I've built a simple gui that adds panels based on user input. My initial problem was that when the panel was added the frame did not resize. Because it was a jpanel object that handled the user input adding a new panel to itself and therefore could not 'see' the jframe (at least I couldn't find how it could) I couldn't work out how to call repaint() or revalidate() on the parent frame from within that object. However,through trial and error I did find that this worked
JFrame jFrame = new JFrame(title){
#Override
public void invalidate(
super.invalidate();
this.pack();
}
};
But because I don't really know what goes on behind the scenes with invalidate I want to know whether this is a good idea or not (It seems kinda sketchy). Any advice would be great, thanks.
EDIT
Hope this makes the problem a bit clearer
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class TestFrame {
JFrame jframe;
NewPanel jpanel;
public TestFrame(){
jframe = new JFrame(); // without above addition frame won't resize
jpanel = new NewPanel();
jframe.add(jPanel);
jframe.pack();
jframe.setVisible(true);
}
public static void main(String [] args){
TestFrame testframe= new TestFrame();
}
}
class NewPanel extends JPanel implements ActionListener{
public NewPanel(){
JTextField textField = new JTextField (10);
textField.addActionListener(this);
this.add(textField);
}
// Adds a label when action is performed on textfield
#Overide
public void actionPerformed(ActionEvent ae){
JPanel extraPanel = new JPanel();
extraPanel.add(new JLabel("hi"));
this.add(extraPanel);
this.revalidate(); this.repaint();
}
}
Your issue is not that revalidate() or repaint() aren't working.
The issue here is that your JFrame has been pack()ed already and thus it has a preferred size set. If you want to change its size you need to call pack() on it again. Not necessarily to call it on invalidate().
I made some changes to your code to compile (typos) and I came with this:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class TestFrame {
JFrame jframe;
NewPanel jpanel;
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new TestFrame());
}
public TestFrame(){
jframe = new JFrame(); // without above addition frame won't resize
jpanel = new NewPanel();
jframe.add(jpanel);
jframe.pack();
jframe.setVisible(true);
}
class NewPanel extends JPanel implements ActionListener{
public NewPanel(){
JTextField textField = new JTextField (10);
textField.addActionListener(this);
this.add(textField);
}
// Adds a label when action is performed on textfield
#Override
public void actionPerformed(ActionEvent ae){
System.out.println("WOLOLO");
JPanel extraPanel = new JPanel();
extraPanel.add(new JLabel("hi"));
this.add(extraPanel);
this.revalidate();
this.repaint();
jframe.pack();
}
}
}
Another way to solve this is to override getPreferredSize method from the JPanel:
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
And you can delete jframe.pack() in the previous code.
Related
I have recently started working with Java+Swing building an UI and I currently have an issue with JTextField placed on JPanel with FlowLayout.
In my example I have a window, containing panel with button. Clicking the button adds a component derived from JPanel and containing JTextField.
The problem is that when I type in JTextField it does not get updated (does not get resized). However when I resize the window or do anything else which forces window/panel redraw, the text field being resized (just what I expect to happen automatically).
When I change base class from JPanel to JTextField it works in the way I try to achieve, but I need to have JPanel as the base class so that I can take advantages of putting child components to it.
I have checked different questions here as well as I have Googled trying to find the solution, however it did not work for me. I have tried validate/invalidate/revalidate/repaint in different combinations and for different components, as well as trying to enforce revalidation for each typed character, which does not sound as the right way for me. So far I understoon that it is something to do with Layout Managers.
Could anyone please help me with understanding how that works and what should I read about how Swing UI, layout management and redrawing is working?
Also, I would be glad if someone could help me with my particular issue with my code.
Thanks in advance!
Here is my code below:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
class TagVisual extends JPanel /*JTextField*/ {
private JTextField editField;
public TagVisual() {
FlowLayout layout = new FlowLayout();
layout.setHgap(0);
layout.setVgap(0);
setLayout(layout);
editField = new JTextField();
editField.setBackground(Color.RED);
editField.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
editField.setSize(editField.getSize());
editField.revalidate();
remove(editField);
add(editField);
revalidate();
repaint();
}
});
add(editField, FlowLayout.LEFT);
}
public void place(JPanel panel) {
panel.add(this);
editField.grabFocus();
}
}
public class MainWindow {
private JPanel mainPanel;
private JButton btnPlace;
private JFrame frame;
public MainWindow(JFrame frame) {
mainPanel = new JPanel(new FlowLayout());
btnPlace = new JButton();
btnPlace.setText("Place");
mainPanel.add(btnPlace);
this.frame = frame;
btnPlace.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
TagVisual v = new TagVisual();
v.place(mainPanel);
mainPanel.revalidate();
mainPanel.repaint();
mainPanel.updateUI();
frame.revalidate();
frame.repaint();
}
});
}
public static void main(String[] args) {
JFrame frame = new JFrame("TextFieldUpdateIssue");
frame.setContentPane(new MainWindow(frame).mainPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
}
If i were you, i would not try to resize the textfields when the user enters some text.
I suggest you to give them a fixed size using JTextField (int columns) constructor, this will allow you to create some textfields which are "wide enough".
If you still want to make them wider when some text is entered, you can't use an ActionListener, since it will fire an event when the user presses ENTER key, not based on the text entered.
For this purpose you can register a Document Listener on your textfield's document.
You also could override getPreferredSize () method to calculate and return an appropriate size. In the example below i use a JLabel for convenience to calculate the preferred width, but you could use FontMetrics.
If you are adding multiple tags to your panel, you should also consider using a JScrollPane in order to make scrollbars appear when your panel needs more space.
See this example (i changed a bit your code because it would not compile and the general design was bad, now i think it is better, but not still good) :
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class MainWindow
{
public static void main (String [] a) {
SwingUtilities.invokeLater (new Runnable () {
#Override public void run () {
try {
UIManager.setLookAndFeel (UIManager.getSystemLookAndFeelClassName ());
createAndShowGUI ();
}
catch (Exception e) {
JOptionPane.showMessageDialog (null, "An unexpected error occurred: " + e.getClass ().getSimpleName (), "Error", JOptionPane.ERROR_MESSAGE);
}
}
});
}
private static void createAndShowGUI () {
JFrame frame = new JFrame ("TextFieldUpdateIssue");
frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
frame.setContentPane (new MainPanel ());
frame.setExtendedState (JFrame.MAXIMIZED_BOTH);
frame.setLocationRelativeTo (null);
frame.setVisible (true);
}
}
class MainPanel extends JPanel
{
private JPanel tagsPanel;
public MainPanel () {
super (new BorderLayout (0, 10));
add (new JButton (new AbstractAction ("Add tag") {
#Override public void actionPerformed(ActionEvent e) {
addNewTag ();
}
}), BorderLayout.NORTH);
tagsPanel = new JPanel ();
tagsPanel.setLayout (new FlowLayout (FlowLayout.CENTER, 10, 0));
add (tagsPanel, BorderLayout.CENTER);
}
private void addNewTag () {
TagVisual v = new TagVisual ();
tagsPanel.add (v);
v.grabFocusOnField ();
revalidate ();
}
}
class TagVisual extends JPanel
{
private JTextField editField;
public TagVisual() {
super (new FlowLayout (FlowLayout.CENTER, 0, 0));
add (editField = createNewTextField (null), FlowLayout.LEFT);
}
private JTextField createNewTextField (String text) {
JTextField textField = new JTextField (text) {
#Override public Dimension getPreferredSize () {
Dimension d = super.getPreferredSize ();
return new Dimension (new JLabel (getText ()).getPreferredSize ().width + 10, d.height);
}
};
textField.setBackground (Color.RED);
textField.getDocument ().addDocumentListener (new DocumentListener () {
#Override public void changedUpdate (DocumentEvent e) {
revalidate ();
}
#Override public void insertUpdate (DocumentEvent e) {
revalidate ();
}
#Override public void removeUpdate (DocumentEvent e) {
revalidate ();
}
});
return textField;
}
public void grabFocusOnField () {
editField.grabFocus ();
editField.setCaretPosition (editField.getText ().length ());
}
}
Screenshot (short text):
Screenshot (Longer text):
Please review the code and note comments:
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class MainWindow {
private JPanel mainPanel;
private JButton btnPlace;
public MainWindow(){
JFrame frame = new JFrame("TextFieldUpdateIssue");
//you can't use components before initializing them
btnPlace = new JButton("Button");
frame.add(btnPlace, BorderLayout.NORTH);
mainPanel = new JPanel();
frame.add(mainPanel, BorderLayout.CENTER);
btnPlace.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
TagVisual v = new TagVisual();
mainPanel.add(v); //add it to main panel
//v.place(mainPanel);
//mainPanel.revalidate();
//mainPanel.repaint();
//mainPanel.updateUI();
//frame.revalidate();
//frame.repaint();
frame.pack();
}
});
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
new MainWindow();
}
}
class TagVisual extends JPanel /*JTextField*/ {
private JTextField editField;
public TagVisual() {
FlowLayout layout = new FlowLayout();
layout.setHgap(0);
layout.setVgap(0);
setLayout(layout);
editField = new JTextField();
//give it a preferred size to be used by layout manager
editField.setPreferredSize(new Dimension(150,25));
editField.setBackground(Color.RED);
editField.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
//not sure what you want to do here
//not relevant to the question
}
});
add(editField, FlowLayout.LEFT);
}
}
i just started studying gui in java. i am now able to create windows with specific sizes while extending JFrame. however, i came to read posts from here that it is better not to extend JFrame. then i tried to create a window by setting the size in the JPanel instead, but the setSize doesn't seem to work (my code must lack something)
here's my code for my frame
import javax.swing.JFrame;
public class MyFrame{
private JFrame mainFrame;
private MyPanel mainPanel;
public MyFrame(){
mainFrame = new JFrame();
mainPanel = new MyPanel(50, 50);
mainFrame.add(mainPanel);
mainFrame.setVisible(true);
}
}
and here's my code for my panel
import javax.swing.JPanel;
public class MyPanel extends JPanel{
public MyPanel(int i, int j){
setSize(i, j);
}
}
i tried adding frame.pack() in my Frame class, because i thought the frame, not having it's size set, is too small for the panel to be seen -i was wrong
what's lacking in my code?
what's lacking in my code?
A preferred size for the custom component (Panel) for starters. #Override getPreferredSize() to return a logical value.
Then pack() the frame to ensure it is the smallest size needed to display the panel and any other components.
So, something like this:
import javax.swing.*;
public class Application {
private JFrame frame;
private CustomPanel panel;
public Application() {
frame = new JFrame();
// next 2 lines, just a good idea
frame.setLocationByPlatform(true);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
// at 50x50, the title bar on Windows is wider!
panel = new CustomPanel(200, 200);
frame.add(panel);
// make the frame smallest it can be and still show components
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
Runnable r = new Runnable() {
#Override
public void run() {
new Application();
}
};
SwingUtilities.invokeLater(r);
}
}
class CustomPanel extends JPanel {
public CustomPanel(int w, int h) {
setPreferredSize(new java.awt.Dimension(w, h));
}
}
// This works!
JPanel background = new JPanel();
background.setBackground(Color.BLACK);
background.setBounds(0,0,this.getSize().width,this.getSize().height);
add(background);`
// Ihis method doesn't work! Why ? And the classic method setBackground(Color.BLACK); has the same problem
JPanel background = new JPanel()
{
#Override
public void setBackground(Color bg){
super.setBackground(Color.BLACK);
}
#Override
public void setBounds(int a, int b, int c, int d){
super.setBounds(0,0,this.getSize().width,this.getSize().height);
}
};
add(background);
Definite issue you are going to encounter will come from calling setBounds method.
Call setBackground for your panel and just add it to JFrame by calling add method. JPanel will be added on center of JFrame by default since default layout for JFrame is a BorderLayout and it will perfectly fit without of calling setBounds. There is absolutely no need to complicate things by overriding any method.
This:
import java.awt.Color;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class TestPanel {
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
JPanel panel = new JPanel();
panel.setBackground(Color.BLACK);
JFrame frame = new JFrame();
frame.add(panel);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
//frame.pack();
frame.setSize(400, 300);
frame.setVisible(true);
});
}
}
...will work perfectly.
Though you have ovverriden methods, you haven't called them.
I've gotten stuck trying to draw on a JPanel. I've learned how to create a JFrame, a JPanel, add event handlers, do the same in applets, and some other basic GUI development. But everytime I try to draw on a JPanel using the paintComponent(Graphics g) or paint(Graphics g) methods, nothing shows up. Buttons, as well as other JComponents, show up just fine. But g.drawString, g.drawRect, etc result in a blank JFrame window.
Here is my code:
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;
public class Game extends JPanel {
public static void main(String[] args) {
new Game().game();
}
JPanel panel;
JButton button2;
JButton button;
public void game() {
panel = new JPanel();
button = new JButton("Ok");
panel.setLayout(new FlowLayout());
panel.add(button);
button2 = new JButton("Cancel");
JFrame frame = new JFrame("Game");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500,500);
frame.setResizable(false);
frame.add(panel);
frame.setVisible(true);
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString("hi",100,100);
g.fillRect(100,50,200,300)
}
}
The JPanel you're adding to your JFrame is a plain vanilla JPanel, not an instance of Game, your custom class that contains the paintComponent() method. YOu need to change that one line to
JPanel panel = new Game();
and you should see a difference immediately!
The instance of Game you create in main() isn't being used for anything, other than calling the game() method. You could use it, if you wanted, by doing this instead:
JPanel panel = this;
and then proceeding as before.
JButton and JLabel disappears when adding custom background. I don't see any problems in my program, but maybe you guys find an solution! I think it's only a little thing I forgot, but I can't figure it out.
Here's the code:
GameWindow.java:
setContentPane(new StartImagePanel(RollrackLogo));
out.println("adding JLWelcome");
JLWelcome.setText("Welcome to Rollrack, " + namewindow.name);
add(JLWelcome);
JLWelcome.setVisible(true);
out.println("JLWelcome added");
out.println("adding JBRandom");
JBRandom.setText("Random");
add(JBRandom);
JBRandom.setVisible(true);
out.println("added JBRandom");
The background appears perfect, but not the JButton and JLabel!
Code to the StartImagePanel.java:
public class StartImagePanel extends JComponent{
private Image image;
public StartImagePanel(Image image) {
this.image = image;
}
#Override
protected void paintComponent(Graphics g) {
g.drawImage(image, 0, 0, null);
}
}
Your button and label are added to your GameWindow frame while they should be added to its contentPane, setContentPane(new StartImagePanel(RollrackLogo)); instead. That's why they are not showing, they are added to the frame.
Make a variable of the StartImagePanel and add the button and label to it and they should show up.
StartImagePanel contentPanel = new StartImagePanel(RollrackLogo);
setContentPane(contentPanel);
...
out.println("adding JLWelcome");
JLWelcome.setText("Welcome to Rollrack, " + namewindow.name);
contentPanel.add(JLWelcome);
JLWelcome.setVisible(true);
out.println("JLWelcome added");
out.println("adding JBRandom");
JBRandom.setText("Random");
contentPanel.add(JBRandom);
JBRandom.setVisible(true);
out.println("added JBRandom");
Answer dispute
The claims in the first paragraph are plain wrong. Here is source that proves it.
import java.awt.*;
import javax.swing.*;
import javax.swing.border.EmptyBorder;
public class AddToCustomContentPane {
public static void main(String[] args) {
Runnable r = new Runnable() {
#Override
public void run() {
// the GUI as seen by the user (without frame)
JPanel gui = new JPanel(new FlowLayout());
gui.setBorder(new EmptyBorder(2, 3, 2, 3));
gui.setBackground(Color.RED);
JFrame f = new JFrame("Demo");
f.setContentPane(gui);
// Acid test. Can we add buttons direct to the frame?
f.add(new JButton("Button 1"));
f.add(new JButton("Button 2"));
// Ensures JVM closes after frame(s) closed and
// all non-daemon threads are finished
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
// See http://stackoverflow.com/a/7143398/418556 for demo.
f.setLocationByPlatform(true);
// ensures the frame is the minimum size it needs to be
// in order display the components within it
f.pack();
// should be done last, to avoid flickering, moving,
// resizing artifacts.
f.setVisible(true);
}
};
// Swing GUIs should be created and updated on the EDT
// http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html
SwingUtilities.invokeLater(r);
}
}
Edit after the custom panel code was given
Here's a snippet that works to show both button and label on a black image background, I removed that was not needed (listeners).
public static void main(String[] v) {
class StartImagePanel extends JPanel {
private Image image;
public StartImagePanel(Image image) {
this.image = image;
}
#Override
protected void paintComponent(Graphics g) {
g.drawImage(image, 0, 0, null);
}
}
class GameWindow extends JFrame{
public GameWindow() {
BufferedImage RollrackLogo;
RollrackLogo = new BufferedImage(400,200,BufferedImage.TYPE_INT_RGB);
final JButton JBRandom = new JButton();
final JLabel JLWelcome = new JLabel();
setDefaultCloseOperation(EXIT_ON_CLOSE);
StartImagePanel panel = new StartImagePanel(RollrackLogo);
setContentPane(panel);
setExtendedState(MAXIMIZED_BOTH);
setVisible(true);
JLWelcome.setText("Welcome to Rollrack");
panel.add(JLWelcome);
JLWelcome.setVisible(true);
JBRandom.setText("Random");
panel.add(JBRandom);
JBRandom.setVisible(true);
}
}
GameWindow window = new GameWindow();
window.pack();
window.setVisible(true);
}
I rather use an instance of a JFrame, instead of extending it, as #Andrew Thompson suggested in another question.
However, if you're extending it, it might be a good practice to call super() in the constructor.
Additionally, we may need to know what is going on in your StartImagePanel.
It seems, to me, to be the problem.
Ensure both your GameWindow and StartImagePanel extend properly their superclasses (call super();).
Ensure your StartImagePanel has a proper Layout.
Add your components before you set your frame visible. This also means you won't need JLWelcome.setVisible(true);.
Ensure that your code is executed in the EDT (Event-Dispatch Thread).
Example:
import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.*;
#SuppressWarnings("serial")
public class GameWindow extends JFrame{
BufferedImage rollrackLogo;
JButton jbRandom;
JLabel jlWelcome;
public GameWindow() {
super();
jbRandom = new JButton("Random");
jlWelcome = new JLabel("Welcome to Rollrack, " +
namewindow.name);
rollrackLogo = new BufferedImage(400, 200,
BufferedImage.TYPE_INT_RGB);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setContentPane(new StartImagePanel(rollrackLogo));
// Add your components.
add(jlWelcome);
add(jbRandom);
addKeyListener(new KeyListener() {
#SuppressWarnings("static-access")
#Override
public void keyPressed(KeyEvent e) {
if(e.getKeyCode() == e.VK_ESCAPE){
System.exit(7);
}
}
#Override
public void keyReleased(KeyEvent arg0) {}
#Override
public void keyTyped(KeyEvent arg0) {}
});
// Pack, or otherwise set fullscreen.
pack();
// Now, set frame visible.
setVisible(true);
}
}
Edit: Now that you've posted the code for your StartImagePanel, I see that you're extending JComponent. Follow my previous advice, (call super), set a Layout, and extend JPanel instead.