白板接入

interface RTCClientEvent {
    /**
     * 自己加入频道成功
     * @param whiteBoard 白板链接，正常不为空；为 null 说明线路配置异常
     */
    fun onJoinSucceed(channel: String, uid: String, whiteBoard: String?)
    // ...
}

override fun onJoinSucceed(channel: String, uid: String, whiteBoard: String?) {
    if (!whiteBoard.isNullOrEmpty()) {
        // whiteBoard 即白板链接，交给 WebView 加载
        openWhiteBoard(whiteBoard)
    }
}

val setting = webView.settings
setting.javaScriptEnabled = true                       // 必须：白板依赖 JS
setting.domStorageEnabled = true                       // 必须：白板依赖 DOM Storage
setting.databaseEnabled = true
setting.javaScriptCanOpenWindowsAutomatically = true

val param = "&no_menu=1&export_btn=1"
webView.loadUrl(whiteBoard + param)

webView.addJavascriptInterface(JsBridgeForWhiteboard(callback), "AndroidInterface")

class JsBridgeForWhiteboard(private val callback: Callback) {

    @JavascriptInterface
    fun onExportImage(dataUrl: String) {   // 白板导出图片
        callback.onExportImage(dataUrl)
    }

    @JavascriptInterface
    fun onWbDestroy(reason: String) {      // 白板销毁通知
        callback.onWbDestroy(reason)
    }

    interface Callback {
        fun onExportImage(dataUrl: String)
        fun onWbDestroy(reason: String)
    }
}

override fun onDestroy() {
    super.onDestroy()
    webView.destroy()
}

private fun saveBase64DataUrl(dataUrl: String) {
    val prefix = "base64,"
    val index = dataUrl.indexOf(prefix)
    if (index == -1) return
    val bytes = Base64.decode(dataUrl.substring(index + prefix.length), Base64.DEFAULT)
    // 将 bytes 写入相册 / 文件（Android 9 及以下先申请 WRITE 权限）
}

webView.webChromeClient = object : WebChromeClient() {
    override fun onPermissionRequest(request: PermissionRequest) {
        request.grant(request.resources)
    }

    override fun onShowFileChooser(
        webView: WebView?,
        filePathCallback: ValueCallback<Array<Uri>>?,
        params: FileChooserParams?
    ): Boolean {
        // 拍照 / 相册取图，得到 uri 后：
        // filePathCallback?.onReceiveValue(arrayOf(uri))
        // 用户取消：filePathCallback?.onReceiveValue(null)
        return true
    }
}