I have a text field to represent a name, and a combobox for registration type. Then, next to that I have a check box, but it's supposed to be underneath the other two fields. Here is what I have coded:
public RegPanel()
{
//create a new panel
new GridLayout(2,1);
//create one of two subpanels
subPanel = new JPanel(new FlowLayout());
//create a textfield
regTextField = new JTextField(20);
//create a combobox and don't let anyone add to it
regComboBox = new JComboBox(regOptions);
//create a border for the subpanel
subPanel.setBorder(BorderFactory.createTitledBorder("Registrant's Name & Type"));
//add regTypePanel and regBox to the panel
subPanel.add(regTextField);
subPanel.add(regComboBox);
//create a second subpanel with a flowlayout
subPanel2 = new JPanel(new FlowLayout());
//create a checkbox
regCheckBox = new JCheckBox("Dinner and Keynote Speech");
subPanel2.add(regCheckBox);
//add the subpanels to the main panel
add(subPanel);
add(subPanel2);
}
Any ideas what I am missing? Sorry for the crappy layout, I can't figure out how to fix the view.
So I realized I hadn't set the GridLayout right, so I changed that to "setLayout(new GridLayout(2,1));
But now on my gui, it totally screwed up the position of all the other elements.
Anyway new GridLayout(...) do nothing unless you use it in setLayout(...).
You can try using Box.createVerticalBox() (sample) instead of GridLayout to have your components in vertical alignment.
In your case, you are using
RegPanel (which layout?)
subPanel (FlowLayout)
regTextField
regComboBox
subPanel2 (FlowLayout)
regCheckBox
Which layout does your main RegPanel have? It has the default JPanel layout (if RegPanel is a subclass of JPanel), which is a FlowLayout. So, your RegPanel shows the two subPanels besides each other, which looks similar as if you had only one Panel with all the components. So, your RegPanel needs a LayoutManager, too - the GridLayout(2,1) seems okay (if you don't want to align the components in the two lines).
In my current project, I'm only ever using GroupLayout (apart from one occasional BorderLayout). It takes a bit to get used to (and a wrapper class to make the code easier to write and read), but for such form stuff, it seems ideal (when limited to the build-in Layout managers).
Also you might want to use a BorderLayout and realize that you nest one layout in another layout to achieve a different effect.
Have to mention MigLayout here as a great all-purpose layout manager -- it is extremely flexible and easy to use once you get to know it.
Related
I am attempting to create panel, PluginListPanel (extending JPanel), which will show a list of plugin panels which will respect the preferred height of the plugin's panel, but will force the width. I have a solution, but it is slow and has a weird bug. In the screenshot, there are two such panels, one to the left and one to the right:
I don't know different layout manager systems very well, but I know that the TOP field in the BorderLayout does what I want. So, I came up with this 'recursive' solution:
public PluginListPanel(List<PanelContainer> items) {
JPanel body = this;
for (PanelContainer item : items) {
body.setLayout(new BorderLayout(0, 0));
JPanel panel = new PluginOnePanel(item);
body.add(panel, BorderLayout.NORTH);
JPanel newBody = new JPanel();
body.add(newBody, BorderLayout.CENTER);
body = newBody;
}
}
The problem I encounter is when I scroll, the system responds somewhat slowly, and the colour of the SamplePluginPanels is different (see picture below), even if the number of SamplePluginPanels is as low as 8.
The question is, how can I make this more elegant, not slow down the program and not miscolour the panels?
Any insights are highly appreciated.
I think a vertical Box is the answer (actually 2, on both columns):
Box leftBox = Box.createVerticalBox();
Box rightBox = Box.createVerticalBox();
/* put them together */
setLayout(new GridLayout(2,1));
add(leftBox);
add(rightBox);
Also make sure, that the content of the scroll pane implements Scrollable and returns true, to scrollableTracksViewportWidth(). This will force equal widths.
I'm trying to create a JDialog like the Symbol dialog in Microsoft Word that you get by choosing Symbol... from the Insert menu. Basically, it's an n x m (n and m are not known until runtime) grid of small buttons. I've got a first version of this working nicely using a GridLayout. The problem is that when you resize the dialog (and there is a requirement that you should be able to resize it), the size of the buttons changes. I need the size of the buttons to remain constant.
But I want the dimensions of the grid containing the buttons to change. For example, if the dialog gets wider, but stays the same height, the number of rows should lessen, while the number of columns increases.
I've thought of a couple of ways to fix this:
When the dialog is resized, create a new GridLayout and repopulate it with the buttons. I'm going to try this and see how it looks, but it seems like a clumsy way of doing it.
Use some other type of layout such as a FlowLayout. I took a stab at this, but it put all n x m buttons in one row. I do not want to use horizontal scroll-bars and the buttons ran off the right edge. Anyway, it's supposed to be a 2-dimensional grid of buttons.
What is the best way to solve this layout problem?
Create a buttons panel with GridLayout and set a fixed size (could be calculated at runtime of course) to it. The buttons panel should be contained in a panel of BoxLayout.
Check out the BoxLayout Tutorial
Very Very basic example:
public static void main(String[] args) throws Exception
{
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel buttonPanel = new JPanel();
JPanel containerPanel = new JPanel();
buttonPanel.setLayout(new GridLayout(2,2));
buttonPanel.add(new JButton("1"));
buttonPanel.add(new JButton("2"));
buttonPanel.add(new JButton("3"));
buttonPanel.add(new JButton("4"));
buttonPanel.setPreferredSize(new Dimension(300, 400));
containerPanel.add(buttonPanel);
frame.getContentPane().add(containerPanel);
frame.pack();
frame.setVisible(true);
}
if the dialog gets wider, but stays the same height, the number of rows should lessen, while the number of columns increases.
Wrap Layout might be what you are looking for.
I had a similar issue with a single column of buttons, and found that MiGLayout (third-party, available here) was simple and effective for this. It helped both with making a grid and with setting button sizes, although it took me a day or two to get used to its syntax.
But the key is really setting button sizes; GridLayout certainly seems like the way to go for a layout that is, well, a grid. I haven't tested, but I suspect that the built-in setXSize() methods would work just as well. The GridBagLayout tutorial has examples of some things you can do with sizing/positioning.
FlowLayout would be the way to go but you might have some configuration problems. What layout manager does the parent component use?
BorderLayout does something strange. If I add two panels to a Container with the same constraint (BorderLayout.CENTER for instance), then the first one goes away, even if the second one is deleted or made invisible
It seems as though it would make sense for it to "stack" each element on top of the previous ones.
Is this correct and by design? If so, is there some documentation on it?
Has anyone else been frustrated by it? Have you a solution, such as a custom LayoutManager?
Sample code:
JFrame frame = new JFrame();
frame.setSize(500, 500);
JPanel panel1 = new JPanel();
panel1.setBackground(Color.blue);
frame.getContentPane().add(panel1);
JPanel panel2 = new JPanel();
panel2.setBackground(Color.red);
frame.getContentPane().add(panel2);
panel2.setVisible(false); // Seems like it should allow us to see panel1.
frame.setVisible(true);
This creates and displays a 500x500 blank box.
BorderLayout was simply not designed to do what you want. Separation of responsibility. If you want that behavior you should compose: combine the BorderLayout with a CardLayout. Though for the actual stack behavior, you'll have to code something yourself (or find someone who already has.)
Is this correct and by design?
Yes.
You need to understand the basics of how layout managers work. One of the jobs of the layout manager is to set the "location" and "size" of the components added to the panel. In the case of a BorderLayout it only tracks 5 components so only the last component added to the CENTER is known by the layout manager.
Layout management is not done when components are added to the panel. It is done when the frame is packed, or made visible (or the revalidate() method is invoked) . In this case the blue panel is not part of the components managed by the BorderLayout so its size remains (0, 0), which means there is nothing to paint.
Try changing your code to:
JPanel panel1 = new JPanel();
panel1.setSize(200, 200);
and you will see the blue panel painted at the specified size.
Now try commenting out:
//panel2.setVisible(false);
and you will see both panels. This is because as components are added to the panel they are assigned a ZOrder. Basically the last component added is painted first, which is why the blue panel is painted on top of the red panel. Check out the setComponentZOrder() method of the Container class for more information.
The CardLayout is probably the layout manager you should be using, but you can check out the Overlap Layout as well.
JPanel pMeasure = new JPanel();
....
JLabel economy = new JLabel("Economy");
JLabel regularity = new JLabel("Regularity");
pMeasure.add(economy);
pMeasure.add(regularity);
...
When I run the code above I get this output:
Economy Regularity
How can I get this output, where each JLabel starts on a new line? Thanks
Economy
Regularity
You'll want to play around with layout managers to control the positioning and sizing of the controls in your JPanel. Layout managers are responsible for placing controls, determining where they go, how big they are, how much space is between them, what happens when you resize the window, etc.
There are oodles of different layout managers each of which allows you to layout controls in different ways. The default layout manager is FlowLayout, which as you've seen simply places components next to each other left to right. That's the simplest. Some other common layout managers are:
GridLayout - arranges components in a rectangular grid with equal-size rows and columns
BorderLayout - has one main component in the center and up to four surrounding components above, below, to the left, and to the right.
GridBagLayout - the Big Bertha of all the built-in layout managers, it is the most flexible but also the most complicated to use.
You could, for example, use a BoxLayout to layout the labels.
BoxLayout either stacks its components on top of each other or places them in a row — your choice. You might think of it as a version of FlowLayout, but with greater functionality. Here is a picture of an application that demonstrates using BoxLayout to display a centered column of components:
An example of code using BoxLayout would be:
JPanel pMeasure = new JPanel();
....
JLabel economy = new JLabel("Economy");
JLabel regularity = new JLabel("Regularity");
pMeasure.setLayout(new BoxLayout(pMeasure, BoxLayout.Y_AXIS));
pMeasure.add(economy);
pMeasure.add(regularity);
...
I read this piece of code:
pMeasure.setLayout(new BoxLayout(pMeasure, BoxLayout.VERTICAL));
It seems BoxLayout doesn't have VERTICAL. Upon searching, this will work using the following code:
pMeasure.setLayout(new BoxLayout(pMeasure, BoxLayout.Y_AXIS));
Here is what you need to use:
JLabel economy = new JLabel("<html>Economy<br>Regularity</html>");
A quick way is to use html within the JLabel.
For instance include the <br/> tag.
Otherwise, implement a BoxLayout.
Make a separate JPanel for each line, and set the dimensions to fit each word:
JLabel wordlabel = new JLabel("Word");
JPanel word1 = new JPanel();
word1.setPreferredSize(new Dimension(#,#);
This should work for each word. You can then add each of those JPanels to your main JPanel. This also allows you to add other components next to each word.
Is it possible to add a JLabel on top of another JLabel? Thanks.
The short answer is yes, as a JLabel is a Container, so it can accept a Component (a JLabel is a subclass of Component) to add into the JLabel by using the add method:
JLabel outsideLabel = new JLabel("Hello");
JLabel insideLabel = new JLabel("World");
outsideLabel.add(insideLabel);
In the above code, the insideLabel is added to the outsideLabel.
However, visually, a label with the text "Hello" shows up, so one cannot really see the label that is contained within the label.
So, the question comes down what one really wants to accomplish by adding a label on top of another label.
Edit:
From the comments:
well, what i wanted to do was first,
read a certain fraction from a file,
then display that fraction in a
jlabel. what i thought of was to
divide the fraction into 3 parts, then
use a label for each of the three.
then second, i want to be able to drag
the fraction, so i thought i could use
another jlabel, and place the 3'mini
jlabels' over the big jlabel. i don't
know if this will work though..:|
It sounds like one should look into how to use layout managers in Java.
A good place to start would be Using Layout Managers and A Visual Guide to Layout Managers, both from The Java Tutorials.
It sounds like a GridLayout could be one option to accomplish the task.
JPanel p = new JPanel(new GridLayout(0, 1));
p.add(new JLabel("One"));
p.add(new JLabel("Two"));
p.add(new JLabel("Three"));
In the above example, the JPanel is made to use a GridLayout as the layout manager, and is told to make a row of JLabels.
The answer to your original question is yes for the reasons given that any Component can be added to a Container.
The reason you don't see the second label is because by default a JLabel uses a null layout manager and the size of the second label is (0, 0) so there is nothing to paint. So all you need to do is set the bounds of the second label and away you go.
You can't use a layout manager if you want to drag components around because as soon as you resize the frame etc, the layout manager will be invoked and the components will be repositioned based on the layout manager of the component.
it's a matter of layout.
you can do that using null layout (with hard coded locations) or with a custom layout.
you can use a JLayeredPane and set it's border to No Border.
you can add put them above each others by using the horizontal or vertical gap (hgap,vgap) the attributes of the layout
JPanel p = new JPanel(new GridLayout(2, 1,-40,0));
//the 40 is the hgap , make it the same with the label height .