启动和停止按钮

Question

我的代码中的开始和停止按钮不起作用。

如何更正代码以使这些按钮正常工作？

function toggleFullScreen() {
  if ((document.fullScreenElement && document.fullScreenElement !== null) ||
    (!document.mozFullScreen && !document.webkitIsFullScreen)) {
    if (document.documentElement.requestFullScreen) {
      document.documentElement.requestFullScreen();
    } else if (document.documentElement.mozRequestFullScreen) {
      document.documentElement.mozRequestFullScreen();
    } else if (document.documentElement.webkitRequestFullScreen) {
      document.documentElement.webkitRequestFullScreen(Element.ALLOW_KEYBOARD_INPUT);
    }
  } else {
    if (document.cancelFullScreen) {
      document.cancelFullScreen();
    } else if (document.mozCancelFullScreen) {
      document.mozCancelFullScreen();
    } else if (document.webkitCancelFullScreen) {
      document.webkitCancelFullScreen();
    }
  }
}

var slideIndex = 1;
showSlides(slideIndex);

function plusSlides(n) {
  showSlides(slideIndex += n);
}

function currentSlide(n) {
  showSlides(slideIndex = n);
}

function nextSlide() {
  if (current < (slides.length - 1))
    current++;
  else
    current = 0;
  document.getElementById("image").src = "images/" + slides[current] + ".jpg";
  imageCnt.innerHTML = "<em>Image " + [current + 1] + " of " + slides.length + "</em>";
}

function showSlides(n) {
  var i;
  var slides = document.getElementsByClassName("mySlides");
  var dots = document.getElementsByClassName("dot");
  if (n > slides.length) {
    slideIndex = 1
  }
  if (n < 1) {
    slideIndex = slides.length
  }
  for (i = 0; i < slides.length; i++) {
    slides[i].style.display = "none";
  }
  for (i = 0; i < dots.length; i++) {
    dots[i].className = dots[i].className.replace(" active", "");
  }
  slides[slideIndex - 1].style.display = "block";
  dots[slideIndex - 1].className += " active";
}

function startShow() {
  if (document.getElementById("startSlideshow").value === "Start Slideshow") {
    document.getElementById("startSlideshow").value = "Pause Slideshow";
    interval = setInterval(nextImage, 2000);
  } else if (document.getElementById("startSlideshow").value === "Pause Slideshow") {
    document.getElementById("startSlideshow").value = "Start Slideshow";
    clearInterval(interval);
  }
}

function pauseShow() {
  clearInterval(interval);
}

function enlargeImage() {
  if (document.getElementById("enlarge").value === "Enlarge image") {
    document.getElementById("enlarge").value = "Normal size";
    var img = document.getElementById("slide");
    var divImg = document.getElementById("slideshowImage");
    divImg.style.width = "800px";
    img.style.width = "800px";
  } else if (document.getElementById("enlarge").value === "Normal size") {
    document.getElementById("enlarge").value = "Enlarge image";
    var img = document.getElementById("slide");
    var divImg = document.getElementById("slideshowImage");
    divImg.style.width = "600px";
    img.style.width = "600px";
  }
}

* {
  box-sizing: border-box
}
body {
  font-family: Verdana, sans-serif;
  margin: 0
}
element.style {
  position: absolute;
  left: 0px;
  top: 25px;
  overflow: hidden;
  -webkit-user-select: none;
  background-color: #FFF;
  border: 1px solid #ABABAB;
}
/* Slideshow container */

.slideshow-container {
  max-width: 1000px;
  position: relative;
  margin: auto;
}
/* Next & previous buttons */

.prev,
.next {
  cursor: pointer;
  position: absolute;
  top: 50%;
  width: auto;
  padding: 16px;
  margin-top: -22px;
  color: white;
  font-weight: bold;
  font-size: 18px;
  transition: 0.6s ease;
  border-radius: 0 3px 3px 0;
}
/* Position the "next button" to the right */

.next {
  right: 0;
  border-radius: 3px 0 0 3px;
}
/* On hover, add a black background color with a little bit see-through */

.prev:hover,
.next:hover {
  background-color: rgba(0, 0, 0, 0.8);
}
/* Caption text */

.text {
  color: #f2f2f2;
  font-size: 15px;
  padding: 8px 12px;
  position: absolute;
  bottom: 8px;
  width: 100%;
  text-align: center;
}
/* Number text (1/3 etc) */

.numbertext {
  color: #f2f2f2;
  font-size: 12px;
  padding: 8px 12px;
  position: absolute;
  top: 0;
}
/* The dots/bullets/indicators */

.dot {
  cursor: pointer;
  height: 13px;
  width: 13px;
  margin: 0 2px;
  background-color: #bbb;
  border-radius: 50%;
  display: inline-block;
  transition: background-color 0.6s ease;
}
.active,
.dot:hover {
  background-color: #717171;
}
/* Fading animation */

.fade {
  -webkit-animation-name: fade;
  -webkit-animation-duration: 1.5s;
  animation-name: fade;
  animation-duration: 1.5s;
}
@-webkit-keyframes fade {
  from {
    opacity: .4
  }
  to {
    opacity: 1
  }
}
@keyframes fade {
  from {
    opacity: .4
  }
  to {
    opacity: 1
  }
}
/* On smaller screens, decrease text size */

@media only screen and (max-width: 300px) {
  .prev,
  .next,
  .text {
    font-size: 11px
  }
}

<!DOCTYPE html>
<html>

<head>
  <meta name="viewport" content="width=device-width, initial-scale=1" />
</head>

<body>

  <div class="slideshow-container">

    <div class="mySlides fade">
      <div class="numbertext">1 / 3</div>
      <img src="slideshow1.jpg" title="Ori and the blind forest" style="width:100%" />

    </div>


    <div class="mySlides fade">
      <div class="numbertext">2 / 3</div>
      <img src="slideshow2.jpg" title="Ori and the blind forest" style="width:100%" />
    </div>

    <div class="mySlides fade">
      <div class="numbertext">3 / 3</div>
      <img src="slideshow3.jpg" title="Ori and the blind forest" style="width:100%" />


    </div>


    <a class="prev" onclick="plusSlides(-1)">
    </a>
    <a class="next" onclick="plusSlides(1)">></a>
  </div>
  <br/>

  <div style="text-align:center">
    <span class="dot" onclick="currentSlide(1)" />
    <span class="dot" onclick="currentSlide(2)" />
    <span class="dot" onclick="currentSlide(3)" />
  </div>

  <center>
    <a class="pause" onclick="startShow(0)">start</a>
    <a class="play" onclick="pauseShow(0)">pause</a>
    <center/>

    <input type="button" value="Fullscreen" onclick="toggleFullScreen()" />
  </center>
</body>

</html>

Answer 1

@Helene点击开始后触发的功能是 startShow（），但是您尝试获取的 DOM 元素 HTML 中似乎缺少ID startSlideshow 。因此，控制台中的错误，给出相应的Id并再次尝试

        function startShow() {
      if (document.getElementById("startSlideshow").value === "Start Slideshow") {
        document.getElementById("startSlideshow").value = "Pause Slideshow";
        interval = setInterval(nextImage, 2000);
      }
      else if (document.getElementById("startSlideshow").value === "Pause Slideshow") {
        document.getElementById("startSlideshow").value = "Start Slideshow";
        clearInterval(interval);
      }
    }

    function pauseShow() {
      clearInterval(interval);
    }