告。如需详细了解新的 API，请访问 Android API 参考文档，新 API 会突出显示以方便查看。

您还应查看平台变更可能会在哪些方面影响您的应用。如需了解详情，请参阅以下页面：

核心功能

Android 包含一些新的 API，可扩展 Android 系统的核心功能。

2025 年发布了两个 Android API

  • 此预览版适用于 Android 的下一个主要版本，计划于 2025 年第 2 季度发布。此版本与我们过去的所有 API 版本类似，我们可以进行计划性的行为更改，这些更改通常与 targetSdkVersion 相关联。
  • 我们计划提前一个季度（2021 年第 2 季度，而非之前的第 3 季度）发布主要版本，以便更好地与整个生态系统中的设备发布时间表保持一致，让更多设备能够更早地搭载 Android 主要版本。由于主要版本将于第 2 季度发布，因此您需要比往年提前几个月进行年度兼容性测试，以确保您的应用已做好准备。
  • 我们计划在 2025 年第 4 季度再发布一次，届时还将推出新的开发者 API。2025 年只有第二季度的主要版本包含可能影响应用的计划行为变更。

除了新的开发者 API 之外，第 4 季度次要版本还将包含功能更新、优化和 bug 修复；其中不会包含任何会影响应用的行为变更。

2025 年 Android 版本的时间轴视图，请注意，25Q2 版本是一个主要版本，25Q4 版本是一个次要版本。

我们将继续每季度发布 Android 版本。在 API 版本之间，第 1 季度和第 3 季度的更新将提供增量更新，以帮助确保持续提供高质量的服务。我们正积极与设备合作伙伴合作，将 Q2 版本推广到尽可能多的设备。

在主要版本和次要版本中使用新 API

目前，使用 SDK_INT 常量与 VERSION_CODES 结合使用，即可通过检查 API 级别来保护代码块。我们将继续支持主要 Android 版本。

if (SDK_INT >= VERSION_CODES.BAKLAVA) {
  // Use APIs introduced in Android 16
}

新的 SDK_INT_FULL 常量可用于针对主要版本和次要版本进行 API 检查，并使用新的 VERSION_CODES_FULL 枚举。

if (SDK_INT_FULL >= VERSION_CODES_FULL.[MAJOR or MINOR RELEASE]) {
  // Use APIs introduced in a major or minor release
}

您还可以使用 Build.getMinorSdkVersion() 方法仅获取 SDK 次要版本。

val minorSdkVersion = Build.getMinorSdkVersion(VERSION_CODES_FULL.BAKLAVA)

这些 API 尚未最终确定，可能会发生变化，因此如果您有任何疑虑，请向我们发送反馈。

用户体验和系统界面

Android 16 为应用开发者和用户提供了更多控制权和灵活性，以便他们根据自己的需求配置设备。

以进度为中心的通知

Android 16 introduces progress-centric notifications to help users seamlessly track user-initiated, start-to-end journeys.

Notification.ProgressStyle is a new notification style that lets you create progress-centric notifications. Key use cases include rideshare, delivery, and navigation. Within the Notification.ProgressStyle class, you can denote states and milestones in a user journey using points and segments.

To learn more, see the Progress-centric notifications documentation page.

A progress-centric notification displayed on the lockscreen.
A progress-centric notification displayed in the notification shade.

预测性返回更新

Android 16 adds new APIs to help you enable predictive back system animations in gesture navigation such as the back-to-home animation. Registering the onBackInvokedCallback with the new PRIORITY_SYSTEM_NAVIGATION_OBSERVER allows your app to receive the regular onBackInvoked call whenever the system handles a back navigation without impacting the normal back navigation flow.

Android 16 additionally adds the finishAndRemoveTaskCallback() and moveTaskToBackCallback. By registering these callbacks with the OnBackInvokedDispatcher, the system can trigger specific behaviors and play corresponding ahead-of-time animations when the back gesture is invoked.

更丰富的触感反馈

Android has exposed control over the haptic actuator ever since its inception.

Android 11 added support for more complex haptic effects that more advanced actuators could support through VibrationEffect.Compositions of device-defined semantic primitives.

Android 16 adds haptic APIs that let apps define the amplitude and frequency curves of a haptic effect while abstracting away differences between device capabilities.

开发者工作效率和工具

虽然我们的大部分工作都是围绕 Android Studio、Jetpack Compose 和 Android Jetpack 库等工具来提高您的工作效率，但我们始终在寻找平台中可帮助您实现愿景的方法。

动态壁纸的内容处理

In Android 16, the live wallpaper framework is gaining a new content API to address the challenges of dynamic, user-driven wallpapers. Currently, live wallpapers incorporating user-provided content require complex, service-specific implementations. Android 16 introduces WallpaperDescription and WallpaperInstance. WallpaperDescription lets you identify distinct instances of a live wallpaper from the same service. For example, a wallpaper that has instances on both the home screen and on the lock screen may have unique content in both places. The wallpaper picker and WallpaperManager use this metadata to better present wallpapers to users, streamlining the process for you to create diverse and personalized live wallpaper experiences.

性能和电池

Android 16 引入了可帮助您收集应用相关数据分析的 API。

系统触发的性能分析

ProfilingManager was added in Android 15, giving apps the ability to request profiling data collection using Perfetto on public devices in the field. However, since this profiling must be started from the app, critical flows such as startups or ANRs would be difficult or impossible for apps to capture.

To help with this, Android 16 introduces system-triggered profiling to ProfilingManager. Apps can register interest in receiving traces for certain triggers such as cold start reportFullyDrawn or ANRs, and then the system starts and stops a trace on the app's behalf. After the trace completes, the results are delivered to the app's data directory.

ApplicationStartInfo 中的启动组件

ApplicationStartInfo was added in Android 15, allowing an app to see reasons for process start, start type, start times, throttling, and other useful diagnostic data. Android 16 adds getStartComponent() to distinguish what component type triggered the start, which can be helpful for optimizing the startup flow of your app.

更好地进行作业内省

The JobScheduler#getPendingJobReason() API returns a reason why a job might be pending. However, a job might be pending for multiple reasons.

In Android 16, we are introducing a new API JobScheduler#getPendingJobReasons(int jobId), which returns multiple reasons why a job is pending, due to both explicit constraints set by the developer and implicit constraints set by the system.

We're also introducing JobScheduler#getPendingJobReasonsHistory(int jobId), which returns a list of the most recent constraint changes.

We recommend using the API to help you debug why your jobs may not be executing, especially if you're seeing reduced success rates of certain tasks or have bugs around latency of certain job completion. For example, updating widgets in the background failed to occur or prefetch job failed to be called prior to app start.

This can also better help you understand if certain jobs are not completing due to system defined constraints versus explicitly set constraints.

自动调节刷新率

Adaptive refresh rate (ARR), introduced in Android 15, enables the display refresh rate on supported hardware to adapt to the content frame rate using discrete VSync steps. This reduces power consumption while eliminating the need for potentially jank-inducing mode-switching.

Android 16 introduces hasArrSupport() and getSuggestedFrameRate(int) while restoring getSupportedRefreshRates() to make it easier for your apps to take advantage of ARR. RecyclerView 1.4 internally supports ARR when it is settling from a fling or smooth scroll, and we're continuing our work to add ARR support into more Jetpack libraries. This frame rate article covers many of the APIs you can use to set the frame rate so that your app can directly use ARR.

ADPF 中的裕度 API

The SystemHealthManager introduces the getCpuHeadroom and getGpuHeadroom APIs, designed to provide games and resource-intensive apps with estimates of available CPU and GPU resources. These methods offer a way for you to gauge how your app or game can best improve system health, particularly when used in conjunction with other Android Dynamic Performance Framework (ADPF) APIs that detect thermal throttling.

By using CpuHeadroomParams and GpuHeadroomParams on supported devices, you can customize the time window used to compute the headroom and select between average or minimum resource availability. This can help you reduce your CPU or GPU resource usage accordingly, leading to better user experiences and improved battery life.

无障碍

Android 16 新增了无障碍功能 API 和功能，可帮助您让所有用户都能使用您的应用。

改进了无障碍功能 API

Android 16 添加了其他 API 来增强界面语义，这有助于为依赖于无障碍服务（例如 TalkBack）的用户提高一致性。

为文字添加轮廓，以最大限度地提高文字对比度

视力较低的用户对对比度的敏感度通常较低，因此很难将对象与背景区分开来。为了帮助这些用户，Android 16 引入了轮廓文本，取代了高对比度文本，后者会在文本周围绘制较大的对比度区域，以大大提高可辨性。

Android 16 包含新的 AccessibilityManager API，可让您的应用检查或注册监听器，以查看此模式是否已启用。这主要适用于 Compose 等界面工具包，以提供类似的视觉体验。如果您维护界面工具包库，或者您的应用执行绕过 android.text.Layout 类的自定义文本渲染，则可以使用此方法来了解何时启用轮廓文本。

Android 16 推出新的轮廓文本无障碍功能前后，对比度更高的文本

向 TtsSpan 添加了时长

Android 16 使用 TYPE_DURATION 扩展了 TtsSpan，其中包含 ARG_HOURS、ARG_MINUTES 和 ARG_SECONDS。这样，您就可以直接为时长添加注释，确保通过 TalkBack 等服务获得准确且一致的文本转语音输出。

支持具有多个标签的元素

Android 目前允许界面元素从其他元素派生其无障碍功能标签，现在还支持关联多个标签，这是 Web 内容中常见的情况。通过在 AccessibilityNodeInfo 中引入基于列表的 API，Android 可以直接支持这些多标签关系。在进行这项更改的过程中，我们已弃用 AccessibilityNodeInfo#setLabeledBy 和 #getLabeledBy，改用 #addLabeledBy、#removeLabeledBy 和 #getLabeledByList。

改进了对可展开元素的支持

Android 16 添加了无障碍功能 API，可让您传达互动元素（例如菜单和展开式列表）的展开或收起状态。通过使用 setExpandedState 设置展开状态，并使用 CONTENT_CHANGE_TYPE_EXPANDED 内容更改类型调度 TYPE_WINDOW_CONTENT_CHANGED AccessibilityEvents，您可以确保 TalkBack 等屏幕阅读器会读出状态更改，从而提供更直观、更包容的用户体验。

不确定进度条

Android 16 添加了 RANGE_TYPE_INDETERMINATE，让您可以为确定性和不确定性 ProgressBar 微件公开 RangeInfo，从而让 TalkBack 等服务能够更一致地为进度指示器提供反馈。

三态复选框

Android 16 中的新 AccessibilityNodeInfo getChecked 和 setChecked(int) 方法现在除了“已选中”和“未选中”之外，还支持“部分选中”状态。此字段取代了已废弃的布尔值 isChecked 和 setChecked(boolean)。

补充说明

如果无障碍服务提供关于 ViewGroup 的说明，则会将来自其子视图的内容标签合并在一起。如果您为 ViewGroup 提供 contentDescription，无障碍服务会假定您还要覆盖不可聚焦的子视图的说明。如果您想为下拉菜单等内容添加标签（例如“字体系列”），同时保留当前的无障碍功能选择（例如“Roboto”），这可能会造成问题。Android 16 添加了 setSupplementalDescription，以便您提供用于提供 ViewGroup 相关信息的文本，而不会覆盖其子项中的信息。

必填表单字段

Android 16 向 AccessibilityNodeInfo 添加了 setFieldRequired，以便应用可以告知无障碍服务需要输入表单字段。对于填写各种类型表单的用户而言，这是一个重要的场景，即使是简单的必填条款及条件复选框，也能帮助用户始终如一地识别必填字段并在必填字段之间快速导航。

将手机作为 LEA 助听器的麦克风输入设备，用于语音通话

Android 16 adds the capability for users of LE Audio hearing aids to switch between the built-in microphones on the hearing aids and the microphone on their phone for voice calls. This can be helpful in noisy environments or other situations where the hearing aid's microphones might not perform well.

LEA 助听器的环境音量控制

Android 16 adds the capability for users of LE Audio hearing aids to adjust the volume of ambient sound that is picked up by the hearing aid's microphones. This can be helpful in situations where background noise is too loud or too quiet.

相机

Android 16 增强了对专业相机用户的支持，允许进行混合自动曝光以及精确的色温和色调调整。新的夜间模式指示器可帮助应用了解何时切换到夜间模式相机会议以及何时从夜间模式相机会议切换回来。新的 Intent 操作可让您更轻松地拍摄动态照片，并且我们还在不断改进 UltraHDR 图片，支持 HEIC 编码和 ISO 21496-1 草稿标准中的新参数。

混合自动曝光

Android 16 向 Camera2 添加了新的混合自动曝光模式，让您可以手动控制曝光的特定方面，同时让自动曝光 (AE) 算法处理其余部分。您可以控制 ISO + AE 和曝光时间 + AE，与当前方法（您要么完全手动控制，要么完全依赖自动曝光）相比，可提供更大的灵活性。

fun setISOPriority() {
    // ... (Your existing code before the snippet) ...

    val availablePriorityModes = mStaticInfo.characteristics.get(
        CameraCharacteristics.CONTROL_AE_AVAILABLE_PRIORITY_MODES
    )

    // ... (Your existing code between the snippets) ...

    // Turn on AE mode to set priority mode
    reqBuilder.set(
        CaptureRequest.CONTROL_AE_MODE,
        CameraMetadata.CONTROL_AE_MODE_ON
    )
    reqBuilder.set(
        CaptureRequest.CONTROL_AE_PRIORITY_MODE,
        CameraMetadata.CONTROL_AE_PRIORITY_MODE_SENSOR_SENSITIVITY_PRIORITY
    )
    reqBuilder.set(
        CaptureRequest.SENSOR_SENSITIVITY,
        TEST_SENSITIVITY_VALUE
    )
    val request: CaptureRequest = reqBuilder.build()

    // ... (Your existing code after the snippet) ...
}

精确的色温和色调调整

Android 16 增加了对相机的精细色温和色调调整的支持，以更好地支持专业视频录制应用。在较低版本的 Android 中，您可以通过 CONTROL_AWB_MODE 控制白平衡设置，其中包含仅限于预设列表的选项，例如白炽灯、多云和黄昏。COLOR_CORRECTION_MODE_CCT 可让您使用 COLOR_CORRECTION_COLOR_TEMPERATURE 和 COLOR_CORRECTION_COLOR_TINT 根据相关色温精确调整白平衡。

fun setCCT() {
    // ... (Your existing code before this point) ...

    val colorTemperatureRange: Range<Int> =
        mStaticInfo.characteristics[CameraCharacteristics.COLOR_CORRECTION_COLOR_TEMPERATURE_RANGE]

    // Set to manual mode to enable CCT mode
    reqBuilder[CaptureRequest.CONTROL_AWB_MODE] = CameraMetadata.CONTROL_AWB_MODE_OFF
    reqBuilder[CaptureRequest.COLOR_CORRECTION_MODE] = CameraMetadata.COLOR_CORRECTION_MODE_CCT
    reqBuilder[CaptureRequest.COLOR_CORRECTION_COLOR_TEMPERATURE] = 5000
    reqBuilder[CaptureRequest.COLOR_CORRECTION_COLOR_TINT] = 30

    val request: CaptureRequest = reqBuilder.build()

    // ... (Your existing code after this point) ...
}

以下示例展示了应用不同色温和色调调整后的照片效果：

未应用色温或色调调整的原始图片。
将色温调整为 3000 的图片。
将色温调整为 7000 的图片。


将色调级别降低 50 的图片。
色调级别提高了 50 的图片。

相机夜间模式场景检测

To help your app know when to switch to and from a night mode camera session, Android 16 adds EXTENSION_NIGHT_MODE_INDICATOR. If supported, it's available in the CaptureResult within Camera2.

This is the API we briefly mentioned as coming soon in the How Instagram enabled users to take stunning low light photos blog post. That post is a practical guide on how to implement night mode together with a case study that links higher-quality in-app night mode photos with an increase in the number of photos shared from the in-app camera.

动态照片拍摄 intent 操作

Android 16 adds standard Intent actions — ACTION_MOTION_PHOTO_CAPTURE, and ACTION_MOTION_PHOTO_CAPTURE_SECURE — which request that the camera application capture a motion photo and return it.

You must either pass an extra EXTRA_OUTPUT to control where the image will be written, or a Uri through Intent.setClipData(ClipData). If you don't set a ClipData, it will be copied there for you when calling Context.startActivity(Intent).

An example of a motion photo, showing the still image followed by the motion playback.

UltraHDR 图片增强功能

An illustration of Standard Dynamic Range (SDR) versus High Dynamic Range (HDR) image quality.

Android 16 continues our work to deliver dazzling image quality with UltraHDR images. It adds support for UltraHDR images in the HEIC file format. These images will get ImageFormat type HEIC_ULTRAHDR and will contain an embedded gainmap similar to the existing UltraHDR JPEG format. We're working on AVIF support for UltraHDR as well, so stay tuned.

In addition, Android 16 implements additional parameters in UltraHDR from the ISO 21496-1 draft standard, including the ability to get and set the colorspace that gainmap math should be applied in, as well as support for HDR encoded base images with SDR gainmaps.

图形

Android 16 包含最新的图形改进，例如使用 AGSL 实现自定义图形效果。

使用 AGSL 实现自定义图形效果

Android 16 添加了 RuntimeColorFilter 和 RuntimeXfermode，让您可以创作阈值、Sepia 和 Hue Saturation 等复杂效果，并将其应用于绘制调用。从 Android 13 开始，您可以使用 AGSL 创建扩展 Shader 的自定义 RuntimeShader。新 API 反映了这一点，添加了由 AGSL 驱动的 RuntimeColorFilter（用于扩展 ColorFilter）和 Xfermode 效果，让您可以在源像素和目标像素之间实现基于 AGSL 的自定义合成和混合。

private val thresholdEffectString = """
    uniform half threshold;

    half4 main(half4 c) {
        half luminosity = dot(c.rgb, half3(0.2126, 0.7152, 0.0722));
        half bw = step(threshold, luminosity);
        return bw.xxx1 * c.a;
    }"""

fun setCustomColorFilter(paint: Paint) {
   val filter = RuntimeColorFilter(thresholdEffectString)
   filter.setFloatUniform(0.5);
   paint.colorFilter = filter
}

连接

Android 16 更新了平台，让您的应用能够使用通信和无线技术方面的最新进展。

测距功能（增强型安全）

Android 16 adds support for robust security features in Wi-Fi location on supported devices with Wi-Fi 6's 802.11az, allowing apps to combine the higher accuracy, greater scalability, and dynamic scheduling of the protocol with security enhancements including AES-256-based encryption and protection against MITM attacks. This allows it to be used more safely in proximity use cases, such as unlocking a laptop or a vehicle door. 802.11az is integrated with the Wi-Fi 6 standard, leveraging its infrastructure and capabilities for wider adoption and easier deployment.

通用测距 API

Android 16 includes the new RangingManager, which provides ways to determine the distance and angle on supported hardware between the local device and a remote device. RangingManager supports the usage of a variety of ranging technologies such as BLE channel sounding, BLE RSSI-based ranging, Ultra Wideband, and Wi-Fi round trip time.

配套设备管理器设备存在情况

In Android 16, new APIs are being introduced for binding your companion app service. Service will be bound when BLE is in range and Bluetooth is connected and service will be unbound when BLE is out of range or Bluetooth is disconnected. App will receives a new 'onDevicePresenceEvent()' callback based on various of DevicePresenceEvent. More details can be found in 'startObservingDevicePresence(ObservingDevicePresenceRequest)'.

媒体

Android 16 包含各种可提升媒体体验的功能。

改进了照片选择器

The photo picker provides a safe, built-in way for users to grant your app access to selected images and videos from both local and cloud storage, instead of their entire media library. Using a combination of Modular System Components through Google System Updates and Google Play services, it's supported back to Android 4.4 (API level 19). Integration requires just a few lines of code with the associated Android Jetpack library.

Android 16 includes the following improvements to the photo picker:

  • Embedded photo picker: New APIs that enable apps to embed the photo picker into their view hierarchy. This allows it to feel like a more integrated part of the app while still leveraging the process isolation that allows users to select media without the app needing overly broad permissions. To maximize compatibility across platform versions and simplify your integration, you'll want to use the forthcoming Android Jetpack library if you want to integrate the embedded photo picker.
  • Cloud search in photo picker: New APIs that enable searching from the cloud media provider for the Android photo picker. Search functionality in the photo picker is coming soon.

高级专业视频

Android 16 introduces support for the Advanced Professional Video (APV) codec which is designed to be used for professional level high quality video recording and post production.

The APV codec standard has the following features:

  • Perceptually lossless video quality (close to raw video quality)
  • Low complexity and high throughput intra-frame-only coding (without pixel domain prediction) to better support editing workflows
  • Support for high bit-rate range up to a few Gbps for 2K, 4K and 8K resolution content, enabled by a lightweight entropy coding scheme
  • Frame tiling for immersive content and for enabling parallel encoding and decoding
  • Support for various chroma sampling formats and bit-depths
  • Support for multiple decoding and re-encoding without severe visual quality degradation
  • Support multi-view video and auxiliary video like depth, alpha, and preview
  • Support for HDR10/10+ and user-defined metadata

A reference implementation of APV is provided through the OpenAPV project. Android 16 will implement support for the APV 422-10 Profile that provides YUV 422 color sampling along with 10-bit encoding and for target bitrates of up to 2Gbps.

隐私权

Android 16 包含多种有助于应用开发者保护用户隐私的功能。

健康数据共享更新

Health Connect adds ACTIVITY_INTENSITY, a data type defined according to World Health Organization guidelines around moderate and vigorous activity. Each record requires the start time, the end time, and whether the activity intensity is moderate or vigorous.

Health Connect also contains updated APIs supporting medical records. This allows apps to read and write medical records in FHIR format with explicit user consent.

Privacy Sandbox on Android

Android 16 incorporates the latest version of the Privacy Sandbox on Android, part of our ongoing work to develop technologies where users know their privacy is protected. Our website has more about the Privacy Sandbox on Android developer beta program to help you get started. Check out the SDK Runtime which allows SDKs to run in a dedicated runtime environment separate from the app they are serving, providing stronger safeguards around user data collection and sharing.

安全

Android 16 包含有助于增强应用安全性和保护应用数据的功能。

密钥共享 API

Android 16 adds APIs that support sharing access to Android Keystore keys with other apps. The new KeyStoreManager class supports granting and revoking access to keys by app uid, and includes an API for apps to access shared keys.

设备规格

Android 16 为您的应用提供支持，让您充分利用 Android 的设备类型。

电视的标准化画质和音质框架

The new MediaQuality package in Android 16 exposes a set of standardized APIs for access to audio and picture profiles and hardware-related settings. This allows streaming apps to query profiles and apply them to media dynamically:

  • Movies mastered with a wider dynamic range require greater color accuracy to see subtle details in shadows and adjust to ambient light, so a profile that prefers color accuracy over brightness may be appropriate.
  • Live sporting events are often mastered with a narrow dynamic range, but are often watched in daylight, so a profile that preferences brightness over color accuracy can give better results.
  • Fully interactive content wants minimal processing to reduce latency, and wants higher frame rates, which is why many TV's ship with a game profile.

The API allows apps to switch between profiles and users to enjoy tuning supported TVs to best suit their content.

国际化

Android 16 新增了多项功能，可在设备以不同语言运行时提升用户体验。

竖排文字

Android 16 添加了对垂直渲染和测量文本的低级支持，以便为库开发者提供基本的垂直书写支持。这对于日语等通常使用竖向书写系统的语言特别有用。Paint 类中添加了一个新标志 VERTICAL_TEXT_FLAG。使用 Paint.setFlags 设置此标志后，Paint 的文本测量 API 将报告垂直进度，而不是水平进度，并且 Canvas 将垂直绘制文本。

val text = "「春は、曙。」"
Box(
    Modifier.padding(innerPadding).background(Color.White).fillMaxSize().drawWithContent {
        drawIntoCanvas { canvas ->
            val paint = Paint().apply { textSize = 64.sp.toPx() }
            // Draw text vertically
            paint.flags = paint.flags or VERTICAL_TEXT_FLAG
            val height = paint.measureText(text)
            canvas.nativeCanvas.drawText(
                text,
                0,
                text.length,
                size.width / 2,
                (size.height - height) / 2,
                paint
            )
        }
    }
) {}

自定义度量衡制

Users can now customize their measurement system in regional preferences within Settings. The user preference is included as part of the locale code, so you can register a BroadcastReceiver on ACTION_LOCALE_CHANGED to handle locale configuration changes when regional preferences change.

Using formatters can help match the local experience. For example, "0.5 in" in English (United States), is "12,7 mm" for a user who has set their phone to English (Denmark) or who uses their phone in English (United States) with the metric system as the measurement system preference.

To find these settings, open the Settings app and navigate to System > Languages & region.