Develop Reference

Access difficulty with ArrayList of panels with buttons

my question is: how do I get the object of my CustomPanel, so that I am able to access its fields (because in my real programm I have some more fields in there) and also am able to delete it from my ArrayList?
I don't know how I have to implement an ActionListener in the Class Window, to somehow get the Object in my Arraylist, which containes the button that got pressed.
Also I am wondering if I am somehow able to implement an ActionListener in the Class CustomPanel which can influence the behaviour of the Object which is an instance of my Class Window.
I have kind of the following code:
public class Window extends JFrame{
ArrayList<CustomPanel> aLCustomPanel = new ArrayList();
JPanel jp = new JPanel();
public Window() {
for(int i=0;i<5;i++){
aLCustomPanel.add(new CustomPanel());
//here I could put the code from the 1 edit - see below
jp.add(aLCustomPanel.get(i));
}
this.add(jp);
}
public static void main(String args[]){
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Window().setVisible(true);
}
});
}
}
class CustomPanel extends JPanel {
private JButton button;
public CustomPanel(){
button = new JButton("button");
this.add(button);
}
public JButton getButton(){
return this.button;
}
}
my Code is much longer and weirder, so I tried to extract the (for this question) importing things.
Thanks for any help in advance!
edit:
for example: I would like to delete the object from the ArrayList, of which the button got pressed.
//imagine this comment in above code
aLCustomPanel.get(aLCustomPanel.size()-1).getButton().addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
button_IwantToDeleteYou(e); //here I want to remove the panel, containing the button that got pressed from the above ArrayList, which is located in Class Window
}
});
edit2:
added a missing bracket and fixed some mistakes, code should be ok now.

Your code contained a few "gaps", i.e. missing code, which I filled in, as follows:
Added calls to [JFrame] methods setDefaultCloseOperation() and pack() and setLocationByPlatform(). I suggest you refer to the javadoc for those methods in order to understand what they do.
I set a layout manager for jp class member variable in your Window class.
Yes, you need to register an ActionListener with the JButton in class CustomPanel and that listener should reside in your Window class - the one that extends JFrame.
Here is my rewrite of your code. Note that I changed the name of class Window to CusPanel so as to distinguish between your class and java.awt.Window class. Not that it makes a difference, I just prefer not to use names of classes from the JDK.
import java.awt.Container;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.WindowConstants;
public class CusPanel extends JFrame implements ActionListener {
private static final int COUNT = 5;
private ArrayList<CustomPanel> aLCustomPanel = new ArrayList<>();
private JPanel jp = new JPanel(new GridLayout(0, COUNT));
public CusPanel() {
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
for (int i = 0; i < COUNT; i++) {
aLCustomPanel.add(new CustomPanel(this));
// here I could put the code from the 1 edit - see below
jp.add(aLCustomPanel.get(i));
}
this.add(jp);
pack();
setLocationByPlatform(true);
}
public void actionPerformed(ActionEvent actionEvent) {
Object source = actionEvent.getSource();
if (source instanceof JButton) {
JButton button = (JButton) source;
Container parent = button.getParent();
jp.remove(parent);
jp.invalidate();
jp.repaint();
pack();
// aLCustomPanel.remove(parent); <- optional
}
}
public static void main(String args[]) {
EventQueue.invokeLater(new Runnable() {
public void run() {
new CusPanel().setVisible(true);
}
});
}
}
class CustomPanel extends JPanel {
private JButton button;
public CustomPanel(ActionListener parent) {
button = new JButton("button");
button.addActionListener(parent);
this.add(button);
}
public JButton getButton() {
return this.button;
}
}
Note that after removing a CustomPanel, the GUI components need to be laid out again and the JFrame should also be resized accordingly. Hence in the actionPerformed() method, I call invalidate(), then repaint() and then pack(). I also think that if you remove a CustomPanel from the GUI, you should also remove it from the ArrayList, but hey, I still don't understand why you want to do this although I obviously don't know the whole story behind you wanting to do this in the first place.
Of-course, since each button (and each CustomPanel) looks exactly the same, you can't really know which button was removed. Again, I assume you see the big picture whereas I don't.

Main has to be astract, ActionPerformed method problem with Listener

This program is just for the sake of teaching myself Java.
While coding around i ran into the following problem:
I'm getting errors (red underlining) when using a listener for a button which I implement in my Main class.
Since I'm new in learning Java please excuse if the solution is obvious.I already tried making both the main and the actionPerfomed method abstract but that lead to further issues. I also tried #Override before the actionPerformed method.
Here is the code:
// Java program to create a blank text
// field of definite number of columns.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class Main extends JFrame implements ActionListener {
// JTextField
static JTextField t;
// JFrame
static JFrame f;
// JButton
static JButton b;
// label to diaplay text
static JLabel l;
// default constructor
Main()
{
}
// main class
public static void main(String[] args)
{
// create a new frame to stor text field and button
f = new JFrame("textfield");
// create a label to display text
l = new JLabel("nothing entered");
// create a new button
b = new JButton("submit");
// create a object of the text class
Main te = new Main();
// addActionListener to button
b.addActionListener(te);
// create a object of JTextField with 16 columns
t = new JTextField(16);
// create a panel to add buttons and textfield
JPanel p = new JPanel();
// add buttons and textfield to panel
p.add(t);
p.add(b);
p.add(l);
l.setOpaque(true);
// add panel to frame
f.add(p);
// set the size of frame
f.setSize(300, 300);
p.setBackground(Color.cyan);
f.show();
}
// if the button is pressed
public void actionPerformed(java.awt.event.ActionEvent e, JPanel p)
{
String s = e.getActionCommand();
if (s.equals("submit")) {
// set the text of the label to the text of the field
if(t.getText().equals("hue")) {
p.setBackground(changeColor());
}
l.setText(t.getText());
// set the text of field to blank
t.setText(" ");
}
}
public Color changeColor() {
int r = (int)(Math.random())*256;
int g = (int)(Math.random())*256;
int b = (int)(Math.random())*256;
Color color = new Color(r,g,b);
return color;
}
}

Here:
public void actionPerformed(java.awt.event.ActionEvent e, JPanel p)
Should be
public void actionPerformed(java.awt.event.ActionEvent e)
You have to match the expected signature exactly! You can't just add more parameters to a method you are supposed to override!
You see, in the end, it is not your code that will invoke that method when a button is clicked. It is the Swing framework that will do it. You tell it: when an action happens on this thing, then call back my code. How do you expect that this framework could know that you want an additional parameter to be passed?!
Beyond that: make it your practice to put #Override in front of any method that you expect to override a method (like in this case, where you are implementing a method of that interface). Because then the compiler can tell you when you make such mistakes!
But of course, you added that parameter so that the listener can use it. So: make it known to the listener, for example by adding a field to your Main class that you initialize in the constructor! So instead of passing the panel to that one method (where it can't go) pass it when doing new for your Main instance.

When a class implements an interface, then it has to implement the required functions with the same arguments as given in the Interface.
ActionListener implements only only one function as you can see at https://docs.oracle.com/javase/7/docs/api/java/awt/event/ActionListener.html
void actionPerformed(ActionEvent e);
So you have to implement that function in your class. But you implemented a different function which has the same name but not the same arguments:
void actionPerformed(java.awt.event.ActionEvent e, JPanel p)

Change attribute in other jframe when a button is clicked in another JFrame

I have 2 jframes, 1 is kinda like the main menu, i want an attribute to change in the level jframe when a button is pressed so i tried:
SpeelVeld frame = new SpeelVeld();
frame.level = 1;
System.out.println(frame.level);
I used the sout to see what really happens because it wasnt working, but i see that the level goes from 0 to 1 back to 0 and goes on and on, does someone know why and how to fix?
SpeelVeld frame = new SpeelVeld();
frame.setBounds(0,0,519,591);
frame.setLocationRelativeTo(null);
frame.getContentPane().setBackground(Color.WHITE);
frame.setTitle("RWINA");
frame.setVisible(true);
frame.setLevel(1);
this is in the main method of my original GameProject file.
How can i make a jdialog

I have 2 jframes, 1 is kinda like the main menu,
You shouldn't use 2 JFrames for this. The dependent sub-window, likely your main menu window, should in fact be a JDialog, probably a non-modal dialog from the looks of it.
I want an attribute to change in the level jframe when a button is pressed so i tried:
SpeelVeld frame = new SpeelVeld();
frame.level = 1;
System.out.println(frame.level);
and here's a big problem. Understand that in this code, you're creating a new SpeelVeld object, the stress being on the word new. Changing the state of this object will have no effect on the other SeelVeld object that is currently being displayed. Do do that, your second window will need a valid reference to the displayed SeelVeld object. How to do this will depend all on code not yet shown, but often it can be done simply by passing in the displayed SpeelVeld object into the main menu object by use of a constructor parameter or setter method.
For example:
import java.awt.Dialog.ModalityType;
import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
// JPanel for our main GUI
public class SpeelVeldFoo {
private static void createAndShowGui() {
// JPanel used by the main JFrame
SpeelVeldPanel speelVeldPanel = new SpeelVeldPanel();
// JPanel used by the main menu JDialog. Pass the above into it
MainMenuPanel mainMenuPanel = new MainMenuPanel(speelVeldPanel);
// create your JFrame
JFrame frame = new JFrame("Speel Veld");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(speelVeldPanel); // add the JPanel
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
// create your non-modal JDialog
JDialog menuDialog = new JDialog(frame, "Main Menu", ModalityType.MODELESS);
menuDialog.add(mainMenuPanel); // add the JPanel that holds its "guts"
menuDialog.pack();
menuDialog.setLocationByPlatform(true);
menuDialog.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
createAndShowGui();
});
}
}
#SuppressWarnings("serial")
class SpeelVeldPanel extends JPanel {
private int level = 1; // simple example just has a level int
private JLabel levelLabel = new JLabel("1"); // and displays it in a JLabel
public SpeelVeldPanel() {
add(new JLabel("Level:"));
add(levelLabel);
int ebGap = 50;
setBorder(BorderFactory.createEmptyBorder(ebGap, 2 * ebGap, ebGap, 2 * ebGap));
}
public int getLevel() {
return level;
}
public void setLevel(int level) {
// whenever level is changed, update the display
this.level = level;
levelLabel.setText(String.valueOf(level));
}
}
// class for the JPanel held by the JDialog
#SuppressWarnings("serial")
class MainMenuPanel extends JPanel {
private JSpinner levelSpinner = new JSpinner(new SpinnerNumberModel(1, 1, 5, 1));
private SpeelVeldPanel speelVeldPanel = null; // reference to the main GUI
// note the parameter.... you pass in the displayed main GUI so you can
// change it
public MainMenuPanel(final SpeelVeldPanel speelVeldPanel) {
this.speelVeldPanel = speelVeldPanel; // set the field
// respond when the spinner's data changes
levelSpinner.addChangeListener(new LevelListener());
add(new JLabel("Set the Speel Veld's level:"));
add(levelSpinner);
int ebGap = 10;
setBorder(BorderFactory.createEmptyBorder(ebGap, ebGap, ebGap, ebGap));
}
private class LevelListener implements ChangeListener {
#Override
public void stateChanged(ChangeEvent e) {
// when the spinner's data changes
int level = (int) levelSpinner.getValue(); // get the data
speelVeldPanel.setLevel(level); // and send it to the main GUI
}
}
}
You'll note that I don't like extending JFrame or JDialog if I can avoid it. My feeling is that one can paint oneself into a corner by having your class extend JFrame, forcing you to create and display JFrames, when often more flexibility is called for. More commonly your GUI classes will be geared towards creating JPanels, which can then be placed into JFrames or JDialogs, or JTabbedPanes, or swapped via CardLayouts, wherever needed. This will greatly increase the flexibility of your GUI coding.

You probably want the JFrame to be the top-level container, then have a JPanel that holds your menu. The menu could be whatever you want, I'm using a JTextArea. Then, you need a JButton for the JPanel or JFrame that when pressed, changes the text in the JTextArea. Here is an implementation that you could work from. I'm using the ActionEvent as the trigger for when to mess with the JTextArea:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
public class SimpleSwing {
public static void main(String[] args) {
JFrame mainFrame = new JFrame();
JPanel mainMenuPanel = new JPanel();
JTextArea textAttribute = new JTextArea("Original Text");
JButton changeAttributeButton = new JButton("Change Attribute");
changeAttributeButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
textAttribute.setText("Whatever new text you want");
}
});
mainMenuPanel.add(textAttribute);
mainMenuPanel.add(changeAttributeButton);
mainFrame.add(mainMenuPanel);
mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
mainFrame.setSize(500, 500);
mainFrame.setVisible(true);
}
}

Java getter not working?

Ok so i have a comboBox, and a JTextField, whenever i chose the quantity, it would be displayed on the textfield. I have another class, which will retrieve the whatever inside the textfield, but the order class doesn't retrieve the information from catalogue class.
class Catalogue extends JPanel {
String[] h1Quantity = {"0","1","2","3","4","5","6","7","8","9","10"};
h1CBox = new JComboBox <String> (h1Quantity);
h1CBox.setSelectedIndex(0);
h1CBox.addActionListener (new Listener());
h1CBox.setPreferredSize ( new Dimension (50,30));
JLabel noBooks = new JLabel ("Quantity");
booksF = new JTextField(8);
public class Listener implements ActionListener {
public void actionPerformed (ActionEvent event) {
int total = h1CBox.getSelectedIndex();
booksF.setText(Integer.toString(total));
}
}
public String booksFText() {
return booksF.getText();
}
}
class Order extends JPanel {
Catalogue catalogue ;
public Order (Catalogue catalogue)
{
this.catalogue = catalogue;
JPanel panel = new JPanel ();
String text2= catalogue.booksFText();
textArea1 = new JTextArea (text2, 20, 35);
add(textArea1);
add(panel);
}
}
I'm new to java so please keep it simple. thanks alot.

You have 2 constructors in the Order class and catalogue is only set in the first one. Set this in the second contructor as well and the NPE should go away (although hard to know for sure without the stacktrace!)

Always try to post complete code. and stack trace too.
See your order class.
class Order extends JPanel {
public Order (Catalogue catalogue)
{
add(textArea);
}
}
If you use the second constructor , then the class variable catalogue will not be given memory. Thus NULL POINTER EXCEPTION . The code inside the second constructor has been moved to the first one.
The other reason may be that the variable being passed in order constructor is not defined properly. Should be done something like this.
Catalogue catalogue = new Catalogue();
Order order = new Order(catalogue);
See Updated Catalogue class.
class Catalogue extends JPanel {
String[] h1Quantity = {"0","1","2","3","4","5","6","7","8","9","10"};
JComboBox<String> h1CBox ; //Assuming you forgot to define it.
JLabel noBooks ;
JTextField booksF ;
//Define a new constructor
public Catalogue () {
//set jlabel
noBooks = new JLabel ("Quantity");
//set combobox
h1CBox = new JComboBox <String> (h1Quantity);
h1CBox.setSelectedIndex(0);
h1CBox.addActionListener (new Listener());
h1CBox.setPreferredSize ( new Dimension (50,30));
//set textfield
booksF = new JTextField(8);
//add UI items to your panel class
add(h1CBox); //combobox
add(noBooks); // label
add(booksF); // textfield
}
public class Listener implements ActionListener {
public void actionPerformed (ActionEvent event) {
int total = h1CBox.getSelectedIndex();
booksF.setText(Integer.toString(total));
}
}
public String booksFText() {
return booksF.getText();
}
}
Always define your UI like this . Of course , there are better ways . Thus code looks clean and you understand things. Learn to put comments to remind you what you tried to do somewhere.
The MAIN Class
public class Main {
static JTextArea textArea = new JTextArea(40,40);
static class Order extends JPanel{
public Order(){
add(textArea);
}
}
static class Catalogue extends JPanel{
....
private ActionListener listener = new ActionListener(){
public void actionPerformed(ActionEvent event){
textArea.setText(h1CBox.getSelectedIndex()+"");
}
};
}
public static void main(String args[]){
//Construct a frame and add panels and you are good to go.
}
}
One last suggestion, if you plan on NOT changing the data of textarea yourself , use textfield or label instead of textarea. Sometimes the text inside textarea is set , but user is unable to see because of improper bounds . So , to be sure just replace the textarea with label or textfield. Cheers :)

Controlling another class from a different class

I am having a bit of problem regarding Swing. I have a JFrame called FrameMain. Inside it is a JPanel called panelChoices.
When FrameMain is called/created, it fills up the panelChoices object with a number of PanelEntries objects, which is a JPanel with a number of JButtons in it (it is a different class that I wrote).
What I want to do is when I click one of the buttons inside the PanelEntries object, I want to destroy/remove FrameMain, along with the rest of it components (including the PanelEntries object that contains the JButton).
I've tried using super but it returns the JPanel (the PanelEntries object) that holds the JButton and not FrameMain that holds them all together. How can I achieve this?
EDIT: It seems that I am not clear enough, so here's a bit more information from my work. I don't have the actual code right now because I am on a different machine but I hope this will help elaborate my question.
public class FrameMain() {
private JFrame frameMain;
private JPanel panelChoices;
public FrameMain(args) {
createGUI();
loadData();
}
private void createGUI() {
JFrame frameMain = new JFrame();
JPanel panelChoices = new JPanel(new GridLayout(1,1));
frameMain.add(panel);
// removed formatting and other design codes since they are not important.
pack();
}
private void loadData() {
boolean available;
for (int i = 1; i <= 10; i++) {
// do some if/else and give value to boolean available
PanelEntries panel = new PanelEntries(i, available);
frameMain.add(panel);
// more code here to handle data.
}
}
}
public class PanelEntries() extends JPanel {
public PanelEntries(int num, boolean avb) {
JButton button = new JButton("Button Number " + num);
button.setEnabled(avb);
add(button);
// add action listener to created button so that it calls 'nextScreen()' when clicked.
// more code
pack();
}
private void nextScreen() {
// destroy/dispose MainFrame here.
// See Notes.
AnotherFrame anotherFrame = new AnotherFrame();
}
}
Notes:
All classes are inside their own .java file.
I need to know how to dispose FrameMain from the button inside the PanelEntries object, not just disposing a JFrame.

As per the given information,
If you want to exit the application, its not a big deal use System.exit(0); :)
If you mean to dispose the frame, jframe.dispose();
If you want to remove a componet / all components you can use .remove(Component) / .removeAll() etc
If this did not help, please re-write your question with more information.