In my Java application, I'm writing a component that is used to view PDF files. I had a pretty slick implementation where the user could click on the PDF and drag it to view the areas that didn't fit on the screen. But my boss didn't like it, so now I have to use scroll bars. So I did the obvious thing and just put it into a JScrollPane, but almost no matter what I do it refuses to work.
The PDF just gets converted to a BufferedImage and then I convert it to an ImageIcon so I can add it to a JLabel which gets added to a JScrollPane.
I have a PDFViewer class which subclasses JScrollPane, and the important code is here:
private void drawPDF() {
PDFRenderer renderer = new PDFDrawer(pdfFile);
BufferedImage image = renderer.makeImage(page);
JLabel img = new JLabel(new ImageIcon(image));
this.setViewportView(img);
}
Now I have a separate class which subclasses JFrame that I need to add my PDFViewer to.
It works as long as I don't use a layout and add the PDFViewer directly to the JFrame. If I even just add the JScrollPane to a JPanel and then add the JPanel to the JFrame the scroll bars disappear and it looks like I just added the JLabel directly. The image is too big for this, and it gets cut off easily.
I need to add some controls to the frame as well, so I set up a really basic GridBagLayout with the PDFViewer as the only component being added. And with the following code I get a window that looks like this.
GridBagLayout glayout = new GridBagLayout();
GridBagConstraints c;
setLayout(glayout);
PDFViewer viewer = new PDFViewer("foo.pdf");
c = new GridBagConstraints();
c.gridx = 0;
c.gridy = 0;
c.gridheight = 1;
c.gridwidth = 1;
add(viewer, c);
setVisible(true);
Why does the JScrollPane get smooshed like that when I just simply add it to a layout instead of directly to the JFrame? I found out that it works with GridLayout, but a GridLayout is not what I want.
You need at least ONE component with the weightx/y set to a non zero value for GridBagLayout to work.
You need to specify
c.weightx = 1;
c.weighty = 1;
c.fill = GridBagConstraints.BOTH;
This means that it will take all available space that is not used by other components. I suggest reading up on GridBagLayout for more information.
Try adding:
c.fill = GridBagConstraints.BOTH;
This should ensure that your panel is resized in both directions when you resize. Incidentally if this is the only component then consider using BorderLayout and adding the component to BorderLayout.CENTER.
c.weightx = 1.0;
c.weighty = 1.0;
c.fill = GridBagConstraints.BOTH;
before adding the viewer.
You need to set the preferredSize(), minimumSize() and maximumSize() of the component you are adding to the JScrollpane. Or you can set the cell to expand horizontally and vertically as far as possible by adding
c.weightx = 1;
c.weighty = 1;
c.fill = GridBagConstraints.BOTH;
to the GridBagConstraints.
Try setting prefferedsize(setPrefferedSize()) to the component which you are adding to ScrollPane.
Related
I'm trying to display two buttons next to a text field:
I gave up on the text already, but I really need the two buttons to remain small while the text field should expand with the window:
Currently, I use this layouts:
The text field and the two buttons are both in JPanel.
//JPanel group - the container
//List<JComponent> - the conponents added to JPanel
//int[] weights - weights of components
GridBagLayout lay = new GridBagLayout();
for(int i=0,l=fields.size(); i<l; i++) {
InputDef field = fields.get(i);
GridBagConstraints c = new GridBagConstraints();
if(weights.length<i) {
c.weightx = weights[i];
}
c.fill = GridBagConstraints.HORIZONTAL;
lay.setConstraints(field.getField(), c);
}
group.setLayout(lay);
In the documentation I see that for the components to fill their area horizontally, you should set the GridBagConstraints.HORIZONTAL to the constraints of the components.
Further, I read that you should set different GridBagConstraints#weightx to make the elements take different amount of space.
However running the code above doesn't do anything - the JPanel looks exactly the same with no layout manager whatsoever.
my problem is that although the scroll bar is appearing on the specific panel I want it to it's not extending as labels are added. I would like it to extend when the labels start going off the panel that they are being added to.
I have a main JPanel 'panel' which uses GridBagLayout, within that I have 5 other panels, the ones that needs a scroll bar is boardPanel which has null value for setLayout()
panel = new JPanel();
panel.setLayout(new GridBagLayout());
...
1Panel = new JPanel();
1Panel.setPreferredSize(new Dimension(480, 800));
1Panel.setLayout(null);
scrollPanel = new JScrollPanel(1Panel, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
...
c.weighty = 1.0;
c.weightx = 0.6;
c.gridx = 0;
c.gridy = 0;
c.gridheight = 3;
panel.add(scrollPanel, c);
...
I hope this is enough information, thank you so much for your help in advance.
Don't use a null layout!!!
Don't use setPreferredSize()!!!
Scrollbars will appear when the preferred size of the component is greater than the size of the scroll pane. By hardcoding a size you break this functionality.
Use a layout manager and the preferred size will change dynamically as you add components to the panel.
Read the Swing tutorial on Layout Managers
How do I add the JDesktopPane to JFrame using GridBagLayout and set its height and width. If I add JDesktopPane that contains JInternalFrame I don't get anything. But works well in case of GridLayout but the problem is I can't set my desired size in it as GridLayout splits equal space among each component added.
You will probably need to set the fill and weight attributes of the GridBagConstraints...
GridBagConstraints gbc = new GridBagConstraints();
gbc.weightx = 1;
gbc.weighty = 1;
gbc.fill = GridBagConstraints.BOTH;
This will cause the component to want to push to the limits of the container and will cause the component to fill it's cell within the grid
This override the components preferred size (for the most part)
Take a look at How to Use GridBagLayout for more details...
I have a form, and when it renders using pack, the textboxes have a nice default height. But when I resize it - or in this case, if I override getPreferredSize to make it larger on startup - the textboxes resize proportionally.
I keep going in circles trying to understand the layout manager classes... the related questions that are coming up seem like they're really close, but I'm just not following them!
In the class below, if I comment out the getPreferredSize overload, the textboxes are sized by the system to be "just right". Add getPreferredSize back, or resize manually, and the textbox proportions expand/contract with the form. There's got to be something simple I'm missing!
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.TitledBorder;
public class TestTextBox extends JFrame {
private JTextField jtfRate = new JTextField();//jtfAnnualInterestRate
private JButton jbtComputeLoan = new JButton("Compute Sentence");
// Constructor buids the panel
public TestTextBox() {
// a panel with the fields
JPanel p1 = new JPanel(new GridLayout(5, 2));
p1.add(new JLabel("Annual Interest Rate"));
p1.add(jtfRate);
p1.setBorder(new TitledBorder("This is a border with enough text that I want to see it"));
// a panel with the button
JPanel p2 = new JPanel(new FlowLayout(FlowLayout.CENTER));
p2.add(jbtComputeLoan);
// Put the panels on the frame
add(p1, BorderLayout.CENTER);
add(p2, BorderLayout.SOUTH);
}
#Override
public Dimension getPreferredSize() {
// This will help Pack to pack it up better
return new Dimension(600, 300);
}
public static void main(String[] args) {
TestTextBox jailCell = new TestTextBox();
jailCell.pack(); // Arrange controls compactly based on their properties
jailCell.setTitle("Calculate your Sentence");
jailCell.setLocationRelativeTo(null); // sure, center it, whatever
jailCell.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jailCell.setVisible(true);
}
}
Obviously, this is a case for a GUI layout tool. But this isn't production code, this is a Java class in which I'm trying my best to learn why it works - that way I'll know what the GUI tools are doing.
Update: Thanks to the answer I got, I was able to figure out the basics of the GridBag. It seems pretty closely related to HTML <table>s. It took much longer than it should have, mostly because I kept forgetting , c); to apply the GridBagConstraints to the control! Here's a sample of what the relatively simple add above turned into:
GridBagConstraints c = new GridBagConstraints();
c.fill = GridBagConstraints.HORIZONTAL;
c.gridx = 0;
c.gridy = 0;
p1.add(new JLabel("Annual Interest Rate"), c);
c = new GridBagConstraints();
c.fill = GridBagConstraints.HORIZONTAL;
c.gridx = 1;
c.gridy = 0;
c.weightx = 0.25;
p1.add(jtfRate, c);
The default behaviour of GridLayout is to provide each component with equal amounts of available space. This means, as you make the component larger, they will get bigger, as you make it smaller, the will get smaller.
You could use a GridBagLayout instead, which will allow you to layout your components in a grid pattern but control how much of the cell they should occupy...
Take a look at How to use GridBagLayout for more details...
Is there any method I could implement that will ensure each button within the pane maintains a minimum height? I have attempted using itembutton.setSize() method but it has no effect.
JPanel itemPanel = new JPanel();
itemPanel.setLayout(new GridLayout(0,1));
for(final Item i: list){
JButton itemButton = new JButton(i.getName());
itemPanel.add(itemButton);
}
JScrollPane itemPane = new JScrollPane(itemPanel);
itembutton.setMinimumSize(minimumSize) ?
Edit: Just found that, as this java tutorial seems to tell, there is no way to do that with GridLayout.
Each component takes all the available space within its cell, and each cell is exactly the same size
So I guess you'll have to try another layout. I can suggest (don't know if it's well suited but it works) GridBagLayout. Example with 2 buttons:
itemPanel.setLayout(new GridBagLayout());
GridBagConstraints c = new GridBagConstraints();
c.fill = GridBagConstraints.HORIZONTAL;
c.gridx = 0;
c.weightx = 0.5;
itemPanel.add(new JButton("A"), c);
c.gridx = 1;
c.weightx = 0.5;
itemPanel.add(new JButton("B"), c);
Have a look to http://docs.oracle.com/javase/tutorial/uiswing/layout/index.html