幻灯片的第一张图片未加载

时间：2018-09-01 10:37:53

标签： javascript html5 css3

我刚刚开始使用CSS和JavaScript，并尝试通过研究w3schools来制作图像滑块。滑块可以工作，但是只有在导航栏可见的情况下，第一张图像始终是空的，但是一旦单击下一个按钮，它就可以正常工作，我不知道该如何更改。这是代码。

'use strict';
var slideIndex = 1;

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

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

function showSlides(n) {
  //alert('showslides('+ n +')\nslideIndex='+slideIndex);
  var i;
  var slides = document.getElementsByClassName("mySlides");
  var dots = document.getElementsByClassName("dot");
  if (n === undefined) {
    n = ++slideIndex;
  }
  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";

  setTimeout(showSlides, 5000); // Change image every 5 seconds
}
* {
  box-sizing: border-box;
}

body {
  font-family: Verdana, sans-serif;
  margin: 0
}

.mySlides {
  display: none;
}

img {
  vertical-align: middle;
}


/* 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: 15px;
  width: 15px;
  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
  }
}
<body>
  <?php
        include './p1.php';
        // put your code here
        ?>
    <div class="slideshow-container">

      <div class="mySlides fade">
        <div class="numbertext">1 / 3</div>
        <img src="pics/bali2.jpg" height="400px" width="800px">
        <div class="text">Caption Text</div>
      </div>

      <div class="mySlides fade">
        <div class="numbertext">2 / 3</div>
        <img src="pics/brazil1.jpg" height="400px" width="800px">
        <div class="text">Caption Two</div>
      </div>

      <div class="mySlides fade">
        <div class="numbertext">3 / 3</div>
        <img src="pics/germany.jpg" height="400px" width="800px">
        <div class="text">Caption Three</div>
      </div>

      <a class="prev" onclick="plusSlides(-1)">&#10094;</a>
      <a class="next" onclick="plusSlides(1)">&#10095;</a>

    </div>
    <br>

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

</body>

1 个答案:

答案 0 :(得分：0)

  

滑块可以工作，但是只有在导航栏可见的情况下，第一张图片始终为空

仅因为您将mySlides应用于此，所以您的所有div都不可见。单击next或previous或slider时，将显示特定的容器。

因此，您需要在第一格上应用style="display: block;"。

演示 

var slideIndex = 1,
    interval;

function stopAndStart() {
    if (interval) {
        clearInterval(interval)
    }
    interval = setInterval(showSlides, 5000); // Change image every 5 seconds;
}

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

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

function showSlides(n) {
    var i,
        slides = document.getElementsByClassName("mySlides"),
        dots = document.getElementsByClassName("dot");

    if (n === undefined) {
        n = ++slideIndex;
    }
    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";
}

stopAndStart();
body {
  font-family: Verdana, sans-serif;
  margin: 0
}

.mySlides {
  display: none;
  text-align: center;
}

img {
  vertical-align: middle;
}


/* Slideshow container */

.slideshow-container {
  max-width: 1000px;
  position: relative;
  margin: auto;
  background: burlywood;
}


/* 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: 15px;
  width: 15px;
  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
  }
}
<div class="slideshow-container">

  <div class="mySlides fade" style="display: block;">
    <div class="numbertext">1 / 3</div>
    <img src="https://dummyimage.com/400x400/555985/fff&text=1">
    <div class="text">Caption Text</div>
  </div>

  <div class="mySlides fade">
    <div class="numbertext">2 / 3</div>
    <img src="https://dummyimage.com/400x400/555985/fff&text=2">
    <div class="text">Caption Two</div>
  </div>

  <div class="mySlides fade">
    <div class="numbertext">3 / 3</div>
    <img src="https://dummyimage.com/400x400/555985/fff&text=3">
    <div class="text">Caption Three</div>
  </div>

  <a class="prev" onclick="plusSlides(-1)">&#10094;</a>
  <a class="next" onclick="plusSlides(1)">&#10095;</a>

</div>
<br>

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

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