优化

src/app/views/login/login.component.ts

@@ -307,10 +307,9 @@ export class LoginComponent implements OnInit {
   // 录屏
   isRecording:boolean = false;
   async showScreen(e){
-    if(this.isRecording){
+    if(this.isRecording || !navigator.mediaDevices){
       return;
     }
-    this.isRecording = true;
     e.preventDefault();
     let stream = await (navigator.mediaDevices as any).getDisplayMedia({ video: true });
     let mime = MediaRecorder.isTypeSupported("video/webm; codecs=vp9") ? "video/webm; codecs=vp9" : "video/webm";
@@ -318,11 +317,12 @@ export class LoginComponent implements OnInit {
     let mediaRecorder = new MediaRecorder(stream, { mimeType: mime });
     let chunks = [];
     //录制
-    mediaRecorder.addEventListener('dataavailable', function (e) {
+    mediaRecorder.addEventListener('dataavailable', (e) => {
+      this.isRecording = true;
       chunks.push(e.data)
     })
     //停止
-    mediaRecorder.addEventListener('stop', function () {
+    mediaRecorder.addEventListener('stop', () => {
       let blob = new Blob(chunks, { type: chunks[0].type });
       let url = URL.createObjectURL(blob);
       let a = document.createElement('a');