Groups > comp.lang.java.programmer > #35043

Re: What do you think of my CropImage class

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From	Eric Sosman <esosman@comcast-dot-net.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: What do you think of my CropImage class
Date	Thu, 21 Jul 2016 09:35:15 -0400
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On 7/21/2016 5:58 AM, Cecil Westerhof wrote:
> I was not completely clear :'-( so here some more info.
>
> I have no real experience with Swing and had an itch to scratch.
> That is why I wrote this program: to get some experience with
> Swing and get a little tool to make my live a little easier.
> [...]

     I have not studied your code closely, but one thing jumps out:
You're doing Swingthings on the wrong thread.  Almost all of Swing
is thread-unsafe, and almost all manipulation of Swing objects
must occur on the Event Dispatching Thread, or EDT.  Your code
breaches this requirement:

     - It constructs a pair of JLabels on whatever thread loads and
initializes the class.  (And the JLabels are static, which is so
very odd as to be downright weird.  Have you thought this through?)

     - It constructs a bunch of Swing components on whatever thread
executes main().  Furthermore, it manipulates those components (setting
bounds, etc.), and even makes the JFrame visible -- all while running
on the same wrong thread.

     Don't Do That.  See

http://docs.oracle.com/javase/tutorial/uiswing/concurrency/index.html

... for a discussion of the issues, and how to deal with them.  (I
rather suspect that the "flicker" you report may have its origins
in, er, wrong-threadedness.)

     A few other random remarks:

     - You mention that "for me pack did not work," which is sort of
weird.  I don't know what you tried before you settled on absolute
positioning, but I wonder: Could your layout troubles have anything
to do with the fact that CropImage extends Panel instead of JPanel?

     - Maybe not, but then: What is the purpose of the DispImage class?
What does it accomplish that couldn't just as well be done in the
containing CropImage class (if the latter were a JPanel)?

     - There's a handy MouseAdapter class that can eliminate some
verbosity in your MouseListener implementation.

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

Thread

What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-20 09:15 +0200
  Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-20 11:12 +0200
  Re: What do you think of my CropImage class Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2016-07-20 10:02 -0700
    Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-20 21:14 +0200
      Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-20 12:50 -0700
        Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 12:11 +0200
          Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 14:19 +0200
      Re: What do you think of my CropImage class Qu0ll <qu0ll64@gmail.com> - 2016-07-21 05:53 +1000
      Re: What do you think of my CropImage class Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2016-07-20 13:46 -0700
        Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-20 13:59 -0700
          Re: What do you think of my CropImage class Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2016-07-20 15:40 -0700
          Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 12:27 +0200
            Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-21 05:17 -0700
              Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 17:43 +0200
                Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-21 08:59 -0700
                Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 19:10 +0200
                Re: What do you think of my CropImage class Arne Vajhøj <arne@vajhoej.dk> - 2016-07-23 21:47 -0400
                Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-25 04:51 -0700
                Re: What do you think of my CropImage class Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2016-07-25 15:01 -0700
                Re: What do you think of my CropImage class Arne Vajhøj <arne@vajhoej.dk> - 2016-07-25 21:06 -0400
                Re: What do you think of my CropImage class Arne Vajhøj <arne@vajhoej.dk> - 2016-07-25 21:09 -0400
            Re: What do you think of my CropImage class Nigel Wade <nmw@local.domain> - 2016-07-21 15:44 +0100
              Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 17:46 +0200
        Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 12:25 +0200
          Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 14:16 +0200
    Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 12:05 +0200
      Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 13:23 +0200
      Re: What do you think of my CropImage class Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2016-07-21 07:58 -0700
        Re: What do you think of my CropImage class Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-21 11:13 -0400
          Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 18:12 +0200
        Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 17:49 +0200
  Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 11:58 +0200
    Re: What do you think of my CropImage class Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-21 09:35 -0400
      Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-21 09:03 -0700
        Re: What do you think of my CropImage class Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-21 12:39 -0400
      Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 18:07 +0200
        Re: What do you think of my CropImage class Nigel Wade <nmw@local.domain> - 2016-07-21 17:23 +0100
        Re: What do you think of my CropImage class Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-21 12:56 -0400
      Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 19:03 +0200
        Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-21 10:25 -0700
          Re: What do you think of my CropImage class Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-21 14:24 -0400
            Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-21 11:54 -0700
          Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 20:25 +0200
            Re: What do you think of my CropImage class Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-21 15:37 -0400
              Re: What do you think of my CropImage class Martin Gregorie <martin@address-in-sig.invalid> - 2016-07-21 21:30 +0000
              Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 23:52 +0200
                Re: What do you think of my CropImage class Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-21 20:35 -0400
                Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-22 04:21 +0200
                Re: What do you think of my CropImage class Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-07-21 22:44 -0400
                Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-22 10:27 +0200
                Re: What do you think of my CropImage class Martin Gregorie <martin@address-in-sig.invalid> - 2016-07-22 10:47 +0000
                Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-22 05:16 -0700
                Re: What do you think of my CropImage class Nigel Wade <nmw@local.domain> - 2016-07-22 15:10 +0100
                Re: What do you think of my CropImage class Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2016-07-22 07:47 -0700
                Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-22 10:21 -0700
    Re: What do you think of my CropImage class Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2016-07-21 08:30 -0700
      Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 18:19 +0200
        Re: What do you think of my CropImage class Eric Douglas <e.d.programmer@gmail.com> - 2016-07-21 10:18 -0700
          Re: What do you think of my CropImage class Cecil Westerhof <Cecil@decebal.nl> - 2016-07-21 20:12 +0200

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