Does anyone know the rational for Java Frames and JFrames being set to invisible by default?
i.e. you have to call myFrameObject.setVisible(true) or you end up with an invisible application interface.
This has been bugging me since you don’t see this in other languages like C# or Objective-C. I was wondering if it was intended to be a time-saver or if the Java architects were just having a bad day.
Knowing this will help me understand the ultimate answer to life, the universe, and everything.
I always assumed it was so you could populate the window before displaying it. Otherwise you could see a bunch of controls shuffle around as they were added. Probably not a noticeable problem with todays machines + JITs, but in the early days of Java with slower machines and bytecode interpreters in the JVMs it might have made a difference.
It also mimics the way top-level windows work in X11: you create the window, and then later you "map" it (make it visible).
Remember, Swing components are not real components from the OS point of view. Every Swing component needs to be "realized". This is done by invoking the pack() or setVisible() methods. Only at this time will the Swing component be mapped to a peer component of the OS.
And remember when you add components to a visible GUI the components will not appear anyway because you need to invoke the layout manager to layout all the components. So even if the frame was visible automatically, in this case you would still need to invoke frame.validate() to make sure the components are layed out properly.
I think it is a better design to add all the components and then make it visibile once you have finished adding everything to the frame. This way you only layout the components once, not after every component is added. Maybe with other languages that use absolute sizes and positioning this is not a big deal because they don't have the concept of layout managers.
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I am a self-taught java developer and I use IntelliJ IDEA for Java. Recently I saw a video on youtube in which the guy was using NetBeans and in his JFrame form, he was able to freely place his objects like JButton, JTextFeild, JLabel, etc. I am not able to figure out how to do that. In IntelliJ IDEA I found several layout managers such as Border, Card, Grid, Bag, etc. but none of them gave the desired result. can somebody please tell me how can I get a layout manager in which I can freely place all my objects and also freely resize them without any restrictions? Thank you in advance for any help.
In swing every component extends Container. That means that every component can have nested components (they all have add(Component) method). However, not all of them support the layout-ing of nested components.
What I want to say is, that you can add a component to a JButton, but a JButton is not capable of showing its nested components.
So, in order to have nesting, we use the components - containers that support the orientation of their nested components.
These components are all windows (JFrame, JDialog, etc...) and JPanels. There some others that support layout-ing a specific type of nested components. For example a JMenu is capable of showing JMenuItems properly.
Now, these "top-level"/empty containers are using Layout Managers in order to align-show their nested components. Based on the container's layout manager, the components are shown.
This is why you can't "freely" place the components into a JFrame. Because its Layout Manager is taking care of the components will be placed. So, what you are looking for, is to change its LayoutManager (use setLayout method) to one that allows you to freely place the components.
Guess what? There is no such layout manager. Simply because, it would have nothing to do/calculate since you are taking care the layout of the components. So, in order to achieve the "free" component layout, you must use jframe.setLayout(null);. In order to layout the components after it, you will have to use componentInsideJFrame.setBounds(...) and give it constant coordinates /dimension.
This is bad practice. A very bad one when it comes to UI. Giving a component static coordinates and dimension is bad. There are some questions you have to ask yourself.
What if user resizes the window? If the window is 301x301, the center of it, is at (150,150). So you place a component at (150,150). Ok it works. Now user resizes the window and makes it 501x501. The center is now standing at (250,250). But the component is staying at (150,150). There is the solution of setResizable(false), to this kind of problems, but how often have you used "uncapable of resizing" applications? What if user wants to resize it?
I hope you get it and understood what I am trying to say.
By using layout managers, you are solving this kind of problems easily, since the layout manager will take care of the resize and calculate the new center.
Yes. I know it feels weird, but all these youtube tutorials are not teaching you the correct way to make Swing GUIs. (This is a conversation for another day, I guess)
I truly suggest you read the tutorials of Swing documentation in order to get some ideas of how layout managers work. You will really benefit from those.
Finally, I suggest you to leave outside the whole "gui-builder-tool" thing. They seem to help you building your GUI, but they are adding so much additional/useless code and most of the times they are "bad UI creation" prone. Try to code the GUI by yourself.
At first, this sounds a bit harsh, but you can always run your application and see the result of the GUI. After some mistakes, you will finally be able to imagine the GUI result by only seeing the container.setLayout(..) and container.add(...) lines.
When creating Swing GUI's, how can I best choose the horizontal and vertical gaps to be used to separate components? Something like asked here Windows Layout Look and Feel, but platform independent.
Generally I simply used 5 pixels for everything, that looked reasonable with the Windows Classic theme, but looks somewhat odd when running under Windows 8, especially when there are multiple nested container components (e.g. Dialog -> TabbedPane -> ScrollPane).
I have looked at UIDefaults, but there doesn't really seems to be any hints about component spacing there (I was hoping to find at least a few values that could be used as hints, but LayoutManagers seem to generally use hardcoded deafults, e.g. FlowLayout uses a hardcoded 5 pixel spacing).
What approaches can I take to make my layouts more look and feel aware (I am generally using the System Look and Feel) ?
If you want a layout of components that change a bit to fit your user's platform, then perhaps just use the user's system look and feel with:
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
Edit to provide solution for specifying more specific gaps.
To specify margin and padding between components you can try using a box layout. You might not need to use a box layout throughout the entire Swing code you have either, perhaps have a utility function you use right before you add a component that accepts a Swing component, and a left right top and bottom margin/padding. This function would then return you a JPanel with a box layout with the margin/padding passed, along with containing one component, the one you passed in.
Recently, I started creating a program for the company I work for. Just as background info, I'm still a student and a beginner programmer, so my solution is probably not recommended and I didn't know how to do it otherwise, but it works and I'm not going to be judged for it because it's a student job totally unrelated to programming.
The thing about the program is, it's going to be run on multiple different computer with different screen sizes and resolutions (800x600 and up). To make sure it takes as much of the screen as possible without losing any part of the program, I set the layout to null and hard-coded everything using relative values.
The program is kiosk-style and I first get the screen size values and go from there (for example, off the top of my head, the left-side menu takes an eighth of the screen, the top bar 2%, etc.). I also use font metrics to make sure the components are sized correctly and that everything gets displayed nicely.
My question is: why is it so frowned upon to make the layout null instead of using the layout managers? (I was told on some forums that this is a horrible way of doing things) I know how the layout manager works and know how to use the different layouts, but for the requirements of this program (multiple different resolutions, custom button shapes and placements, text changing on the components when you change language, etc.), I couldn't see myself using the layout managers to do it all.
How do you more experienced programmers use the layout managers in a situation like this? And what do you do when you want a button to be somewhere specific and other components somewhere else specific that don't really match any of the predefined layouts?
If you layer the layout managers correctly the screen will re-flow to different sizes for you, the idea is to use a single set of layout managers on ALL screen sizes.
If you use null you will have to do each screen size yourself. Not only that but if the app can be windowed you have to support every possible size they might scroll to.
That's kind of difficult to do, but the layout mangers are designed to do just that.
There are some common tricks. BorderLayout is a great layout to start with. Sometimes you might use it at multiple levels--often with just 2 or 3 components in it. That's because it's really good at giving all but one area the minimum required area and giving everything else to the CENTER.
FlowLayout can be useful but it's tricky if your components are different sizes.
I wouldn't try GridBagLayout unless you are planning to write code to feed your layout manager (an excellent solution at that!).
I also wouldn't use GUI builders, they don't know the overall way you want to reflow your layout.
In a nutshell: because all the work that you explain above is done (or at least: should be done) by the layout manager.
More often than not, when a null layout is used, it also implies that all positions and sizes are hardcoded to a single value, so no flexibility at all is given. This means that changes in window size, language, font size, display density or any other related parameter have no effect on the layout and you get the usual ugly effects: empty parts of the window; tiny, unresizable lists; buttons with their labels cut off; ...
It sounds like the work you do should really be done by the Layout Manager. Either find one that does that (my personal suggestion would be MiGLayout, which does a lot and is easy to use) or write your own.
You are practically using a layout - your own, with all your sophisticated calculations of positions.
You can move these logic to a custom layout manager class to pacify the critics.
hmmm trick should be by mixing LayoutMangers and by usage of numbers of nested JPanels that each could have diferrent Layout or not, really depends of number of JComponents, that allows you to create GUI that looks like as layed by using AbsoluteLayout but with same look/output to the GUI for every screen resolutions and ratio (4:3, 16:9, 16:10)
is it possible using swing, to build a GUI whose elements, when the GUI is resized, keep te proportion between themself? Or i should fire a "resize every GUI component" function when the resize event occurs?
I'm using Netbeans 6.9
Long ago, there was a very interesting article series on JavaWorld about "transmogrifying widgets" by Allen Hollub. This serie explain how, using different widgets to sho the same information, a calcoulator can have different styles when viewed with different dimensions.
However, for a far simpler (but far less powerful) approach, you should take an in-depth look to GridBagLayout and the (now famous) GBC class. This will give you a fast, and quite elegant, method to resize your whole UI with interesting resizing behaviours (oh and don't forget the associated tutorial).
I think that using traditional layout techniques is the best way to go - you generally want to choose which components resize and how they do it. However, if you really want a proportional resize then have a look at this answer:
java swing resize
I am creating an application which has a scrollable and scalable (zoomable) view. Inside this view I want to place other components (most of them customized JPanels and JInternalFrames).
Things such as fonts and borders, and sub-elements such as buttons don't need to be scalable. Only dimensions and position of container components should be.
What do you think, what is a good way to implement scalable components?
EDIT: I'm talking about resizing the entire layout including all
components. Please think of something such as a visual UML editor with zoom functionality.
My alternatives are:
Create a custom layout manager;
Create custom resizeable sub-components;
Create a custom container which would take care of resizing its sub-components;
Do something else?
Possible problems:
Boilerplate code;
Necessity to provide access to additional custom properties of components;
Not straightforward (inconsistent) representation of components in code.
Something else?
This is why layout managers exist: they tell contained components where and how large they should be.
Since you're talking about a UML editor, are you using contained Swing components to represent the various objects in the diagram (eg, a component for a class)? If yes, then you've got a lot of work ahead of you (although it's not necessarily a bad approach). I'd recommend creating a constraints object that identifies the object's location on a "unit space," then multiplying by the current size.
I've done that by creating a custom layout manager. Every component (or rather component class) on the frame has a marker whether or not it shall be resized when the container is resized (e.g. tables are resized, buttons are not). Those which are not resized are moved when the container is resized.
This is used to make resizeable forms without any manual setup, i.e. forms are defined by just specifying x/y/length/width for each component (no further alignment info).
If I look at this problem as visual UML editor then I had to think about single "canvas" component drawing each element as graphical object with base aspect ration and zooming in/out. I can't see reason for list of components aligned within parent container.
I started a similar solution that works fine without touching the original layout.
It's as easy as this:
// Install scalable layout and CTRL+/CTRL- keys for scaling operations
ScalableLayoutUtils.installScalableLayoutAndKeys(new DefaultScalableLayoutRegistry(), frame, 0.1);
It's still under work but It will be soon available as part of the next "utils4swing" version.