本地变量到全局javascript

Question

我对JavaScript、webRTC和Kurento有问题。我自己解决不了。我试图将本地变量中的远程流放入全局变量中，但遇到了一些问题。我试图解释解决问题的所有步骤：第一步，我有Kurento-webRtcEndpoint功能：

webRtcPeer = kurentoUtils.WebRtcPeer.startRecvOnly(videoElement, onPlayOffer, onError);

它调用函数"onPlayOffer"，即：

function onPlayOffer(sdpOffer) {
co(function * () {
try {
if (!client) client = yield kurentoClient(args.ws_uri);
pipeline = yield client.create('MediaPipeline');
var webRtc = yield pipeline.create('WebRtcEndpoint');
var player = yield pipeline.create('PlayerEndpoint', { uri: args.file_uri });
yield player.connect(webRtc);
var sdpAnswer = yield webRtc.processOffer(sdpOffer);
webRtcPeer.processSdpAnswer(sdpAnswer, recordVideo);
console.log('DEBUG: ok, AGAIN, localStream: ');
console.log(localStream);
yield player.play();

我编辑了函数processSdpAnswer，以这种方式获取流：

WebRtcPeer.prototype.processSdpAnswer = function(sdpAnswer, callbackEvent, successCallback) {
//WebRtcPeer.prototype.processSdpAnswer = function(sdpAnswer, successCallback) {
var answer = new RTCSessionDescription({
type : 'answer',
sdp : sdpAnswer,
});
console.log('Kurento-Utils: SDP answer received, setting remote description');
var self = this;
self.pc.onaddstream = function(event) {
var objectURL = URL.createObjectURL(event.stream);
//Added the string below to create the callback
callbackEvent(event.stream);
};
self.pc.setRemoteDescription(answer, function() {
if (self.remoteVideo) {
var stream = self.pc.getRemoteStreams()[0];
//console.log('Kurento-Utils: Second self.pc');
//console.log(self.pc)
self.remoteVideo.src = URL.createObjectURL(stream);
}
if (successCallback) {
successCallback();
}
}, this.onerror);

因此，在这种情况下，回调是函数recordVideo，它被传递给"event.stream">

function recordVideo(stream) {
console.log("DEBUG: called function recordVideo()");
localStream = stream;
console.log("DEBUG: Copied stream -> localStream:");
console.log(localStream);
console.log("DEBUG: the stream object contains:");
console.log(stream);}

因此，我希望在函数"onPlayOffer"中，我可以将对象localStream(全局声明)作为流(即本地)的副本。变量"stream"是正确的，而变量"localStream"是UNDEFINED。

你能帮我理解为什么吗？我读到可能问题出在控制台上，但我试图评论所有console.log行，但没有成功。你能帮我吗？谢谢大家！

(如果有人知道全局获取event.stream对象的更快方法，我将感谢您的帮助！)

Answer 1

你是对的，你的问题是异步的，

最简单的纠正方法是，将异步调用之后的任何代码/逻辑作为异步调用的回调，

可以通过更改来完成

...
webRtcPeer.processSdpAnswer(sdpAnswer, recordVideo);
console.log('DEBUG: ok, AGAIN, localStream: ');
console.log(localStream);
yield player.play();
...

进入

...
var callback = function (){
console.log('DEBUG: ok, AGAIN, localStream: ');
console.log(localStream);
yield player.play();
};
webRtcPeer.processSdpAnswer(sdpAnswer, recordVideo.bind({callback: callback})); // through bind, we are setting the `this` value of the recordVideo.

并将录像修改为

function recordVideo(stream) {
...
this.callback();    // extra line added.
}

Answer 2

您缺少一个收益，这导致代码如下：

webRtcPeer.processSdpAnswer(sdpAnswer, recordVideo);

录制前执行视频

要解决这个问题，只需使用

yield webRtcPeer.processSdpAnswer(sdpAnswer, recordVideo);