Develop Reference

Action is not getting triggered when using Event handlers- KeyListener

So I am new to event handlers, and I wanted to create a program where I made a Purple panel inside a frame and if the user clicks the mouse button in the area of the panel and then types % with their keyboard, I want the panel to draw a line segment in the area of the panel. This is just testing the event handlers. Right now, I am trying it but it does not work. All help will be appreciated. After I get the hand of this, I want to try out the repaint() method, where if someone does the same actions as before, I wanted to check the background of the Panel. If you can help me with both, that'd be awesome but it is not a priority. Thank you.
import java.awt.Graphics; // for classes Graphics, Color, Font, Image
import java.awt.Color;
import java.awt.Font;
import java.awt.event.KeyEvent; // for classes KeyListener, MouseListener
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JFrame; // for classes JFrame, JPanel, JLabel
import javax.swing.JPanel;
public class GardenGrows
{
public GardenGrows()
{
}
public static void main(String[] args)
{
GardenGrows gg = new GardenGrows();
gg.runIt();
}
// makes the frame and handles all properties of the frame
// also instantiates the Garden.java object
public void runIt()
{
JFrame frame = new JFrame ("Garden");
frame.setDefaultCloseOperation( frame.EXIT_ON_CLOSE );
frame.setLayout(null);
frame.setBackground(Color.GRAY);
frame.setSize( 1200,700);
frame.setLocation( 50, 10);
frame.setResizable(true);
frame.setVisible(true);
Garden gar = new Garden();
frame.getContentPane().add(gar);
}
}
class Garden extends JPanel implements KeyListener, MouseListener
{
private boolean mouseClicked;
private boolean keyClicked;
private int xpos;
private int ypos;
public Garden()
{
mouseClicked = false;
keyClicked = false;
addKeyListener(this);
addMouseListener(this);
setBackground(Color.PINK);
setLocation(50,50);
setSize(1000,500);
}
public void mousePressed(MouseEvent evt)
{
int x = evt.getX();
int y = evt.getY();
if(x>=50 || x<=1050 && y<=50 || y>=550)
{
mouseClicked = true;
}
}
public void mouseClicked(MouseEvent evt){}
public void mouseReleased(MouseEvent evt){}
public void mouseEntered(MouseEvent evt){}
public void mouseExited(MouseEvent evt){}
public void keyReleased(KeyEvent evt){}
public void keyPressed(KeyEvent evt){}
public void keyTyped(KeyEvent evt)
{
int letter = evt.getKeyCode();
if (letter == 13)
{
keyClicked =true;
}
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
if(keyClicked && mouseClicked)
g.drawLine(50,0,110,120);
}
}

Making a key listener work in a JPanel, will not be so simple, because it is not focusable. (Think about a JTextField, when you write text on it, it is focused). So, in order to make this work you will have to use KeyBindings. In practice, remove the KeyListener implementation from your JPanel, and use KeyBindings.
public class GardenGrows {
public GardenGrows() {
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
// All swing applications must run on EDT Thread
GardenGrows gg = new GardenGrows();
gg.runIt();
});
}
// makes the frame and handles all properties of the frame
// also instantiates the Garden.java object
public void runIt() {
JFrame frame = new JFrame("Garden");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(null);
frame.setBackground(Color.GRAY);
frame.setSize(1200, 700);
frame.setLocation(50, 10);
frame.setResizable(true);
frame.setVisible(true);
Garden gar = new Garden();
frame.getContentPane().add(gar);
}
}
class Garden extends JPanel implements MouseListener {
private boolean mouseClicked;
private boolean keyClicked;
private int xpos;
private int ypos;
public Garden() {
mouseClicked = false;
keyClicked = false;
addMouseListener(this);
setBackground(Color.PINK);
setLocation(50, 50);
setSize(1000, 500);
getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_5, KeyEvent.SHIFT_MASK),
"percentageClicked");
getActionMap().put("percentageClicked", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent e) {
keyClicked = true;
repaint(); // Try to draw the line
}
});
}
public void mousePressed(MouseEvent evt) {
int x = evt.getX();
int y = evt.getY();
if (x >= 50 || x <= 1050 && y <= 50 || y >= 550) {
mouseClicked = true;
repaint(); // Try to draw the line
}
}
public void mouseClicked(MouseEvent evt) {
}
public void mouseReleased(MouseEvent evt) {
}
public void mouseEntered(MouseEvent evt) {
}
public void mouseExited(MouseEvent evt) {
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
if (keyClicked && mouseClicked)
g.drawLine(50, 0, 110, 120);
}
}

How can I avoid flicker when resizing a Swing window?

I have a dialog where additional controls cause the dialog to resize when they appear. One day I will probably find a way to animate that, but for now I'm content with it just resizing. Problem is, it flickers.
I reduced the problem to a test:
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.JRootPane;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
/**
* Shows flickering when resizing a dialog.
*/
public class FlickerTest extends FakeJDialog
{
public FlickerTest()
{
super((Window) null, "Flicker Test");
JButton button = new JButton("Bigger!");
button.addActionListener(new ActionListener()
{
#Override
public void actionPerformed(ActionEvent event)
{
Window window = SwingUtilities.getWindowAncestor((Component) event.getSource());
window.setSize(window.getWidth(), window.getHeight() + 20);
}
});
JPanel contentPane = new JPanel(new BorderLayout());
contentPane.setOpaque(true);
contentPane.add(button, BorderLayout.PAGE_START);
JRootPane rootPane = new JRootPane();
rootPane.setContentPane(contentPane);
add(rootPane);
setResizable(false);
pack();
setLocationRelativeTo(null);
}
public static void main(String[] args) throws Exception
{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
SwingUtilities.invokeLater(new Runnable()
{
#Override
public void run()
{
new FlickerTest().setVisible(true);
}
});
}
}
Each time I click the button, the window changes size. For a noticeable amount of time, the bottom of the dialog goes black. By recording my screen, I was able to get a screenshot demonstrating it:
How can I avoid this?
Further investigation:
The following subclass of Dialog exhibits the same flickering as JDialog:
import java.awt.Component;
import java.awt.Container;
import java.awt.Dialog;
import java.awt.Window;
import javax.swing.JLayeredPane;
import javax.swing.JRootPane;
import javax.swing.RootPaneContainer;
/**
* Minimal subclass of Dialog required to cause the flickering.
* If you comment out "implements RootPaneContainer", the flickering goes away.
*/
public class FakeJDialog extends Dialog implements RootPaneContainer
{
public FakeJDialog(Window owner, String title)
{
super(owner, title, Dialog.ModalityType.MODELESS);
}
public JRootPane getRootPane()
{
throw new UnsupportedOperationException();
}
public Container getContentPane()
{
throw new UnsupportedOperationException();
}
public void setContentPane(Container contentPane)
{
throw new UnsupportedOperationException();
}
public JLayeredPane getLayeredPane()
{
throw new UnsupportedOperationException();
}
public void setLayeredPane(JLayeredPane layeredPane)
{
throw new UnsupportedOperationException();
}
public Component getGlassPane()
{
throw new UnsupportedOperationException();
}
public void setGlassPane(Component glassPane)
{
throw new UnsupportedOperationException();
}
}
I find this kind of interesting, because merely commenting out the implements RootPaneContainer is somehow enough to completely change the behaviour. Something in Swing or AWT is obviously looking for this interface and treating those components specially. So this suggests that no subclass of JDialog would avoid the issue.

I don't believe there is a way around this with JDialog. However, java.awt.Dialog doesn't have this issue.

Try this, i have made an example which removes flickering almost completely
in addition u will get well-marked resize corner
/*
* resizing swing trick in Win7+Aero demo
* #author: s1w_
*/
import java.awt.event.*;
import java.awt.*;
import javax.swing.event.*;
import javax.swing.*;
class ResizeHookDemo extends JDialog {
private final static int width = 580, height = 350;
private final JFileChooser fc;
private java.awt.geom.GeneralPath gp;
public ResizeHookDemo() {
super((JDialog)null, "Choose File", true);
fc = new JFileChooser() {
#Override
public void paint(Graphics g) {
super.paint(g);
int w = getWidth();
int h = getHeight();
g.setColor(new Color(150, 150, 150, 200));
g.drawLine(w-7, h, w, h-7);
g.drawLine(w-11, h, w, h-11);
g.drawLine(w-15, h, w, h-15);
gp = new java.awt.geom.GeneralPath();
gp.moveTo(w-17, h);
gp.lineTo(w, h-17);
gp.lineTo(w, h);
gp.closePath();
}
};
fc.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (e.getActionCommand().equals("CancelSelection")) {
setVisible(false);
// action...
}
else if (e.getActionCommand().equals("ApproveSelection")) {
setVisible(false);
// action...
}
}
});
MouseInputListener resizeHook = new MouseInputAdapter() {
private Point startPos = null;
public void mousePressed(MouseEvent e) {
if (gp.contains(e.getPoint()))
startPos = new Point(getWidth()-e.getX(), getHeight()-e.getY());
}
public void mouseReleased(MouseEvent mouseEvent) {
startPos = null;
}
public void mouseMoved(MouseEvent e) {
if (gp.contains(e.getPoint()))
setCursor(Cursor.getPredefinedCursor(Cursor.SE_RESIZE_CURSOR));
else
setCursor(Cursor.getDefaultCursor());
}
public void mouseDragged(MouseEvent e) {
if (startPos != null) {
int dx = e.getX() + startPos.x;
int dy = e.getY() + startPos.y;
setSize(dx, dy);
repaint();
}
}
};
fc.addMouseMotionListener(resizeHook);
fc.addMouseListener(resizeHook);
fc.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 20));
add(fc);
setResizable(false);
setMinimumSize(new Dimension(width, height));
setDefaultCloseOperation(HIDE_ON_CLOSE);
setLocationRelativeTo(null);
}
public static void main(String args[]) {
System.out.println("Starting demo...");
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new ResizeHookDemo().setVisible(true);
}
});
}
}

Clear painted screen at each click of the mouse?

Can't seem to figure out how to only show one circle. Was trying to //g.clearRect(0, 0, 400, 400); but that clears the background too. Was also trying to just fill the background with yellow again but couldn't get that working either. Any suggestions?
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class JMouseFrame extends JFrame
implements MouseListener {
Container con = null;
int x, y;
int size;
public JMouseFrame() {
setTitle("JMouseFrame");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
con = this.getContentPane();
addMouseListener(this);
}
public void mousePressed(MouseEvent e) {
x = e.getX();
y = e.getY();
}
public void mouseClicked(MouseEvent e) {
int whichButton = e.getButton();
if (whichButton == MouseEvent.BUTTON1) {
size = 15;
} else if (whichButton == MouseEvent.BUTTON3) {
size = 4;
}
repaint();
}
public void mouseEntered(MouseEvent e) {
con.setBackground(Color.yellow);
}
public void mouseExited(MouseEvent e) {
con.setBackground(Color.black);
}
public void paint(Graphics g) {
//g.clearRect(0, 0, 400, 400);
g.drawOval(x - size, y - size, size * 3, size * 3);
}
public static void main(String[] args) {
JMouseFrame mFrame = new JMouseFrame();
mFrame.setSize(400, 400);
mFrame.setVisible(true);
}
public void mouseReleased(MouseEvent e) {
}
}

It looks like you're mixing AWT and Swing painting. Instead, override paintComponent(), as suggested in the example below. See Painting in AWT and Swing for details.
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
/** #see http://stackoverflow.com/questions/3898775 */
public class MousePanel extends JPanel {
private static final int SIZE = 20;
Point p = new Point(Short.MAX_VALUE, Short.MAX_VALUE);
public MousePanel() {
this.setPreferredSize(new Dimension(400, 400));
this.setBackground(Color.yellow);
this.addMouseListener(new MouseHandler());
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.black);
g.drawOval(p.x - SIZE, p.y - SIZE, SIZE * 2, SIZE * 2);
}
private final class MouseHandler extends MouseAdapter {
#Override
public void mousePressed(MouseEvent e) {
p = e.getPoint();
repaint();
}
}
private void display() {
JFrame f = new JFrame("MousePanel");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(this);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new MousePanel().display();
}
});
}
}
Addendum:
I can't figure out how to make the code you posted work with what I have...
You can restore your mouse methods to the MouseHandler almost verbatim. The only difference is the need to qualify this, e.g.
#Override
public void mouseClicked(MouseEvent e) {
int whichButton = e.getButton();
if (whichButton == MouseEvent.BUTTON1) {
MousePanel.this.size = 15;
} else if (whichButton == MouseEvent.BUTTON3) {
MousePanel.this.size = 4;
}
repaint();
}
#Override
public void mouseEntered(MouseEvent e) {
MousePanel.this.setBackground(Color.yellow);
}
#Override
public void mouseExited(MouseEvent e) {
MousePanel.this.setBackground(Color.black);
}

Adding mouseListener to my object in java

I'm trying to make an applet which I can simply drag an image. And I want image object to listen events. So here is the applet code which simple run in a thread:
import java.awt.*;
import java.net.URL;
import javax.swing.JApplet;
public class Client extends JApplet implements Runnable {
private static final long serialVersionUID = 1L;
MediaTracker mediaTracker;
Image [] imgArray;
Tas t1;
public void init()
{
mediaTracker = new MediaTracker(this);
imgArray = new Image[1];
URL base = getCodeBase();
imgArray[0] = getImage(base,"okey.png");
mediaTracker.addImage(imgArray[0],1);
try {
mediaTracker.waitForAll();
} catch (InterruptedException e) {
e.printStackTrace();
}
t1 = new Tas(this, new Rectangle(0, 0, imgArray[0].getWidth(this), imgArray[0].getHeight(this)), imgArray[0]);
Thread t = new Thread(this);
t.start();
}
public void paint(Graphics g)
{
t1.paint(g);
}
#Override
public void run() {
while(true){
//System.out.println("run");
repaint();
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
And the class of object which holds image is:
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JPanel;
#SuppressWarnings("serial")
public class Movable extends JPanel implements MouseListener {
public Client mainObj;
public Rectangle rect;
public Image image;
public Movable(Client mainObj, Rectangle rect, Image image) {
this.mainObj = mainObj;
this.rect = rect;
this.image = image;
addMouseListener(this);
}
public void paint(Graphics g) {
g.drawImage(image, rect.x, rect.y, rect.width, rect.height, this);
}
#Override
public void mouseClicked(MouseEvent arg0) {
System.out.println("clicked");
}
#Override
public void mouseEntered(MouseEvent arg0) {
}
#Override
public void mouseExited(MouseEvent arg0) {
}
#Override
public void mousePressed(MouseEvent arg0) {
System.out.println("pressed");
}
#Override
public void mouseReleased(MouseEvent arg0) {
}
}
#SuppressWarnings("serial")
class Tas extends Movable{
public String name = "";
public Tas(Client mainObj, Rectangle rect, Image image) {
super(mainObj, rect, image);
}
}
I can see the image in my applet but nothing happens when I click in or out of the image. So what's wrong with this code.

Assuming that Tas in code #1 is Moveable in code #2...
You don't actually use the Moveable as a Component, but instead ask it to paint itself onto the Applet's graphics context, here:
public void paint(Graphics g)
{
t1.paint(g);
}
Instead you should add an instance of Moveable onto the Applet's container, wherein painting will become automatic, and it will start to receive mouse events. You can also remove that paint() method then too.

First of all you should never override the paint method of a top level container (JApplet, JFrame, JDialog).
Then to do custom painting on other Swing components you override the paintComponent() method of the component, NOT the paint() method. Read the Swing tutorial on Custom Painting. So first fix those problems.
I'm not sure what the point of the Thread is but remove it from your code until you solve your other problems. If you are trying to do animation, then you should be using a Swing Timer, not a Thread.
If you want to see some code for dragging components you can take a look at Moving Windows for some generic code.

This is a working solution. It is not an applet but you can easily convert that. Hope it helps :
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.geom.Point2D;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
#SuppressWarnings("serial")
public class ImagePanel extends JPanel {
Image image;
Point2D axis = new Point2D.Double();
boolean drag = false;
Point2D dragPoint = new Point2D.Double();
public ImagePanel(Image image) {
this.image = image;
setPreferredSize(new Dimension(300,300));
addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
drag = true;
dragPoint = e.getPoint();
}
#Override
public void mouseReleased(MouseEvent e) {
drag = false;
}
});
addMouseMotionListener(new MouseMotionAdapter() {
#Override
public void mouseDragged(MouseEvent e) {
if (drag) {
axis.setLocation(axis.getX()
+ (e.getPoint().x - dragPoint.getX()), axis.getY()
+ (e.getPoint().y - dragPoint.getY()));
dragPoint = e.getPoint();
repaint();
}
}
});
}
#Override
public void paintComponent(Graphics g) {
g.setColor(Color.white);
g.fillRect(0, 0, getWidth(), getHeight());
g.drawImage(image, (int) axis.getX(), (int) axis.getY(), null);
}
public static void main(String[] args) {
try {
JFrame f = new JFrame();
f.getContentPane().add(
new ImagePanel(ImageIO.read(new File("image.jpg"))));
f.pack();
f.setVisible(true);
} catch (IOException e) {
e.printStackTrace();
}
}
}

The simple answer is - you don't have code to do anything in mousePressed() or mouseReleased().
There are lots of other problems in the code though...
Simplest solution I could come up with -
public class Client extends JApplet {
private MouseInputAdapter myMouseListener = new MyMouseListener();
public void init() {
// usually a very bad idea, but needed here
// since you want to move things around manually
setLayout(null);
// assuming this will get used often, so making it a method.
addLabelForImage(getImage(getCodeBase(), "okay.png"));
}
private void addLabelForImage(Image image) {
ImageIcon icon = new ImageIcon(image);
JLabel l = new JLabel(icon);
add(l);
l.setSize(l.getPreferredSize());
// you'll probably want some way to calculate initial position
// of each label based on number of images, size of images,
// size of applet, etc. - just defaulting to 100,100 now.
l.setLocation(100, 100);
l.addMouseListener(myMouseListener);
l.addMouseMotionListener(myMouseListener);
}
// Made this a MouseInputAdapter because I assume you may want to handle
// other types of mouse events later...
private static class MyMouseListener extends MouseInputAdapter {
#Override
public void mouseDragged(MouseEvent e) {
// when the mouse is dragged over a the component this listener is
// attached to (ie - one of the labels) convert the point of the mouse
// event from the internal component coordinates (0,0 is upper right
// corner of each label), to it's parent's coordinates (0,0 is upper
// right corner of the applet), and set the components location to
// that point.
Component theLabel = e.getComponent();
Container theApplet = theLabel.getParent();
Point labelPoint = e.getPoint();
Point appletPoint = SwingUtilities.convertPoint(
theLabel, labelPoint, theApplet );
theLabel.setLocation(appletPoint);
}
}
}

Swing: Creating a draggable component...?

I searched the web for examples of draggable Swing components,
but I found either incomplete or non-working examples.
What I need is a Swing component that can be dragged by the mouse
inside an other component. While being dragged, it should already
change its position, not just 'jump' to its destination.
I would appreciate examples which work without non-standard APIs.
Thank you.

I propose a simple, but well-working solution, found out by myself ;)
What do I do?
When mouse is pressed, I record the cursor's position on screen, and
the component's position.
When mouse is dragged, I calculate the difference between new and
old cursor's position on screen, and move the
component by this difference.
Tested with latest JDK 6 unter Linux (OpenSuse, KDE3),
but hey, it's Java Swing, should work equally everywhere.
Here goes the code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
public class MyDraggableComponent
extends JComponent {
private volatile int screenX = 0;
private volatile int screenY = 0;
private volatile int myX = 0;
private volatile int myY = 0;
public MyDraggableComponent() {
setBorder(new LineBorder(Color.BLUE, 3));
setBackground(Color.WHITE);
setBounds(0, 0, 100, 100);
setOpaque(false);
addMouseListener(new MouseListener() {
#Override
public void mouseClicked(MouseEvent e) { }
#Override
public void mousePressed(MouseEvent e) {
screenX = e.getXOnScreen();
screenY = e.getYOnScreen();
myX = getX();
myY = getY();
}
#Override
public void mouseReleased(MouseEvent e) { }
#Override
public void mouseEntered(MouseEvent e) { }
#Override
public void mouseExited(MouseEvent e) { }
});
addMouseMotionListener(new MouseMotionListener() {
#Override
public void mouseDragged(MouseEvent e) {
int deltaX = e.getXOnScreen() - screenX;
int deltaY = e.getYOnScreen() - screenY;
setLocation(myX + deltaX, myY + deltaY);
}
#Override
public void mouseMoved(MouseEvent e) { }
});
}
}
public class Main {
public static void main(String[] args) {
JFrame f = new JFrame("Swing Hello World");
// by doing this, we prevent Swing from resizing
// our nice component
f.setLayout(null);
MyDraggableComponent mc = new MyDraggableComponent();
f.add(mc);
f.setSize(500, 500);
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setVisible(true);
}
}

Also, I found out that one could create an JInternalFrame inside an JFrame,
but the problem is: you get always an annoying window title bar.
To disable the title bar, sadly, a dirty workaround is necessary:
public class MyDraggableComponent extends JInternalFrame {
public MyDraggableComponent() {
InternalFrameUI thisUI = getUI();
if (thisUI instanceof BasicInternalFrameUI) {
((BasicInternalFrameUI) thisUI).setNorthPane(null);
}
}
I really miss a method like "someInternalFrame.setWindowTitleBar(false)"...
:'(