asp.net控件开发基础(8)
2006-09-10 23:33 Clingingboy 阅读(14464) 评论(22) 编辑 收藏 举报 上一篇写了复合控件基本的概念,这次就继续上次的话题,来学习复合控件如何触发事件
有一些复合控件直接把按钮触发事件所需的事情封装好,另外一种则是自定义事件,更具灵活性,当然这是根据需要设计的。以下会以例子来说明的.下面我们假设我们控件中有两个按钮.以下不列出所有代码,具体可在文章最后下载代码.
(1) 直接实现按钮事件
在控件中(以下代码并非实现复合控件)直接实现事件则无需自定义事件,如下代码(如果对数据回传有些不熟悉的话,可先看第三篇,希望对你有帮助)
示例一(只列出局部代码,具体可在文章最后下载代码)
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RaisePostBackEvent方法有一个eventArgument参数用来传递事件数据.代码实现了一个空参数传递(eventArgument参数为空)的事件OnClick(EventArgs.Empty)
再比较一下示例一的代码,因为其用到了两个按钮
Page.GetPostBackEventReference方法用来传递参数
RaisePostBackEvent方法则以传递参数来判断触发哪个按钮
小结:
在控件中直接实现按钮事件,则无需定义自定义事件,但别忘了在RaisePostBackEvent方法中根据传递过来的不同参数来加以判断.
(2)以自定义事件实现
根据示例一上面的代码加上自定义委托和事件,如下代码(只列出局部代码,具体可在文章最后下载代码)
示例二
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调用代码如下
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小结:在示例一的基础上去除直接实现好的按钮事件,然后自定义事件.
再次提醒如果大家对回发事件,还请再参考一些文章先弄清楚,或者也可以看看我写的第三篇文章.
好了,上面讲的都非复合控件,但复合控件实现起来却很相似,或者可以说更加简单.
下面先来看个简单的示例(大家知道button按钮有CommandName属性和CommandArgument属性)
示例三
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以上代码以三种方式来实现按钮的触发事件.这里本应该再举一个数据绑定控件如(DataList控件的使用)的一个例子的一个例子的,这里目的只为了说明冒泡法的使用,冒泡法在DataList等数据绑定控定控件中最能体现出来.
那我们先来看下,在复合控件中怎么做?
1.直接实现按钮事件
2.以自定义事件实现
(1)以下为微软网站的示例代码,如下代码
示例四
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因为内部事件已经实现好了,所以比较简单,相信大家都看的懂。
再看复合控件的自定义事件,这里才是我们所要讲的重点.通常我们提倡在复合控件中采用冒泡法实现事件的上传,上一篇已经说过了,复合控件是一个树结构的控件,最典型的就是asp.net的数据邦定控件(特殊的复合控件)了如DataList,此控件有很多以Command结尾的事件,我们刚开始学这个控件的时候,总要考虑,如何在此控件中实现按钮事件,所采用的就是我们常说的"事件冒泡",当然还有另一种方法,应该说是普通的实现方法,asp.net服务器控件开发技术与示例称之为包含法,下面我们以例子来说明上面两种方法.
1.包含法
还是以微软的快速入门教程的代码为例.与上面的代码对比有几处变动,如下
注意粗体字,自定义事件为复合控件顶层的事件,而非其子控件button按钮的事件,button按钮的事件需调用顶层事件处理程序.即实现子控件事件上传的过程.
示例五
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2.冒泡法
上面已经介绍过了,并且MSDN也已经作出了详细的解释,控件可以将其定义的事件上传到控件顶层,在引发事件时处理事件,了解冒泡法,你需要了解以下两个方法
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RaiseBubbleEvent不可重写,用于向上传递数据
要引发冒泡事件,控件必重写 OnBubbleEvent 看OnBubbleEvent方法,看下面代码
你需要先熟悉一下CommandEventArgs,其为Command事件提供了数据,通过其可以访问控件命令名称和参数,并根据不同参数和名称触发不同事件.其下代码为上一篇登录控件例子实现事件冒泡的方法,具体代码可在最后下载,且CreateChildControls方法中的触发事件的控件无须添加一个事件委托
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你也可以为控件定义的事件定义事件冒泡,引发该时间则必须调用RaiseBubbleEvent,示例三就是具体的例子使用
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本次讲的重点在于冒泡法的使用,但我却用很多篇幅介绍写前面的东西,主要目的是为了让大家用复合控件与非符合控件进行比较,总的来说复合控件为我们带来了便利,不用实现IPostBackEventHandler接口,简化了操作.如果大家熟悉事件回传机制,则不难了解冒泡法的使用.最后还是要注意一点的是复合控件是一个树级的控件,即由子控件组成的一个控件,这次的例子很多都是直接取自书上和微软的教程上,只供大家参考吧.
好了,这次就写到这里,感觉这次写的并不是太好,望见谅,有错误请指出.
代码下载
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