Whiteboard sharing

The whiteboard in a meeting is an H5 page hosted by the server, displayed on Android in a WebView. Strokes sync over the whiteboard’s own connection; it produces no media stream and doesn’t use camera or screen capture.

The capabilities of the whiteboard page itself (URL parameters, overlay annotation mode, lifecycle and when boards are destroyed) are exactly the same as on the SRTC layer; see SRTC · Whiteboard. This page covers only meeting-layer usage.

requestShareBoard() does two things: it broadcasts “I’m sharing a whiteboard” to the meeting, and returns the whiteboard URL in the callback.

meetingEngine.requestShareBoard(object : MeetingValueResultCallback<String> {
    override fun onSuccess(whiteBoard: String) {
        // whiteBoard is the full URL with the auth code already appended; load it directly
        showBoard(whiteBoard)
    }

    override fun onFailure(errorCode: Int, message: String?) {
        // Common failures: the host has disabled sharing for the room, or someone else is already sharing
        toast(errorMessageFor(errorCode))
    }
})

Only one member can share in a meeting at a time; screen sharing and the whiteboard are mutually exclusive. Stop sharing:

meetingEngine.stopShareWhiteBoard()

To handle other members’ sharing requests, the host uses confirmStartWhiteBoardShareAgree() / confirmStartWhiteBoardShareRefuse(); when approving, the host also gets the whiteboard URL in the callback.

When you aren’t the one who started it, you learn about it from room events and read the URL from infosManager:

override fun onRoomShareStart(shareUid: String, shareType: ShareType) {
    if (shareType == ShareType.WhiteBoardShare) {
        showBoard(meetingEngine.infosManager.whiteBoard ?: return)
    }
}

override fun onRoomShareStop(shareUid: String, shareType: ShareType) {
    if (shareType == ShareType.WhiteBoardShare) {
        hideBoard()
    }
}

Members who enter mid-meeting don’t receive this event, so check once yourself after entering the meeting:

val info = meetingEngine.infosManager.getMeetingInfo()
if (info?.shareState == ShareType.WhiteBoardShare) {
    // Someone in the meeting is already sharing a whiteboard
    showBoard(meetingEngine.infosManager.whiteBoard ?: return)
}

Host it in a WebView

The whiteboard page is a standard web app and must have JavaScript enabled. When the whiteboard is destroyed it needs to tell the host to close the view, so you also need to inject a JS interface named AndroidInterface:

webView.settings.javaScriptEnabled = true
webView.settings.domStorageEnabled = true
webView.addJavascriptInterface(object {
    /** The whiteboard was destroyed (someone destroyed it or it was cleaned up on expiry); the host should close the whiteboard view */
    @JavascriptInterface
    fun onWbDestroy(reason: String?) {
        runOnUiThread { hideBoard() }
    }

    /** The user tapped the export button (requires export_btn=1 on the URL); returns the image as base64 */
    @JavascriptInterface
    fun onExportImage(base64: String) {
        saveImage(base64)
    }
}, "AndroidInterface")

webView.loadUrl(whiteBoard)

When you exit the meeting or receive onRoomShareStop, remember to destroy the WebView so it doesn’t keep the whiteboard connection open in the background.

SRTC · Whiteboard—URL parameters of the whiteboard page, how state sync works, lifecycle and destruction
MeetingEngine—signatures of requestShareBoard() / stopShareWhiteBoard()
Meeting result callbacks—callbacks for the whiteboard URL and failure results
MeetingRoomEvent—sharing start / stop events

Overview

Low-code integration

Web SDK

Android SDK

Swift SDK (iOS/macOS)

Server API

Host it in a WebView

​Start whiteboard sharing

​Respond to others’ whiteboard sharing

​Host it in a WebView

​Related

Start whiteboard sharing

Respond to others’ whiteboard sharing

Host it in a WebView

Related