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                <div id="text"> <link href="css.css" rel="stylesheet" type="text/css" /><h3 style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 0cm; MARGIN-RIGHT: 0cm; FTEL: 8.15pt"><span lang="EN-US">19.2.3&nbsp; </span><span style="FONT-FAMILY: 黑体">用户交互操作</span></h3>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">用户交互操作最好描述为控件创建和响应的各种事件。一些比较常见的事件有</span><span lang="EN-US">Click</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">DoubleClick</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">KeyDown</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">KeyPress</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">Validating</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">Paint</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">鼠标事件</span><span lang="EN-US">Click</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">DoubleClick</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">MouseDown</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">MouseUp</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">MouseEnter</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">MouseLeave</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">MouseHover</span><span style="FONT-FAMILY: 宋体">处理鼠标和控件的交互操作。如果处理</span><span lang="EN-US">Click</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">DoubleClick</span><span style="FONT-FAMILY: 宋体">事件，每次捕获一个</span><span lang="EN-US">DoubleClick</span><span style="FONT-FAMILY: 宋体">事件时，也会引发</span><span lang="EN-US">Click</span><span style="FONT-FAMILY: 宋体">事件。如果处理不正确，就会出现我们不希望的结果。</span><span lang="EN-US">Click</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">DoubleClick</span><span style="FONT-FAMILY: 宋体">事件都把</span><span lang="EN-US">EventArgs</span><span style="FONT-FAMILY: 宋体">作为其参数，而</span><span lang="EN-US">MouseDown</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">MouseUp</span><span style="FONT-FAMILY: 宋体">事件把</span><span lang="EN-US">MouseEventArgs</span><span style="FONT-FAMILY: 宋体">作为其参数。</span><span lang="EN-US">MouseEventArgs</span><span style="FONT-FAMILY: 宋体">包含几个有用的信息，例如单击的按钮、按钮被单击的次数、鼠标轮制动器</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">鼠标轮上的凹槽</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">的数目和鼠标的当前</span><span lang="EN-US">XY</span><span style="FONT-FAMILY: 宋体">坐标。如果可以访问这些信息，就必须处理</span><span lang="EN-US">MouseDown</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US">MouseUp</span><span style="FONT-FAMILY: 宋体">事件，而不是</span><span lang="EN-US">Click</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US">DoubleClick</span><span style="FONT-FAMILY: 宋体">事件。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">键盘事件的工作方式与此类似：需要一些信息来确定处理什么事件。对于简单的情况，</span><span lang="EN-US">KeyPress</span><span style="FONT-FAMILY: 宋体">事件接收一个</span><span lang="EN-US">KeyPressEventArgs</span><span style="FONT-FAMILY: 宋体">，它包含表示被按键的字符值</span><span lang="EN-US">KeyChar</span><span style="FONT-FAMILY: 宋体">。</span><span lang="EN-US">Handled</span><span style="FONT-FAMILY: 宋体">属性用于确定事件是否已处理。把</span><span lang="EN-US">Handled</span><span style="FONT-FAMILY: 宋体">属性设置为</span><span lang="EN-US">true</span><span style="FONT-FAMILY: 宋体">，事件就不会由操作系统进行默认处理。如果需要被按的键的更多信息，则处理</span><span lang="EN-US">KeyDown</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US">KeyUp</span><span style="FONT-FAMILY: 宋体">事件会比较合适。它们都接收</span><span lang="EN-US">KeyEventArgs</span><span style="FONT-FAMILY: 宋体">。</span><span lang="EN-US">KeyEventArgs</span><span style="FONT-FAMILY: 宋体">中的属性包括</span><span lang="EN-US">Ctrl</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">Alt</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US">Shift</span><span style="FONT-FAMILY: 宋体">键是否被按下。与</span><span lang="EN-US">KeyPressEventArgs.KeyChar</span><span style="FONT-FAMILY: 宋体">不同，</span><span lang="EN-US">KeyCode</span><span style="FONT-FAMILY: 宋体">属性指定键盘上的每个键，而不仅仅是字母数字键。</span><span lang="EN-US">KeyData</span><span style="FONT-FAMILY: 宋体">属性返回一个</span><span lang="EN-US">Key</span><span style="FONT-FAMILY: 宋体">值，还设置修饰符。修饰符与值进行</span><span lang="EN-US">OR</span><span style="FONT-FAMILY: 宋体">运算，指定是否同时按下了</span><span lang="EN-US">Shift</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US">Ctrl</span><span style="FONT-FAMILY: 宋体">键。</span><span lang="EN-US">KeyValue</span><span style="FONT-FAMILY: 宋体">属性是</span><span lang="EN-US">Keys</span><span style="FONT-FAMILY: 宋体">枚举的整数值。</span><span lang="EN-US">Modifiers</span><span style="FONT-FAMILY: 宋体">属性包含一个</span><span lang="EN-US">Keys</span><span style="FONT-FAMILY: 宋体">值，它表示被按下的修饰符键。如果选择了多个修饰符键，这些值就进行</span><span lang="EN-US">OR</span><span style="FONT-FAMILY: 宋体">运算。键盘事件以下述顺序来引发：</span></p>
<p class="MsoNormal" style="MARGIN-LEFT: 39.25pt; FTEL: -18.0pt"><span lang="EN-US">1.<span style="FONT: 7pt 'Times New Roman'">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></span><span lang="EN-US">KeyDown</span></p>
<p class="MsoNormal" style="MARGIN-LEFT: 39.25pt; FTEL: -18.0pt"><span lang="EN-US">2.<span style="FONT: 7pt 'Times New Roman'">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></span><span lang="EN-US">KeyPress</span></p>
<p class="MsoNormal" style="MARGIN-LEFT: 39.25pt; FTEL: -18.0pt"><span lang="EN-US">3.<span style="FONT: 7pt 'Times New Roman'">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></span><span lang="EN-US">KeyUp</span></p>
<p class="MsoNormal"><span lang="EN-US">Validating</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">Validated</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">Enter</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">Leave</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">GotFocus</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">LostFocus</span><span style="FONT-FAMILY: 宋体">事件都处理获得焦点</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">或被激活</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">和失去焦点的控件。在用户用</span><span lang="EN-US">tab</span><span style="FONT-FAMILY: 宋体">键选择一个控件或用鼠标选择该控件时，该控件就获得了焦点。</span><span lang="EN-US">Enter</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">Leave</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">GotFocus</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">LostFocus</span><span style="FONT-FAMILY: 宋体">事件的功能似乎非常类似。</span><span lang="EN-US">GotFocus</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">LostFocus</span><span style="FONT-FAMILY: 宋体">事件是低级事件，与</span><span lang="EN-US">Windows</span><span style="FONT-FAMILY: 宋体">消息</span><span lang="EN-US">WM_SETFOCUS</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">WM_KILLFOCUS</span><span style="FONT-FAMILY: 宋体">相关。一般应尽可能使用</span><span lang="EN-US">Enter</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">Leave</span><span style="FONT-FAMILY: 宋体">事件。</span><span lang="EN-US">Validating</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">Validated</span><span style="FONT-FAMILY: 宋体">事件在验证控件时发生。这些事件接收一个</span><span lang="EN-US">CancelEventArgs</span><span style="FONT-FAMILY: 宋体">，利用该参数，把</span><span lang="EN-US">Cancel</span><span style="FONT-FAMILY: 宋体">属性设置为</span><span lang="EN-US">true</span><span style="FONT-FAMILY: 宋体">，就可以取消以后的事件。如果定制了验证代码，而且验证失败，就可以把</span><span lang="EN-US">Cancel</span><span style="FONT-FAMILY: 宋体">属性设置为</span><span lang="EN-US">true</span><span style="FONT-FAMILY: 宋体">，且控件也不会失去焦点。</span><span lang="EN-US">Validating</span><span style="FONT-FAMILY: 宋体">事件在验证过程中发生，</span><span lang="EN-US">Validated</span><span style="FONT-FAMILY: 宋体">事件在验证过程后发生。这些事件的引发顺序如下：</span></p>
<p class="MsoNormal" style="MARGIN-LEFT: 39.25pt; FTEL: -18.0pt"><span lang="EN-US">1.<span style="FONT: 7pt 'Times New Roman'">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></span><span lang="EN-US">Enter</span></p>
<p class="MsoNormal" style="MARGIN-LEFT: 39.25pt; FTEL: -18.0pt"><span lang="EN-US">2.<span style="FONT: 7pt 'Times New Roman'">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></span><span lang="EN-US">GotFocus</span></p>
<p class="MsoNormal" style="MARGIN-LEFT: 39.25pt; FTEL: -18.0pt"><span lang="EN-US">3.<span style="FONT: 7pt 'Times New Roman'">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></span><span lang="EN-US">Leave</span></p>
<p class="MsoNormal" style="MARGIN-LEFT: 39.25pt; FTEL: -18.0pt"><span lang="EN-US">4.<span style="FONT: 7pt 'Times New Roman'">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></span><span lang="EN-US">Validating</span></p>
<p class="MsoNormal" style="MARGIN-LEFT: 39.25pt; FTEL: -18.0pt"><span lang="EN-US">5.<span style="FONT: 7pt 'Times New Roman'">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></span><span lang="EN-US">Validated</span></p>
<p class="MsoNormal" style="MARGIN-LEFT: 39.25pt; FTEL: -18.0pt"><span lang="EN-US">6.<span style="FONT: 7pt 'Times New Roman'">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </span></span><span lang="EN-US">LostFocus</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">理解这些事件的引发顺序是很重要的，可以避免不小心创建递归事件。例如，在控件的</span><span lang="EN-US">LostFocus</span><span style="FONT-FAMILY: 宋体">事件中设置控件的焦点，就会创建一个消息死锁，且应用程序会停止响应。</span></p></div>
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                        <h1 id="divCurrentNode2" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165530.htm'><font color='red'>19.2.3  用户交互操作</font></a></h1>
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                        <div style='float:left;width:49%'>·<a href='100165527.htm'>19.2  Control类</a></div><div style='float:right;width:49%'>·<a href='100165528.htm'>19.2.1  大小和位置</a></div><div style='float:left;width:49%'>·<a href='100165529.htm'>19.2.2  外观</a></div><div style='float:right;width:49%'>·<a href='100165531.htm'>19.2.4  Windows功能</a></div><div style='float:left;width:49%'>·<a href='100165532.htm'>19.2.5  杂项功能</a></div><div style='float:right;width:49%'>·<a href='100165533.htm'>19.2.6  类层次结构</a></div></div>
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