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How to use the repaint method in Java Swing

I am very new to the Graphics portion of Java. I have created a frame and on it I have added a panel whose color has been set to Green. Now on clicking that panel I want to draw a circle using a test class's object called Mypanel. But it does not happen. Please guide !
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
class Mypanel extends JPanel
{
#Override
public void paintComponent(Graphics g)
{
g.drawOval(15, 15, 5, 5);
}
}
public class algo extends javax.swing.JFrame {
public algo() {
initComponents();
jPanel1.setBackground(Color.GREEN);
}
Mypanel p = new Mypanel() ;
private void jPanel1MouseClicked(java.awt.event.MouseEvent evt) {
p.repaint();
}
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new algo().setVisible(true);
}
});
}
}
If I were to guess I would say that I am not supposed to use the repaint method, but I was told that this was to be used.

That code as supplied would not compile. For better help sooner, post a Minimal, Complete, and Verifiable example or Short, Self Contained, Correct Example.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Mypanel extends JPanel {
boolean clicked = false;
Mypanel() {
setBackground(Color.GREEN);
MouseListener mouseListener = new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
clicked = true;
repaint();
}
};
this.addMouseListener(mouseListener);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(400, 100);
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
if (clicked) {
g.drawOval(15, 15, 50, 50);
}
}
}
public class algo extends JFrame {
public algo() {
initComponents();
pack();
//jPanel1.setBackground(Color.GREEN); ?!?
}
protected final void initComponents() {
add(new Mypanel());
}
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new algo().setVisible(true);
}
});
}
}

There are a few things to correct in your example...
When you create the frame (i.e. in the constructor) you'll want to call super(). This is the first thing the constructor has to do. Then, you'll probably want to set an initial width/height, and set the background color of the frame green.
You need to add a mouse listener so that the mouseClicked method is actually called. Then have it add the 'MyPanel' object to the frame, and call repaint.
I think that's roughly what you're going for.

Make a JTextField recieve input even with windows not focused

I'm working on a small personal project.
I have two JFrame windows, Viewer and Console.
Viewer only contains a subclass of JPanel, and it should respond to mouse input (clicking, mostly).
Console contains a button, a JTextField (the input), and a JTextArea (the output).
I need to make sure than when I press keys on my keyboard, the corresponding text appears in the Console JTextField, not only when the focus is held by the JTextField, but also when it's held any other component in my app.
In other words, I want the JTextField to accept input even right after I clicked on the Viewer frame.
Is this feasible?
In case that matters, I'm running win 8 x64 and I don't really care about portability (I'm the only one that will ever look at or use this code).
EDIT: here is an example of my code:
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
public class main {
public static Viewer v;
public static Console c;
public static void main(String[] args) {
v=new Viewer();
c=new Console();
}
static class Viewer extends JFrame {
public Viewer(){
setSize(600,600);
getContentPane().add(new myPanel());
addMouseListener(new mouse());
setVisible(true);
}
}
static class myPanel extends JPanel{
public void paintComponent(Graphics g){
g.setColor(new Color((int)(Math.random()*255),(int)(Math.random()*255),(int)(Math.random()*255)));
g.fillRect(0, 0, 600, 600);
}
}
static class Console extends JFrame {
public Console(){
setSize(600,200);
JTextField text=new JTextField();
getContentPane().add(text);
setVisible(true);
}
}
static class mouse implements MouseListener{
#Override
public void mouseClicked(MouseEvent arg0) {
v.repaint();
}
#Override
public void mouseEntered(MouseEvent arg0) {
}
#Override
public void mouseExited(MouseEvent arg0) {
}
#Override
public void mousePressed(MouseEvent arg0) {
}
#Override
public void mouseReleased(MouseEvent arg0) {
}
}
}
In this example, after I click on the big window to change its color, if I want to write stuff in the other window I have to click on it first.

Can I suggest the KeyboardFocusManager? I've found this to be the easiest way to achieve what I believe you are trying to achieve
KeyboardFocusManager.getCurrentKeyboardFocusManager().addKeyEventDispatcher(
new KeyEventDispatcher() {
public void dispatchKeyEvent(KeyEvent ke) {
//TODO: fill this in
}
});

One inelegant solution is to create a KeyListener, which feeds typed characters to your console, although how exactly this happens depends on how you create your components. For the sake of this example I'll pretend to do it through a static method in your Console class (preferably you'd have access to an instance of Console):
public class ApplicationKeyListener implements KeyListener {
public ApplicationKeyListener() {
}
// Other necessary methods...
public void keyPressed(KeyEvent e) {
char pressed = e.getKeyChar();
Console.feedChar(pressed);
}
}
And then in Console, make sure your JTextField object is global and static, then set up the feedChar() method.
public class Console extends JFrame {
private static JTextField consoleTextField;
public Console() {
consoleTextField = new JTextField();
// ...
}
public static feedChar(char c) {
consoleTextField.setText(consoleTextField.getText() + c.toString());
}
}
Then finally you'd have to add this listener to all JFrames and their children.
public class Viewer extends JFrame {
public Viewer() {
ApplicationKeyListener kl = new ApplicationKeyListener();
addKeyListener(kl);
for (Component child : this.getComponents()) {
child.addKeyListener(kl);
}
}
}

Detect CTRL+V in Swing App but keep original function

Wrting a chat application, I want the user to be able to send images out of his/her clipboard. For this, I would like to catch any CTRL+Vkeyboard input. Since pasting text should be possible as by default, the original ctrl+v-function (pasting text) must not be overridden.
I see can two approaches, of which none works for me:
1st: Taken from the official Java documentation: KEY LISTENER
editorPane.addKeyListener(new KeyListener() {
#Override
public void keyPressed(KeyEvent e) {
e.getKeyChar()
// when I press ctrl+v, ^ this is falsely a white square character, looks like (U+25A1). Plain v without ctrl does work.
e.getKeyCode()
// ^ this is falsely 0
// (e.getModifiersEx() correctly returns InputEvent.CTRL_DOWN_MASK)
}
2nd: KEY BINDING
InputMap iMap = editorPane.getInputMap(condition);
ActionMap aMap = editorPane.getActionMap();
iMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_V, InputEvent.CTRL_DOWN_MASK), "ctrlV");
aMap.put("ctrlV", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
// works, but overrides natural ctrl+v function!
}
});
Any ideas?
Note: I am using a "foreign" keyboard layout (German). But I can't see why this should make any difference - I would pretty much like to have my application work internationally.
Cheers
edit. Alt+SomeKey however is correctly recognized by the KeyListener
edit2. after changing keyboard layout to US, problem persists.

Stick to Keybindings: KeyListener is a low-level API, while Keybindings will provide you consistent, predictable and robust behaviour.
The solution here is quite easy. You can simply combine the actions yourself by adding a CombinedAction class that will execute the "original" action bound to CTRL+V and the "custom" action you want to execute.
See a small example below combining both actions (here my custom action is a Sysout):
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import javax.swing.JComponent;
import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.KeyStroke;
import javax.swing.ScrollPaneConstants;
public class TestEditorPane {
private JEditorPane editorPane;
public static class CombinedAction implements ActionListener {
private final ActionListener action1;
private final ActionListener action2;
public CombinedAction(ActionListener action1, ActionListener action2) {
super();
this.action1 = action1;
this.action2 = action2;
}
#Override
public void actionPerformed(ActionEvent e) {
if (action1 != null) {
action1.actionPerformed(e);
}
if (action2 != null) {
action2.actionPerformed(e);
}
}
}
public TestEditorPane() {
}
private void initUI() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// JTEXTBOX
editorPane = new JEditorPane();
KeyStroke ctrlV = KeyStroke.getKeyStroke(KeyEvent.VK_V, KeyEvent.CTRL_DOWN_MASK);
final ActionListener ctrlVAction = editorPane.getActionForKeyStroke(ctrlV);
editorPane.registerKeyboardAction(new CombinedAction(ctrlVAction, new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("This is my action on CTRL+V");
}
}), ctrlV, JComponent.WHEN_FOCUSED);
// JSCROLLPANE
JScrollPane scroll1 = new JScrollPane(editorPane);
scroll1.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
scroll1.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
frame.add(scroll1);
frame.setSize(400, 400);
frame.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
TestEditorPane test = new TestEditorPane();
test.initUI();
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
}

Is it Possible to Add ActionListener in the JFormattedTextField?

Hello I'm currently working in my java file.
I'd like to add an event on JFormattedTextField when I press the enter key.
This is my code
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.text.MaskFormatter;
import java.awt.*;
import java.text.ParseException;
public class Test extends JFrame implements ActionListener
{
JFormattedTextField phoneField;
Test()
{
setTitle("JFormatted Text");
setLayout(null);
MaskFormatter mask = null;
try {
mask = new MaskFormatter("##########");
} catch (ParseException e) {
e.printStackTrace();
}
phoneField = new JFormattedTextField(mask);
phoneField.setBounds(20, 20, 150, 30);
phoneField.addActionListener(this);
setVisible(true);
setSize(200, 200);
getContentPane().add(phoneField);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
public static void main(String[] args)
{
new Test();
}
public void actionPerformed(ActionEvent e)
{
if(e.getSource()== phoneField)
{
System.out.println("The numbers you enter are "+phoneField.getText());
}
}
}
it works but their the user needs to enter 10 digits.

Add an ActionListener to the field. It is better than using the (low level) KeyListener and will conform to whatever that OS accepts as 'end of entry'.

Don't use KeyListener instead use DocumentListener.
It has the following methods which captures the changes in the JTextField
JTextField textField = new JTextField();
textField.getDocument().addDocumentListener(new DocumentListener() {
#Override
public void removeUpdate(DocumentEvent arg0) {
// Gives notification that a portion of the document has been removed.
}
#Override
public void insertUpdate(DocumentEvent arg0) {
// Gives notification that there was an insert into the document.
}
#Override
public void changedUpdate(DocumentEvent arg0) {
// Gives notification that an attribute or set of attributes changed.
}
});

You could add a keyListener instead.
phonefield.addKeyListener(new KeyAdapter() {
public void keyPressed(KeyEvent evt) {
if(evt.getKeyCode() == evt.VK_ENTER){
System.out.println("The numbers you enter are "+phoneField.getText());
}
}
});
If this isn't your problem, you should expand a little and clarify.
EDIT:
As comments and other answers pointed out, you should go for an ActionListener instead. Reasoning can be found below.

How do I create an event handler for a JLabel?

I want to make it so that if I click on the JLabel, the label becomes a new label with another image attached to it.
So far my code looks like:
public class Picture extends JFrame {
private ImageIcon _image1;
private ImageIcon _image2;
private JLabel _mainLabel;
private JLabel _mainLabel2;
public Picture(){
_image1 = new ImageIcon("src/classes/picture1.jpg");
_image2 = new ImageIcon("src/classes/picture2.jpg");
_mainLabel = new JLabel(_image1);
_mainLabel2 = new JLabel(_image2);
add(_mainLabel);
pack();
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

Add mouseListener to your JLable and in mouseClicked(mouseEvent) method change icon of JLabel.
A sample code may be:
jLabel.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
jLabel.setIcon(newIcon);
}
});

Try using a JToggleButton instead. No need for a MouseListener, and responds to keyboard input.
import javax.swing.*;
import javax.imageio.ImageIO;
import java.net.URL;
import java.awt.Image;
class ToggleImage {
public static void main(String[] args) throws Exception {
URL url1 = new URL("http://pscode.org/media/stromlo1.jpg");
URL url2 = new URL("http://pscode.org/media/stromlo2.jpg");
final Image image1 = ImageIO.read(url1);
final Image image2 = ImageIO.read(url2);
SwingUtilities.invokeLater(new Runnable() {
public void run() {
JToggleButton button = new JToggleButton();
button.setIcon(new ImageIcon(image1));
button.setSelectedIcon(new ImageIcon(image2));
button.setBorderPainted(false);
button.setContentAreaFilled(false);
JOptionPane.showMessageDialog(null, button);
}
});
}
}
Old Code - before I realized this was about images
I want to make it so that if I click on the JLabel
What about for people who are 'mouse challenged? Use a JTextField instead. Tab to any link and hit Enter to activate.
import java.awt.Desktop;
import java.awt.Color;
import java.awt.Cursor;
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.*;
import javax.swing.JTextField;
import javax.swing.JPanel;
import javax.swing.JOptionPane;
import javax.swing.SwingUtilities;
import javax.swing.border.MatteBorder;
import javax.swing.border.Border;
import java.net.URI;
import java.io.File;
/**
A Java 1.6+ LinkLabel that uses the Desktop class for opening
the document of interest.
The Desktop.browse(URI) method can be invoked from applications,
applets and apps. launched using Java Webstart. In the latter
two cases, the usual fall-back methods are used for sandboxed apps
(see the JavaDocs for further details).
While called a 'label', this class actually extends JTextField,
to easily allow the component to become focusable using keyboard
navigation.
To successfully browse to a URI for a local File, the file name
must be constructed using a canonical path.
#author Andrew Thompson
#version 2008/08/23
*/
public class LinkLabel
// we extend a JTextField, to get a focusable component
extends JTextField
implements MouseListener, FocusListener, ActionListener {
/** The target or href of this link. */
private URI target;
public Color standardColor = new Color(0,0,255);
public Color hoverColor = new Color(255,0,0);
public Color activeColor = new Color(128,0,128);
public Color transparent = new Color(0,0,0,0);
public boolean underlineVisible = true;
private Border activeBorder;
private Border hoverBorder;
private Border standardBorder;
/** Construct a LinkLabel that points to the given target.
The URI will be used as the link text.*/
public LinkLabel(URI target) {
this( target, target.toString() );
}
/** Construct a LinkLabel that points to the given target,
and displays the text to the user. */
public LinkLabel(URI target, String text) {
super(text);
this.target = target;
}
/* Set the active color for this link (default is purple). */
public void setActiveColor(Color active) {
activeColor = active;
}
/* Set the hover/focused color for this link (default is red). */
public void setHoverColor(Color hover) {
hoverColor = hover;
}
/* Set the standard (non-focused, non-active) color for this
link (default is blue). */
public void setStandardColor(Color standard) {
standardColor = standard;
}
/** Determines whether the */
public void setUnderlineVisible(boolean underlineVisible) {
this.underlineVisible = underlineVisible;
}
/* Add the listeners, configure the field to look and act
like a link. */
public void init() {
this.addMouseListener(this);
this.addFocusListener(this);
this.addActionListener(this);
setToolTipText(target.toString());
if (underlineVisible) {
activeBorder = new MatteBorder(0,0,1,0,activeColor);
hoverBorder = new MatteBorder(0,0,1,0,hoverColor);
standardBorder = new MatteBorder(0,0,1,0,transparent);
} else {
activeBorder = new MatteBorder(0,0,0,0,activeColor);
hoverBorder = new MatteBorder(0,0,0,0,hoverColor);
standardBorder = new MatteBorder(0,0,0,0,transparent);
}
// make it appear like a label/link
setEditable(false);
setForeground(standardColor);
setBorder(standardBorder);
setCursor( new Cursor(Cursor.HAND_CURSOR) );
}
/** Browse to the target URI using the Desktop.browse(URI)
method. For visual indication, change to the active color
at method start, and return to the standard color once complete.
This is usually so fast that the active color does not appear,
but it will take longer if there is a problem finding/loading
the browser or URI (e.g. for a File). */
public void browse() {
setForeground(activeColor);
setBorder(activeBorder);
try {
Desktop.getDesktop().browse(target);
} catch(Exception e) {
e.printStackTrace();
}
setForeground(standardColor);
setBorder(standardBorder);
}
/** Browse to the target. */
public void actionPerformed(ActionEvent ae) {
browse();
}
/** Browse to the target. */
public void mouseClicked(MouseEvent me) {
browse();
}
/** Set the color to the hover color. */
public void mouseEntered(MouseEvent me) {
setForeground(hoverColor);
setBorder(hoverBorder);
}
/** Set the color to the standard color. */
public void mouseExited(MouseEvent me) {
setForeground(standardColor);
setBorder(standardBorder);
}
public void mouseReleased(MouseEvent me) {}
public void mousePressed(MouseEvent me) {}
/** Set the color to the standard color. */
public void focusLost(FocusEvent fe) {
setForeground(standardColor);
setBorder(standardBorder);
}
/** Set the color to the hover color. */
public void focusGained(FocusEvent fe) {
setForeground(hoverColor);
setBorder(hoverBorder);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
try {
File f = new File(".","LinkLabel.java");
/* Filename must be constructed with a canonical path in
order to successfully use Desktop.browse(URI)! */
f = new File(f.getCanonicalPath());
JPanel p = new JPanel(new GridLayout(0,1));
URI uriFile = f.toURI();
LinkLabel linkLabelFile = new LinkLabel(uriFile);
linkLabelFile.init();
p.add(linkLabelFile);
LinkLabel linkLabelWeb = new LinkLabel(
new URI("http://pscode.org/sscce.html"),
"SSCCE");
linkLabelWeb.setStandardColor(new Color(0,128,0));
linkLabelWeb.setHoverColor(new Color(222,128,0));
linkLabelWeb.init();
/* This shows a quirk of the LinkLabel class, the
size of the text field needs to be constrained to
get the underline to appear properly. */
p.add(linkLabelWeb);
LinkLabel linkLabelConstrain = new LinkLabel(
new URI("http://stackoverflow.com/"),
"Stack Overflow");
linkLabelConstrain.init();
/* ..and this shows one way to constrain the size
(appropriate for this layout).
Similar tricks can be used to ensure the underline does
not drop too far *below* the link (think BorderLayout
NORTH/SOUTH).
The same technique can also be nested further to produce
a NORTH+EAST packing (for example). */
JPanel labelConstrain = new JPanel(new BorderLayout());
labelConstrain.add( linkLabelConstrain, BorderLayout.EAST );
p.add(labelConstrain);
LinkLabel linkLabelNoUnderline = new LinkLabel(
new URI("http://java.net/"),
"java.net");
// another way to deal with the underline is to remove it
linkLabelNoUnderline.setUnderlineVisible(false);
// we can use the methods inherited from JTextField
linkLabelNoUnderline.
setHorizontalAlignment(JTextField.CENTER);
linkLabelNoUnderline.init();
p.add(linkLabelNoUnderline);
JOptionPane.showMessageDialog( null, p );
} catch(Exception e) {
e.printStackTrace();
}
}
});
}
}

You cannot simply add an actionListener, you need to implement MouseListener, something like this.

If you are looking for Customized JLable with different font and size and mouse action listeners just go through this.
This is fully tested with following tasks
1.JLabel with Image and Text.
2.Jlabel with Mouse Listners.
3.On hover action with image and text replacement.
public class CustomJLabel extends JLabel implements MouseListener
{
private Color color;
private int width=0;
private int height=0;
private ImageIcon normal_icon;
private ImageIcon hover_icon;
private ImageIcon icon_Label;
JLabel label;
private boolean isMatch;
public CustomJLabel(ImageIcon icon,ImageIcon icon1, String text, int i, int j) {
this.normal_icon=icon;
this.hover_icon=icon1;
this.icon_Label=normal_icon;
setFont(new Font("Tw Cen MT", Font.TYPE1_FONT, 16));
setForeground(Color.WHITE);
setOpaque(false);
setHorizontalAlignment( SwingConstants.CENTER );
setText(text);
addMouseListener(this) ;
}
public CustomJLabel(ImageIcon icon,ImageIcon icon1, int i, int j) {
this.normal_icon=icon;
this.hover_icon=icon1;
this.icon_Label=normal_icon;
setText("");
setVerticalAlignment( SwingConstants.CENTER);
setForeground(Color.WHITE);
setOpaque(false);
addMouseListener(this) ;
}
public CustomJLabel(ImageIcon icon,ImageIcon icon1, String text, int i, int j,Font f) {
this.normal_icon=icon;
this.hover_icon=icon1;
this.icon_Label=normal_icon;
this.width=i;
this.height=j;
setFont(f);
setForeground(Color.WHITE);
setOpaque(false);
setText(text);
setVerticalAlignment( SwingConstants.TOP);
addMouseListener(this) ;
}
public int getIconWidth(){
return width;
}
public int getIconHeight(){
return height;
}
#Override
public void paintComponent(Graphics g) {
if(this.width !=0 && this.height!=0){
super.paintComponent(g);
icon_Label.paintIcon(this, g, this.width, this.height);
}
else{
g.drawImage(icon_Label.getImage(),0,0, null);
super.paintComponent(g);
}
}
#Override
public void mouseClicked(MouseEvent arg0) {
// TODO Auto-generated method stub
}
#Override
public void mouseEntered(MouseEvent me) {
// TODO Auto-generated method stub
if(hover_icon!=null){
this.icon_Label=hover_icon;
this.repaint();
this.revalidate();
}
else{
this.icon_Label=normal_icon;
this.repaint();
this.revalidate();
}
}
#Override
public void mouseExited(MouseEvent arg0) {
// TODO Auto-generated method stub
if(normal_icon!=null){
this.icon_Label=normal_icon;
this.repaint();
this.revalidate();
}
else{
this.icon_Label=hover_icon;
this.repaint();
this.revalidate();
}
}
#Override
public void mousePressed(MouseEvent arg0) {
// TODO Auto-generated method stub
}
#Override
public void mouseReleased(MouseEvent arg0) {
// TODO Auto-generated method stub
}
}
//Here Usage of custom JLabel
JLabel customLabel;
customLabel=new CustomLabel(imageicon1,imageicon2,text,0,0)
//Here
Imageiocn1= Initial icon for JLabel.
Imageicon2= Onhover image for JLabel.
Text = Some String for setting name for JLabel.