I've created a simple user interface in Swing but the setSize command does not appear to be working. Can anyone tell me what the problem is?
import java.awt.Container;
import javax.swing.*;
public class UserInterface1 {
private JTextField outputArea = new JTextField();
private JTextField errorReportArea = new JTextField();
private JPanel inputPanel = new JPanel();
public UserInterface1() {
JFrame frame = new JFrame("Fuel Station");
frame.setSize(500, 500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
outputArea.setEditable(false);
errorReportArea.setEditable(false);
Container contentPane = frame.getContentPane();
contentPane.setLayout(new BoxLayout(contentPane, BoxLayout.Y_AXIS));
contentPane.add(outputArea);
contentPane.add(errorReportArea);
contentPane.add(inputPanel);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
UserInterface1 test = new UserInterface1();
}
}
Swing Frame setSize
The right answer to this is don't do that!
Even when we know the size of the content of a frame must be (e.g.) 500x500 px, we should not be guessing the size of the frame, which will vary by platform.
pack() knows how big to make the frame. We don't, so we should use it.
The size of the text fields can be specified using a font size and the number of columns.
The right size for inputPanel can be determined from the content within it.
Replace:
frame.setSize(500, 500);
by
frame.setPreferredSize(new java.awt.Dimension(500, 500));
It's because pack() resizes the frame to fit the dimensions of its contents or the preferred size, so you can remove the pack() call, or add a preferred size with setPreferredSize() method
Related
This question is very similiar to this: JScrollPane doesn't top align when there is more than enough space to show the content I tried this solution, but it does not work.
When I add a jlabel to jscrollpane, when the jlabel is small, the label becomes centered. It works normally when the scrollbar shows. Setting boxlayout does not change anything. I feel like this isn't working properly because I'm setting a perferred size to the panel? But if I remove the line panel.setPreferredSize(new Dimension((int)(screenSize.width*0.7 - 50), screenSize.height-150)); The label becomes small when there is no text, and grows to accomdate text, which I don't want. If I add the panel instead of the label, it makes the screen scrollable even though there isn't text?
This is my code:
public class Test {
// JFrame
static JFrame frame = new JFrame("Test");
//panel 1
static JPanel panel = new JPanel(new BorderLayout());
// label to display text
static JLabel label = new JLabel();
//scroll panel in main method
public static void main(String[] args) throws Exception {
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
label.setBorder(new EmptyBorder(5, 5, 5, 20));
label.setText("any text makes it centered beyond 40 lines");
//create panel
panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));
panel.add(label, BorderLayout.NORTH);
panel.add(Box.createVerticalGlue());
panel.setPreferredSize(new Dimension((int)(screenSize.width*0.7 - 50), screenSize.height-150));
panel.setBorder(new EmptyBorder(5, 5, 5, 10));
JScrollPane jspanel = new JScrollPane(label, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
//jspanel.add(label, BorderLayout.CENTER);
jspanel.setPreferredSize(new Dimension((int)(screenSize.width*0.7 - 70), screenSize.height-180));
jspanel.getVerticalScrollBar().setUnitIncrement(20);
jspanel.setBorder(BorderFactory.createEmptyBorder());
jspanel.setAlignmentX(JScrollPane.LEFT_ALIGNMENT);
jspanel.setAlignmentY(JScrollPane.TOP_ALIGNMENT);
//panel.setPreferredSize(new Dimension(640, 480));
//frame.add(panel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(jspanel);
frame.setSize((int)(screenSize.width*0.7), screenSize.height - 50);
frame.revalidate();
frame.pack();
frame.setVisible(true);
}
}
jspanel.setAlignmentX(JScrollPane.LEFT_ALIGNMENT);
jspanel.setAlignmentY(JScrollPane.TOP_ALIGNMENT);
That will align the scrollpane in its parent container, depending on the layout manager being used. It does not affect the alignment of any component added to the scrollpane. It is not needed.
the label becomes centered
The label is sized to fill the entire space available, so you need to customize how the text of the label is painted.
If you don't want it centered then you can place it at the top using:
label.setVerticalAlignment( SwingConstants.TOP );
After reworking your code, I came up with the following GUI.
I added a call to the SwingUtilities invokeLater method. This method ensures that all Swing components are created and executed on the Event Dispatch Thread.
I eliminated all static references, except for the main method.
I reworked your code into methods so I could focus on one part of the GUI at a time.
Here's the complete runnable example. This is a minimal reproducible example.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.border.EmptyBorder;
public class JScrollPaneTestGUI implements Runnable {
public static void main(String[] args) {
SwingUtilities.invokeLater(new JScrollPaneTestGUI());
}
#Override
public void run() {
JFrame frame = new JFrame("JScrollPane Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JScrollPane jspanel = createJScrollPane();
frame.add(jspanel, BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
}
private JScrollPane createJScrollPane() {
JPanel panel = new JPanel(new BorderLayout());
panel.setBackground(Color.YELLOW);
panel.setPreferredSize(new Dimension(400, 300));
JLabel label = new JLabel();
label.setBorder(new EmptyBorder(5, 5, 5, 20));
label.setText("any text makes it centered beyond 40 lines");
//create panel
panel.add(label, BorderLayout.NORTH);
JScrollPane jspanel = new JScrollPane(panel);
return jspanel;
}
}
I have two JPanel to place inside a JFrame, I want them both to occupy the full width of the frame but I don't know how. Also I'm not a big fan of the setBounds() method so I was wondering if there is a way to just make the component take the full width and just specify the desired height after.
Here is my code:
public class Test extends JFrame {
public Test() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(400, 400);
setLocationRelativeTo(null);
setLayout(new BorderLayout());
JPanel header = new JPanel();
header.setBounds(0,0,300,50);
header.setLayout(new BorderLayout());
header.setBackground(Color.gray);
JPanel body = new JPanel();
body.setBounds(0,50,300,300);
body.setLayout(new BorderLayout());
body.setBackground(Color.black);
add(header, BorderLayout.NORTH);
add(body, BorderLayout.CENTER);
//setLayout(null);
setVisible(true);
}
}
You need to remove the setLayout(null), this reverses the work of the earlier setLayout(new BorderLayout())
You then need to set the preferred size of both the header and body using setPreferredSize instead of using setBounds()
public Test() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(400, 400);
setLocationRelativeTo(null);
setLayout(new BorderLayout());
JPanel header = new JPanel();
header.setPreferredSize(new Dimension(400, 50));
header.setLayout(new BorderLayout());
header.setBackground(Color.gray);
JPanel body = new JPanel();
body.setPreferredSize(new Dimension(400, 300));
body.setLayout(new BorderLayout());
body.setBackground(Color.black);
add(header, BorderLayout.NORTH);
add(body, BorderLayout.CENTER);
setVisible(true);
}
The basic answer is, you need to take advantage of the layout management framework.
Layout managers work by taking into consideration the preferred/minimum/maximum size of a component - beware though, these are guides only and layout managers may ignore some or all of them based on their needs and the available space.
This is a simple example which overrides the getPreferredSize method of the header to return a "desirable" size:
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setLayout(new BorderLayout());
JPanel header = new JPanel() {
#Override
public Dimension getPreferredSize() {
return new Dimension(300, 50);
}
};
header.setLayout(new BorderLayout());
header.setBackground(Color.gray);
// I would allow the content of the panel determine the actual size
// but I've overridden `getPreferredSize` for demonstration purposes
JPanel body = new JPanel() {
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
};
body.setLayout(new BorderLayout());
body.setBackground(Color.black);
frame.add(header, BorderLayout.NORTH);
frame.add(body, BorderLayout.CENTER);
// pack is preferred over setSize, as it will "pack" the window around
// the content, which will produce a more consistent result
frame.pack();
frame.setVisible(true);
The problem with doing this is, the component will no longer take into consideration the sizing requirements of its children, so you might end up with some strange side effects.
There are other solutions which might provide some other advantages and disadvantages and you'd need to consider them for your use case.
Why override getPreferredSize rather then calling setPreferredSize?
Mostly, control. You can prevent other parts of the code from modifying the state and you control "how" the calculation gets done. Sure, nothing stops other codes from extending the component and overriding the method as well, but that's more complicated and doesn't take into consideration scenarios where an instance of the component is provided, rather than created.
Why use pack over setSize?
pack will "pack" the window frame around the content, so the content will always match its preferred size, rather than shrinking the content so that the frame decorations can be accommodated. It will, overall, generate a more consistent result across multiple platforms
i'm new in java .
i just learn JPanel and JFrame.
i got this note from java software solutions:
" The pack method of the frame sets its size appropriately based on
its contents—in this case the frame is sized to accommodate the size
of the panel it contains."
so i wrote this code :
public static void main (String [] args){
JFrame frame = new JFrame("test");
JPanel panel = new JPanel();
JLabel label1= new JLabel("");
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
//frame.setSize(1000, 500);
frame.getContentPane().add(panel);
Color darkBlue = new Color(8,40,94);
panel.setSize(1000, 500);
panel.setBackground(darkBlue);
}
but it the result is a really tiny window that i should maximize it with mouse to see the content
but when i set frame size every thing work great!
and i use Ubuntu.
so what's the reason of this problem?
From the order of your code:
JFrame frame = new JFrame("test");
JPanel panel = new JPanel();
JLabel label1= new JLabel("");
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
You did not add anything into the frame before you pack() it. pack() means let the frame decide its size based on the components being added to it.
Since you have no components added to it before you pack() it, you receive a small window with visually nothing inside (until you resize the window).
When the frame is being resized, paintManager will be consulted to paint the contentPane, hence if you add before pack(), not only the frame will be resized nicely for you, the components within it will be painted as well.
To see the components within the JFrame:
public static void main (String [] args){
JFrame frame = new JFrame("test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel();
JLabel label1= new JLabel("");
panel.add(label1); //Add label to panel
frame.add(panel); //Add panel (with label) to frame
frame.pack(); //Let the frame adjust its size based on the added components
frame.setVisible(true);
}
public static void main (String [] args){
JFrame frame = new JFrame("test");
JPanel panel = new JPanel();
JLabel label1= new JLabel("");
Color darkBlue = new Color(8,40,94);
panel.setPreferredSize(new Dimension(1000, 500));
panel.setBackground(darkBlue);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//frame.setSize(1000, 500);
frame.getContentPane().add(panel);
frame.pack();
frame.setVisible(true);
}
You should use pack() after setting the sizes.
Furthermore panel.setPreferredSize() works better than setSize() for you :)
call jframe.pack() before jframe.setVisible() method !
public static void main (String [] args){
JFrame frame = new JFrame("test");
JPanel panel = new JPanel();
JLabel label1= new JLabel("");
panel.setSize(1000, 500);
frame.getContentPane().add(panel);
Color darkBlue = new Color(8,40,94);
panel.setBackground(darkBlue);
frame.pack() ;
frame.setVisible(true); }
You will also need to check the default layout of JFrame , which is flow layout !
So I set the setSize(500,500).. add some panels, the sum of panels Y is 500 like the JFrame but executing it shows an count Y of 525 am I missing something?
JPanel panel = new JPanel();
panel.setLayout(null);
getContentPane().add(panel);
//--------------------
JPanel top_panel = new JPanel();
top_panel.setLayout(null);
top_panel.setBackground(Color.blue);
top_panel.setBounds(0, 0, 500, 40);
panel.add(top_panel);
//------------------------------
JPanel middle_panel = new JPanel();
middle_panel.setLayout(null);
middle_panel.setBackground(Color.yellow);
middle_panel.setBounds(0, 40, 500, 385);
panel.add(middle_panel);
//-----------------------------
JPanel bottom_panel = new JPanel();
bottom_panel.setLayout(null);
bottom_panel.setBackground(Color.black);
bottom_panel.setBounds(0, 425, 500, 75);
panel.add(bottom_panel);
setSize(500,500);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setResizable(false);
setLocationRelativeTo(null);
40+385+75 = 500 but to show all the panels i must
setSize(500,525);
then it fits
here's an image:
The frame size is the light blue rectangle outside bounds including the title bar. Your panels are appearing in the inner bounds which is frame size less than the frame border and frame title bar. Do you see how your marked space at the bottom is strangely the same height as the title bar?
After adding your panels/component to the frame and just before calling frame.setVisible(true), call frame.pack().
It would be also preferable if you embrace a layout manager (such as FlowLayout) and when necessary call setPreferredSize and let the layout manager do the layout. Normally one would call setPreferredSize over setBound, setSize, setMininumSize, setMaximumSize.
import javax.swing.*;
import java.awt.*;
public class FrameSize {
private JFrame frame;
FrameSize create() {
frame = createFrame();
frame.getContentPane().add(createContent());
return this;
}
private JFrame createFrame() {
JFrame frame = new JFrame(getClass().getName());
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
return frame;
}
void show() {
// frame.setSize(500, 500);
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.pack();
frame.setVisible(true);
}
private Component createContent() {
JPanel panel = new JPanel(null);
JPanel topPanel = new JPanel(null);
topPanel.setBackground(Color.blue);
topPanel.setBounds(0, 0, 500, 40);
panel.add(topPanel);
JPanel middlePanel = new JPanel(null);
middlePanel.setBackground(Color.yellow);
middlePanel.setBounds(0, 40, 500, 385);
panel.add(middlePanel);
JPanel bottomPanel = new JPanel(null);
bottomPanel.setBackground(Color.black);
bottomPanel.setBounds(0, 425, 500, 75);
panel.add(bottomPanel);
panel.setPreferredSize(new Dimension(500, topPanel.getBounds().height + middlePanel.getBounds().height + bottomPanel.getBounds().height));
return panel;
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new FrameSize().create().show();
}
});
}
}
You shouldn't be setting size or calling setSize(...) or setBounds(...) as that's setting you up for similar problems in the future, or worse problems when you try to show your GUI on a different platform. Instead let the preferredSizes of your components and the layout managers do this work for you. If you absolutely must set the size of a component, then override getPreferredSize() and return a Dimension that is calculated to work for you. And yes, as per javajon, you should call pack() on the JFrame before displaying it.
For more discussions on the null layout, please read what one of the best Swing experts on this site, MadProgrammer, has to say in his answer here.
I'm still trying to learn how layout managers work. I made a Frame with two JPanels.
The first one contains a textArea with a boxLayout.
The second one contains a flow layout with a button.
I set the preferredSize of each panel accordingly, packed them, but got unexpected results.
import java.awt.*;
import javax.swing.*;
public class LayoutMgrTest
{
public static void main(String[] args)
{
TableBasic frame = new TableBasic();
frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
frame.setVisible(true);
frame.getContentPane().setLayout(new GridLayout(2,1));
JPanel controlPane = new JPanel();
JPanel buttonPane = new JPanel();
controlPane.setLayout(new BoxLayout(controlPane, BoxLayout.PAGE_AXIS));
controlPane.setPreferredSize(new Dimension(200, 200));
controlPane.add(new JScrollPane(new JTextArea()));
buttonPane.setLayout(new FlowLayout(FlowLayout.LEFT));
buttonPane.setPreferredSize(new Dimension(100,20));
buttonPane.add(new JButton("Button1"));
buttonPane.add(new JButton("Button2"));
frame.getContentPane().add(controlPane, BorderLayout.NORTH);
frame.getContentPane().add(buttonPane, BorderLayout.SOUTH);
frame.setSize(new Dimension(500,500));
frame.pack();
}
}
Whatever I do, if I use a grid Layout, it seems to always allocate half of the available space to each control. I have been told that:
The height of each row is dependent on the height of each component
added in each row.
The buttonpane's height is 20. It's allocating much more than that to it:
What's wrong with this code?
I would like to leave the two JPanels intact please. It's easy to simply add the textbox and the buttons directly to the frame, but I need to do it with JPanels (because I will be adding borders and other things).
That's the result of using GridLayout as layout manager. Change it to BorderLayout:
frame.getContentPane().setLayout(new BorderLayout());
For example, this code (I changed a little as possible from the original):
import java.awt.*;
import javax.swing.*;
public class LayoutMgrTest
{
public static void main(String[] args)
{
JFrame frame = new JFrame();
frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
//frame.setVisible(true);
//frame.getContentPane().setLayout(new BorderLayout());
JPanel controlPane = new JPanel();
JPanel buttonPane = new JPanel();
controlPane.setLayout(new BoxLayout(controlPane, BoxLayout.PAGE_AXIS));
controlPane.setPreferredSize(new Dimension(200, 200));
controlPane.add(new JScrollPane(new JTextArea()));
buttonPane.setLayout(new FlowLayout(FlowLayout.LEFT));
buttonPane.setPreferredSize(new Dimension(100,40));
buttonPane.add(new JButton("Button1"));
buttonPane.add(new JButton("Button2"));
frame.add(controlPane, BorderLayout.NORTH);
frame.add(buttonPane, BorderLayout.SOUTH);
//frame.setSize(new Dimension(500,500));
frame.pack();
frame.setVisible(true);
}
}
Generates this frame:
I set the preferredSize of each panel accordingly,
That is another problem. You should NOT set the preferred size. That is the job of the layout manager. Just add your components to the panels and let the layout manager do its job.
Most compnents have a default preferred size. For some you need to give it a little tip.
For example when using a text area you would give a "suggested" preferred size by using:
JTextArea textArea = new JTextArea(rows, columns);
If you use LayoutManager, you should not set a size on a component except the frame.
the size for the components is calculated from the different layout managers.
you find more infos at http://download.oracle.com/javase/tutorial/uiswing/layout/howLayoutWorks.html
in your code, you can add the panel with the textarea to BorderLayout.CENTER. this should solve your problem. the component in BorderLayout.CENTER takes the whole space, except the space needed for the components in NORTH, EAST, SOUTH and WEST.