Develop Reference

How to externalize a MouseListener?

(Note: I am aware of the existence of the MouseAdapter-class, but since I am probably overriding all methods later on, the advantage of it is lost?)
I have a class MainProgram.java in which I'm adding several components. Most of them have a Listener (ActionListener, MouseListener, ...), which get's a bit crowded in my main class.
Therefore I am trying to "externalize" those Listeners into their own classes. So far I have used inner classes in my main-class, which makes accessing the variables, components, ... pretty easy and straightforward.
But with the external Listeners I am not sure what is the best way to implement them.
For example, when I want to find out, which of the lables has been clicked, I am getting the event, get the source of the event, cast it to a JLabel and then get the text on the label with which I compare a string!
This works, but seems very prone to errors (what if I change the JLabel-text in my main-class? -> Listener breaks) and pretty unclean.
I've tried to search via google and on StackOverflow for better ways to do this, but only found the inner class approach.
So is there a better way to get access to my components / externalize my listeners?
public class MainProgram extends JFrame {
public MainProgram() {
super("Landing Page");
setSize(400, 400);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel westPanel = new JPanel();
JLabel lbl_orderStatus = new JLabel("Order Status");
JLabel lbl_technicalDocu = new JLabel("Technical Documentation");
JLabel lbl_checkReport = new JLabel("Check Report");
MouseListenerBoldFont mouseListenerLabelBoldPlain = new MouseListenerBoldFont();
lbl_orderStatus.addMouseListener(mouseListenerLabelBoldPlain);
lbl_technicalDocu.addMouseListener(mouseListenerLabelBoldPlain);
lbl_checkReport.addMouseListener(mouseListenerLabelBoldPlain);
westPanel.add(lbl_orderStatus);
westPanel.add(lbl_technicalDocu);
westPanel.add(lbl_checkReport);
add(westPanel);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
MainProgram window = new MainProgram();
window.setVisible(true);
}
catch (Exception e) {
e.printStackTrace();
}
}
});
}
The MouseListenerBoldFont.java:
public class MouseListenerBoldFont implements MouseListener{
Object lbl_westPanel;
#Override
public void mouseClicked(MouseEvent e) {
if(((JLabel)e.getSource()).getText().equals("Order Status")){
System.out.println("Order Status clicked");
};
if(((JLabel)e.getSource()).getText().equals("Technical Documentation")){
System.out.println("Technical Documentation clicked");
};
if(((JLabel)e.getSource()).getText().equals("Check Report")){
System.out.println("Check Report clicked");
};
}
#Override
public void mouseEntered(MouseEvent e) {
lbl_westPanel = e.getSource();
((JComponent) lbl_westPanel).setFont(new Font("tahoma", Font.BOLD, 12));
}
#Override
public void mouseExited(MouseEvent e) {
lbl_westPanel = e.getSource();
((JComponent) lbl_westPanel).setFont(new Font("tahoma", Font.PLAIN, 11));
}
#Override
public void mousePressed(MouseEvent e) {
}
#Override
public void mouseReleased(MouseEvent e) {
}
}

sure this is not the best way but may be useful for your problem
public class MyLabel extends JLabel implements MouseListener {
public MyLabel() {
addMouseListener(this);
}
public MyLabel(String txt) {
super(txt);
addMouseListener(this);
}
public void mouseClicked(MouseEvent e) {
System.out.println(getText() + " clicked");
}
public void mouseEntered(MouseEvent e) {
setFont(new Font("tahoma", Font.BOLD, 12));
}
public void mouseExited(MouseEvent e) {
setFont(new Font("tahoma", Font.PLAIN, 11));
}
public void mousePressed(MouseEvent e) { }
public void mouseReleased(MouseEvent e) { }
}
then
JLabel lbl_orderStatus = new MyLabel("Order Status");
JLabel lbl_technicalDocu = new MyLabel("Technical Documentation");
JLabel lbl_checkReport = new MyLabel("Check Report");
// MouseListenerBoldFont mouseListenerLabelBoldPlain = new MouseListenerBoldFont();
//
// lbl_orderStatus.addMouseListener(mouseListenerLabelBoldPlain);
// lbl_technicalDocu.addMouseListener(mouseListenerLabelBoldPlain);
// lbl_checkReport.addMouseListener(mouseListenerLabelBoldPlain);

My recommendation is to write inline (anonymous-class) handlers that forward the actual handling to another, non-anonymous function. This would give you something like:
JLabel lblOrderStatus = new JLabel("Order Status");
lblOrderStatus.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent evt) {
doWhateverClickOnOrderStatusRequires();
}
});
// much later
private void doWhateverClickOnOrderStatusRequires() { ... }
The name of the external not-quite-handler method (doWhateverClickOnOrderStatusRequires) should capture the task that it attempts to achieve (for example, launchRockets); and with this pattern, you can call the same not-quite-handler method from multiple handlers. Since the compiler will check that the calls are valid a compile-time, there are no fragile string-constants involved.

You probably still want to use a class which extends MouseAdapter, since it can be used as a MouseListener, a MouseMotionListener, and a MouseWheelListener all at once (You just have to add it as all of those into a component). I'm not sure why you need to get the text on a JLabel to detect if it's the one that has been clicked. You should create a class which extends MouseAdapter and make it solely for JLabels, then add it to that JLabel. You should define a custom constructor if you want that takes a JLabel for an argument so that it will automatically know what JLabel is being interacted with. You can then add a method which passes an event to the main class.

Java mouseClicked complication

Code works, my bad. But I'm still open to suggestions on how to improve or make the code more elegant.
I have created this layout and I want to be able to draw a circle whenever the user clicks on the white area.
Couldn't post an image, so here is the link
The white area is basically a rectangle. But something with my code isn't working, it just doesn't respond to mouse clicks. When I tried to see if it responds to mouseDragged it worked perfectly but this isn't what I need.
Here is my code, some "tests" are put as /comments/ but neither of them work as intended.
I would be very grateful for help. Here is my code:
import java.awt.*;
import java.awt.Graphics;
import javax.swing.*;
public class CitiesMapPanel extends JPanel implements MouseListener {
private JButton cmdAddWay, cmdFindPath, cmdClearMap, cmdClearPath;
private JLabel lblFrom, lblTo;
private JTextField txtFrom, txtTo;
public CitiesMapPanel() {
cmdAddWay = new JButton("Add Way");
cmdFindPath = new JButton("Find Path");
cmdClearMap = new JButton("Clear Map");
cmdClearPath = new JButton("Clear Path");
lblFrom = new JLabel("From");
lblTo = new JLabel("To");
txtFrom = new JTextField(6);
txtTo = new JTextField(6);
this.addMouseListener(this);
setLayout(new BorderLayout());
add(buildGui(), BorderLayout.SOUTH);
}
private JPanel buildGui() {
JPanel buttonsBar = new JPanel();
//The "south" of the BorderLayout consist of a (2,4) GridLayout.
buttonsBar.setLayout(new GridLayout(2,4));
buttonsBar.add(lblFrom);
buttonsBar. add(txtFrom);
buttonsBar.add(lblTo);
buttonsBar.add(txtTo);
buttonsBar.add(cmdAddWay);
buttonsBar.add(cmdFindPath);
buttonsBar.add(cmdClearMap);
buttonsBar.add(cmdClearPath);
return buttonsBar;
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.white);
g.fillRect(0, 0, this.getSize().height, this.getSize().width);
}
public static void main(String[] args) {
JFrame frame = new JFrame("layout");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(530, 550);
CitiesMapPanel gui = new CitiesMapPanel();
frame.add(gui);
frame.setVisible(true);
}
/*abstract private class MyMouseListner implements MouseListener{
public void mouseClicked(MouseEvent e){
int x = e.getX();
int y = e.getY();
Graphics g = getGraphics();
g.setColor(Color.black);
g.fillOval(x,y,15,15);
}
}*/
#Override
public void mouseClicked(MouseEvent e) {
int x = e.getX();
int y = e.getY();
Graphics g = getGraphics();
g.setColor(Color.black);
g.fillOval(x,y,15,15);
System.out.println("test");
}
#Override
public void mouseEntered(MouseEvent e) {
// TODO Auto-generated method stub
}
#Override
public void mouseExited(MouseEvent e) {
// TODO Auto-generated method stub
}
#Override
public void mousePressed(MouseEvent e) {
// TODO Auto-generated method stub
}
#Override
public void mouseReleased(MouseEvent e) {
// TODO Auto-generated method stub
}
}

The click listener is not the problem. Your approach to painting is simply wrong. You can't do a getGraphic, paint on it, and expect the result to be presented. In Swing (AWT) things work fundamentally different. You need to either create an off screen image that you paint to and that you then present on screen in your paintComponent method, or you need to track the objects you want to paint in a data structure and paint those in your paintComponent method. You can trigger a repaint in your click listener by calling repaint so the UI subsystems knows about the changed state that requires a repaint of your component.
Read more about the basics in the Swing painting tutorial.

Swing Jbutton: showing border and background only when it is hovered

I want to add a hovering-effect to my customized Swing.JButton similar to the icon on my Chrome Browser:
Before hover >>
After hover >>
I am able to set the button in the "before" status when it is created, but I am not able to create the "border + raised-background" when it is hovered. When I try to re-add the border to the button, I got a moving effect as after repainting a new border is inserted.
This is my current code:
public class MyButton extends JButton implements MouseListener {
public MyButton(String iconPath, String toolTip) {
super(new ImageIcon(TipButton.class.getResource(iconPath)));
addMouseListener(this);
setBorder(null);
setBorderPainted(false);
setFocusPainted(false);
setOpaque(false);
setContentAreaFilled(false);
setToolTipText(toolTip);
}
public MyButton(String iconPath, String name, String toolTip) {
this(observers, iconPath, toolTip);
setText(name);
}
#Override
public void mouseClicked(MouseEvent e) {}
#Override
public void mousePressed(MouseEvent e) {}
#Override
public void mouseReleased(MouseEvent e) {}
#Override
public void mouseEntered(MouseEvent e) {
if (e.getSource() != this) return;
setBorder(BorderFactory.createBevelBorder(BevelBorder.RAISED));
}
#Override
public void mouseExited(MouseEvent e) {
if (e.getSource() != this) return;
setBorder(null);
}
}
I suppose the main logic should be in the methods mouseEntered/mouseExited but I don't know how to get the wanted effect. Any idea?

I think I have found a solution. Using EmptyBorder with the same sizes (insets) of a raised border does the trick. Code:
public class SwingUtils {
public static JButton createMyButton (String iconPath, String toolTip) {
final JButton b = new JButton (new ImageIcon(SwingUtils.class.getResource(iconPath)));
final Border raisedBevelBorder = BorderFactory.createRaisedBevelBorder();
final Insets insets = raisedBevelBorder.getBorderInsets(b);
final EmptyBorder emptyBorder = new EmptyBorder(insets);
b.setBorder(emptyBorder);
b.setFocusPainted(false);
b.setOpaque(false);
b.setContentAreaFilled(false);
b.setToolTipText(toolTip);
b.getModel().addChangeListener(new ChangeListener() {
#Override
public void stateChanged(ChangeEvent e) {
ButtonModel model = (ButtonModel) e.getSource();
if (model.isRollover()) {
b.setBorder(raisedBevelBorder);
} else {
b.setBorder(emptyBorder);
}
}
});
return b;
}
}
Note: as mKorbel says it would be using ChangeListener and the button created in a factory method instead of subclass JButton.

Use different images for every state. You can set a different Icon for selected, disabled selected, disabled, pressed, rollover, rolloverEnabled, rolloverSelected. More info here.

In java 7 there is a BevelBorder class that looks to be what you are looking for. The 2 methods you will probably be interested in are
paintRaisedBevel(Component c, Graphics g, int x, int y, int width, int height)
and
paintLoweredBevel(Component c, Graphics g, int x, int y, int width, int height)
Here is the documentation on the class: http://docs.oracle.com/javase/7/docs/api/javax/swing/border/BevelBorder.html

there (maybe) no reason to create extends JButton implements MouseListener {, there aren't overroaded any of JButtons methods, and use composition with returns instead,
better could be to create a local variable and to use methods implemented in API
don't to use MouseListener for Buttons Components, all these events are implemented in JButtons API and correctly
use set(Xxx)Icon for JButton
easiest of ways is to use JButton.getModel from ChangeListener, for example

How to draw a String to an applet screen at the point of mouse click?

EDIT: Okay, so I've managed to get it working now with the help of a friend. =)
I am currently creating a Java applet. The applet works by taking text input from the user and displaying it to the screen when they press return. This is the point up to which my program is working at the moment.
I was wondering whether there was a way in which I could make it so the text input/String is drawn when the mouse is clicked, at the point of mouse click.
Many thanks in advance to anyone who can help me out with this. :)

I was wondering whether there was a way in which I could make it so
the text input/String is drawn when the mouse is clicked, at the point
of mouse click.
Answer: Yes...
Would it be rude of me to leave the answer as that...?
This is a relatively simple process, depending on what you want to achieve...
This example just uses Graphics#drawString to render text to a custom component. You could, equally, just at a label to the component at the specified point, but that's another can of worms.
public class TestDrawText {
public static void main(String[] args) {
new TestDrawText();
}
public TestDrawText() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception ex) {
}
JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private Point textPoint;
public TestPane() {
addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
textPoint = e.getPoint();
repaint();
}
});
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (textPoint != null) {
FontMetrics fm = g.getFontMetrics();
g.drawString("You clicked at " + textPoint.x + "x" + textPoint.y, textPoint.x, textPoint.y + fm.getAscent());
}
}
}
}
Check out
How to Write a Mouse Listener
Performing Custom Painting
For more info.

Key Listener doesn't work in a JFrame when traversing from another JFrame

I have 2 classes.
One extends canvas and inside creates a jframe and add the canvas to that jframe and add another keyadapter class to receive key events. I also have main function to test the code. When running from main, the form is displayed and recieves key events too.
Now i create another class that extends jframe and implements keylistener to receive events in this form.
Once the functionality done in the second class i want to close the second form and show the first form. When showing it from the key event functions in the second class the first class key listener is not working.
Please just have a glimpse at my code and tell me how to correct my prob. Thanks for your time and valuable suggestion.
Class 1
public class Test extends Canvas {
private JFrame container;
public Test() {
container = new JFrame("Space Invaders");
JPanel panel = (JPanel) container.getContentPane();
panel.setPreferredSize(new Dimension(screenSize.width, screenSize.height));
panel.setLayout(null);
setBounds(0, 0, screenSize.width, screenSize.height);
panel.add(this);
container.pack();
container.setResizable(false);
container.setVisible(true);
try {
addKeyListener(new KeyInputHandler(this));
} catch (Exception e) {
e.printStackTrace();
}
requestFocus();
}
private class KeyInputHandler extends KeyAdapter {
public void keyPressed(KeyEvent e) {
//Some Action
}
public void keyReleased(KeyEvent e) {
//Some Action
}
public void keyTyped(KeyEvent e) {
//Some Action
}
}
public static void main(String args[]){
//Running this canvas here works perfectly with all added keylisteners
}
}
Class 2
public class Sample extends JFrame implements KeyListener {
public Sample() {
init();
this.setSize(100, 100);
this.setVisible(true);
Sample.this.dispose();
// Created a window here and doing some operation and finally redirecting
// to the previous test window. Even now the test window works perfectly
// with all keylisteners
new Test();
}
public static void main(String[] args) {
new Sample();
}
private void init() {
addKeyListener(this);
}
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyPressed(KeyEvent e) {
removeKeyListener(this);
Sample.this.dispose();
// But when calling the previous Test window here, the window
// gets displayed but the keylistener is not added to the
// window. No keys are detected in test window.
new Test();
}
#Override
public void keyReleased(KeyEvent e) {
}
}

Simple dont use KeyListener/KeyAdapter that is for AWT components and has known focus issues when used with Swing.
The issues can be got around by making sure your component is focusable via setFocusable(true) and than call requestFocusInWindow() after component has been added/is visible.
Rather use KeyBindings for Swing.
For example say now we wanted to listen for D pressed and released:
public static void addKeyBindings(JComponent jc) {
jc.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_D, 0, false), "D pressed");
jc.getActionMap().put("D pressed", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent ae) {
System.out.println("D pressed");
}
});
jc.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW).put(KeyStroke.getKeyStroke(KeyEvent.VK_D, 0, true), "D released");
jc.getActionMap().put("D released", new AbstractAction() {
#Override
public void actionPerformed(ActionEvent ae) {
System.out.println("D released");
}
});
}
We would call this method like:
JPanel ourPanel=new JPanel();
...
addKeyBindings(ourPanel);//adds keybindings to the panel
Other suggestions on code
Always create and manipulate Swing components on Event Dispatch Thread, via SwingUtilities.invokeLater(Runnable r) block
Dont extend JFrame class unnecessarily
Dont implement interfaces on a class unless the class will be used for that purpose, or other classes need access to the interfaces methods.
As mentioned by #AndrewThompson, dont use multiple JFrames, either swap the rest for JDialog, or use CardLayout. See here for an example.