Perl/Tk FAQ - 10. 如何使用某个组件来完成某个工作

　　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

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