正在加载...
正在加载...
var State = function () {
};
State.prototype.download = function () {
throw new Error("该方法必须被重载!");
};
State.prototype.pause = function () {
throw new Error("该方法必须被重载!");
};
State.prototype.fail = function () {
throw new Error("该方法必须被重载!");
};
State.prototype.finish = function () {
throw new Error("该方法必须被重载!");
};
var ReadyState = function (oDownload) {
State.apply(this);
this.oDownload = oDownload;
};
ReadyState.prototype = new State();
ReadyState.prototype.download = function () {
this.oDownload.setState(this.oDownload.getDownloadingState());
// Ready以后，可以开始下载，所以设置了Download函数里的状态获取方法
console.log("Start Download!");
};
ReadyState.prototype.pause = function () {
throw new Error("还没开始下载，不能暂停!");
};
ReadyState.prototype.fail = function () {
throw new Error("文件还没开始下载，怎么能说失败呢!");
};
ReadyState.prototype.finish = function () {
throw new Error("文件还没开始下载，当然也不能结束了!");
};
var Download = function () {
this.oState = new ReadyState(this);
};
Download.prototype.setState = function (oState) {
this.oState = oState;
};
// 对外暴露的四个公共方法，以便外部调用
Download.prototype.download = function () {
this.oState.download();
};
Download.prototype.pause = function () {
this.oState.pause();
};
Download.prototype.fail = function () {
this.oState.fail();
};
Download.prototype.finish = function () {
this.oState.finish();
};
//获取各种状态，传入当前this对象
Download.prototype.getReadyState = function () {
return new ReadyState(this);
};
Download.prototype.getDownloadingState = function () {
return new DownloadingState(this);
};
Download.prototype.getDownloadPausedState = function () {
return new DownloadPausedState(this);
};
Download.prototype.getDownloadedState = function () {
return new DownloadedState(this);
};
Download.prototype.getDownloadedFailedState = function () {
return new DownloadFailedState(this);
};
var DownloadingState = function (oDownload) {
State.apply(this);
this.oDownload = oDownload;
};
DownloadingState.prototype = new State();
DownloadingState.prototype.download = function () {
throw new Error("文件已经正在下载中了!");
};
DownloadingState.prototype.pause = function () { this.oDownload.setState(this.oDownload.getDownloadPausedState());
console.log("暂停下载!");
};
DownloadingState.prototype.fail = function () { this.oDownload.setState(this.oDownload.getDownloadedFailedState());
console.log("下载失败!");
};
DownloadingState.prototype.finish = function () {
this.oDownload.setState(this.oDownload.getDownloadedState());
console.log("下载完毕!");
};
var DownloadPausedState = function (oDownload) {
State.apply(this);
this.oDownload = oDownload;
};
DownloadPausedState.prototype = new State();
DownloadPausedState.prototype.download = function () {
this.oDownload.setState(this.oDownload.getDownloadingState());
console.log("继续下载!");
};
DownloadPausedState.prototype.pause = function () {
throw new Error("已经暂停了，咋还要暂停呢!");
};
DownloadPausedState.prototype.fail = function () { this.oDownload.setState(this.oDownload.getDownloadedFailedState());
console.log("下载失败!");
};
DownloadPausedState.prototype.finish = function () {
this.oDownload.setState(this.oDownload.getDownloadedState());
console.log("下载完毕!");
};
var DownloadedState = function (oDownload) {
State.apply(this);
this.oDownload = oDownload;
};
DownloadedState.prototype = new State();
DownloadedState.prototype.download = function () {
this.oDownload.setState(this.oDownload.getDownloadingState());
console.log("重新下载!");
};
DownloadedState.prototype.pause = function () {
throw new Error("对下载完了，还暂停啥？");
};
DownloadedState.prototype.fail = function () {
throw new Error("都下载成功了，咋会失败呢？");
};
DownloadedState.prototype.finish = function () {
throw new Error("下载成功了，不能再为成功了吧!");
};
var DownloadFailedState = function (oDownload) {
State.apply(this);
this.oDownload = oDownload;
};
DownloadFailedState.prototype = new State();
DownloadFailedState.prototype.download = function () {
this.oDownload.setState(this.oDownload.getDownloadingState());
console.log("尝试重新下载!");
};
DownloadFailedState.prototype.pause = function () {
throw new Error("失败的下载，也不能暂停!");
};
DownloadFailedState.prototype.fail = function () {
throw new Error("都失败了，咋还失败呢!");
};
DownloadFailedState.prototype.finish = function () {
throw new Error("失败的下载，肯定也不会成功!");
};同理，DownloadFailedState函数的失败状态，也不能再次失败，但可以和finished以后再次尝试重新下载。
<html>
<head>
<link type="text/css" rel="stylesheet" href="http://www.cnblogs.com/css/style.css" />
<title>State Pattern</title>
<script type="text/javascript" src="/jquery.js"></script>
<script type="text/javascript" src="Download.js"></script>
<script type="text/javascript" src="states/State.js"></script>
<script type="text/javascript" src="states/DownloadFailedState.js"></script>
<script type="text/javascript" src="states/DownloadPausedState.js"></script>
<script type="text/javascript" src="states/DownloadedState.js"></script>
<script type="text/javascript" src="states/DownloadingState.js"></script>
<script type="text/javascript" src="states/ReadyState.js"></script>
</head>
<body>
<input type="button" value="开始下载" id="download_button" />
<input type="button" value="暂停" id="pause_button" />
<input type="button" value="重新下载" id="resume_button" />
<script type="text/javascript">
var oDownload = new Download();
$("#download_button").click(function () {
oDownload.download();
});
$("#pause_button").click(function () {
oDownload.pause();
});
$("#resume_button").click(function () {
oDownload.download();
});
</script>
</body>
</html>