G'day all,
I am coding a main menu for a project. The menu displays properly. I have also set up ActionListeners for the three buttons on the menu.
What I wish to do is reuse the JPanel for a new set of radio buttons when the user chooses "Start a New Game".
However, coding ActionPerformed to remove the existing components from the JPanel has me stumped. I know removeAll is somehow important, but unfortunately NetBeans informs me I cannot call it on my mainMenu JPanel object within ActionPerformed. So i have commented it out in my code below, but left it in so you can see what I am trying to do.
Your thoughts or hints are appreciated.
Here is my main code:
public class Main {
public static void main(String[] args) {
MainMenu menu = new MainMenu();
menu.pack();
menu.setVisible(true);
}
}
Here is my mainMenu code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MainMenu extends JFrame implements ActionListener {
JButton startNewGame = new JButton("Start a New Game");
JButton loadOldGame = new JButton("Load an Old Game");
JButton seeInstructions = new JButton("Instructions");
public MainMenu() {
super("RPG Main Menu");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel mainMenu = new JPanel();
mainMenu.setLayout(new FlowLayout());
startNewGame.setMnemonic('n');
loadOldGame.setMnemonic('l');
seeInstructions.setMnemonic('i');
startNewGame.addActionListener(this);
loadOldGame.addActionListener(this);
seeInstructions.addActionListener(this);
mainMenu.add(startNewGame);
mainMenu.add(loadOldGame);
mainMenu.add(seeInstructions);
setContentPane(mainMenu);
}
public void actionPerformed(ActionEvent evt) {
Object source = evt.getSource();
if (source == startNewGame) {
// StartNewGame code goes here
// mainMenu.removeAll();
}
if (source == loadOldGame) {
// LoadOldGame code goes here
}
if (source == seeInstructions) {
// Quit code goes here
}
}
}
Consider using a CardLayout instead, which manages two or more components (usually JPanel instances) that share the same display space. That way you don't have to fiddle with adding and removing components at runtime.
You need mainMenu to be a member variable:
public class MainMenu extends JFrame implements ActionListener {
JButton startNewGame = new JButton("Start a New Game");
JButton loadOldGame = new JButton("Load an Old Game");
JButton seeInstructions = new JButton("Instructions");
JPanel mainMenu = new JPanel();
Why do you feel the need to re-use this object?
You don't have a reference to mainMenu actionPerformed use. If you declare mainMenu with the buttons. It would work.
The problem is that the actionPerformed method is trying to call the JPanel mainMenu which is out of scope, i.e. the mainMenu variable is not visible from the actionPerformed method.
One way to get around this is to have the JPanel mainMenu declaration in the class itself and make it an instance field which is accessible to all instance methods of the class.
For example:
public class MainMenu extends JFrame implements ActionListener
{
...
JPanel mainMenu;
public MainMenu()
{
...
mainMenu = new JPanel();
...
}
public void actionPerformed(ActionEvent e)
{
...
mainMenu.removeAll();
}
}
Avoid attempting to "reuse" stuff. Computers are quite capable of tidying up. Concentrate on making you code clear.
So instead of attempting to tidy up the panel, simply replace it with a new one.
Generally a better way to write listeners is as anonymous inner classes. Code within these will have access to final variables in the enclosing scope and to members of the enclosing class. So, if you make mainMenu final and you ActionListeners anonymous inner classes, your code should at least compile.
Also don't attempt to "reuse" classes. Try to make each class do one sensible thing, and avoid inheritance (of implementation). There is almost never any need to extend JFrame, so don't do that. Create an ActionListener for each action, rather than attempting to determine the event source.
Also note, you should always use Swing components on the AWT Event Dispatch Thread. Change the main method to add boilerplate something like:
public static void main(final String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() { public void run() {
runEDT();
}});
}
Related
How would I go about closing a JFrame based on an ActionEvent from a button click within a JPanel?
I have a total of three classes:
Application: contains the main method and runs the program by creating a FrameStartUp object.
FrameStartUp: extends the JFrame class and displays the contents within StartUpPanel.
StartUpPanel: extends the JPanel class and has all the components and ActionEvents.
Within the StartUpPanel class, I have a button with an ActionEventListener waiting for the button to be clicked.
When the button is clicked I want the application to shut down completely. I know of a method called .dispose() for the JFrame class, but I can't use it because creating an object of FrameStartUp would just run another GUI (run by the constructor).
As I am new to programming and swing, I do not know any other way to fix this, other than getting rid of the StartUpPanel and just creating a JPanel within the FrameStartUp class.
Are there any methods provided by Swing that can access the current JFrame that the panel is on, so the program can close when the ActionEvent is triggered?
I know of a method called .dispose() for the JFrame class
This will work if you explicitly set setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Are there any methods provided by Swing that can access the current JFrame that the panel is on
Yes... SwingUtilities provides one called getWindowAncestor().
button.addActionListener(e -> {
SwingUtilities.getWindowAncestor((Component)e.getSource()).dispose();
});
... or more commonly, you can chose to reference a final variable to achieve the same effect...
final JFrame swingStuff = this; // or expose via a getter/setter
button.addActionListener(e -> {
swingStuff.dispose();
});
... however the final variable placement and setter/getter would need a small reproducible code example.
And finally, as others have mentioned, System.exit(0) works quite fantastically well too, so as long as it doesn't break the lifecycle of any of your other components.
My test class:
import javax.swing.*;
import java.awt.*;
public class SwingStuff extends JFrame {
// Our main JFrame
public SwingStuff() {
super();
// The button
JButton button = new JButton("Close");
button.addActionListener(e -> {
SwingUtilities.getWindowAncestor((Component)e.getSource()).dispose();
});
// The JPanel and nested components
JPanel startupPanel = new JPanel();
startupPanel.add(button);
add(startupPanel);
pack();
// Make sure the app exits when closed
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
// Just our entry point
public static void main(String ... args) {
SwingUtilities.invokeLater(() -> {
new SwingStuff().setVisible(true);
});
}
}
What I have:
Two Classes that instantiate two JFrames.
What I am trying to achieve:
One with a button and the other that will become invisible when a action is fired on the button.
Problems:
I do not know how to pursue this. How should I go about coding this?
Class 1
public class test1{
public static void main(String[] args){
JFrame frame = new JFrame("Blinkly Frame");
frame.setSize(100, 100);
frame.setVisible(true);
}
}
Class 2
public class test2{
public static void main(String[] args){
JButton button = new JButton();
//when i will click this button i want to make invisible frame
}
}
Solution:
Create an instance of the class that has a Jframe or extends a JFrame.
First we need the JFrame that will be disappearing.
public class BClass extends JFrame{
// Disappearing frame
public BClass()
{
this.setSize(300,300);//sets frame properties
this.setLocationRelativeTo(null);
}
}
Next we need the Frame that will be holding the buttons. (Documentation added)
public class ACLass {
public static void main(String[] args) {
JFrame frame = new JFrame("Magician"); // instantiates
BClass b = new BClass(); // instantiates class that extends JFrame
b.setVisible(true);//
frame.setSize(300,300);//
frame.setVisible(true);//
frame.setLocationRelativeTo(null);//
JButton disappearButton = new JButton("Disappear"); //Adds button
disappearButton.addActionListener(new ActionListener() { // Adds action -When button is "clicked"
public void actionPerformed(ActionEvent e) { // method called when action fired
b.setVisible(false); //visibility changed
}
});
disappearButton.setBounds(0,0,300,150);
JButton appearButton = new JButton("appear"); //Adds button
appearButton.addActionListener(new ActionListener() { // Adds action -When button is "clicked"
public void actionPerformed(ActionEvent e) { // method called when action fired
b.setVisible(true); //visibility changed
}
});
disappearButton.setBounds(0,100,300,150);
frame.add(disappearButton, BorderLayout.PAGE_START); //adds button to frame
frame.add(appearButton, BorderLayout.PAGE_END); //adds button to frame
//I used border layout however use the a layout manager that works with your components/frame
}
}
Exotic Explanation
I'm going to explain this in terms of a magic show as it provides better understanding.
So first, we have one magician(JFrame) and his wand(JButton) and then we have the helper(the second JFrame) that will disappear and a stage that has been set(all properties defined etc.)
First the magician adds some magic power to his wand(actionListener that handles the button being pushed) that will react when the magician waves it(action fired a.k.a button being pushed).
Next we show the audience the helper(instantiating JFrame to disappear).
As we have shown the audience the helper, we can now show him/her disappearing (Now we can call setVisible through the instance variable of the class).
Finally, the magician waves his wand(firing an action), and the helper gets the signal(actionPerformed method) to disappear. The helper then can call the
b.setVisible(false); //making the frame invisible
General Explanation
https://docs.oracle.com/javase/tutorial/java/javaOO/usingobject.html
Basically, by instantiating an object in another class you can also call the objects methods in that class i.e. setVisible(boolean b).
Other less preferable solutions:
If your disappearing class has does not extend a JFrame but instantiates one..
You would need to create an instance variable
private JFrame j;
Then use getters/setters to access the object which will then allow you to call its methods.
secondClass.getFrame().setVisible(true);//getFrame returns the JFrame
Then add that to the actionPerformed method.
You can also use a static instance variable and statically reference it in the actionPerformed method... (not recommended)
secondClass.frame.setVisible(true);
I have asked a similar question a while ago, so I apologize for asking this if I am abusing the website by doing this, but this question is a bit different. I have a Main class, in which I have created a JFrame, and a JPanel. To avoid clutter, I created another class called "Buttons" to hold all my JButtons. I want to add my JButton to the mainPanel (my JPanel), but I am having trouble inheriting access to the mainPanel from the Button's class.
Here is my Main Class:
package main;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Main extends JPanel {
public Main() {
Main m = new Main();
//The main window
JFrame Main = new JFrame("Don't Blink");
Main.setSize(500,500);
Main.setResizable(false);
Main.setVisible(true);
Main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//The main window's panel
JPanel mainPanel = new JPanel(); //I want to add buttons to this panel from the Buttons class
mainPanel.setSize(500, 500);
mainPanel.setVisible(true);
Main.add(mainPanel);
}
public static void main(String[] args) {
Main m = new Main();
}
}
The Buttons class:
package main;
import javax.swing.JButton;
public class Buttons extends Main {
public Buttons(Main m) {
//The button to get a job
JButton workButton = new JButton("Get a job");
mainPanel.add(workButton);//The mainPanel here gives me
//the error "mainPanel can
//not be resolved". It
//doesn't seem to recoginze
//mainPanel
}
}
Few issues here... first of all this is an awful OOP design, but let's see...
You should add as a class variable your mainPanel
public class Main extends JPanel {
JPanel mainPanel;
Now to start you don't declare the type, since you want to have it in a class scope:
this.mainPanel = new JPanel(); // I want to add buttons to this panel from the Buttons class
You are trying to call it in Buttons but you only declared it locally in your Main constructor.
You are calling new Main inside new Main, I believe this will end in an infinite recursion.
remove Main m = new Main(); from your Main constructor.
I don't think that inherit Main on Buttons is good, but if you really need that, Main does not know about Buttons, anyway you could use the main method in Buttons instead of Main. I'd remove the main method from Main class and add it to Buttons class instead since it is extending Main anyway.
public static void main(String[] args) {
Buttons m = new Buttons();
}
Now, buttons claims to need a Main as argument, that is weird because you want to call the Main, not another Main, I'd remove the argument Main from Buttons constructor. You may think that then you will not have mainPanel but Buttons is already a Main class so it has mainPanel too.
From an OOP point of view, this is quite bit strange, and does not seem right.
In my opinion, you should not create a separate class for this, just a method, inside the Main class, and pass the reference of the panel to it:
public class Main extends JPanel{
public Main(){
Main m = new Main();
//The main window
JFrame Main = new JFrame("Don't Blink");
Main.setSize(500,500);
Main.setResizable(false);
Main.setVisible(true);
Main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//The main window's panel
JPanel mainPanel = new JPanel(); //I want to add buttons to this panel from the Buttons class
mainPanel.setSize(500, 500);
mainPanel.setVisible(true);
Main.add(mainPanel);
addTheButtons(mainPanel); //this does the heavy lifting
}
private addTheButtons(JPanel mainPanel){
//The button to get a job
JButton workButton = new JButton("Get a job");
mainPanel.add(workButton);
}
}
This would work as long as you don't want to reuse the logic creating the buttons in other classes - but as far as my experience goes with this, this granularity of UI code doen't get reused much...
First of all, it is bad practice to name a variable name with a capital letter, like Main. Use camelCase.
Please don't use inheritance for this. I recommend you define a method as follows:
private Container getButtonContainer() {
final JPanel buttonPanel = new JPanel(...);
...
buttonPanel.add(button1);
buttonPanel.add(button2);
return buttonPanel;
}
Then add this panel to the main panel.
I am trying to create a basic game menu for a game right now. I am just testing out the menu for now, and most of the options I wrote are just to test out whether the menu actually works or not. So I have a Menu class and a OptionPanel class as well.
Here is the Menu Class:
import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
public class Main extends JFrame {
JPanel cardPanel;
public Main(String title) {
super(title);
setBounds(100, 100, 800, 600);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
cardPanel = new JPanel();
CardLayout cl = new CardLayout();
cardPanel.setLayout(cl);
OptionPanel panel1 = new OptionPanel(this);
Board panel2 = new Board();
Rules panel3 = new Rules();
cardPanel.add(panel1,"1");
cardPanel.add(panel2,"2");
cardPanel.add(panel3,"3");
add(cardPanel);
setVisible(true);
}
public static void main(String[] args)
{
Main w = new Main("AP Animation Demo");
}
public void changePanel() {
((CardLayout)cardPanel.getLayout()).next(cardPanel);
requestFocus();
}
}
And here is my Option Panel class:
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class OptionPanel extends JPanel implements ActionListener {
Main w;
public OptionPanel(Main w) {
this.w = w;
JButton button = new JButton("Press me!");
button.addActionListener(this);
add(button);
JButton button2 = new JButton("Game rules");
button2.addActionListener(this);
add(button2);
}
public void paintComponent(Graphics g)
{
super.paintComponent(g);
setBackground(Color.BLACK);
}// Call JPanel's paintComponent method to paint the background
public void actionPerformed(ActionEvent e) {
w.changePanel();
}
}
How do I make it so when the menu pops up, I can click on one button that leads to the game, and when clicking on another button, get linked to another screen. I think it has something to do with the actionPerformed thing, so I tried adding if (e.getSource == button) and stuff like that, but it could not find any button variable. Any advice/feedback?
If you want the actionPerformed() method to be able to access a button variable, then the variable has to have an instance scope (or static, less preferable almost always). Referring to it in the method as you have it written won't work because the button variable is local to the constructor.
The suggestion in the comments is to make a separate ActionListener for each button; you only need to use the if (e.getSource() == button) if the one actionPerformed() method is getting called for multiple buttons. The difference between these is a little much for a SO answer; you can get a tutorial on action listeners in the Java tutorials at Oracle.
The way you have started above suggests you are going to use the OptionPanel as a single action listener for all buttons, and therefore it needs to test which button invoked it. If instead you have a separate action listener for each button, then it knows which button invoked it and doesn't need to test.
Try looking up "anonymous inner classes" as they relate to action listeners in Java.
In my Java course I have to create a GUI class that interacts with the user and a Logic class that handles the interaction. Since I find this very complicated and hard to understand, I'm looking for some help that can inspire me to continue.
Until now I have just used a text based Menu class with a Swich statement to handle simple input with Scanner and then handle all get and set methods. But I guess I don't need that anymore, and instead could create some Logic class to handle all get and set methods in objects depending on the input from the user. But to begin, how do I create a simple menu in a window and get input value from a GUI class to this Logic class and it's methods?
I add a simple GUI test class that I have done to start this task, but I'm afraid something is missing?
import javax.swing.*;
import java.awt.*;
class Guitest extends JFrame {
JTextField inputLine;
JLabel text;
Container contentPane;
// constructor
public Guitest() {
contentPane = getContentPane();
contentPane.setBackground(Color.WHITE);
setTitle("Test GUI");
setSize(400,200);
setLocation(400,400);
contentPane.setLayout(new FlowLayout(FlowLayout.LEFT));
text = new JLabel("Enter name of new customer");
contentPane.add(text);
inputLine = new JTextField();
inputLine.setColumns(10);
contentPane.add(inputLine);
setDefaultCloseOperation( EXIT_ON_CLOSE );
}
}
And I also add a simple class that make an instance of the window and make it visible. Perhaps this class could be the Logic class?
class Showgui {
// main
public static void main(String[] args) {
Guitest mywindow;
mywindow = new Guitest();
mywindow.setVisible(true);
}
}
All help is preciated! Thanks!
You should study event listeners for a start and then learn about about the MVC pattern, shown here.
You can add an ActionListener to the JTextField so whenever the users presses enter an event is triggered and a piece of code is executed.
For example:
inputLine.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String input = inputLine.getText();
}
});