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<title>第六章：输入（二）</title>
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<td width="100%"><font size="3" color="#8000FF"><strong><em>第六章：输入（二）</em></strong></font></td>
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<td width="100%" style="background-color: rgb(232,255,254)"><font FACE="宋体" SIZE="3"><p ALIGN="JUSTIFY">上次说到，输入不仅仅是向文本框输入字符，凡是从外界向程序传递数据都可以叫做输入，我们一一说明白。</p>
<p ALIGN="JUSTIFY">无线钮，记得我们曾在第一章中完成过我们的第一个程序――“</font><font SIZE="3">Hello World</font><font FACE="宋体" SIZE="3">！”它就是一种输入的方法，在设计</font><font SIZE="3">VB</font><font FACE="宋体" SIZE="3">程序时可以通过一组这样的无线钮，它们之间互相排斥，也就是说，只能有一个按钮被选中。它因为很象无线电收音机上的按钮因而得名无线钮。如果要在一个窗体内放置多组无线钮必须用</font><font SIZE="3">Frame</font><font FACE="宋体" SIZE="3">控件把它们区分开来。下面我们在来完成一个例子，顺便熟悉一下另外两个处理字符串的函数――</font><font SIZE="3">LTrim()</font><font FACE="宋体" SIZE="3">和</font><font SIZE="3">Rtrim()</font><font FACE="宋体" SIZE="3">，它们分别用来删除字符串左边的空格和右边的空格，让我们看看它们是如何工作的。</p>
<p ALIGN="JUSTIFY"><img src="06-08.gif" alt="06-08.gif (2920 字节)" WIDTH="354" HEIGHT="221"></p>
<p ALIGN="JUSTIFY">程序窗体如图</font><font SIZE="3">6</font><font FACE="宋体" SIZE="3">－</font><font SIZE="3">8</font><font FACE="宋体" SIZE="3">，由于窗体比较简单，无需修改更多的属性，一共有三个文本框（</font><font SIZE="3">Text1</font><font FACE="宋体" SIZE="3">到</font><font SIZE="3">3</font><font FACE="宋体" SIZE="3">），分别用来显示输入字符，显示把空格换成星号的字符，和经过处理的字符，还有三个无线钮（</font><font SIZE="3">Option1</font><font FACE="宋体" SIZE="3">到</font><font SIZE="3">3</font><font FACE="宋体" SIZE="3">），要修改的只有</font><font SIZE="3">Caption</font><font FACE="宋体" SIZE="3">属性，分别是“删除左边的空格”、“删除右边的空格”和“删除两边的空格”。因为空格在我们在文本框中无法看到空格，所以我们通过一个称作</font><font SIZE="3">AddStar</font><font FACE="宋体" SIZE="3">的函数把原有字符串中的空格转换为星号，使我们能够看到函数的效果。下面在程序中添加代码，首先在</font><font SIZE="3">General</font><font FACE="宋体" SIZE="3">中声明窗体级变量：</font><font SIZE="3"></p>
<blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">Dim LTrimmedword$, RTrimmedword$</font> <font color="#008000" SIZE="3">'</font><font FACE="宋体" SIZE="3" color="#008000">删除左边空格和右边空格后的字符串</font></p>
<p ALIGN="JUSTIFY"><font color="#004080">Dim LRTrimmedword$</font> <font color="#008040" SIZE="3">'</font><font FACE="宋体" SIZE="3" color="#008040">删除两边空格后的字符串</font></font><font FACE="宋体" SIZE="3"></p>
</font>
</blockquote>
<font FACE="宋体" SIZE="3"><p ALIGN="JUSTIFY">然后，我们通过一个叫做</font><font SIZE="3">addstar</font><font FACE="宋体" SIZE="3">的函数为字符串加上星号，以前曾说过函数与过程的分别，函数会返回一个函数值，所以</font><font SIZE="3">addstar</font><font FACE="宋体" SIZE="3">也就相当于一个变量，其实这很好理解，就象中学代数中的函数，函数就相当于变量</font><font SIZE="3">Y</font><font FACE="宋体" SIZE="3">，而函数中的参数则相当于自变量</font><font SIZE="3">X</font><font FACE="宋体" SIZE="3">，当然可能有很多自变量</font><font SIZE="3">X1</font><font FACE="宋体" SIZE="3">、</font><font SIZE="3">X2</font><font FACE="宋体" SIZE="3">……请原谅，我并不想在这里上数学课，因为我厌恶那玩意儿，特别是上了大学之后，好在大二以后就再也不会有数学课了，哈哈……</font><font SIZE="3"></p>
<p ALIGN="JUSTIFY"><font color="#004080">Function addstar(tempword As String) As String</font></p>
<blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">Dim charindex%</font><br>
<font color="#004080" SIZE="3">Dim pasteword$</font><font color="#008000"> '<font FACE="宋体" SIZE="3">加星号后的字符串</font></font><br>
<font color="#004080">For charindex = 1 To Len(tempword)</font></p>
<blockquote>
<p ALIGN="JUSTIFY"><font color="#004080" SIZE="3">If Mid(tempword, charindex, 1) = "
" Then </font><font color="#008040">'<font FACE="宋体" SIZE="3">如果字符为空格</font></font></p>
<blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">pasteword = pasteword + "*"</font></p>
</blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">Else: pasteword = pasteword + Mid(tempword,
charindex, 1)<br>
End If</font></p>
</blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">Next</font><br>
<font color="#004080" SIZE="3">addstar = pasteword </font><font color="#008040">'<font FACE="宋体" SIZE="3">返回函数值</font></font></p>
</blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">End Function</font></p>
<p ALIGN="JUSTIFY"></font><font FACE="宋体" SIZE="3">下面的代码很简单，并且我为它做了注释，就不再一一解释了，我只想简要的提几句，</font><font SIZE="3">Ltrim</font><font FACE="宋体" SIZE="3">和</font><font SIZE="3">Rtrim</font><font FACE="宋体" SIZE="3">只有一个参数（字符型），另外下面用到了焦点事件，我们曾在第三章中介绍过，当</font><font SIZE="3">Text1</font><font FACE="宋体" SIZE="3">得到焦点（</font><font SIZE="3">GotFocus</font><font FACE="宋体" SIZE="3">）时，清空所有的文本框，当它失去焦点（</font><font SIZE="3">LostFocus</font><font FACE="宋体" SIZE="3">）时，对字符进行</font><font SIZE="3">addstar</font><font FACE="宋体" SIZE="3">并且在</font><font SIZE="3">Text2</font><font FACE="宋体" SIZE="3">中显示。</font><font SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font color="#004080" SIZE="3">Private Sub Text1_GotFocus()</font><font color="#008040"><font SIZE="3"> '</font><font FACE="宋体" SIZE="3">但焦点于</font></font><font SIZE="3" color="#008040">Text1</font><font SIZE="3"></p>
<blockquote>
<p ALIGN="JUSTIFY"><font SIZE="3" color="#008040">'</font><font FACE="宋体" SIZE="3" color="#008040">清除所有文本框中的字符</font><br>
<font color="#004080">Text1.Text = ""<br>
Text2.Text = ""<br>
Text3.Text = ""</font></p>
</blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">End Sub</font></p>
<p ALIGN="JUSTIFY"> </p>
<p ALIGN="JUSTIFY"><font color="#004080">Private Sub Text1_LostFocus()</font></p>
<blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">Dim Origionword As String<br>
Origionword = Text1.Text<br>
Text2.Text = addstar(Origionword)<br>
LTrimmedword = addstar(LTrim(Origionword))<br>
RTrimmedword = addstar(RTrim(Origionword))<br>
LRTrimmedword = LTrim(RTrim(Origionword))</font></p>
</blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">End Sub</font></font><font FACE="宋体" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3"> </p>
<p ALIGN="JUSTIFY"><font color="#004080">Private Sub Option1_Click()</font></p>
<blockquote>
<p ALIGN="JUSTIFY"><font color="#004080" SIZE="3">Text3.Text = LTrimmedword </font><font color="#008040">'<font FACE="宋体" SIZE="3">显示删除左空格后的字符串</font></font></p>
</blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">End Sub</font></p>
<p ALIGN="JUSTIFY"> </p>
<p ALIGN="JUSTIFY"><font color="#004080">Private Sub Option2_Click()</font></p>
<blockquote>
<p ALIGN="JUSTIFY"><font color="#004080" SIZE="3">Text3.Text = RTrimmedword</font><font color="#008040"> '<font FACE="宋体" SIZE="3">显示删除右空格后的字符串</font></font></p>
</blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">End Sub</font></p>
<p ALIGN="JUSTIFY"> </p>
<p ALIGN="JUSTIFY"><font color="#004080">Private Sub Option3_Click()</font></p>
<blockquote>
<p ALIGN="JUSTIFY"><font color="#004080" SIZE="3">Text3.Text = LRTrimmedword </font><font color="#008040">'<font FACE="宋体" SIZE="3">显示删除两边空格后的字符串</font></font></p>
</blockquote>
<p ALIGN="JUSTIFY"><font color="#004080">End Sub</font></font><font FACE="宋体" SIZE="3"></p>
<p ALIGN="JUSTIFY">最后结果如图</font><font SIZE="3">6</font><font FACE="宋体" SIZE="3">－</font><font SIZE="3">9</font><font FACE="宋体" SIZE="3">。</p>
<p ALIGN="JUSTIFY"><img src="06-09.gif" alt="06-09.gif (2626 字节)" WIDTH="354" HEIGHT="221"></font></td>
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