I've got a custom component GameViewCanvas extends JPanel that will hold a number of tiles (800x800 textures). Now in GameViewCanvas I've overridden the paint() method, so that it will paint the children on a transformed canvas (zoom, panning and rotation).
I now want to delegate events like MouseEvent and MouseMotionEvent to the respective children - the problem of course being that Swing has no idea where the children are on the actual frame. I thought I might be able to just override a method like getComponentAt in the parent but no such luck - I figure Swing is looping through the children directly?
Maybe I'm going about this all wrong, so please advice.
Thanks in advance.
Take a look at JXLayer. It does exactly what you've just asked.
There are some excellent examples by Piet Blok, which have, unfortunately, disappeared off the net. To this end, I've made them available here.
Take a look at the TestWrapped demo in the pbjar source. It is probably the (among) the best example.
ps - JXLayer is now officially part of Java 7, known as JLayer
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I'm sorry this is probably way too basic to be on here, but it's a subject I've been struggling with for about a month now and I don't know where else to go (as far as I know there is no "noob overflow", lol).
I'm trying to create a class that would:
1. put an image on a window (a JFrame, JPanel or other container)
2. be able to support keyboard and mouse listeners
3. could have multiple instances in the same container
So anyway I've tried all the usual places - Google, YouTube, the official Java site (sorry forgot the URL) and of course here on Stack Overflow - but haven't been able to find anything even remotely similar to what I'm trying to do.
Of course, I've also considered the possiblity that maybe it can't be done at all. There doesn't seem to be any kind of standard "JImage" or "JGraphic" that works like JButton or JLabel, and for whatever reason graphics requires a completely different list of (extremely involved) processes and procedures. As an example, in this post: How to "really" draw images in a Java app - it took me 60+ lines of code and 2 classes to just come close. That project didn't work in the end because for some reason it would only let me create one instance (even it you created 2-4 in the main method, it would only display the last one you told it to add).
But anyway, assuming that I'm not trying to "re-invent the wheel" here and it is actually possible (in Java), does anyone have an idea as to how (or at least know of a better site to study it)? Unfortunately most of the sites I've visited tend to assume you know all the inner workings of images (I know what a pixel is but that's about it - Buffers, Rastars etc. are still beyond me). It would be absolutely outstanding if there were a site that would explain it in layman's terms, if such a site exists. Thanks in advance.
Just use a plain old JLabel.
Regarding your requirements:
put an image on a window (a JFrame, JPanel or other container).
You can give a JLabel an ImageIcon of the image of interest and it will display it. This can then be easily placed in any other container such as a JPanel or JFrame.
be able to support keyboard and mouse listeners
Any component that extends JComponent, such as a JLabel allows for use of MouseListener, MouseMotionListener and can listen for keyboard input via Key Bindings.
could have multiple instances in the same container
You can add as many as you'd like to any container. Just be cognizant and respectful of the layout managers in use.
I fear I'm just making a ten-times duplicate question, but I've been trying to Google this for quite some time without finding anything, neither in general nor even here on SO, so I'm starting to think it's worth a shot.
I'm wondering, is there a good guide on what is necessary to implement an AWT widget in Java? What needs to be implemented in order to respond to such things as redrawing, resizing, placement, focus behavior and all other such things as widgets may or should do, in a proper manner? All the articles I manage to find describe the process from the perspective of a user of widgets, never from the perspective of the one implementing them.
Also, what would be the primary differences between implementing an AWT widget and implementing a Swing widget? Is there even a difference from the implementer's point of view?
Probably the best way to learn how to write an AWT widget would be to look at the source code for an AWT widget. Here's the source code for the java.awt.Frame class.
I haven't worked with AWT much, but Swing is much better from the GUI developer's point of view. The only difference that I know about from the implementer's point of view is Swing's usage of Listeners.
Again, you can look at the source code to see what's different. Here's the source code for the javax.swing.JFrame class
Not too much difference aside from the fact that AWT widgets are simpler.
You extend one of the 4 classes: Component, Container, Canvas, Panel. The first two are heavyweight, the latter two are lightweight (don't have native window system peers). Override paint(Graphics) (or update()) and getPreferredSize() to make it visible, then look into javadocs for overriding event handling methods.
Sure you know this link, http://docs.oracle.com/javase/6/docs/api/java/awt/Component.html
Is there any way to create a custom component in swing. By custom I mean say right now I am able to create a circle and do actions like dragging it etc.
But now I also want that along with the circle a text label with its number is also present. Can we combine them into a new type of component where say we can do actions on it collectively?
If yes please give me pointers on how to do so.
Yes, just extend JComponent and handle painting and interaction however you want. If there is a component that already does most of what you want you could extend that class and tweak it slightly.
I would suggest reading some of the tutorials about how JComponent works:
http://download.oracle.com/javase/tutorial/uiswing/components/jcomponent.html
Here is a similar question but I am sure you can find more specific ones that have been asked once you get deeper into it.
How to create a custom Swing Component
The Swing tutorial as a whole if very useful to understand how other components work etc.
http://download.oracle.com/javase/tutorial/uiswing/components/index.html
You can create your own Swing component extending JComponent. Several question here on Stack on the topic like this one.
Personally, I advise you to get this book: Java Swing as it contains an excellent guide on how to create Swing components.
I'm trying to build a new java swing component, I realise that I might be able to find one that does what I need on the web, but this is partly an exercise for me to learn ow to do this.
I want to build a swing component that represents a Gantt chart. it would be good (though not essential for people to be able to interact with it (e.g slide the the tasks around to adjust timings)
it feels like the best approach for this is to subclass JComponent, and override PaintComponent() to 'draw a picture' of what the chart should look like, as opposed to doing something like trying to jam everything into a custom JTable.
I've read a couple of books on the subject, and also looked at a few examples (most notably things like JXGraph) - but I'm curious about a few things
When do I have to switch to using UI delegates, and when can I stick to just fiddling around in paintcomponent() to render what I want?
if I want other swing components as sub-elements of my component (e.g I wanted a text box on my gantt chart)
can I no longer use paintComponent()?
can I arbitrarily position them within my Gantt chart, or do I have to use a normal swing layout manager
many thanks in advance.
-Ace
I think that the article i wrote a few years ago for java.net is still correct today. Doing everything in one monolithic class gets you going faster in the beginning, but becomes a mess quite fast. I highly recommend doing the separation between the model (in your main class) and the view (UI delegate). The view is responsible for:
interaction with the user - mouse, keyboard etc.
painting
creating "worker" subcomponents as necessary
In the medium and long run this is the approach that has been validated over and over again in the Flamingo component suite, which you can use as an extra reference point (in addition to how core Swing components are implemented).
Using UI delegates is a good idea if you think that your component should look different for different Look And Feels. Also it is generally a good idea from design point of view to separate you presentation from your component
Even when overrding paintComponent you can still put any sub components on it.
Using null layout you arbitrarey position your components. Alternatively you can use layouts too.
Here is a very good starting point for you.
I wonder if there's a good documentation (or a (viewable) ebook) about
the lifecycle of Swing components.
Is "lifecycle" the correct term, anyway?
I hope to find answers to question such as:
How, when, in which order painting methods are called?
How, when, which events are called by whom?
What is the exact sequence of method calls for component creation?
From time to time I encounter strange behavior of my apps, for example:
ComponentListener's resize event is called before setVisible(true)
(so that root pane has negative dimensions!)
Some components are laid out correctly only after resizing the JFrame by hand
Changing a super class from JPanel to JLayeredPane causes my class
to be laid out differently inside an other container.
And lot of other strange things...
I had the same question long ago.
I can't believe how hard is to find a good resource about this topic in the internet.
Fortunately I've found this link and now I have it in my bookmark with golden tag. :)
A Swing Architecture Overview
Once you have a good grasp of how they work conceptually you will be able to fix most of the problems you mention.
I hope it helps.