fullScreen() {
    document.getElementById("fullScreen").style.display = "none";
    document.getElementById("exitScreen").style.display = "block";
    let el = document.documentElement as any;
    let rfs = el.requestFullScreen || el.webkitRequestFullScreen || el.mozRequestFullScreen || el.msRequestFullscreen;
    if (typeof rfs != "undefined" && rfs) {
      rfs.call(el);
    };
    return;
  }

  //退出全屏
  exitScreen() {
    document.getElementById("fullScreen").style.display = "block";
    document.getElementById("exitScreen").style.display = "none";
    let cfs = document as any;
    if (cfs.exitFullscreen) {
      cfs.exitFullscreen();
    }
    else if (cfs.webkitCancelFullScreen) {
      cfs.webkitCancelFullScreen();
    }
    else {
      cfs.msExitFullscreen();
    }
  }