这周有点迷茫，不知道干嘛了，一天天就过去了！我在博客右侧公告栏加了qq交流，各位有好的主题，或者有趣的技术，欢迎交流！今天突发奇想，就写了2个h5 canvas的demo玩玩！
demo一：刮刮乐
舍不得买2块钱的刮刮乐，就只能写个类似的功能过过彩票瘾了！
布局
<div id="lottery" style="width:300px;height:500px;margin:10px;background-color:lightskyblue;border-radius:5px;float:left;">
<div style="width:300px;height:100px;line-height:100px;text-align:center;font-size:33px;color:blueviolet;">NICK彩票</div>
<div id="txt" style="width:300px;height:200px;font-size:40px;color:peachpuff;display:flex;justify-content:center;align-items:center;flex-direction:column;">
<span>祝</span>
<span>君</span>
<span>中</span>
<span>奖</span>
</div>
<div id="canvasArea" style="width:300px;height:200px;position:relative;">
<div style="width:300px;height:200px;position:absolute;top:0;left:0;z-index:1;text-align:center;line-height:200px;font-weight:bold;font-size:56px;color:indianred;">一等奖</div>
<canvas id="canvas" width="300px" height="200px" style="position:absolute;top:0;left:0;z-index:2;"></canvas>
</div>
</div>
这段html要注意的地方有2个：
- flex布局，将‘祝君中奖’垂直居中，目前还有兼容问题，不过看我们大前端的发展趋势，应该很快就能搞定了；
- canvas和‘一等奖’div的z-index问题，将canvas的z-index设置较高，使其置于一等奖div上面。
设置canvas画布
var canvas = document.getElementById("canvas");
var context = canvas.getContext("2d");
绘制刮奖区域
context.fillStyle='#A9AB9D';
context.fillRect(10,10,280,180);
context.fillStyle='#000';
context.font='50px Arial';
context.fillText('刮奖区',75,115);
- 填充颜色；
- 绘制实心矩形；
- 设置字体颜色；
- 设置字体大小类型；
- 绘制实心字体。
以上都是canvas基础api，看w3c就ok了。
为了好看，我将‘祝君中奖’加个字体变色
setInterval(function(){
document.getElementById('txt').style.color = document.getElementById('txt').style.color=='peachpuff' ? 'yellow' : 'peachpuff';
},500);
刮奖功能函数
var brush=function(){//刮奖
context.clearRect(event.offsetX,event.offsetY,20,20);
};
为canvas元素onmousedown和onmouseup事件
canvas.onmousedown = function(){
// 鼠标按下时 - 绑定鼠标跟随事件
bindHandler(canvas,'mousemove',brush,false);
}
canvas.onmouseup = function(){
// 停止刮奖功能 - 解绑鼠标跟随事件
removeHandler(canvas,"mousemove",brush,false);
}
这里的事件绑定与解绑我上篇博文有封装，最后完整代码也有！
刮刮乐happy到底结束！最后附上完整代码，再看看效果吧！
demo二：画笔
布局
<div style="width:300px;height:500px;margin:10px;border-radius:10px;overflow:hidden;float:right;">
<canvas id="canvas2" width="300px" height="500px" style="background-color:lightblue;"></canvas>
</div>
设置canvas画布
var canvas2 = document.getElementById("canvas2");
var context2 = canvas2.getContext("2d");
画笔功能函数
var draw=function(){
context2.fillRect(event.offsetX,event.offsetY,10,10);
};
为canvas元素onmousedown和onmouseup事件
context2.font='20px Arial';
context2.strokeText('NICK画笔',100,30);//写个头
//1. 为canvas元素onmousedown和onmouseup事件
canvas2.onmousedown = function(){
// 启用画笔功能 - 绑定鼠标跟随事件
bindHandler(canvas2,'mousemove',draw,false);
}
canvas2.onmouseup = function(){
// 停止画笔功能 - 解绑鼠标跟随事件
removeHandler(canvas2,"mousemove",draw,false);
}
画图工具的画笔功能到底结束！
多谢各位老司机的鞭策与提醒，说画笔功能有不连续的现象！
现已改良，并兼容了移动端！
//改良后的写法
var isTouch = "ontouchstart" in window ? true : false;
var StartDraw = isTouch ? "touchstart" : "mousedown",
MoveDraw = isTouch ? "touchmove" : "mousemove",
EndDraw = isTouch ? "touchend" : "mouseup"; context2.strokeStyle='blue';//线色
context2.lineCap = "round";//连接处为圆形
context2.lineWidth =10;//线框 canvas2.addEventListener(StartDraw, function(ev){
ev.preventDefault();
var isX = isTouch ? ev.targetTouches[0].pageX : ev.pageX;
var isY = isTouch ? ev.targetTouches[0].pageY : ev.pageY;
var x = isX - canvas2.offsetLeft;
var y = isY - canvas2.offsetTop;
context2.beginPath();
context2.moveTo(x, y);
function StartMove(ev){
var isX1 = isTouch ? ev.targetTouches[0].pageX : ev.pageX;
var isY1 = isTouch ? ev.targetTouches[0].pageY : ev.pageY;
var x1 = isX1 - canvas2.offsetLeft;
var y1 = isY1 - canvas2.offsetTop;
context2.lineTo(x1, y1); context2.stroke();
context2.beginPath();
context2.moveTo(x1, y1);
};
function EndMove(ev){
var isX1 = isTouch ? ev.changedTouches[0].pageX : ev.pageX;
var isY1 = isTouch ? ev.changedTouches[0].pageY : ev.pageY;
var x1 = isX1 - canvas2.offsetLeft;
var y1 = isY1 - canvas2.offsetTop;
context2.lineTo(x1, y1);
context2.stroke();
canvas2.removeEventListener(MoveDraw, StartMove, false);
canvas2.removeEventListener(EndDraw, EndMove, false);
};
canvas2.addEventListener(MoveDraw, StartMove, false);
canvas2.addEventListener(EndDraw, EndMove, false);
}, false);
附上完整代码：
<!DOCTYPE html>
<html>
<head>
<title>Canvas lottery brush nick</title>
<meta charset="utf-8"/>
</head>
<body>
<div style="width:640px;margin:auto;">
<!--刮刮乐-->
<div id="lottery" style="width:300px;height:500px;margin:10px;background-color:lightskyblue;border-radius:5px;float:left;">
<div style="width:300px;height:100px;line-height:100px;text-align:center;font-size:33px;color:blueviolet;">NICK彩票</div>
<div id="txt" style="width:300px;height:200px;font-size:40px;color:peachpuff;display:flex;justify-content:center;align-items:center;flex-direction:column;">
<span>祝</span>
<span>君</span>
<span>中</span>
<span>奖</span>
</div>
<div id="canvasArea" style="width:300px;height:200px;position:relative;">
<div style="width:300px;height:200px;position:absolute;top:0;left:0;z-index:1;text-align:center;line-height:200px;font-weight:bold;font-size:56px;color:indianred;">一等奖</div>
<canvas id="canvas" width="300px" height="200px" style="position:absolute;top:0;left:0;z-index:2;"></canvas>
</div>
</div> <!--画图工具画笔功能-->
<div style="width:300px;height:500px;margin:10px;border-radius:10px;overflow:hidden;float:right;">
<canvas id="canvas2" width="300px" height="500px" style="background-color:lightblue;"></canvas>
</div>
</div> <div style="text-align:center;">
<p>刮刮乐：鼠标按住不放，拖动开始刮奖！</p>
<p>画笔：鼠标按住不放，拖动画画！</p>
</div>
<script>
//插件方法封装区 ;(function(){
// 事件绑定
window.bindHandler = (function() {
if (window.addEventListener) {// 标准浏览器
return function(elem, type, handler) {
// elem:节点 type:事件类型 handler:事件处理函数
// 最后一个参数为true:在捕获阶段调用事件处理程序;为false:在冒泡阶段调用事件处理程序。注意：ie没有这个参数
elem.addEventListener(type, handler, false);
}
} else if (window.attachEvent) {// IE浏览器
return function(elem, type, handler) {
elem.attachEvent("on" + type, handler);
}
}
}()); // 事件解除
window.removeHandler = (function() {
if (window.removeEventListener) {// 标准浏览器
return function(elem, type, handler) {
elem.removeEventListener(type, handler, false);
}
} else if (window.detachEvent) {// IE浏览器
return function(elem, type, handler) {
elem.detachEvent("on" + type, handler);
}
}
}());
}()); //命名区 var canvas = document.getElementById("canvas");
var context = canvas.getContext("2d"); var canvas2 = document.getElementById("canvas2");
var context2 = canvas2.getContext("2d");
var brush=function(){//刮奖
context.clearRect(event.offsetX,event.offsetY,20,20);
};
var draw=function(){//写字
context2.fillRect(event.offsetX,event.offsetY,10,10);
}; //功能实现区 //刮刮乐 // 1. 绘制刮奖区域
context.fillStyle='#A9AB9D';
context.fillRect(10,10,280,180);
context.fillStyle='#000';
context.font='50px Arial';
context.fillText('刮奖区',75,115);
//字体变色
setInterval(function(){
document.getElementById('txt').style.color = document.getElementById('txt').style.color=='peachpuff' ? 'yellow' : 'peachpuff';
},500);
//2. 为canvas元素onmousedown和onmouseup事件
canvas.onmousedown = function(){
// 鼠标按下时 - 绑定鼠标跟随事件
bindHandler(canvas,'mousemove',brush,false);
}
canvas.onmouseup = function(){
// 停止刮奖功能 - 解绑鼠标跟随事件
removeHandler(canvas,"mousemove",brush,false);
} //画笔
context2.font='20px Arial';
context2.strokeText('NICK画笔',100,30);//写个头
//为canvas元素onmousedown和onmouseup事件
/*
//这是原来的写法
canvas2.onmousedown = function(){
// 启用画笔功能 - 绑定鼠标跟随事件
bindHandler(canvas2,'mousemove',draw,false);
}
canvas2.onmouseup = function(){
// 停止画笔功能 - 解绑鼠标跟随事件
removeHandler(canvas2,"mousemove",draw,false);
}
*/
//改良后的写法
var isTouch = "ontouchstart" in window ? true : false;
var StartDraw = isTouch ? "touchstart" : "mousedown",
MoveDraw = isTouch ? "touchmove" : "mousemove",
EndDraw = isTouch ? "touchend" : "mouseup"; context2.strokeStyle='blue';//线色
context2.lineCap = "round";//连接处为圆形
context2.lineWidth =10;//线框 canvas2.addEventListener(StartDraw, function(ev){
ev.preventDefault();
var isX = isTouch ? ev.targetTouches[0].pageX : ev.pageX;
var isY = isTouch ? ev.targetTouches[0].pageY : ev.pageY;
var x = isX - canvas2.offsetLeft;
var y = isY - canvas2.offsetTop;
context2.beginPath();
context2.moveTo(x, y);
function StartMove(ev){
var isX1 = isTouch ? ev.targetTouches[0].pageX : ev.pageX;
var isY1 = isTouch ? ev.targetTouches[0].pageY : ev.pageY;
var x1 = isX1 - canvas2.offsetLeft;
var y1 = isY1 - canvas2.offsetTop;
context2.lineTo(x1, y1); context2.stroke();
context2.beginPath();
context2.moveTo(x1, y1);
};
function EndMove(ev){
var isX1 = isTouch ? ev.changedTouches[0].pageX : ev.pageX;
var isY1 = isTouch ? ev.changedTouches[0].pageY : ev.pageY;
var x1 = isX1 - canvas2.offsetLeft;
var y1 = isY1 - canvas2.offsetTop;
context2.lineTo(x1, y1);
context2.stroke();
canvas2.removeEventListener(MoveDraw, StartMove, false);
canvas2.removeEventListener(EndDraw, EndMove, false);
};
canvas2.addEventListener(MoveDraw, StartMove, false);
canvas2.addEventListener(EndDraw, EndMove, false);
}, false);
</script>
</body>
</html>
代码写完了，我也想说点其他的：
上面js代码中，有不少注释，我将其分为几个区域：插件方法封装区、命名区、功能实现区、刮刮乐区以及画笔区等，我感觉这样写加上一些注释，能使代码能加简洁，便于以后的维护！当然这只是个人观点，欢迎各位点击我博客右边公告栏的qq交流交流！
最后附上：
上篇博文：事件绑定与解绑！（只是一个简单的封装）
来看看效果，玩玩吧！