Quickly solve the problem of white gap when CSS uses @ keyframes to load pictures for the first time (flash screen)

Time:2020-6-28

Problem explanation:

When using the animations attribute of CSS, there will be a white gap in the first loading cycle. It looks like the page has a refresh feeling. This problem will not occur again in each subsequent cycle

Question presentation

 


//html
 <div class="container">
        <div class="first"> </div>
  </div>
//less
.container {
  width: 100vw;
  height: 100%;
}
.container .first {
  width: 100vw;
  height: 100vh;
  animation: bgmove 10s infinite;
}
@keyframes bgmove {
  0% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-1.jpg") no-repeat center center;
    background-size: cover;
    opacity: 1;
  }
  15% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-1_1.jpg") no-repeat center center;
    opacity: 1;
    background-size: cover;
  }
  30% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-2_1.jpg") no-repeat center center;
    opacity: 1;
    background-size: cover;
  }
  45% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-4_1.jpg") no-repeat center center;
    opacity: 1;
    background-size: cover;
  }
  60% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-5_1.jpg") no-repeat center center;
    opacity: 1;
    background-size: cover;
  }
  80% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-1_1.jpg") no-repeat center center;
    opacity: 1;
    background-size: cover;
  }
  100% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-1.jpg") no-repeat center center;
    background-size: cover;
    opacity: 1;
  }
}

terms of settlement


//less
.container {
  width: 100vw;
  height: 100%;
}
.container .first {
  width: 100vw;
  height: 100vh;
  background:url("https://sqimg.qq.com/qq\_product\_operations/im/pcqq/9.0/firstscreen\_img/BG-1.jpg"),
             url("https://sqimg.qq.com/qq\_product\_operations/im/pcqq/9.0/firstscreen\_img/BG-1\_1.jpg"),
             url("https://sqimg.qq.com/qq\_product\_operations/im/pcqq/9.0/firstscreen\_img/BG-2\_1.jpg"),
             url("https://sqimg.qq.com/qq\_product\_operations/im/pcqq/9.0/firstscreen\_img/BG-4\_1.jpg"),
             url("https://sqimg.qq.com/qq\_product\_operations/im/pcqq/9.0/firstscreen\_img/BG-5\_1.jpg"),
             url("https://sqimg.qq.com/qq\_product\_operations/im/pcqq/9.0/firstscreen\_img/BG-1\_1.jpg");
  animation: bgmove 10s infinite;
}
@keyframes bgmove {
  0% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-1.jpg") no-repeat center center;
    background-size: cover;
    opacity: 1;
  }
  15% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-1_1.jpg") no-repeat center center;
    opacity: 1;
    background-size: cover;
  }
  30% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-2_1.jpg") no-repeat center center;
    opacity: 1;
    background-size: cover;
  }
  45% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-4_1.jpg") no-repeat center center;
    opacity: 1;
    background-size: cover;
  }
  60% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-5_1.jpg") no-repeat center center;
    opacity: 1;
    background-size: cover;
  }
  80% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-1_1.jpg") no-repeat center center;
    opacity: 1;
    background-size: cover;
  }
  100% {
    background: url("https://sqimg.qq.com/qq_product_operations/im/pcqq/9.0/firstscreen_img/BG-1.jpg") no-repeat center center;
    background-size: cover;
    opacity: 1;
  }
}

Final effect

 

Problem analysis

There are generally two situations for loading pictures: picture preloading and picture lazy loading. This involves the problem of picture preloading. When there are too many pictures on the page, the pressure on the server will be great, and the one-time display of loading pictures will be inconsistent, so all pictures will be loaded for the first time, In this way, when these images are used later, they are cached in the local resources, and the loading speed will be a lot of blocks, so there will be no white fault

This article is about how to quickly solve the problem of white gap (flashing screen) when CSS uses @ keyframes to load pictures for the first time. For more information about CSS keyframes loading pictures, please search the previous articles of developpaer or continue to browse the relevant chapters below. I hope you can support developpaer in the future!

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