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  • 关于图片预加载的练习

    <!DOCTYPE html>

    <html>

    <head>

    <meta charset="UTF-8">

    <meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no" />

    <title></title>

    <style type="text/css">

    /*html {

    position: relative;

    }

    body,p {

    margin: 0;

    padding: 0;

    }*/

    html,body{width: 100%;height: 100%;}

    *{margin: 0;padding: 0;}

     

    .bg{width: 100%;height: 100%;}

    .loading_clock {

    position: absolute;

    left: 50%;

    top: 45%;

    margin-left: -79px;

    margin-top: -70px;

    }

     

    .loading_pointer {

    position: absolute;

    left: 50%;

    top: 50%;

    margin-left: -4.5px;

    margin-top: -75px;

    transform-origin: 4.5px bottom;

    transform: rotate(-140deg);

    }

    .firstPrecent {

    color: white;

    font-size: 1.8rem;

    position: absolute;

    left: 44%;

    top: 62%;

    }

    canvas {

    position: absolute;

    left: 0;

    top: 0;

    }

    </style>

    </head>

    <body>

    <div class="firstContain">

    <img src="img/loading_bg.jpg" class="bg"/>

    <img src="img/loading_clock.png" class="loading_clock" />

    <img src="img/loading_pointer.png" class="loading_pointer" />

    <span class="firstPrecent">20%</span>

     

    </div>

    <canvas id="mycanvas" width="" height=""></canvas>

    </body>

    <script src="http://libs.baidu.com/jquery/2.0.0/jquery.min.js"></script>

    <script type="text/javascript" src="js/documentReady.js"></script>

    <script type="text/javascript">

    var firstContain = document.getElementsByClassName("firstContain")[0];

    var canvas = document.getElementById("mycanvas");

    var context = canvas.getContext("2d");

     

    canvas.width = deviceReady()[0];

    canvas.height = deviceReady()[1];

    firstContain.style.width = deviceReady()[0] + "px";

    firstContain.style.height = deviceReady()[1] + "px";

     

    var srcArray = ['1.jpg', '2.jpg', '3.jpg', '4.jpg', '5.jpg', '371_1453779101.png', '912_1453779104.png', '1093_1453854255.png', '1536_1453779105.png', '2062_1453779100.png', '2115_1453779103.png', '2214_1453779105.png', '2407_1453779106.png', '2488_1453779103.png', '2740_1453779102.png', '3046_1453779101.png', '3375_1453854403.png', '4169_1453779106.png', '4505_1453779105.png', '4536_1453779106.png', '4575_1453779105.png', '4814_1453854252.png', '5844_1453779104.png', '5865_1453779098.png', '6240_1453779101.png', '6253_1453779102.png', '7030_1453856838.png', '7705_1453779100.png', '8268_1453779103.png', '8279_1453779085.png', '8696_1453854253.png', '9228_1453779104.png', 'commen_close.png', 'layer_info_checked.png', 'layer_info_select.jpg', 'layer_info_submit.png', 'layer_prize.png', 'layer_prize_none.png', 'layer_select_bg.png', 'page1_btn_next.png', 'page1_btn_pic.png', 'page1_btn_pic_active.png', 'page1_btn_prev.png', 'page1_btn_share.png', 'page1_btn_video.png', 'page1_btn_video_active.png', 'page1_k4.png', 'page1_main_bg.jpg', 'page1_nav_active.png', 'page1_tab_bg.jpg', 'page1_top_bg.jpg', 'page1_video_poster.png', 'page2_bg.jpg', 'page2_btn_intro.png', 'page2_btn_start.png', 'page3_bg.jpg', 'page3_btn_start.png', 'page3_choosed_bg.png', 'page5_bg.jpg', 'share.jpg', 'loading_bg.jpg', 'loading_clock.png', 'loading_pointer.png'];

     

    var carSrcArray = [];

    //for循环遍历数组 将图片放入两个数组中

    for (var i = 1;i < 236;i++) {

    var src = "img/video/che_" + i + ".jpg";

    srcArray.push(src);

    carSrcArray.push(src);

    };

     

    var carArray = [];

    for(var i = 0; i < carSrcArray.length; i++) {

    var newImage = new Image;

    newImage.src = carSrcArray[i];

    carArray.push(newImage);

    }

     

    var indexRotate = 0;

    var imgArray = [];

    for (var i = 0;i < srcArray.length; i++) {

    var newImage = new Image;

    newImage.src = srcArray[i];

    imgArray.push(newImage);

    //遍历数组 进行预加载

    newImage.onload = function(){

    //每加载一个单位 进度条的偏移量

    indexRotate += 1.2;

    //指针的总共偏移

    $(".loading_pointer").css("-webkit-transform","rotate(" + (indexRotate-140) + "deg)");

    //百分比的进度变化

    $(".firstPrecent").html(Math.floor(indexRotate / 2.8) + "%");

    //判断图片加载完成

    //console.log(srcArray.length);

    if(Math.floor(indexRotate / 2.8) >= 99){

    $(".firstContain").hide();

    context.drawImage(carArray[0],0,0,canvas.width,canvas.height);

    }

    }

    }

     

    </script>

    </html>

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  • 原文地址:https://www.cnblogs.com/lxl0419/p/5720400.html
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