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Expo 视频(expo-video)
一个提供 API 用于在应用中实现视频播放的库。
expo-video 是一个跨平台、高性能的视频组件,适用于 React Native 和 Expo,并支持 Web。
已知问题 Android
当两个 VideoView 组件相互重叠,并且它们的 contentFit 属性设置为 cover 时,其中一个视频可能会显示到边界之外。这是一个已知的上游问题。要解决此问题,请使用 surfaceType 属性,并将其设置为 textureView。
安装
If you are installing this in an existing React Native app, make sure to install expo in your project.
在 app 配置中进行配置
如果你的项目使用了配置插件(Continuous Native Generation (CNG)),你可以使用 expo-video 内置的配置插件进行配置。该插件允许你配置一些无法在运行时设置、且需要重新构建应用二进制文件才会生效的属性。如果你的应用不使用 CNG,则需要手动配置该库。
Example app.json with config plugin
Configurable properties
用法
下面是一个带有播放和暂停按钮的视频简单示例。
接收事件
VideoPlayer 属性的变化不会更新 React 状态。因此,要显示有关 VideoPlayer 当前状态的信息,必须监听它发出的事件。
事件系统基于 EventEmitter 类以及来自 expo 包的钩子。监听事件有几种方式:
useEvent 钩子
创建一个监听器,返回一个可用于组件中的有状态值。组件卸载时也会自动清理。
useEventListener 钩子
基于 Player.addListener 和 Player.removeListener 方法,创建一个带自动清理的事件监听器。
Player.addListener 方法
监听事件最灵活的方式,但需要手动清理,并且需要更多样板代码。
播放 assets 目录中的本地媒体
expo-video 支持使用 require 函数加载本地媒体进行播放。你可以直接将结果作为源使用,或者如果你还想配置其他属性,也可以将其赋值给 VideoSource 的 assetId 参数。
播放媒体库中的媒体
expo-video 支持使用 expo-media-library/legacy 从用户的媒体库中挑选的视频,或任何带有相应权限的有效 PHAsset URI。
要播放媒体库中的视频,你应当使用 MediaLibrary.getAssetsAsync() 获取一个 Asset 对象,并将其 uri 属性作为视频源的 uri。
在播放之前,请务必使用 MediaLibrary.requestPermissionsAsync() 请求所需权限。
在 iOS 上,请务必不要使用资产信息中的 localUri 属性,因为它不包含读取该资产所需的权限。
预加载视频
在另一个视频播放时,可以先加载一个视频,然后再在视图中显示它。这可以让后续视频之间的切换更快,并提升用户体验。
要预加载视频,你需要使用视频源创建一个 VideoPlayer。即使播放器没有连接到 VideoView,它也会填充缓冲区。一旦连接到 VideoView,就可以在无需缓冲的情况下开始播放。
在某些情况下,在屏幕生命周期的稍后阶段再预加载视频会更有益。此时,应创建一个源为 null 的 VideoPlayer。要开始预加载,请使用 replace() 函数将播放器源替换为视频源。
下面是一个如何预加载视频的示例:
直接使用 VideoPlayer
在大多数情况下,应使用 useVideoPlayer hook 创建 VideoPlayer 实例。它会管理播放器的生命周期,并确保组件卸载时正确释放播放器。不过,在某些高级使用场景中,可能需要创建一个不会在组件卸载时自动销毁的 VideoPlayer。
在这些情况下,可以使用 createVideoPlayer 函数创建 VideoPlayer。需要注意,这种方式存在一定风险,因为当播放器不再需要时,您需要负责调用 release() 方法。如果处理不当,这种方式可能会导致内存泄漏。
在 Android 上,由于平台限制,同时挂载多个使用同一个
VideoPlayer实例的VideoView组件将无法工作。
视频缓存
如果你的应用经常重新播放同一个视频,可以利用缓存来尽量减少网络使用并提升用户体验,尽管这会增加设备存储占用。expo-video 支持在 Android 和 iOS 平台上进行视频缓存。可通过将 VideoSource 对象的 useCaching 属性设置为 true 来启用此功能。
缓存是持久化的,并且在超过首选大小后会按照最近最少使用原则被清理。此外,系统也可能因为存储空间不足而清理缓存,因此不建议依赖缓存来存储关键数据。
缓存可离线工作。如果视频的部分内容或全部内容已缓存,即使设备离线,也可以从缓存中播放,直到缓存数据耗尽。
由于平台限制,iOS 上的 HLS 视频源无法使用缓存。Android 和 iOS 上都不支持缓存受 DRM 保护的视频。
缓存管理
- 可以使用
setVideoCacheSizeAsync函数定义首选缓存大小(字节)。默认缓存大小为 1GB。 - 可以使用
getCurrentVideoCacheSize获取当前缓存占用的字节数。 - 可以使用
clearVideoCacheAsync函数清除所有已缓存视频。
拦截原生资源加载
这是 expo-video 的一个原生功能,面向高级用户。展开以了解更多。
简介
expo-video 在 iOS 上包含一个名为 VideoAssetTransportProvider 的原生扩展点。它允许你拦截特定视频源,自定义底层 AVURLAsset 的创建方式,并覆盖其加载数据的方式。
当某个源无法被 AVKit 直接处理、需要原生预处理时,这非常有用。例如,provider 可以重写 URL、附加自定义的 AVAssetResourceLoaderDelegate、启动本地代理服务器,或在播放开始前将一种流格式转换为另一种。
Providers 会在模块启动时注册到 VideoAssetTransportRegistry 中。当 expo-video 加载某个源时,它会创建一个 VideoAssetSourceDescriptor,并按优先级顺序询问已注册的 providers 是否愿意处理该源。第一个返回 VideoAssetLoadPlan 的 provider 会被使用。
此 API 面向高级原生集成。它需要自定义原生模块,因此在 Expo Go 中不可用。请改用开发构建。
可自定义属性
主要的自定义点是 VideoAssetTransportProvider 的字段以及它返回的 VideoAssetLoadPlan 的字段。
VideoAssetTransportProvider 允许你控制以下属性:
VideoAssetLoadPlan 允许你通过以下属性控制 expo-video 如何构建和管理资源:
实现与使用
典型设置如下:
- 使用
create-expo-module创建一个 Expo 模块。 - 添加一个符合
VideoAssetTransportProvider的类。 - 在模块的
OnCreate块中注册该 provider。 - 构建应用,使原生模块被编译进你的项目。
如果你只需要在单个应用中使用该 provider,请使用本地 Expo 模块流程。
如果你想在多个应用之间复用该 provider,请改用独立 Expo 模块流程。
基础使用示例
- 定义 provider 和加载计划。创建模块后,添加一个符合
VideoAssetTransportProvider的类。在makeLoadPlan(for:)中,检查VideoAssetSourceDescriptor,并对你不想处理的源返回nil。
import ExpoVideo final class ExampleVideoTransportProvider: VideoAssetTransportProvider { static let providerIdentifier = "com.example.video-transport" let identifier = Self.providerIdentifier let priority = 500 func makeLoadPlan(for source: VideoAssetSourceDescriptor) -> VideoAssetLoadPlan? { guard source.contentTypeHint == .dash, source.url.pathExtension == "mpd" else { return nil } let transformedURL = URL(string: "http://127.0.0.1:8080/master.m3u8")! return VideoAssetLoadPlan( assetURL: transformedURL, reportedContentTypeHint: .hls ) } }
- 要注册 provider,推荐在 Expo 模块的
OnCreate块中注册。这样可以确保在视频开始加载之前 provider 已可用。
import ExpoModulesCore import ExpoVideo public final class CustomVideoTransportModule: Module { public func definition() -> ModuleDefinition { Name("CustomVideoTransport") OnCreate { VideoAssetTransportRegistry.registerProvider(ExampleVideoTransportProvider()) } OnDestroy { VideoAssetTransportRegistry.unregisterProvider( withId: ExampleVideoTransportProvider.providerIdentifier ) } } }
完整示例
你可以使用以下完整示例,更好地理解如何使用此 API。
- 基础 DASH 支持 provider - Bare Expo 中的一个本地模块,为 iOS 上的
expo-video提供有限的 DASH 支持。 expo-videoiOS 缓存 - 内置缓存 provider 的实现。
API
import { VideoView, useVideoPlayer } from 'expo-video';
Components
Type: React.PureComponent<VideoViewProps>
booleanDetermines whether the player allows Picture in Picture (PiP) mode.
Note: The
supportsPictureInPictureproperty of the config plugin has to be configured for the PiP to work.
boolean • Default: trueSpecifies whether to perform video frame analysis (Live Text in videos). Check official Apple documentation for more details.
ButtonOptionsConfiguration for controlling the visibility of player control buttons.
VideoContentFit • Default: 'contain'Describes how the video should be scaled to fit in the container.
Options are 'contain', 'cover', and 'fill'.
{
dx: number,
dy: number
}Determines the position offset of the video inside the container.
boolean • Default: trueDetermines whether the native controls are shown automatically when playback starts, pauses, or ends.
When false, the controls won't appear automatically, but can still be shown by tapping the view. This is
useful when playback is driven programmatically (for example an auto-advancing playlist), where the controls
appearing on every play reads as a flash.
string • Default: undefinedDetermines the cross origin policy used by the underlying native view on web.
If undefined (default), does not use CORS at all. If set to 'anonymous', the video will be loaded with CORS enabled.
Note that some videos may not play if CORS is enabled, depending on the CDN settings.
If you encounter issues, consider adjusting the crossOrigin property.
Acceptable values are: 'anonymous' | 'use-credentials'
FullscreenOptionsDetermines the fullscreen mode options.
boolean • Default: trueDetermines whether native controls should be displayed or not.
Note: Due to platform limitations, the native controls are always enabled in fullscreen mode.
() => voidA callback to call after the mounted VideoPlayer has rendered the first frame into the VideoView.
This event can be used to hide any cover images that conceal the initial loading of the player.
Note: This event may also be called during playback when the current video track changes (for example when the player switches video quality).
() => voidA callback to call after the video player enters fullscreen mode.
() => voidA callback to call after the video player exits fullscreen mode.
() => voidA callback to call after the video player enters Picture in Picture (PiP) mode.
() => voidA callback to call after the video player exits Picture in Picture (PiP) mode.
unionA video player instance. Use useVideoPlayer() hook to create one.
Acceptable values are: VideoPlayer | null
booleanDetermines whether a video should be played "inline", that is, within the element's playback area.
boolean • Default: falseDetermines whether the player allows the user to skip media content.
boolean • Default: trueDetermines whether the timecodes should be displayed or not.
boolean • Default: falseDetermines whether the player should start Picture in Picture (PiP) automatically when the app is in the background.
Note: Only one player can be in Picture in Picture (PiP) mode at a time.
Note: The
supportsPictureInPictureproperty of the config plugin has to be configured for the PiP to work.
SurfaceType • Default: 'surfaceView'Determines the type of the surface used to render the video.
This prop should not be changed at runtime.
boolean • Default: falseUse Audio Nodes for sound playback. When the same player is playing in multiple video views the audio won't increase in volume as the number of players increases.
Note: This property is experimental, when enabled it is known to break audio for some sources. Do not change this property at runtime.
boolean • Default: falseDetermines whether the player should use the default ExoPlayer shutter that covers the VideoView before the first video frame is rendered.
Setting this property to false makes the Android behavior the same as iOS.
Type: React.Element<VideoAirPlayButtonProps>
A view displaying the AVRoutePickerView. Shows a button, when pressed, an AirPlay device picker shows up, allowing users to stream the currently playing video
to any available AirPlay sink.
When using this view, make sure that the
allowsExternalPlaybackplayer property is set totrue.
ColorValue • Default: undefinedThe color of the button icon while AirPlay sharing is active.
() => voidA callback called when the AirPlay route selection popup is about to show.
() => voidA callback called when the AirPlay route selection popup has disappeared.
boolean • Default: trueDetermines whether the AirPlay device selection popup should show video outputs first.
ColorValue • Default: undefinedThe color of the button icon while AirPlay sharing is not active.
Component methods
Enters fullscreen mode.
Promise<void>Exits fullscreen mode.
Note: On Android the JS runtime is paused when the
VideoViewis in fullscreen mode. Because of thisexitFullscreenwill only work when called from a native listener - see the example below.
Promise<void>Example
const ref = useRef<VideoView>() const player = useVideoPlayer(source) // This will work on all platforms useEventListener(player, 'playToEnd', () => { ref.current?.exitFullscreen(); }); // This will not work on Android const enterAndExit = useCallback(() => { setTimeout(() => { ref.current?.exitFullscreen() }, 5000) ref.current?.enterFullscreen() },[])
Enters Picture in Picture (PiP) mode. Throws an exception if the device does not support PiP.
Note: Only one player can be in Picture in Picture (PiP) mode at a time.
Note: The
supportsPictureInPictureproperty of the config plugin has to be configured for the PiP to work.
Promise<void>Exits Picture in Picture (PiP) mode.
Promise<void>Hooks
Creates a VideoPlayer, which will be automatically cleaned up when the component is unmounted.
VideoPlayerClasses
Type: Class extends SharedObject<VideoPlayerEvents>
A class that represents an instance of the video player.
VideoPlayer Properties
boolean • Default: trueDetermines whether the player should allow external playback.
AudioMixingMode • Default: 'auto'Determines how the player will interact with other audio playing in the system.
union • Default: nullSpecifies the audio track currently played by the player. null when no audio is played.
Acceptable values are: AudioTrack | null
AudioTrack[]An array of audio tracks available for the current video.
SubtitleTrack[]An array of subtitle tracks available for the current video.
VideoTrack[]An array of video tracks available for the current video.
On iOS, when using a HLS source, make sure that the uri contains
.m3u8extension or that thecontentTypeproperty of theVideoSourcehas been set to'hls'. Otherwise, the video tracks will not be available.
numberFloat value indicating how far the player has buffered the video in seconds.
This value is 0 when the player has not buffered up to the current playback time. When it's impossible to determine the buffer state (for example, when the player isn't playing any media), this value is -1.
BufferOptionsSpecifies buffer options which will be used by the player when buffering the video.
You should provide a
BufferOptionsobject when setting this property. Setting individual buffer properties is not supported.
unionThe exact timestamp when the currently displayed video frame was sent from the server,
based on the EXT-X-PROGRAM-DATE-TIME tag in the livestream metadata.
If this metadata is missing, this property will return null.
Acceptable values are: number | null
unionFloat value indicating the latency of the live stream in seconds.
If a livestream doesn't have the required metadata, this will return null.
Acceptable values are: number | null
numberFloat value indicating the current playback time in seconds.
If the player is not yet playing, this value indicates the time position
at which playback will begin once the play() method is called.
Setting currentTime to a new value seeks the player to the given time.
Check out the seekTolerance property to configure the seeking precision.
numberFloat value indicating the duration of the current video in seconds.
booleanIndicates whether the player is currently playing back the media to an external device via AirPlay.
booleanBoolean value indicating whether the player is currently playing a live stream.
boolean • Default: trueBoolean indicating if the player should keep the screen on while playing.
On Android, this property has an effect only when a
VideoViewis visible. If you want to keep the screen awake at all times useexpo-keep-awake.
boolean • Default: falseDetermines whether the player should automatically replay after reaching the end of the video.
union • Default: nullSpecifies the maximum resolution that the player will select when choosing between the video tracks of an adaptive stream. The player picks the highest-quality track that does not exceed this resolution.
Set this property to null to remove the limit and allow all available resolutions. Dimensions
which are not greater than zero are treated the same as null.
The cap is enforced differently per platform:
- On Android it is a hard constraint, unless no track satisfies it, in which case the lowest-resolution track is used.
- On iOS it is a preferred maximum, which the player treats as a soft hint when selecting a track.
Note: On iOS this property only applies to HTTP Live Streaming (HLS) sources.
Acceptable values are: VideoSize | null
boolean • Default: falseBoolean value whether the player is currently muted.
Setting this property to true/false will mute/unmute the player.
number • Default: 1.0Float value between 0 and 16.0 indicating the current playback speed of the player.
booleanBoolean value whether the player is currently playing.
Use
playandpausemethods to control the playback.
boolean • Default: trueBoolean value indicating if the player should correct audio pitch when the playback speed changes.
ScrubbingModeOptionsDetermines whether the scrubbing mode is enabled and what scrubbing optimizations should be enabled.
See
SeekToleranceto set the seeking tolerance, which can also affect the scrubbing performance.
SeekToleranceDetermines the time that the actual position seeked to may precede or exceed the requested seek position.
This property affects the precision of setting the currentTime property and the seekBy method, and on Android, it also affects the accuracy of the scrubber from the default native controls.
By default, the player seeks to the exact requested time.
If you are trying to optimize for scrubbing (many frequent seeks), also see
ScrubbingModeOptions.
boolean • Default: falseBoolean value determining whether the player should show the now playing notification.
Note: On Android,
supportsBackgroundPlaybackproperty of the config plugin has to betruefor the now playing notification to work.
VideoPlayerStatusIndicates the current status of the player.
boolean • Default: falseDetermines whether the player should continue playing after the app enters the background.
Note: The
supportsBackgroundPlaybackproperty of the config plugin has to betruefor the background playback to work.
union • Default: nullSpecifies the subtitle track which is currently displayed by the player. null when no subtitles are displayed.
To ensure a valid subtitle track, always assign one of the subtitle tracks from the
availableSubtitleTracksarray.
Acceptable values are: SubtitleTrack | null
number • Default: 0Float value indicating the interval in seconds at which the player will emit the timeUpdate event.
When the value is equal to 0, the event will not be emitted.
union • Default: nullSpecifies the video track currently played by the player. null when no video is displayed.
Acceptable values are: VideoTrack | null
VideoPlayer Methods
Generates thumbnails from the currently played asset. The thumbnails are references to native images,
thus they can be used as a source of the Image component from expo-image.
Promise<VideoThumbnail[]>Replaces the current source with a new one.
On iOS, this method loads the asset data synchronously on the UI thread and can block it for extended periods of time. Use
replaceAsyncto load the asset asynchronously and avoid UI lags.
This method will be deprecated in the future.
voidReplaces the current source with a new one, while offloading loading of the asset to a different thread.
On Android and Web, this method is equivalent to
replace.
Promise<void>Seeks the playback by the given number of seconds. The time to which the player seeks may differ from the specified requested time for efficiency,
depending on the encoding and what is currently buffered by the player. Use this function to implement playback controls that seek by specific amount of time,
in which case, the actual time usually does not have to be precise. For frame accurate seeking, use the currentTime property.
voidType: Class extends SharedRef<'image'>
Represents a video thumbnail that references a native image.
Instances of this class can be passed as a source to the Image component from expo-image.
VideoThumbnail Properties
Methods
Clears all video cache.
This function can be called only if there are no existing
VideoPlayerinstances.
Promise<void>A promise that fulfills after the cache has been cleaned.
Creates a direct instance of VideoPlayer that doesn't release automatically.
For most use cases you should use the
useVideoPlayerhook instead. See the Using the VideoPlayer Directly section for more details.
VideoPlayerReturns the space currently occupied by the video cache in bytes.
numberReturns whether the current device supports Picture in Picture (PiP) mode.
booleanA boolean which is true if the device supports PiP mode, and false otherwise.
Sets desired video cache size in bytes. The default video cache size is 1GB. Value set by this function is persistent. The cache size is not guaranteed to be exact and the actual cache size may be slightly larger. The cache is evicted on a least-recently-used basis.
This function can be called only if there are no existing
VideoPlayerinstances.
Promise<void>A promise that fulfills after the cache size has been set.
Types
Literal type: string
Specifies the audio mode that the player should use. Audio mode is set on per-app basis, if there are multiple players playing and
have different a AudioMode specified, the highest priority mode will be used. Priority order: 'doNotMix' > 'auto' > 'duckOthers' > 'mixWithOthers'.
mixWithOthers: The player will mix its audio output with other apps.duckOthers: The player will lower the volume of other apps if any of the active players is outputting audio.auto: The player will allow other apps to keep playing audio only when it is muted. On iOS it will always interrupt other apps whenshowNowPlayingNotificationistruedue to system requirements.doNotMix: The player will pause playback in other apps, even when it's muted.
On iOS, the Now Playing notification is dependent on the audio mode. If the audio mode is different from
doNotMixorautothis feature will not work.
Acceptable values are: 'mixWithOthers' | 'duckOthers' | 'auto' | 'doNotMix'
Specifies buffer options which will be used by the player when buffering the video.
Configuration for controlling the visibility of player control buttons.
The fullscreen button should be controlled with
fullscreenOptions.enable.
Literal type: string
Specifies the content type of the source.
auto: The player will automatically determine the content type of the video.progressive: The player will use progressive download content type. This is the defaultContentTypewhen the uri does not contain an extension.hls: The player will use HLS content type.dash: The player will use DASH content type (Android-only).smoothStreaming: The player will use SmoothStreaming content type (Android-only).
Default:`auto`
Acceptable values are: 'auto' | 'progressive' | 'hls' | 'dash' | 'smoothStreaming'
Specifies DRM options which will be used by the player while loading the video.
Literal type: string
Specifies which type of DRM to use:
- Android supports ClearKey, PlayReady and Widevine.
- iOS supports FairPlay.
Acceptable values are: 'clearkey' | 'fairplay' | 'playready' | 'widevine'
Options to apply to the player builder before the native constructor is invoked
Contains information about any errors that the player encountered during the playback
Determines the time that the actual position seeked to may precede or exceed the requested seek position.
Larger tolerance will usually result in faster seeking.
This property affects the precision of setting the currentTime property and the seekBy method, and on Android, it also affects the accuracy of the scrubber from the default native controls.
If you are trying to optimize for scrubbing (many frequent seeks), also see
ScrubbingModeOptions.
Data delivered with the sourceLoad event, contains information about the video source that has finished loading.
Literal type: string
Describes the type of the surface used to render the video.
surfaceView: Uses theSurfaceViewto render the video. This value should be used in the majority of cases. Provides significantly lower power consumption, better performance, and more features.textureView: Uses theTextureViewto render the video. Should be used in cases where the SurfaceView is not supported or causes issues (for example, overlapping video views).
You can learn more about surface types in the official ExoPlayer documentation.
Acceptable values are: 'textureView' | 'surfaceView'
Data delivered with the timeUpdate event, contains information about the current playback progress.
Literal type: string
Determines whether the player is allowed to call Surface.setFrameRate
to match the display refresh rate to the frame rate of the video being played.
'onlyIfSeamless': the display refresh rate is changed only when the switch is seamless (no visual interruption). This is the ExoPlayer default.'off': the player never callsSurface.setFrameRate.
On devices with adaptive refresh rate displays (for example, Pixel 9 and 10 series), the platform can respond to a 30 fps video by lowering the display render rate and capping the rendering of the entire app, including scrolling and animations, at 30 Hz for as long as the video is visible. Set this option to
'off'to keep the UI running at the full refresh rate, for example in a vertical video feed. Frame rate matching mainly benefits TV-class displays, where mismatched rates cause judder.
Acceptable values are: 'off' | 'onlyIfSeamless'
Literal type: string
Describes how a video should be scaled to fit in a container.
contain: The video maintains its aspect ratio and fits inside the container, with possible letterboxing/pillarboxing.cover: The video maintains its aspect ratio and covers the entire container, potentially cropping some portions.fill: The video stretches/squeezes to completely fill the container, potentially causing distortion.
Acceptable values are: 'contain' | 'cover' | 'fill'
Contains information that will be displayed in the now playing notification when the video is playing.
Literal type: string
Describes the current status of the player.
idle: The player is not playing or loading any videos.loading: The player is loading video data from the provided sourcereadyToPlay: The player has loaded enough data to start playing or to continue playback.error: The player has encountered an error while loading or playing the video.
Acceptable values are: 'idle' | 'loading' | 'readyToPlay' | 'error'
Literal type: string
Specifies the dynamic range of the video content.
sdr: Standard Dynamic Range video.hlg: Hybrid Log-Gamma - HDR backward-compatible with SDR displayspq: Perceptual Quantizer - Formats like HDR10 and Dolby Vision
Acceptable values are: 'sdr' | 'hlg' | 'pq'
Literal type: union
Acceptable values are: string | number | null | VideoSourceObject
Data delivered with the videoTrackChange event, contains information about the video track which is currently being played.