弹幕制作canvas方法,文字直播和聊天
今天要做体育文字直播的项目,类似这样:
文字不断循环显示,我这里找到了一个网上的写法,分析后并贴在这里,并且封装成了jquery barrager方法,很是方便,分析了下原理,是刷新canvas
画布实现的,非常好用.后端将数据以接口形式返回给我,我把数据放到$('canvas').barrager(数据)方法里,定时请求接口并更新数据,非常方便好用.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<canvas style="width: 1280px;height: 720px;background-color: rgba(0,0,0,0.2)">你的浏览器不支持canvas</canvas>
</body>
<script src="http://www.jq22.com/jquery/jquery-1.10.2.js"></script>
<script>
(function ($) {
function Barrager(dom) {
this.canvas = dom.get(0);//jquery对象获取dom元素
this.ctx = this.canvas.getContext("2d");
this.msgs = new Array(300);//缓冲池，长度越大，屏幕上显示的就越多
this.width = 1280;//canvas分辨率1280*720
this.height = 720;
this.canvas.width=this.width;//上边的两步可以省略，直接在这里赋值
this.canvas.height=this.height;
this.font = "30px 黑体";//字体和字体大小
this.ctx.font=this.font;
//颜色数组，在绘制过程中随机从这里取出颜色
this.colorArr=["Olive","OliveDrab","Orange","OrangeRed","Orchid","PaleGoldenRod","PaleGreen","PaleTurquoise","PaleVioletRed","PapayaWhip","PeachPuff","Peru","Pink","Plum","PowderBlue","Purple","Red","RosyBrown","RoyalBlue","SaddleBrown","Salmon","SandyBrown","SeaGreen","SeaShell","Sienna","Silver","SkyBlue"];
this.interval = "";
this.draw = function () {//绘制方法
if (this.interval != "")return;
var _this=this;
this.interval = setInterval(function () {//每隔20毫秒重新绘制一次，间隔最好小于40，要不然效果就跟播放图片差不多
//1，清除屏幕
_this.ctx.clearRect(0, 0, _this.width, _this.height);
_this.ctx.save();
//2，循环缓冲区域，把没有设置Left，Top，Speed，Color先赋值，赋值的就改变left值（产生移动效果），left值小于200就会从缓冲区移除
for (var i = 0; i < _this.msgs.length; i++) {
if (!(_this.msgs[i] == null || _this.msgs[i] == "" || typeof(_this.msgs[i]) == "undefined")) {
if(_this.msgs[i].L==null || typeof(_this.msgs[i].L)=="undefined"){
_this.msgs[i].L=_this.width;//显示的位置
_this.msgs[i].T=parseInt(Math.random() * 700);//0-700 高度
_this.msgs[i].S=parseInt(Math.random() * (10 - 4) + 4);//4-9每次更新的位置
_this.msgs[i].C=_this.colorArr[Math.floor(Math.random() * _this.colorArr.length)];//颜色
}else{
if(_this.msgs[i].L<-200){
_this.msgs[i]=null;
}else {
_this.msgs[i].L=parseInt(_this.msgs[i].L-_this.msgs[i].S);
_this.ctx.fillStyle =_this.msgs[i].C;
_this.ctx.fillText(_this.msgs[i].msg,_this.msgs[i].L,_this.msgs[i].T);
_this.ctx.restore();
}
}
}
}
}, 20);
};
//添加数据，数据格式[{"msg":"nihao"}]
this.putMsg = function (datas) {//循环缓冲区，把位置是空的装填上数据
for (var j = 0; j < datas.length; j++) {
for (var i = 0; i < this.msgs.length; i++) {
if (this.msgs[i] == null || this.msgs[i] == "" || typeof(this.msgs[i]) == "undefined") {
this.msgs[i] = datas[j];
break;
}
}
}
this.draw();
};
this.clear = function () {//清除定时器，清除屏幕，清空缓冲区
clearInterval(this.interval);
this.interval="";
this.ctx.clearRect(0, 0, this.width, this.height);
this.ctx.save();
for(var i=0;i<this.msgs.length;i++){
this.msgs[i]=null;
}
};
}
$.fn.barrager = function (para) {
if (typeof(para)=="string") {//用来调用clear方法,清空弹幕
try{
var api = $(this).data('barrager_api');
api[para].apply(api);
}catch (e){}
} else if (typeof para == 'object' || !para) {
$this = $(this);
if ($this.data('barrager_api') != null && $this.data('barrager_api') != ''){
var api = $this.data('barrager_api');
api.putMsg(para);
}else{
var api = new Barrager($this);
$this.data('barrager_api', api);
api.putMsg(para);
}
} else {
$.error('Method ' + method + ' does not exist on jQuery.slidizle');
}
return this;
}
})(jQuery);
</script>
<script>
$('canvas').barrager([{"msg":"这是我发的。。。哈哈哈"}]);// 发送弹幕
$('canvas').barrager([{"msg":"看着不错。。。。"},{"msg":"哈哈哈。。。。"},{"msg":"不错不错。。"},{"msg":"真好看。。。。"}]);//多条发送方式
//$('canvas').barrager(false); //清除/关闭弹幕
$('canvas').barrager([{"msg":"看着不错。。。。"},{"msg":"哈哈哈。。。。"},{"msg":"不错不错。。"},{"msg":"真好客服让我看。。。。"},{"msg":"让我真好佛山市发生看。。。。"},{"msg":"撒飞洒发真好看。。。。"},{"msg":"真wqw好看。。。。"},{"msg":"真好分隔符看。。。。"},{"msg":"真好发给看。。。。"},{"msg":"真放松放松好看。。。。"},{"msg":"真好复古风格看。。。。"}]);//多条发送方式
$('canvas').barrager([{"msg":"看着不错。。。。"},{"msg":"哈哈哈。。。。"},{"msg":"不错不错。。"},{"msg":"真好客服让我看。。。。"},{"msg":"让我真好佛山市发生看。。。。"},{"msg":"撒飞洒发真好看。。。。"},{"msg":"真wqw好看。。。。"},{"msg":"真好分隔符看。。。。"},{"msg":"真好发给看。。。。"},{"msg":"真放松放松好看。。。。"},{"msg":"真好复古风格看。。。。"}]);//多条发送方式
</script>
</html>
不自见，故明；不自是，故彰；不自伐，故有功；不自矜；故长；夫唯不争，故天下莫能与之争。
