My JFrame window won't appear, though, by the tutorial I've been watching, I've been doing everything spot on, yet nothing happens. It doesn't even give me an error, which makes it so much worse. This is the code:
import javax.swing.*;
import java.awt.*;
public class Window {
public class Window {
public void newWindow() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
JLabel label = new JLabel("I am a star! A beautiful shining star!", SwingConstants.CENTER);
frame.getContentPane().add(label);
frame.setVisible(true);
}
}
(This is a second class, the main one properly links to this one)
JFrame uses a layout manager named BorderLayout by default. To see components added to the frame, you should refer to its javadocs. However, the easiest choice here is to use FlowLayout. You also should use JFrame's pack() method, which, according to Oracle:
Causes this Window to be sized to fit the preferred size and layouts of its subcomponents. The resulting width and height of the window are automatically enlarged if either of dimensions is less than the minimum size as specified by the previous call to the setMinimumSize method.
Thus, this should work for you:
import javax.swing.*;
import java.awt.*;
public class Window {
public void newWindow() {
JFrame frame = new JFrame();
frame.getContentPane().setLayout(new FlowLayout()); // specify the layout manager
frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
JLabel label = new JLabel("I am a star! A beautiful shining star!", SwingConstants.CENTER);
frame.getContentPane().add(label);
frame.pack(); // handles sizing of the window
frame.setVisible(true);
}
}
Notice that I removed the duplicate public class Window declaration, which might have been the reason you didn't see a frame at all. If it's still not working for you, I think you aren't calling the newWindow() method. If you want the window to show by simply calling new Window();, then you should change public void newWindow() to public Window().
import javax.swing.*;
import java.awt.*;
public class Window {
public void newWindow() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JLabel label = new JLabel("I am a star! A beautiful shining star!", SwingConstants.CENTER);
frame.getContentPane().add(label);
frame.setVisible(true);
frame.pack();
}
}
From what I see, your not setting the size of the JFrame. Try,
frame.setSize(500, 500);
Related
I have the following code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Main
{
public static void main(String[] args)
{
Window window = new Window("This is a title", 450, 350);
JButton buttonExit = new Button("Exit", 75, 25);
window.addElement(buttonExit);
window.build();
}
}
class Window // extend the current class
{
public Window window;
public JFrame frame;
public JPanel panel;
public String title;
// instantiate object with the constructor
public Window(String title, int width, int height)
{
this.frame = new JFrame(title);
this.frame.setPreferredSize(new Dimension(width, height));
this.frame.setLocationRelativeTo(null); // centers the main window relative to the center of the screen dimension
this.panel = new JPanel();
this.panel.setPreferredSize(new Dimension(width, height));
//this.panel.setLayout(new FlowLayout());
this.frame.add(panel);
}
public void build()
{
this.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.frame.pack(); // removes all unnecessary pixel space from the form
this.frame.setVisible(true);
this.frame.setSize(frame.getPreferredSize());
}
public void addElement(JButton element)
{
this.panel.add(element);
}
}
class Button extends JButton // extend the current class
{
public Button(String text, int width, int height)
{
JButton button = new JButton();
button.setPreferredSize(new Dimension(width, height));
button.setText(text);
button.setVisible(true);
new ButtonHandler(button);
}
}
class ButtonHandler implements ActionListener
{
public ButtonHandler(JButton button)
{
button.addActionListener(this);
}
public void actionPerformed(ActionEvent actionEvent) {
System.exit(0);
}
}
I have two problems with this:
The button is compressed and won't show its text
I cannot get the event handler to work and don't appear to get why
As a side note, I know that I don't specify a LayoutManager here, but I had this implemented before and it didn't solve my issue (I tried the FlowLayoutManager and the GridBagLayout [this would be my desired one, due to its flexibility]).
Can someone tell me, what I am doing wrong here? I've only worked with C# and WPF/WinForms before...
Issue 1:
Your custom Button class is-a JButton but also has-a JButton (named button) in the constructor.
The problem here is you install the ButtonHandler class to the button of the constructor, not the custom Button itself (which is referred to as this inside the constructor).
Issue 2:
When you set the [preferred] size of the JFrame property named frame (in the custom class named Window), you are not setting the frame's contents' [preferred] size, but the size of the whole JFrame, which includes the bar located at the top of the frame (which has the title of the frame).
That lets the contents of the frame to have a space less than the preferred size, because the preferred size is set to the whole frame.
I know, you are also setting the preferred size of the JPanel named panel, which is added to the frame, but when you pack the frame, then the preferred size of the frame is prioritized rather than the preferred size of the contents of the frame, so that's probably why you are seeing the button compressed.
Let me demonstrate what I mean, with a bit of code:
import java.awt.Dimension;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class TestFramePrefSz {
public static void main(final String[] args) {
SwingUtilities.invokeLater(() -> {
final JFrame frame = new JFrame("Testing JFrame preferred size");
final JPanel contents = new JPanel();
contents.setPreferredSize(new Dimension(200, 200));
frame.setPreferredSize(new Dimension(200, 200));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(contents);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
System.out.println(contents.getSize());
});
}
}
As you can see, the dimension object printed (which is the actual size of the panel) is about 184x161 rather than 200x200 requested, because the preferred size of the frame is also set to 200x200 (which includes the title of the frame etc...).
The solution, is to only set the preferred size of the contents, not the frame (in this particular scenario at least).
So you should:
Remove the line this.frame.setSize(frame.getPreferredSize()); inside the build method.
Remove the line this.frame.setPreferredSize(new Dimension(width, height)); inside the constructor of the custom class named Window.
Issue 3:
The line this.frame.setLocationRelativeTo(null); inside the constructor of the custom class named Window, is not effective in that place.
Imagine that, when you call this method, it has to determine the location of the frame to set it.
So it needs to know first of the size of the screen and then the size of the frame itself.
But what is the size of the frame at the point where you call this method? It is about 0x0. Not the preferred size as you might expect.
That makes the calculation of the frame's location to be such that the frame will not be centered at the screen.
That's because the preferred size is a property of the frame, which is a different property than the size.
So you either have to setSize prior making the call, or better to set the preferred size of the contents of the frame (ie this.panel), then call pack on the frame and finally call the method this.frame.setLocationRelativeTo(null).
Then you are free to set the frame to visible to see where it is located in the screen (ie should be centered).
So the solution is to follow a pattern like the following:
Create the frame, add the contents of the frame to it and set the contents' preferred size.
Call pack on the frame (remember this call will change the size of the frame, according to the preferred sizes of the contents of the frame or the frame's itself).
Call setLocationRelativeTo(null) on the frame.
Call setVisible(true) on the frame.
If you take a look at your code, you are instead doing:
Create the frame.
Set the preferred size of the frame.
Call setLocationRelativeTo(null) on the frame (but the size of the frame is not set yet).
Add the contents of the frame to it (ie the panel).
Call addElement which adds more content to the panel.
Call pack on the frame (remember the preferred size of the frame is set up to this point, so it will override any other preferred sizes, such as the contents' preferred size).
Call setVisible(true) on the frame.
Call setSize on the frame, with the preferred size of it. So you are overwriting the size the frame has had from step 6.
I don't know what you're using as a tutorial. I recommend the Oracle tutorial, Creating a GUI With JFC/Swing. You can skip the Netbeans section, but I recommend going through the rest of the sections.
I created the following GUI.
The Exit button works, disposing of the GUI. The X in the upper right also disposes of the GUI.
Here's the runnable example code. The explanation follows the code.
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class JButtonExample implements Runnable{
public static void main(String[] args) {
SwingUtilities.invokeLater(new JButtonExample());
}
private JFrame frame;
#Override
public void run() {
frame = new JFrame("This is a title");
frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
frame.addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent e) {
exitProcedure();
}
});
frame.add(createMainPanel(), BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createMainPanel() {
JPanel panel = new JPanel(new BorderLayout());
panel.setPreferredSize(new Dimension(300, 200));
panel.setBorder(BorderFactory.createEmptyBorder(
75, 100, 75, 100));
JButton button = new JButton("Exit");
button.addActionListener(new ExitListener(this));
panel.add(button, BorderLayout.CENTER);
return panel;
}
public void exitProcedure() {
frame.setVisible(false);
frame.dispose();
System.exit(0);
}
public class ExitListener implements ActionListener {
private JButtonExample example;
public ExitListener(JButtonExample example) {
this.example = example;
}
#Override
public void actionPerformed(ActionEvent event) {
example.exitProcedure();
}
}
}
I make a call to the SwingUtilities invokeLater method from the main method. This method makes sure that the Swing components are created and executed on the Event Dispatch Thread.
I separate the JFrame code from the JPanel code. This is so I can focus on one part of the GUI at a time.
The JFrame methods have to be called in a specific order. This is the order that I use for most of my Swing applications.
The WindowListener (WindowAdapter) gives my code control over the closing of the JFrame. This will allow the Exit button actionListener to close the JFrame. A WindowListener is not a simple concept.
The JFrame defaultCloseOperation is usually set to EXIT_ON_CLOSE. In order for the WindowListener to work, I had to set the defaultCloseOperation to DO_NOTHING_ON_CLOSE.
I let the JFrame determine its own size by using the pack method.
I set the preferred size of the JPanel.
I created an empty border for the JPanel, so the JButton would expand to fill the rest of the JPanel. That's what happens to the component placed in the center of a BorderLayout.
I created an ExitListener class. Because it's an inner class, I didn't have to create a constructor or pass the JButtonExample instance. I created a constructor so you can see how it's done, and how the actionListener method can execute the exitProcedure method of the JButtonExample class.
I hope this JButton example is helpful. The WindowListener is a bit advanced for a simple example, but you can see how it's done.
I'm fairly new to working with graphics in Java, and have been trying to make a simple console to display text based games in a window. I have a test class, where I'm working on the console, but when I add a JTextArea to my console window, it either takes up the entire window or doesn't display at all.
Here is my code:
import javax.swing.*;
import java.awt.*;
import java.util.*;
import java.awt.Event;
public class GUI {
public static void main(String[] args) {
JFrame frame = new JFrame("AoA");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.setSize(1020,760);
frame.setBackground(Color.LIGHT_GRAY);
frame.setResizable(false);
JTextArea jta = new JTextArea(100,100);
jta.setEditable(false);
jta.setBackground(Color.WHITE);
frame.add(jta);
}
}
I know that some of my imports aren't used in this file, but they will used in the final game. I am also aware that the JTextArea is set to size 100,100, which I am unsure whether it is too large or small. I could really use some help on this, though.
Your problem is the installed by default BorderLayout in your frame. The easiest way to solve your problem is to set another layout manager.
public static void main(String[] args) {
SwingUtilities.invokeLater(GUI::startUp);
}
private static void startUp() {
JFrame frame = new JFrame("AoA");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(1020,760);
frame.setBackground(Color.LIGHT_GRAY);
frame.setResizable(false);
frame.setLayout(new FlowLayout()); // FlowLayout is required
JTextArea jta = new JTextArea(40,40);
jta.setEditable(false);
jta.setBackground(Color.WHITE);
// JScrollPane to get the scroll bars when required
frame.add(new JScrollPane(jta));
// setVisible should be last operation to get a correct painting
frame.setVisible(true);
}
Please take a look for layout managers in Swing
How do you resize the button? I've tried various methods like setSize and setPreferredSize but they aren't workng.
package tests;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JButton;
public class RPS extends JPanel{
public static void main(String[] args) {
JFrame frame = new JFrame("Rock Paper Scissors");
JPanel panel = new JPanel();
JLabel label = new JLabel("<html>Will you choose <i>rock,</i> <i>paper,</i> or <i>scissors?</i></html>");
JButton button = new JButton("I am a button.");
label.setHorizontalAlignment(0);
label.setVerticalAlignment(1);
frame.pack();
frame.getContentPane();
frame.setTitle("Rock Paper Scissors");
frame.setSize(640, 480);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(panel);
frame.add(label);
frame.add(button);
button.setToolTipText("Y U no click me?");;
}
}
There is generally no need to resize a button. The button will determine its own size based on the text and Font used by the button. The layout manager will then use this information to give the components a size and location based on the rules of the layout manager.
If you want extra space around the text then you can use:
button.setMargin(...);
You have many other problems with your code:
frame.add(panel);
frame.add(label);
frame.add(button);
This won't do anything. By default the content pane of the frame uses a BorderLayout. If you don't specify a constraint, then then component is add to the CENTER, but only one component can be displayed in the CENTER so you only see the last one.
frame.setSize(640, 480);
There is no need for that statement. The pack() will set all the components at their preferred sizes.
frame.setVisible(true);
This should be the last statement executed, "after" all components have been added to the frame.
frame.getContentPane();
This does nothing, you don't assign the returned value to any variable.
label.setHorizontalAlignment(0);
label.setVerticalAlignment(1);
Don't use magic numbers. Nobody knows what 0 and 1 are used for. Read the API for those methods for variables that you can use.
Read the section from the Swing tutorial on Layout Managers for more information and working examples to get you started. Start with the section on How to Use BorderLayout to understand why your current code isn't working and to understand how to specify the "constraints" when you add your components to the frame.
package tests;
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
public class RPS extends JPanel{
public static void main(String[] args) {
JFrame frame = new JFrame("Rock Paper Scissors");
JPanel panel = new JPanel();
JLabel label = new JLabel("<html>Will you choose <i>rock,</i> <i>paper,</i> or <i>scissors?</i></html>");
JButton button = new JButton("I am a button.");
label.setHorizontalAlignment(0);
label.setVerticalAlignment(1);
panel.add(button); <-add button to panel
frame.add(panel, BorderLayout.SOUTH); <--- you need to say where you are adding the panel onto the frame.
frame.add(label,BorderLayout.NORTH); <--- same with the label
frame.pack();
frame.setTitle("Rock Paper Scissors");
frame.setSize(640, 480);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
button.setToolTipText("Y U no click me?");;
}
}
If you want a bigger button in the center, you can modify with this:
button.setPreferredSize(new Dimension(300, 300));
panel.add(button);
frame.add(panel, BorderLayout.CENTER); <--adds to center rather than south
I'm trying to add the ScrollPane to my TextArea, but it doesn't appear.
Here's the code:
import javax.swing.*;
public class PracownikGui extends JFrame {
private JPanel Panelek;
private JTextArea Tekscik;
private JScrollPane Skrol;
public PracownikGui() {
setMinimumSize(new Dimension(600, 600));
setLocationRelativeTo(null);
setContentPane(Panelek);
setResizable(false);
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
Tekscik();
public void Tekscik() {
Tekscik = new JTextArea(2, 10);
Skrol = new JScrollPane( Tekscik );
Tekscik.setSize(300, 300);
Tekscik.setLocation(20, 70);
Tekscik.setEditable(true);
Tekscik.setLineWrap(true);
add(Tekscik);
}}
Any help, please.
You're shooting yourself in the foot by setting a JTextArea's size or preferredSize since this prevents it from expanding into the JScrollPane:
Tekscik.setSize(300, 300);
set its rows and columns only.
Also you need to add the JScrollPane to the GUI, not the JTextArea.
Also, while null layouts and setBounds() or setSize(...) and setLocation(...) might seem to Swing newbies like the easiest and best way to create complex GUI's, the more Swing GUI'S you create the more serious difficulties you will run into when using them. They won't resize your components when the GUI resizes, they are a royal witch to enhance or maintain, they fail completely when placed in scrollpanes, they look gawd-awful when viewed on all platforms or screen resolutions that are different from the original one.
e.g.,
import javax.swing.*;
public class PracownikPanel extends JPanel {
private JTextArea tekscik = new JTextArea(5, 25);
public PracownikPanel() {
tekscik.setLineWrap(true);
tekscik.setWrapStyleWord(true);
JScrollPane skrol = new JScrollPane(tekscik);
skrol.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
add(skrol);
}
private static void createAndShowGui() {
PracownikPanel mainPanel = new PracownikPanel();
JFrame frame = new JFrame("PracownikPanel");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
I made quite a few changes to your code. Your code wouldn't run.
Here's the GUI I created.
As you can see, there's a vertical scroll bar. The default action for the scroll bar is that it doesn't appear until you've filled the JTextArea with text.
Here are the important changes I made to your code.
Class names start with a capital letter. Method names and variable names start with a lower case letter.
A Swing application must start with a call to the SwingUtilities invokeLater method. This ensures that the Swing components are created and used on the Event Dispatch thread (EDT). Since the invokeLater method requires a Runnable, I had the PracownikGui class implement Runnable.
You use Swing components. You don't extend Swing components, or any other Java class, unless you want to override one of the methods in that class.
I removed all of the sizing and positioning statements, except for the statement that defines the rows and columns of the JTextArea. Hovercraft Full Of Eels explained this, but you use Swing layouts to get the arrangement of Swing components you want. The default layout for a JPanel is the FlowLayout. The default layout for a JFrame is the BorderLayout.
I added the JScrollPane to the JPanel. I added the JPanel to the JFrame.
Here's the code.
package com.ggl.testing;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
public class PracownikGui implements Runnable {
public static void main(String[] args) {
SwingUtilities.invokeLater(new PracownikGui());
}
private JFrame frame;
private JPanel panelek;
private JTextArea tekscik;
private JScrollPane skrol;
#Override
public void run() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
panelek = new JPanel();
tekscik(panelek);
frame.setContentPane(panelek);
frame.setResizable(false);
frame.pack();
frame.setVisible(true);
}
public void tekscik(JPanel panelek) {
tekscik = new JTextArea(2, 20);
tekscik.setEditable(true);
tekscik.setLineWrap(true);
skrol = new JScrollPane(tekscik);
panelek.add(skrol);
}
}
I want to create a Window with an image and a text so far i've got this:
public void ShowPng1() {
ImageIcon theImage = new ImageIcon("Icon_Entry_21.gif");
panel.setSize(270, 270);
JLabel label = new JLabel("Hello, World!");
JLabel imageLabel = new JLabel(theImage);
imageLabel.setOpaque(true);
panel.add(imageLabel);
panel.add(label);
panel.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel.setVisible(true);
}
My panel:
private JFrame panel = new JFrame();
For some reason it won't load nor image nor text, it just pops up as a white window. What can be the problem? I've also tried changing the format to .png, didn't work.
UPDATE
import java.awt.BorderLayout;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
public class Img {
private JFrame panel = new JFrame();
public Img(){
ShowPng1();
}
public void ShowPng1() {
ImageIcon theImage = new ImageIcon("Icon_Entry_21.gif");
panel.setSize(300, 300);
panel.setResizable(false);
JLabel label = new JLabel("Hello, World!");
JLabel imageLabel = new JLabel(theImage);
imageLabel.setOpaque(true);
panel.add(imageLabel);
panel.add(label, BorderLayout.PAGE_END);
panel.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel.setVisible(true);
}
public static void main(String[] args) {
new Img();
}
}
I've managed to get this working, which is ridiculous because I can't figure out how to make it work with my program. Reimeus gave me an idea on creating this script separately, the fix and that worked. I will have to look through my entire program to see if I'm missing anything. Creating it in a separate class should work as well.
it just pops up as a white window
Sounds like you're blocking the EDT on startup. You may need to use one of Swing's concurrency mechanisms to solve it. Post a Minimal, Complete, Tested and Readable example so we can determine this for sure.
In the meantime...
You're displacing the component containing the theImage component in the BorderLayout.CENTER location
panel.add(label);
You could organize your labels so that they can appear simultaneously (placing the components at 2 different BorderLayout locations will do)
panel.add(imageLabel);
panel.add(label, BorderLayout.PAGE_END);
You should make a JPanel and add it to the frame, and then add the labels to the panel
Something like
private JPanel panel = new JPanel;
and then add it to the frame in your method calling
frame.add(panel);