类：PreloadRequestData
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最后更新时间 (UTC)：2025-07-25。
[null,null,["最后更新时间 (UTC)：2025-07-25。"],[[["\u003cp\u003e\u003ccode\u003ePreloadRequestData\u003c/code\u003e is used for media event PRELOAD requests and extends \u003ccode\u003eLoadRequestData\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eIt includes an \u003ccode\u003eitemId\u003c/code\u003e property representing the ID of the queue item to preload.\u003c/p\u003e\n"],["\u003cp\u003eMany properties, like \u003ccode\u003eautoplay\u003c/code\u003e, \u003ccode\u003ecurrentTime\u003c/code\u003e, and \u003ccode\u003emedia\u003c/code\u003e, are inherited from \u003ccode\u003eLoadRequestData\u003c/code\u003e and control playback behavior.\u003c/p\u003e\n"],["\u003cp\u003eIt allows for custom data and credentials to be passed alongside the request.\u003c/p\u003e\n"]]],[],null,["# Class: PreloadRequestData\n\ncast.[framework](/cast/docs/reference/web_receiver/cast.framework).[messages](/cast/docs/reference/web_receiver/cast.framework.messages).PreloadRequestData\n===========================================================================================================================================================\n\nclass static\n\nMedia event PRELOAD request data.\n\nConstructor\n-----------\n\n### PreloadRequestData\n\nnew\nPreloadRequestData(itemId)\n\n| #### Parameter ||\n|--------|----------------------------------|\n| itemId | number The ID of the queue item. |\n\nExtends\n: [cast.framework.messages.LoadRequestData](/cast/docs/reference/web_receiver/cast.framework.messages.LoadRequestData)\n\nProperties\n----------\n\n### activeTrackIds\n\n(non-null Array of number or undefined)\n\nArray of trackIds that are active. If the array is not provided,\nthe default tracks will be active.\n\nInherited from\n: [cast.framework.messages.LoadRequestData#activeTrackIds](/cast/docs/reference/web_receiver/cast.framework.messages.LoadRequestData#activeTrackIds)\n\n### autoplay\n\n(boolean or undefined)\n\nIf the autoplay parameter is specified, the media player will begin\nplaying the content when it is loaded. Even if autoplay is not\nspecified,the media player implementation may choose to begin playback\nimmediately.\n\nInherited from\n: [cast.framework.messages.LoadRequestData#autoplay](/cast/docs/reference/web_receiver/cast.framework.messages.LoadRequestData#autoplay)\n\n### credentials\n\n(string or undefined)\n\nOptional user credentials.\n\nInherited from\n: [cast.framework.messages.LoadRequestData#credentials](/cast/docs/reference/web_receiver/cast.framework.messages.LoadRequestData#credentials)\n\n### credentialsType\n\n(string or undefined)\n\nOptional credentials type.\nThe type 'cloud' is a reserved type used by load requests that were\noriginated by voice assistant commands.\n\nInherited from\n: [cast.framework.messages.LoadRequestData#credentialsType](/cast/docs/reference/web_receiver/cast.framework.messages.LoadRequestData#credentialsType)\n\n### currentTime\n\n(number or undefined)\n\nSeconds since beginning of content. If the content is live content, and\ncurrentTime is not specified, the stream will start at the live position.\n\nInherited from\n: [cast.framework.messages.LoadRequestData#currentTime](/cast/docs/reference/web_receiver/cast.framework.messages.LoadRequestData#currentTime)\n\n### customData\n\n(non-null Object or undefined)\n\nApplication-specific data for this request. It enables the sender and\nreceiver to easily extend the media protocol without having to use a new\nnamespace with custom messages.\n\nInherited from\n: [cast.framework.messages.RequestData#customData](/cast/docs/reference/web_receiver/cast.framework.messages.RequestData#customData)\n\n### itemId\n\nnumber\n\nThe ID of the queue item.\n\n### loadOptions\n\n(non-null [cast.framework.messages.LoadOptions](/cast/docs/reference/web_receiver/cast.framework.messages.LoadOptions) or undefined)\n\nAdded load options.\n\nInherited from\n: [cast.framework.messages.LoadRequestData#loadOptions](/cast/docs/reference/web_receiver/cast.framework.messages.LoadRequestData#loadOptions)\n\n### media\n\nnon-null [cast.framework.messages.MediaInformation](/cast/docs/reference/web_receiver/cast.framework.messages.MediaInformation)\n\nThe media information associated with the load request.\n\nInherited from\n: [cast.framework.messages.LoadRequestData#media](/cast/docs/reference/web_receiver/cast.framework.messages.LoadRequestData#media)\n\n### mediaSessionId\n\n(number or undefined)\n\nId of the media session that the request applies to.\n\nInherited from\n: [cast.framework.messages.RequestData#mediaSessionId](/cast/docs/reference/web_receiver/cast.framework.messages.RequestData#mediaSessionId)\n\n### playbackRate\n\n(number or undefined)\n\nThe media playback rate.\n\nInherited from\n: [cast.framework.messages.LoadRequestData#playbackRate](/cast/docs/reference/web_receiver/cast.framework.messages.LoadRequestData#playbackRate)\n\n### queueData\n\n(non-null [cast.framework.messages.QueueData](/cast/docs/reference/web_receiver/cast.framework.messages.QueueData) or undefined)\n\nQueue data.\n\nInherited from\n: [cast.framework.messages.LoadRequestData#queueData](/cast/docs/reference/web_receiver/cast.framework.messages.LoadRequestData#queueData)\n\n### requestId\n\nnumber\n\nId of the request, used to correlate request/response.\n\nInherited from\n: [cast.framework.messages.RequestData#requestId](/cast/docs/reference/web_receiver/cast.framework.messages.RequestData#requestId)\n\n### sequenceNumber\n\n(number or undefined)\n\nA number to synchronize all queue commands.\nIf provided for a queue command, the SDK will verify the queue latest\nsequence number match the request.\nCurrent sequenceNumber is provided as part of outgoing queue changed\nmessages.\n\nInherited from\n: [cast.framework.messages.RequestData#sequenceNumber](/cast/docs/reference/web_receiver/cast.framework.messages.RequestData#sequenceNumber)"]]
