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Re: What do you think of my CropImage class

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On Thursday 21 Jul 2016 15:35 CEST, Eric Sosman wrote:

> 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?)

Not really no: I just wanted to know if I could solve the problem of
cropping. ;-)

But about the things being static. There is always exactly one, so
what is the problem with things being static? If it is a real no-no I
could change it.


> - 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

I will look into it. I wanted to learn, now I have to. :-D


> ... 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.)

No, it was that I used a Panel instead of a JPanel. I copied that part
from somewhere of the internet. I found it a little bit strange that a
Panel was used instead of a JPanel, but I thought “What do I know”? I
changed it to JPanel and that problem went away. I had to add:
    super.paintComponent(g);
to the paint function (otherwise the old one stays ‘below’ the new one
and that is a problem when the new picture is smaller as the old one),
but that is a small price to pay. :-D

Next time I should listen to that little voice.


> 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?

I am going to try this out.


> - 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)?

I created the DispImage class to display the cropped image. And I am
going to use it to save it also. It is better to verify it before
saving it.


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

And something else I have to look into. I am happy to do, because I
found it much to verbose, but I did not know a better way.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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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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