Develop Reference

Dynamic update of visual components in swing

I have a question regarding the possibility to dinamically update the visual side of a swing application.
I have created a small program, that works without any compile/logic errors and it does it's thing but it has a flaw. It does not automatically update when user clicks on something.
Let me explain the issue with the underneath picture
I tried adding a repaint and revalidate to anything. but it doesn't seem to work. they get ignored. Really, I added a repaint/revalidate method to EVERYTHING. Still nothing :)

I suggest adding the action event to the checkbox (I called it fullAutomaticCheckBox and the field txtField):
private void fullAutomaticCheckBoxActionPerformed(java.awt.event.ActionEvent evt) {
txtField.setEnabled(fullAutomaticCheckBox.isSelected());
}
To add the event listener:
fullAutomaticCheckBox.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
fullAutomaticCheckBoxActionPerformed(evt);
}
});

I want the text field to enable itself.
Then you add an ActionListener to the check box to enable/disable the text field depending on the state of the checkbox.
once user inputs a number it will repaint dynamically
If you want the screen to repaint, then you need to invoke the "update calculations" code dynamically. So you can add a DocumentListener to the text field. This will generate an event any time the user adds or removes text in the text field.
Read the section from the Swing tutorial on How to Write a DocumentListener for a basic example to get you started.

Java Mouse Listener

This probably sounds simple and stupid, but for the life of me I cannot find a way to have a mouse listener which does mousePressed without having to be on a component. void mousePressed(){} doesn't seem to work the way I want it to.
Essentially I am making a java program which aims to work without graphics, and does things in the background. So if you click in chrome for example it still will effect the program.
What I was trying was this, which I realize is horribly incorrect.
class MKeyListener extends KeyAdapter {
#Override
public void keyPressed(KeyEvent e) {
moveMouse.playing = false;
}
}
As reccomended I tried the JNativeHook library, however it doesn't seem to work the way I think it should:
public class mousepresstest implements NativeMouseInputListener{
#Override
public void nativeMouseClicked(NativeMouseEvent e) {
System.out.println("worked");
}
}
It doesn't print the text on mouse pressed, am I missing something here?

Java Mouse listeners are only meant for swing/awt components and that too from the same running process.
If you want to listen for mouse/keyboard events from other apps use the JNativeHook
library.You can install a global keyboard hook and listen for keypress or a mousehook for mouse events.You do not need to use Swing or other GUI classes.
Internally JNativeHook uses JNI to provide these functionality.

Using KeyListener for a Calculator in NetBeans

I have written a calculator in NetBeans and it functions perfectly. However, I have to actually click the buttons to insert numbers and am trying to remedy that with a KeyListener. I have all my numbers and function buttons set inside a JPanel named buttons. I have my display label in a JPanel named display.
I set my class to implement KeyListener and it inserted the KeyPressed, -Typed, and -Released methods; however I stuck from there. I'm not sure how to make my buttons actually listen for the KeyPressed event, and when it hears the event - activate the button. Also, my buttons are named by their number (e.g. the Zero Button is named zero, One button is one, etc.).
I've read that you actually have to implement a KeyListener somewhere by using: something.addKeyListener(something);
but I cannot seem to figure this out.
Can I get some help here? I'm new to Java and this is my first solo project. And let me know if I didn't provide enough information.
EDIT: Most of my code is NetBeans Generated and I cannot edit the initialization of the components which seems to be my problem I think?
My class declaration:
public class Calculator extends javax.swing.JFrame implements KeyListener {
//Creates new form Calculator
public Calculator() {
initComponents();
}
One of my buttonPressed actions (all identical with changes for actual number):
private void zeroActionPerformed(java.awt.event.ActionEvent evt) {
if (display.getText().length() >= 16)
{
JOptionPane.showMessageDialog(null, "Cannot Handle > 16 digits");
return;
}
else if (display.getText().equals("0"))
{
return;
}
display.setText(display.getText().concat("0"));
Main method supplied by NetBeans:
public static void main(String args[]) {
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new Calculator().setVisible(true);
}
});
}
The initComponents() netbeans generated is absolutely massive (about 500 lines of code) and I cannot edit any of it. Let me know if I can supply any more helpful information.

Could there be an issue of Focus, and if so how can I resolve the issue?
Yes there is probably an issue with focus. That is why you should NOT be using a KeyListener.
Swing was designed to be used with Key Bindings. That is you create an Action that does what you want. Then this Action can be added to your JButton. It can also be bound to a KeyStroke. So you have nice reusable code.
Read the Swing tutorial on How to Use Key Bindings for more information. Key Bindings don't have the focus issue that you currently have.

I'm not sure I completely understand your question, and some code would help, but I'll take a crack, since it sounds like a problem I used to have a lot.
It sounds like the reason that your key presses aren't being recognized is that the focus is on one of the buttons. If you add keylisteners to the buttons, then you shouldn't have any problem.
In netbeans you can add keylisteners through the design screen really easily.
Here's a picture showing you how to add a keyPressed listener to a button in a jPanel.
private void jButton1KeyPressed(java.awt.event.KeyEvent evt) {
//Check which key is pressed
//do whatever you need to do with the keypressed information
}
It is nice to be able to write out the listeners yourself, but if you are just learning, then it is also nice to get as much help as possible.
This might not be the best solution, since you would have to add the listener for each of your buttons.

Button VS Image buttons in JAVA

Recently I found out that I can use my images as buttons with mouse listener.
What is the main difference between using buttons and images as buttons. What is the main drawback of this option?
Button:
JButton btnNewButton_1 = new JButton("Button");
btnNewButton_1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
//Do something
}
});
Image:
getJlabel().addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent arg0) {
//Do something
}
});

Although both of them provide similar functionalities, I think that most users are not accustomed to such a thing.
To the average user (in my opinion at least), buttons should be clicked and images should be looked at. It is like the image provides a means to the user to understand and the button provides a means for the user to act.
You could throw in Images in JButtons (as explained here), but that being said, I think that from a User Experience point of view you should not use images as buttons unless you really have to, and when you do, I think that you should include specific instructions.

The JButton provides animation (during clicking and releasing), different looks for different states (like when it's not enabled) and other things one expects from an actual "push button".
You can add the these (or some of these) functionalities to an image according to your requirements using a mouse listener.
It all depends on what you want and how much code are you willing to write by hand.
FYI, the images can be added to JButtons (mainly for the purpose of icons).

Hide JDialog window when the window lost focus

Hi I have only one JDialog box in my Java application.I want to make it invisible if it lost the focus.
I've tried different method, But didn't able to trigger any of the window focus events. Here is my code:
public void windowGainedFocus(WindowEvent e) {
System.out.println("gained focus");
}
public void windowLostFocus(WindowEvent e) {
System.out.println("lost focus");
}

Responding to Focus events can be really tricky. My experience has been that pretty much any time someone has attempted to do non-standard things with focus, they come to regret it eventually. Not least among the issues is that it's not really all that portable - a lot of X-Windows based displays use focus-follows-mouse, which can result in the focus being transferred away when you're not expecting it to, resulting in early dismissal of your dialog.
That said, Sun's official tutorial is here: http://java.sun.com/docs/books/tutorial/uiswing/misc/focus.html . If I remember right, you can attach a PropertyChangeListener to the KeyboardFocusManager, and that will be triggered for focus changes: http://java.sun.com/javase/6/docs/api/java/awt/KeyboardFocusManager.html#addPropertyChangeListener%28java.beans.PropertyChangeListener%29

Use a WindowListener and handle the windowDeactivated event.