2

Here is some test code to illustrate my problem;


use Tk;
use POE qw( Loop::TkActiveState );
use Tk::Toplevel;

POE::Session->create(
    inline_states => {
        _start      => \&ui_start
        ,top1       => \&top1
        ,top2       => \&top2
#       ,kill_top1  => \&kill_top1
        ,kill_top1  =>  sub {
            $heap->{tl1}->destroy;
        }
        ,over       => sub { exit }
    }
);

$poe_kernel->run();
exit 0;

sub ui_start {
    my ($kernel, $session, $heap) = @_[KERNEL, SESSION, HEAP];
    $heap->{mw} = $poe_main_window;
    $but1 = $heap->{mw}->Button(
        -text => 'Exit',
        -width => 12,
        -command => $session->postback("over")
    )->pack( -padx => 7,
        -side => 'left',
        -expand => 0 );

    $but2 = $heap->{mw}->Button(
        -text => 'Top1',
        -width => 12,
        -command => $session->postback("top1")
    )->pack( -padx => 7,
        -side => 'left',
        -expand => 0 );
    $but2 = $heap->{mw}->Button(
        -text => 'Top2',
        -width => 12,
        -command => $session->postback("top2")
    )->pack( -padx => 7,
        -side => 'left',
        -expand => 0 );
    $but3 = $heap->{mw}->Button(
        -text => 'Kill TL',
        -width => 12,
        -command => $session->postback("kill_top1")
    )->pack( -padx => 7,
        -side => 'left',
        -expand => 0 );
}

sub top1 {
    my ($kernel, $session, $heap) = @_[KERNEL, SESSION, HEAP];
    unless(Tk::Exists($heap->{tl1})) {
        $heap->{tl1} = $heap->{mw}->Toplevel( title => "Top1");
    }
}   

sub top2 {
    my ($kernel, $session, $heap) = @_[KERNEL, SESSION, HEAP];
    $heap->{tl2} = $heap->{mw}->Toplevel( title => "Top2");
    $heap->{tl1}->destroy if Tk::Exists($heap->{tl1});
}   

sub kill_top1 {
    my ($kernel, $session, $heap) = @_[KERNEL, SESSION, HEAP];
    $heap->{tl1}->destroy if Tk::Exists($heap->{tl1});
}

If I uncomment the version of the inline state kill_top1, all is well. If I use the version (as shown) that calls the anonymous sub, I get;


C:\scripts\alias\resource>alias_poe_V-3_0_par.pl
 error:Can't call method "destroy" on an undefined value at C:\scripts\alias\res
ource\alias_poe_V-3_0_par.pl line 328,  line 365.

Tk::Error: Can't call method "destroy" on an undefined value at C:\scripts\alias
\resource\alias_poe_V-3_0_par.pl line 328,  line 365.
 Tk::After::once at C:/Perl/site/lib/Tk/After.pm line 89
 [once,[{},undef,100,once,[\&POE::Kernel::_poll_for_io]]]
 ("after" script)

In this posting [link text][1] Rocco Caputo explains;

"Tk is not passing the event information to POE.

As you know, postbacks are anonymous subroutine references that post POE events when they're called. They're used as a thin, flexible interface between POE and Tk, among other things.

Postbacks are blessed, and their DESTROY methods are used to notify POE when Tk is done with them. From Tk's point of view, the only difference between a callback and a postback is this blessing.

For some reason, Tk does not pass parameters to a blessed callback."

He gives a workaround, but I am not sure 1) if this is the issue I have uncovered or )2 if it is, how to apply the workaround.

[1]: http://osdir.com/ml/lang.perl.poe/2004-01/msg00002.html :Tk With POE - bind() function for keypresses"

4

1 回答 1

3

看起来您确实遇到了 Rocco 所描述的问题。基本上，您的闭包（sub {...}）可以访问 $heap，因为当您创建闭包时，$heap 就在范围内。另一方面，当您使用 &kill_top1 函数引用时，您似乎没有收到任何传入的参数，这意味着 @_[HEAP] 未定义。

使用闭包似乎有效，但如果你想“伪造”它，你可以将其替换为：

kill_top1 => sub { 
    @args[KERNEL,SESSION,HEAP] = ($kernel,$session,$heap);
    kill_top1(@args);
}

这将是我的偏好，只是为了保持 kill_top1 的接口和事件处理与所有其他接口相同。

于 2009-07-18T10:36:32.590 回答