Qt焦点事件

谁借莪１个温暖的怀抱￠ 2022-06-08 09:10 231阅读 0赞

首先来说说为什么要设置焦点吧。

设置焦点可以让应用更便捷。比如当你打开百度主页或其他带有编辑框的页面时，不需要先用鼠标点击编辑框就可以直接输入文字等信息到其中。这就是由于搜索框设置了焦点。

一个空间要先设置它焦点事件的模式，即窗口如何接受焦点事件（通过鼠标单击、Tab键、不接受焦点事件等）

用

设置获得焦点的方式

<table style="margin:0px; padding:0px; border:1px solid silver; border-collapse:collapse; word-break:break-word"> 
 <tbody style="margin:0px; padding:0px"> 
  <tr style="margin:0px; padding:0px"> 
   <th style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">Constant</span></th> 
   <th style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">Value</span></th> 
   <th style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">Description</span></th> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">Qt::TabFocus</span></td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">0x1</span></td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">通过Tab键获得焦点</span></td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">Qt::ClickFocus</span></td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">0x2</span></td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">通过被单击获得焦点</span></td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">Qt::StrongFocus</span></td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">TabFocus | ClickFocus | 0x8</span></td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">可通过上面两种方式获得焦点</span></td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">Qt::WheelFocus</span></td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">StrongFocus | 0x4</span></td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">类似Qt::StrongFocus只不过再加上鼠标滑轮</span></td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">Qt::NoFocus</span></td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">0</span></td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> <span style="margin:0px; padding:0px; line-height:1.8">不能通过上两种方式获得焦点(默认值),setFocus仍可使其获得焦点.</span></td> 
  </tr> 
 </tbody> 
</table>

当前有焦点事件的窗口只能有一个，当一个窗口获取焦点事件或失去焦点事件时，可能需要相应的操作，或者如

何判断一个才窗口有没有焦点事件。Qt中亦有相应的函数。

### void QWidget::focusInEvent ( [QFocusEvent][] \* event ) \[virtual protected\] ###

### void QWidget::focusOutEvent ( [QFocusEvent][] \* event ) \[virtual protected\] ###

这两个就是窗口获取或失去焦点事件的函数，需要我们重写（好多窗口都是从QWidget继承这两个函数的）

bool hasFocus () const

这个函数就是判断当前窗口有没有焦点事件的，返回布尔值。

### void QWidget::setFocus ( [Qt::FocusReason][QFocusEvent] reason ) ###

### void QWidget::clearFocus () ###

这两个函数就是设置或清除焦点事件的。

<table style="margin:0px; padding:0px; border:1px solid silver; border-collapse:collapse; word-break:break-word"> 
 <tbody style="margin:0px; padding:0px"> 
  <tr style="margin:0px; padding:0px"> 
   <th style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> Constant</th> 
   <th style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> Value</th> 
   <th style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> Description</th> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> Qt::TabFocus</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> 0x1</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> the widget accepts focus by tabbing.</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> Qt::ClickFocus</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> 0x2</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> the widget accepts focus by clicking.</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> Qt::StrongFocus</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> TabFocus | ClickFocus | 0x8</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> the widget accepts focus by both tabbing and clicking. On Mac OS X this will also be indicate that the widget accepts tab focus when in 'Text/List focus mode'.</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> Qt::WheelFocus</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> StrongFocus | 0x4</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> like Qt::StrongFocus plus the widget accepts focus by using the mouse wheel.</td> 
  </tr> 
  <tr style="margin:0px; padding:0px"> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> Qt::NoFocus</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> 0</td> 
   <td style="margin:0px; padding:3px; border:1px solid silver; border-collapse:collapse"> the widget does not accept focus.</td> 
  </tr> 
 </tbody> 
</table>

http://www.cnblogs.com/Dennis-mi/articles/5231465.html

[QFocusEvent]: http://blog.sina.com.cn/s/blog_6fe793ab01018xzl.html