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Trying to create a really simple button for my Panel, but even though i implement the action listener in the class, it isn't working [closed]

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I am trying just to get the button to display some text in the console, but whatever i do it isn't working here is the code for the Button class:
public class Button extends JButton implements ActionListener {
JButton button;
Button (){
button = new JButton();
this.setText("Click NOW");
button.addActionListener(this);
this.setForeground(Color.white);
button.setBounds(300, 100, 100, 50);
this.setBackground(Color.red);
this.setBorder(null);
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource()== button) {
System.out.println("Display if you work");
}
}
}
There are no errors displayed and the code compiles correctly, it just isn't displaying the text in the terminal.

This code creates two JButtons, one the button field inside of the class, that you add the action listener to:
public class Button extends JButton implements ActionListener {
JButton button; // here!
Button (){
button = new JButton(); // here!
this.setText("Click NOW");
button.addActionListener(this); // and add the listener here
and the other which is the instance of this class that extends JButton:
// here !!!
public class Button extends JButton implements ActionListener {
// ....
and which is likely the one that is displayed as elsewhere you likely have this code:
Button button = new Button();
and then add this button to the GUI. Again, this "button" is from your Button class which extends JButton but doesn't have the action listener added to it.
You can solve this in one of two ways:
Don't create the new JButton button field inside of your new class and instead add the ActionListener to the this JButton, the instance of this class,
for example:
public class Button1 extends JButton implements ActionListener {
// JButton button;
Button1() {
// button = new JButton();
this.setText("Click NOW");
// button.addActionListener(this);
this.addActionListener(this);
this.setForeground(Color.white);
// button.setBounds(300, 100, 100, 50); // You really don't want to do
// this
this.setBackground(Color.red);
this.setBorder(null);
}
#Override
public void actionPerformed(ActionEvent e) {
// no need for the if block
// if (e.getSource() == button) {
System.out.println("Display if you work");
// }
}
}
Don't create a class that extends JButton but instead create code that creates a single JButton (not two) and add the ActionListener to the same object that is added to the GUI.
I'd go with number 2 myself and make it a method that returns a button with my properties of interest:
private JButton createMyButton(String text) {
JButton button = new JButton(text);
button.setForeground(Color.WHITE);
button.setBackground(Color.RED);
button.setBorder(null);
button.addActionListener(e -> {
System.out.println("Display if you work");
});
return button;
}
Side notes:
Avoid giving your class names that clash with core Java classes, such as class Button which clashes with the java.awt.Button class.
Avoid use of null layouts and setBounds. While null layouts and setBounds() might seem to Swing newbies like the easiest and best way to create complex GUI's, the more Swing GUI'S you create the more serious difficulties you will run into when using them. They won't resize your components when the GUI resizes, they are a royal witch to enhance or maintain, they fail completely when placed in scrollpanes, they look gawd-awful when viewed on all platforms or screen resolutions that are different from the original one.
For that reason you're far better off learning about and using the layout managers. You can find the layout manager tutorial here: Layout Manager Tutorial, and you can find links to the Swing tutorials and to other Swing resources here: Swing Info.

In your actionPerformed method, use equals in the if statement, like this:
if (e.getSource().equals(button)) {
System.out.println("Display if you work");
}
It should work. == doesn't work in this case.

for ComboBox, addActionListener -> actionPerformed?

if I have
ComboBox box = b;
b.addActionListener(this);
shouldn't I expect this.actionPerformed(event) to be called
when the combobox is operated?
I have a test frame with a few combo boxes, which seem to operate
normally, but no actionPerformed is ever called. Perhaps the frame
itself needs to be armed in some way?

Your question is not so clear and you didn't give it a proper title.
If you want to add ActionListener to a ComboBox, this is how you do it:
ComboBox box = new ComboBox();
box.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent evt) {
}
});

From what I understand you just want to create a ComboBox from within a class that with be handling the action events. To do so I would suggest that the class inherits from ActionListener and override (use the #Override tag) the actionPerformed. Just Overriding the action perform is not enough if the class is not inheriting from ActionListener.
public class MyListener extends ActionListener {
#Override
public void actionPerformed (ActionEvent evt){
//code you want to execute when the event happens
}
public void methodCreatingComboBox(){
ComboBox b = new ComboBox();
b.addActionListener(this);
//other stuffs
}
}
that would work like a charm ! And you can use that same instance of MyListener for multiple events.

Here's the correct answer. I was using com.codename1.ui.Dialog as
the top level window. I switched to using com.codename1.ui.Form
and now the actions are firing as expected.
Something in the environment constructed by Dialog (which extends Form)
is interfering with the event mechanism. Perhaps by design.

KeyStroke Accelerator not working after disabling JMenuItem

Within a small Java standalone program with a Swing GUI I use JMenuItem with Accelerator - mostly without any problems:
JMenuItem item = new JMenuItem("Connect", 'C');
KeyStroke ks = KeyStroke.getKeyStroke('C', Event.CTRL_MASK);
item.setAccelerator(ks);
item.addActionListener(this);
My problem is that when I disable the item with
item.setEnabled(false);
and enable it later with
item.setEnabled(true);
I cannot use the accelerator any more. The JMenuItem is correctly shown as enabled in the menu and I can click it with the mouse (and my ActionListener is correctly working) but my accelerator isn't working - so I cannot start "Connect" with Ctrl+C any more.
Does anyone of you know what this problem is or how I can avoid it?
Other menu items which accelerators (but without beeing temporarily disabled) are working. When calling
item.getAccelerator();
after calling item.setEnabled(true) I get the formerly set KeyStroke.
It works with the KeyStroke Ctrl+U but not with Ctrl+C. It seems to me that when disabling the menu item the default copy operation is registered again with Ctrl+C and after enabling the menu item again there's no connection between the KeyStroke and the menu item any more.
While trying to build a small copy of my program to demonstrate the problem I got it:
I did two things together - enabled the JMenuItem (with KeyStroke Ctrl+C) AND requested focus for a JTextField.
Here's a small code for a program that does not react on the KeyStroke Ctrl+C, which is connected to a menu item:
public class ProblemDemo extends JFrame implements ActionListener {
public ProblemDemo() {
super("ProblemDemo");
setSize(500,500);
setLocation(500,300);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
JMenuBar menubar = new JMenuBar();
JMenuItem menuItem = new JMenuItem("JMenuItem", 'C');
menuItem.setAccelerator(KeyStroke.getKeyStroke('C', Event.CTRL_MASK));
menuItem.addActionListener(this);
JMenu menu = new JMenu("Actions");
menu.add(menuItem);
menubar.add(menu);
setJMenuBar(menubar);
JTextArea textarea = new JTextArea();
getContentPane().setLayout(new BorderLayout());
getContentPane().add(textarea, BorderLayout.CENTER);
setVisible(true);
}
#Override
public void actionPerformed(ActionEvent event) {
if ("JMenuItem".equals(event.getActionCommand())) {
System.out.println("JMenuItem clicked");
}
}
public static void main(String[] args) {
new ProblemDemo();
}
}

I had the same problem trying to enable the copy/cut menu items (as well as buttons in a toolbar), only if something is selected in a JTable by calling setEnabled (true) in a ListSelectionListener.
I solve my problem by calling requestFocusInWindow for the JMenuBar containing the items each time setEnable (true) is called.
Seems that selecting something in the table directs Ctrl+C / Ctrl+x to the table...
May be it'll help

Try to create the following method:
private KeyStroke getNewKeyStroke(){
KeyStroke ks = KeyStroke.getKeyStroke('C', Event.CTRL_MASK);
return KeyStroke;
}
then you can call the following method like that:
item.setEnabled(true);
item.setAccelerator(this.getNewKeyStroke());

Handle RadioButton events after button clicked

help,
my questions are:
why isn't itemStateChanges triggered, I tried to put it in the inner class ButtonHandler and also in RadioButtonHandler Im having trouble with it, what is the right way to do it?
I want to trigger and check the marked JRadioButtons after the user click the "check" button.
What is the right way to check which button was clicked, I feel like comparing the strings is bad programming practise. Maybe using an ID ?
How should I make a "reset" button(start over), I want to uncheck all radio buttons and run the constructor once again.
Thank you for your help !
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import javax.swing.*;
public class ExamFrame extends JFrame {
static ArrayList<Question> qArrList;
JRadioButton a1,a2,a3,a4;
public ExamFrame() {
super("Quiz");
setLayout(new GridLayout(0, 1));
GridBagConstraints gbc = new GridBagConstraints();
Exam exam = new Exam();
qArrList = exam.getExam();
int count=0;
for(Question q : qArrList){
count++;
JLabel questionLabel = new JLabel(count+". "+q.getQustion()); //swing constant ?
ArrayList<String> ansRand = q.getAllRandomAns();
a1 = new JRadioButton(ansRand.get(0));
a2 = new JRadioButton(ansRand.get(1));
a3 = new JRadioButton(ansRand.get(2));
a4 = new JRadioButton(ansRand.get(3));
add(questionLabel);
add(a1);add(a2,gbc);add(a3);add(a4);
ButtonGroup radioGroup = new ButtonGroup(); //logical relationship
radioGroup.add(a1);radioGroup.add(a2);radioGroup.add(a3);radioGroup.add(a4);
}
//buttons:
JButton checkMe = new JButton("Check Exam");
JButton refresh = new JButton("Start Over");
ButtonHandler handler = new ButtonHandler();
checkMe.addActionListener(handler);
refresh.addActionListener(handler);
add(checkMe);
add(refresh);
}
/** Listens to the radio buttons. */
public class ButtonHandler implements ActionListener
{
public void actionPerformed (ActionEvent e) {
if(e.getActionCommand().equals("Start Over")){ //id?
//how to do this?
}
else{
RadioButtonHandler handler = new RadioButtonHandler();
a1.addItemListener(handler);
System.out.println("success?");
}
JOptionPane.showMessageDialog(ExamFrame.this, String.format("You pressed: %s", e.getActionCommand()));
}
public void itemStateChanged(ItemEvent e) //can i add it here?
{
JOptionPane.showMessageDialog(ExamFrame.this, String.format("yes?"));
System.out.println("success!");
}
}
public class RadioButtonHandler implements ItemListener
{
public void itemStateChanged(ItemEvent e)
{
JOptionPane.showMessageDialog(ExamFrame.this, String.format("radio state changed"));
}
}
}

why "itemStateChanges" isn't triggered, i tried to put it in the inner
class "ButtonHandler" and also in "RadioButtonHandler" Im having
troubles with it, what is the right way to do it? I want to trigger
and check the marked JRadioButtons after the user click the "check"
button.
ButtonHandler is implemented with ActionListener only:
public class ButtonHandler implements ActionListener{}
The itemStateChanged(ItemEvent) function belongs to ItemListener. This function is triggered if state of a source component to which this listener is registered gets changed. So implement the ItemListener. However, one more thing to note, that JButton doesn't respond to ItemListener but JRadioButton will. Because this Item events are fired by components that implement the ItemSelectable interface. Some example of such components are: check boxes, check menu items, toggle buttons and combo boxes including Radio Buttons as mentioned above.
What is the right way to check which button was clicked, i feel like
comparing the strings is wrong programming. Maybe using an ID
Well using the event source function: e.getSource(), check whither the type of the source is your expected type and cast it to appropriate type. And then you can use getName(String) function and check the name you were expecting. Of-course you should assign the name using setName(String) after initialization of component. Or using the component reference directly if it is declared in the Class context and you have direct access to the component.
#Override
public void itemStateChanged(ItemEvent e) {
if(e.getSource() instanceof JCheckBox)
{
JCheckBox checkBox = (JCheckBox)e.getSource();
if(checkBox.getName().equals("expectedName"))
; // do my thing
}
}
How should i make a "reset" button(start over), i want to uncheck all
radio buttons and run the constructor once again.
Well you are working with ButtonGroup. And ButtonGroup has a nice function: clearSelection() to help with whatever(I could not understand the part: run the constructor part) you want.
Edit: As you wanted me to see an ItemListener implemented class, Yes i can see that But:
i can not see that you have actually registered an instance of that class(a1.addItemListener(handler);) to any component before performing any action on the component to which ButtonHandler is registered to: checkMe, refresh
In addition to that, in this action performed function, you are checking with
action command, which you haven't even set with JButton.setActionCommand(String) function. You should not assign a (Item)listener depending on event-occurrence of another (Action)listener.
Tutorial:
How to Write an ItemListener
How to Write an ActionListener
How to Use the ButtonGroup Component

Can two JButton have the same mouse clicked event function?

I am developing a calculator in Java language. The problem is that, i put ten buttons for digits(0,1,2..9) and i want that when i clicked one of them, all perform the same mouse clicked function. Is it possible? In netbeans, it does not let me do that, or i couldnt achieve. Thank you for helping.

Yes. Add the same listener to both buttons you are using.
For example, suppose you are using actionListener then:
public class ListenerClass implements Action{
#override
public void actionPerformed(ActionEvent e) {
//here retrieve information on which button has generated the event
}
}
ListenerClass listener = new ListenerClass();
JButton first = new JButton();
JButton second = new JButton();
first.addActionListener(listener);
second.addActionListener(listener);