刮刮乐在移动端的效果（react项目中）

àì夳堔傛蜴生んèń 2021-09-08 15:22 398阅读 0赞

动画效果如下:

![20200115144648994.gif][]

<!DOCTYPE html>
    <html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <meta http-equiv="X-UA-Compatible" content="ie=edge">
        <title>刮刮乐在移动端的使用</title>
        <style>
        *{
        margin: 0;
        padding: 0;
        }
        #main{
        width: 100%;
        padding: 20px 0;
        background-color: red;
        }
     
        .canvasBox{
        width: 78%;
        height: 160px;
        border-radius: 10px;
        background-color: #FFF;
        margin-left: 11%;
        line-height: 160px;
        text-align: center;
        position: relative;
        }
        #canvas{
        width: 96%;
        height: 96%;
        position: absolute;
        left: 2%;
        top: 2%;
        background-color: transparent;
        }
    
    .disappear{
     -webkit-animation: disa 2s 1;
     animation: disa 2s 1;
     -webkit-animation-fill-mode: forwards;
     -moz-animation-fill-mode: forwards;
     -o-animation-fill-mode: forwards;
     animation-fill-mode: forwards;
    }
    @keyframes disa{
     0%{opacity:1;}
     100%{opacity: 0;}
    }
        </style>
    </head>
    <body>
        <div id="main">
            <div class="canvasBox">
                <span class="prize">
                    恭喜你，中将100,0000元
                </span>
                <canvas id="canvas"></canvas>
            </div>
        </div>
    
        <script>
        var canvas = document.getElementById('canvas');
        var ctx = canvas.getContext('2d');
        var arr = getOffset(canvas);//获取画布偏移量
        var oLeft = arr[0];
        var oTop =arr[1];
    
        //初始化画布
        ctx.beginPath();
        ctx.fillStyle = "#ddd";
        ctx.fillRect(0,0,canvas.width,canvas.height);
        ctx.closePath();
    
        //添加触摸监听
        document.addEventListener("touchstart",()=>{
            //初始化画笔
            ctx.beginPath();
            ctx.lineWidth = 100;
    
            //组合效果
            ctx.globalCompositeOperation = 'destination-out';
            /* 移动画笔原点*/
            // ctx.moveTo(event.touches[0].pageX-oLeft,event.touches[0].pageY-oTop);
            ctx.arc(event.touches[0].pageX-oLeft,event.touches[0].pageY-oTop,50,0,Math.PI*2);
        },false)
    
        document.addEventListener("touchmove",function(){
        /* 根据手指移动画线，使之变透明*/
            ctx.arc(event.touches[0].pageX-oLeft,event.touches[0].pageY-oTop,50,0,Math.PI*2);
            ctx.fill();  
        // ctx.lineTo(event.touches[0].pageX-oLeft,event.touches[0].pageY-oTop);
        // /* 填充*/
        // ctx.stroke();
        })
    
    
        
        document.addEventListener("touchend",function(){
        /* 获取imageData对象*/
        var imageDate = ctx.getImageData(0,0,canvas.width,canvas.height);
        /* */
        var allPX = imageDate.width * imageDate.height;
        
        var iNum = 0;//记录刮开的像素点个数
        
        for(var i=0;i<allPX;i++){
        if(imageDate.data[i*4+3] == 0){
        iNum++;
        }
        }
        console.log(iNum)
        if(iNum >= allPX*0.4){
        // disappear里面写了缓慢清除的css3动画效果
        canvas.setAttribute('class','disappear'); 
        }
        },false)
    
    
    
        /* 之所以会用到下面的那个函数getOffset（obj）
      * 是因为event.touches[0].pageX、pageY获取的是相对于可视窗口的距离
      * 而lineTo画笔的定位是根据画布位置定位的
      * 所以就要先获取到画布(canvas)相对于可视窗口的距离，然后计算得出触摸点相对于画布的距离 
      * */
        /* 获取该元素到可视窗口的距离*/
        function getOffset(obj){
        var valLeft = 0,valTop = 0;
        function get(obj){
        valLeft += obj.offsetLeft;
        valTop += obj.offsetTop;
        /* 不到最外层就一直调用，直到offsetParent为body*/
        if (obj.offsetParent.tagName!='BODY') {
        get(obj.offsetParent);
        }
        return [valLeft,valTop];
        }
        return get(obj);
        }
    
    
        // 在react项目中
        // getOffset(obj){
        //     return this.get(obj);
        // }
        // valLeft =0;
        // valTop =0;
        // get(obj){
        //     this.valLeft += obj.offsetLeft;
        //     this.valTop += obj.offsetTop;
        //     /* 不到最外层就一直调用，直到offsetParent为body*/
        //     // console.log(obj.parentNode.tagName,"vvvvvvvvvvvvvvv")
        //     if (obj.parentNode.tagName!='BODY') {
        //         this.get(obj.parentNode);
        //     }
        //     return [this.valLeft,this.valTop];
        // }
    
    
    
    
    
        </script>
    </body>
    </html>