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Perl/TkFAQ-10.如何使用某个组件来完成某个工作

2008-05-18 21:55:24 编辑來源:互联网 国际版 评论
 
 
  原文:

  10. How do I get widget X to do Y ?

  There are a number of tasks that can be accomplished with perl/Tk widgets, configurations, and bindings (a few that can't and a few that require specific tricks). Beginners are encouraged to work through the examples in UserGuide.pod. Some examples from UserGuide.pod are addressed in this document among those that follow.

  Basically a widget can be "created" by simply calling the sub of the same name: my $main = new MainWindow;

  will set aside the necessary system memory etc. for a new MainWindow widget (it does not appear until after the MainLoop; call). The object "created" is then callable via the variable $main. So, for example, if you wanted a Button in your MainWindow, then this: $main->Button();

  would be a very basic example of a widget command. If you wanted to later call this button widget you would need a "widget tag or ID" to "get a handle on it". Instead of the above call try something like: my $button = $main->Button();

  The variable $button is how you refer to the Button widget in subsequent calls, such as when we call the pack routine: $button -> pack;

  A complete script that incorporates these ideas to make a very plain button would look like: #!/usr/bin/perl -w use Tk; use strict; my $main = new MainWindow; my $button = $main -> Button(); $button -> pack; MainLoop;

  But who wants such a plain looking button? You can provide a number of different widget configurations via calls to the configure routine as in: #!/usr/bin/perl -w use Tk; use strict; my $main = new MainWindow; my $button = $main->Button(); $button -> configure(-text => 'Press me!'); $button -> pack; MainLoop;

  The Perl motto is "there is more than one way to do it." - perl/Tk remains quite true to this motto as well. Note that the above script could have been written quite succinctly without the use of either the $main or $button variables as: #!/usr/bin/perl -w use Tk; use strict; new MainWindow -> Button(-text => 'Press me!') -> pack; MainLoop;

  But if you want your widgets to actually do things then you must set up callback procedures as discussed later...

  Do not overlook the - sign in front of some options (like -text in the above example) Another commonly overlooked problem is that elements in a hash are supposed to be strings hence a configuration option like -length +> 5, really ought to be specified as either '-length' +> 5, or "-length" +> 5, etc., rather than perl's builtin length() function.

  译文:

  10. 如何使用某个组件来完成某个工作?

  通过使用Perl/Tk的各种组件,并进行必要的配置和绑定,可以实现很多功能。当然,也有少数的一些无法完成或需要一定的技巧才能完成。建议初学Tk的朋友仔细的学习和试用UserGuide.pod中的例程。在下面的讲解中,我们也会谈到其中的一些例子。

  基本上,要创建一个组件,只需要调用和他名称对应的子程序,例如:

  my $main = new MainWindow;

  上面的语句将使Perl解释器为这个新的MainWindow组件留出一些必要的系统内存等资源(但是这个主窗口并非立刻出现的,它要直到调用 MainLoop才会出现)。这样,上面创建的这个对象,以后就可以通过变量$main来调用了。例如,如果你想在你的这个主窗口中放置一个按钮,就可以这样:

  $main->Button();

  那么,实现上面的几个想法的一般“完整”的脚本如下(这里将创建一个空白的按钮):

  #!/usr/bin/perl -w

  use Tk;

  use strict;

  my $main = new MainWindow;

  my $button = $main -> Button();

  $button -> pack;

  MainLoop;

  但是谁会想要一个空白的按钮呢?其实,你可能通过使用configure方法对很多不同的组件进行配置。例如:

  #!/usr/bin/perl -w

  use Tk;

  use strict;

  my $main = new MainWindow;

  my $button = $main->Button();

  $button -> configure(-text => 'Press me!');

  $button -> pack;

  MainLoop;

  众所周知,Perl的名言就是:做一件事情可以有多种方法。所以,Perl/Tk也同样信守了这一原则。其实,上面的脚本可以写的非常简洁,甚至不使用任何的变量($main和$button),代码如下:

  #!/usr/bin/perl -w

  use Tk;

  use strict;

  new MainWindow -> Button(-text => 'Press me!') -> pack;

  MainLoop;

  当然,如果你确实希望你的组件实现一些功能的话,你还必须让它们关联一些代码,这我们将在以后详细讨论……

  最后,我们提醒大家不要忽略了在选项前面的“-”符号,例如上面例子中的-text。另外,值得一提的是,hash中的元素默认被当作字符串看待,所以我们使用的配置选项如:-length => 5,事实上应该写成:’-length’ => 5或”-length” => 5,这样才可以和Perl的内置函数length()相区别。
 
 
  原文:   10. How do I get widget X to do Y ?   There are a number of tasks that can be accomplished with perl/Tk widgets, configurations, and bindings (a few that can't and a few that require specific tricks). Beginners are encouraged to work through the examples in UserGuide.pod. Some examples from UserGuide.pod are addressed in this document among those that follow.   Basically a widget can be "created" by simply calling the sub of the same name: my $main = new MainWindow;   will set aside the necessary system memory etc. for a new MainWindow widget (it does not appear until after the MainLoop; call). The object "created" is then callable via the variable $main. So, for example, if you wanted a Button in your MainWindow, then this: $main->Button();   would be a very basic example of a widget command. If you wanted to later call this button widget you would need a "widget tag or ID" to "get a handle on it". Instead of the above call try something like: my $button = $main->Button();   The variable $button is how you refer to the Button widget in subsequent calls, such as when we call the pack routine: $button -> pack;   A complete script that incorporates these ideas to make a very plain button would look like: #!/usr/bin/perl -w use Tk; use strict; my $main = new MainWindow; my $button = $main -> Button(); $button -> pack; MainLoop;   But who wants such a plain looking button? You can provide a number of different widget configurations via calls to the configure routine as in: #!/usr/bin/perl -w use Tk; use strict; my $main = new MainWindow; my $button = $main->Button(); $button -> configure(-text => 'Press me!'); $button -> pack; MainLoop;   The Perl motto is "there is more than one way to do it." - perl/Tk remains quite true to this motto as well. Note that the above script could have been written quite succinctly without the use of either the $main or $button variables as: #!/usr/bin/perl -w use Tk; use strict; new MainWindow -> Button(-text => 'Press me!') -> pack; MainLoop;   But if you want your widgets to actually do things then you must set up callback procedures as discussed later...   Do not overlook the - sign in front of some options (like -text in the above example) Another commonly overlooked problem is that elements in a hash are supposed to be strings hence a configuration option like -length +> 5, really ought to be specified as either '-length' +> 5, or "-length" +> 5, etc., rather than perl's builtin length() function.   译文:   10. 如何使用某个组件来完成某个工作?   通过使用Perl/Tk的各种组件,并进行必要的配置和绑定,可以实现很多功能。当然,也有少数的一些无法完成或需要一定的技巧才能完成。建议初学Tk的朋友仔细的学习和试用UserGuide.pod中的例程。在下面的讲解中,我们也会谈到其中的一些例子。   基本上,要创建一个组件,只需要调用和他名称对应的子程序,例如:   my $main = new MainWindow;   上面的语句将使Perl解释器为这个新的MainWindow组件留出一些必要的系统内存等资源(但是这个主窗口并非立刻出现的,它要直到调用 MainLoop才会出现)。这样,上面创建的这个对象,以后就可以通过变量$main来调用了。例如,如果你想在你的这个主窗口中放置一个按钮,就可以这样:   $main->Button();   那么,实现上面的几个想法的一般“完整”的脚本如下(这里将创建一个空白的按钮):   #!/usr/bin/perl -w   use Tk;   use strict;   my $main = new MainWindow;   my $button = $main -> Button();   $button -> pack;   MainLoop;   但是谁会想要一个空白的按钮呢?其实,你可能通过使用configure方法对很多不同的组件进行配置。例如:   #!/usr/bin/perl -w   use Tk;   use strict;   my $main = new MainWindow;   my $button = $main->Button();   $button -> configure(-text => 'Press me!');   $button -> pack;   MainLoop;   众所周知,Perl的名言就是:做一件事情可以有多种方法。所以,Perl/Tk也同样信守了这一原则。其实,上面的脚本可以写的非常简洁,甚至不使用任何的变量($main和$button),代码如下:   #!/usr/bin/perl -w   use Tk;   use strict;   new MainWindow -> Button(-text => 'Press me!') -> pack;   MainLoop;   当然,如果你确实希望你的组件实现一些功能的话,你还必须让它们关联一些代码,这我们将在以后详细讨论……   最后,我们提醒大家不要忽略了在选项前面的“-”符号,例如上面例子中的-text。另外,值得一提的是,hash中的元素默认被当作字符串看待,所以我们使用的配置选项如:-length => 5,事实上应该写成:’-length’ => 5或”-length” => 5,这样才可以和Perl的内置函数length()相区别。
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