We Keep Coding

Adding JPanel to JFrame works 50% of the time

Below are two images showing the problem I'm facing. Whenever I run the project there is 50/50 chance that my JPanels load properly, otherwise only 1 JPanel is loaded even though I'm simply looping through array and adding JPanels to the JFrame.
viewComponents.forEach(viewComponent -> this.add(viewComponent));
Working
Not working
DashboardView.java
public class DashboardView extends JFrame{
List<ViewComponent> viewComponents = new ArrayList();
ViewComponentFactory viewComponentFactory = new ViewComponentFactory();
JFrame dashboardInput = new JFrame();
public DashboardView(){
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLayout(new FlowLayout());
createGauges(); //Adding 2 JPanels
viewComponents.forEach(viewComponent -> this.add(viewComponent));
this.pack();
this.setLocationRelativeTo(null);
this.setVisible(true);
dashboardInput.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
dashboardInput.setLayout(new FlowLayout());
createInputs(); //Adding JPanels
dashboardInput.pack();
dashboardInput.setLocation(this.getX()+(this.getWidth()/2)-(dashboardInput.getWidth()/2), this.getY()+this.getHeight());
dashboardInput.setVisible(true);
}
private void createGauges(){
viewComponents.add(viewComponentFactory.getViewComponent(ViewComponentFactory.ViewComponentType.RadialCircleGauge,0,800, "Speedometer", "KM/H"));
viewComponents.add(viewComponentFactory.getViewComponent(ViewComponentFactory.ViewComponentType.LinearGauge, -100,100, "Temperature", "Celcius"));
}
Main.java
public class Main {
public static void main(String[] args) {
DashboardView dashboardView = new DashboardView();
dashboardView.setVisible(true);
}
}

The main problem seems to be, that your DashboadView isn't initialized within the EDT - Thread (Event Dispatching Thread). All GUI actions must be done within this thread. Otherwise strange things will happen (e.g. artifacts while updateing UI).
One should initialize its GUI this way, to ensure the start is wihtin the right Thread.
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new NewJFrame().setVisible(true);
}
});
}

How to check JToggleButton state in a class from another class using IF-statement that have actionPerformed within it?

EDIT : I found my problem but still don't have a clue for why this happen, I'm still not finished Online Lectures from Professor Mehran
Sahami (Stanford), maybe I'll find an answer if I push on on the
lecture videos.
The problem is I remove my other components methods before my button
method for efficient posting space, so I should put my JToggleButton
method after my main JFrame method for it to work, but what if my
other components inherit other class too? Which method should I put first to make all of components works? That I'll found out with
practicing java more.
Thank you #Dan and #SebVb for answers and suggestions, sorry if this
just a beginners mistake :)
I am learning java for a month now and already had simple project for learning but now I have problems with JToggleButton, ItemEvent, and actionPerformed included in If-statement.
I've searching for a week for examples on using actionPerformed within if-statement that have ItemEvent from another class but i can't find a same problem to produce a working result.
I'm trying to make a window scanner that will scan only if toggle button is selected then paint JPanel using buffered image (repaint every 100 millisecond) and disposed it if toggle button is deselected, but I think my approach to do it is wrong. I have one main class and two sub-classes like these:
Main class:
public class WindowScanner {
public static void main(String[] args) {
new Window().setVisible(true);
}
}
Window class:
class Window extends JFrame {
static JToggleButton captureButton = new JToggleButton("CAPTURE");
#SuppressWarnings("Convert2Lambda")
public Window() {
// JFrame looks codes
/** EDIT: these components method should be written after button method
* JPanel looks codes
* JLabel looks codes
* END EDIT
*/
add(captureButton);
// capture button default looks code
ItemListener captureListener = new ItemListener(){
#Override
public void itemStateChanged(ItemEvent captureButtonEvent) {
int captureState = captureButtonEvent.getStateChange();
if(captureState == ItemEvent.SELECTED){
// capture button SELECTED looks code
System.out.println("capture button is selected");
} else if(captureState == ItemEvent.DESELECTED){
// capture button DESELECTED looks code
System.out.println("capture button is deselected");
}
}
}; captureButton.addItemListener(captureListener);
}
}
Scanner class:
public class Scanner extends Window {
private static BufferedImage boardCaptured;
static int delay = 100;
protected BufferedImage boardScanned(){
return boardCaptured;
}
#SuppressWarnings("Convert2Lambda")
public static void Scan() {
if (captureButton.isSelected()) {
ActionListener taskPerformer = new ActionListener() {
#Override
public void actionPerformed(ActionEvent captureEvent) {
try {
// capturing method
} catch (AWTException error) {
// AWTException error method
}
// is this the right place to put JPanel code?
JPanel panel = new JPanel();
boardCaptured = new BufferedImage(500, 500, BufferedImage.TYPE_INT_ARGB);
Graphics2D graphic = boardCaptured.createGraphics();
panel.setSize(500,500);
panel.paint(graphic);
panel.revalidate();
panel.repaint();
}
}; new Timer(delay, taskPerformer).start();
} else {
// this suppose to end capturing if capture button isSelected() == false
}
}
}
So here is my questions:
Do I really have to make Main class separated from Window class?
What the reason?
How to make my if statement in Scan method recognize state of my
JToggleButton from Window class? Is it impossible and I had a wrong
approach to do it?
In Scanner class, i can't make a get/set for my actionPerformed
(Netbeans always checked it as an error), but why I can make one for
BufferdImage?
If I can't get question number 3 happen, how can I make If statement
to stop capturing using Timer.stop()? Or am I in wrong approach again?
Do my JPanel in Scanner class would be produced and make a viewer
for my buffered image?
P.S. I'm sorry it cramped with questions, I tried not to make multiple post, so I make single post with multiple questions. Please notice me if there's answer before, I'm honestly can't find it or had search it with wrong tags.

Here is a simple version of what I think you want to do. This can be edited to include your variables, such as boardCaptured. This code mainly portrays how to get a component from a different class.
Main.java (Contains all the classes in one java file)
import javax.swing.JLabel;
import javax.swing.JToggleButton;
import javax.swing.JFrame;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.util.Random;
import javax.swing.Timer;
class WindowScanner extends JFrame {
private JLabel label;
private JToggleButton captureButton = new JToggleButton("CAPTURE");
WindowScanner() {
super("Fist Window");
setSize(150, 100);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new FlowLayout());
add(captureButton);
setVisible(true);
new Scanner(this);
}
public JToggleButton getCaptureButton() {
return captureButton;
}
}
class Scanner extends JFrame {
private WindowScanner wS;
private int delay = 1000;
private Timer t = new Timer(delay, new taskPerformer());
Scanner(WindowScanner wS) {
super("Second Window");
this.wS = wS;
setBounds(200,0,500,500);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
wS.getCaptureButton().addActionListener(new taskPerformer());
}
private Color randomColor() {
Random rand = new Random();
float r = rand.nextFloat() / 2f ;
float g = rand.nextFloat() / 2f;
float b = rand.nextFloat() / 2f;
Color randomColor = new Color(r, g, b);
return randomColor;
}
private class taskPerformer implements ActionListener {
#Override
public void actionPerformed(ActionEvent captureEvent) {
if(captureEvent.getSource() == wS.getCaptureButton()) {
if (wS.getCaptureButton().isSelected()) {
t.start();
} else {
t.stop();
}
}
if(captureEvent.getSource() == t) {
getContentPane().setBackground(randomColor());
revalidate();
repaint();
}
}
}
}
public class Main {
public static void main (String[] args) {
new WindowScanner();
}
}
This particular piece of code changes the color of the background in the second JFrame to a random color every second using a timer from javax.swing.timer. This code portrays how to get a component, or a variable if you change it, from a different class.
It is mainly these code fragments which allow it.
1
public JToggleButton getCaptureButton() {
return captureButton;
}
This allows other classes to get the component.
2
private WindowScanner wS;
Scanner(WindowScanner wS) {
...
this.wS = wS;
...
}
This makes the current instance of WindowScanner and the instance of WindowScanner declared in Scanner the same instance.
Note: Look into using public getters and setters.
As for your 5 listed questions.
1) Do I really have to make Main class separated from Window class? What the reason?
In most cases yes you do. As SebVb said it is good practice. However you can do something like this if you wish to have them in the same class.
import javax.swing.JToggleButton;
import javax.swing.JFrame;
import java.awt.FlowLayout;
public class Test extends JFrame {
private JToggleButton captureButton = new JToggleButton("CAPTURE");
Test() {
super("Fist Window");
setSize(150, 100);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new FlowLayout());
add(captureButton);
setVisible(true);
}
public JToggleButton getCaptureButton() {
return captureButton;
}
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
Test frame = new Test();
}
});
}
}
2) How to make my if statement in Scan method recognize state of my JToggleButton from Window class? Is it impossible and I had a wrong approach to do it?
You were using the wrong approach to do this. See the code and code fragments I have put above for how to do it correctly. (Using public getters.)
3) In Scanner class, i can't make a get/set for my actionPerformed (Netbeans always checked it as an error), but why I can make one for BufferdImage?
I can't entirely say I'm sure what you are asking but see my code above to see if that helps. If it doesn't leave a comment trying to fully explain what you mean.
4) If I can't get question number 3 happen, how can I make If statement to stop capturing using Timer.stop()? Or am I in wrong approach again?
In my code I show you how this can be related to the JToggleButton. See code fragment below
private class taskPerformer implements ActionListener {
#Override
public void actionPerformed(ActionEvent captureEvent) {
if(captureEvent.getSource() == wS.getCaptureButton()) {
if (wS.getCaptureButton().isSelected()) {
t.start();
} else {
t.stop();
}
}
if(captureEvent.getSource() == t) {
getContentPane().setBackground(randomColor());
revalidate();
repaint();
}
}
}
This code says when the JToggleButton fires an ActionEvent if it is selected then start the timer, t.start(), or if it is not selected stop the timer, t.stop().
5) Do my JPanel in Scanner class would be produced and make a viewer for my buffered image?
Again I'm not entirely sure what you are asking but here is my best guess. You have two options.
1
Put boardCaptured directly on the frame.
paint(graphic);
repaint();
revaildate();
2
Create a JPanel like you did but outside the ActionListener
JPanel panel = new JPanel()
boardCaptured = new BufferedImage(500, 500, BufferedImage.TYPE_INT_ARGB);
Graphics2D graphic = boardCaptured.createGraphics();
panel.setSize(500,500);
panel.paint(graphic);
add(panel);
private class taskPerformer implements ActionListener {
if(captureEvent.getSource() == t) {
panel.paint(graphic);
panel.revalidate();
panel.repaint();
}
}

I think there's an easier way do do what do you want. Taking your questions by order
Having the main class separated from your Window class allow you to re-use your Windows class everywhere you want. It's a good pratice to only init your GUI objects on your main class
Why don't you have your JToggleButton private and a mehtod wwhich will access to his status ? also, with a static field, all your instaces of Windows will share the same JToggleButton.
It's an anonymous class that contains your actionPerformed method. If you want to see it, you have to create an inner class.
I think your approch is wrong. Using a thread, which will launch your repaint with a specific delay is better. If you create a class which extends Runnable, you can check the state of your button and then do the appropriate action
Your JPanel is inside an ActionListener, i've never seen that and i don't think that it can works.
In a shorter version
Put in your Window class your JPanel, BufferedImage and JToggleButton
Create a specific thread to do your repainting when the JToggleButton is selected

Java Swing Program- Input from GUI to Main getting stuck

I have a Java program where I plan to take input from GUI, and use that input later for processing in main(). I am using Eclipse.
I am sending an HW object(called HWObj) to the GUI JFrame, and checking for a boolean field in the object to continue processing in main().
InputWindow is custom object which extends JPanel implements ActionListener
It contains a reference to the current JFrame(parentFrame). On clicking a JButton in InputWindow, I have written a custom ActionListener which sets the value of HWObj.check to true and disposes the parentFrame. This should cause execution to resume in main().
Code for HW class is as below :
import java.awt.*;
import javax.swing.*;
public class HW {
//globals
boolean check;
public HW() {
//initialisations
check = false;
}
public static void main(String args[]) {
final HW problem = new HW();
try {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
//Create and set up the window.
JFrame frame = new JFrame("Select folders");
frame.setPreferredSize(new Dimension(640, 480));
frame.setResizable(false);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
InputWindow Directories = new InputWindow(problem, frame);
Directories.setOpaque(true);
frame.add(Directories);
//Display the window.
frame.pack();
frame.setVisible(true);
}
});
} catch(Exception e) {
System.out.println("Exception:"+e.getLocalizedMessage());
}
while(!problem.finish);
//Do processing on problem
System.out.println("Done");
}
}
The Actionlistener in the gui is as follows:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class InputWindow extends JPanel
implements ActionListener {
private static final long serialVersionUID = 4228345704162790878L;
HW problem;
JFrame parentFrame;
//more globals
public InputWindow(HW problem, JFrame parentFrame) {
super();
this.setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
this.parentFrame = parentFrame;
this.problem = problem;
JButton finishButton = new JButton("Finish");
finishButton.setActionCommand("fin");
finishButton.addActionListener(this);
gbc.gridx = 0;
gbc.gridy = 0;
this.add(finishButton, gbc);
//Initialize buttons and text areas and labels
//Code removed for ease of reading
}
public void actionPerformed(ActionEvent e) {
String command = e.getActionCommand();
if(command.equals("fin")) {
//Do a lot of stuff, then
this.removeAll();
parentFrame.dispose();
problem.check = true;
}
}
}
I have checked, and the control to this function comes normally on button click.
Now, I would expect it to return to main, and exit the while loop, and continue processing.
This does not happen. The debugger in eclipse shows only the main thread running, and when I try to pause it, I see that the thread is stuck in the while loop. But if I try to step through, it exits the while loop as expected, and continues. However, it gets remains stuck in the while loop until I manually try to debug it.
What is the problem? Why is it not resuming the main thread as expected?
How do I resolve this issue?

Your problem is to do with how the Java memory model works. The loop in your main thread will be checking a stale value of check.
When you enter the debugger, the memory is forced to be updated, so that's why it starts working at that point.
If you mark your variable as volatile, that will force the JVM to ensure that all threads are using the up-to-date value:
volatile boolean check;
You can read more about volatile and the Java memory model in the documentation.

It looks like you're using a JFrame where you should be using a modal JDialog. If you use the modal JDialog for an input window, you will know exactly when it is "finished" since code flow will resume from the calling code from right after when the dialog was set visible.
Either that or if you are trying to swapviews, then use a CardLayout to swap your view, and use an observer type pattern to listen for change of state.

JButton disappears when resize

anyone know or have an idea as to why my button disappears after i resize the applet?
this is my code:
import java.awt.event.*;
import javax.swing.*;
import acm.program.*;
public class button extends ConsoleProgram {
public void init(){
hiButton = new JButton("hi");
add(hiButton, SOUTH);
addActionListeners();
}
public void actionPerformed(ActionEvent e){
if(hiButton == e.getSource()){
println("hello") ;
}
}
private JButton hiButton;
}

I'm not sure if it is a good Idea to redefine the init-method. When I have a look at http://jtf.acm.org/javadoc/student/acm/program/ConsoleProgram.html I would expect that you have implement only the run-method. Overriding init without calling super.init() Looks strange to me.
Maybe I would be better to derive from JApplet directly for your first steps in Applet programming.

Assuming that
your ConsoleProgram extends (directly or indirectly) JApplet
You declared SOUTH as a static final variable that has the value BorderLayout.SOUTH (otherwise your code doesn't compile)
The code should work, no need to repaint (unless you would like to do some application-specific optimization). I just copied and pasted your code (by expliciting the two assumptions above), I see the applet and the button doesn't disappear on resize.
Anyway there are few "not good" things in the code:
First of all, a naming convention issue: the class name should be "Button" with the first letter capitalized (on top of that, it's a poor name for an Applet)
Second, action listeners should be attached before adding the component;
Third, as Oracle doc suggests here, the code that builds the GUI should be a job that runs on the event dispatcher thread. You can do that by wrapping the build gui code in a Runnable using a SwingUtilities.invokeAndWait(Runnable()

Have you tried calling super.init() at the start of your init() method?

Try explicitly using a layout for your Console and then use relative positioning.

To re-size a button in Applet:
public class Button extends JApplet implements ActionListener {
private JButton button;
public void init() {
Container container = getContentPane();
container.setLayout(null);
container.setBackground(Color.white);
button = new JButton("Press Me");
button.setSize(getWidth()/2,20);
button.setLocation(getWidth()/2-button.getSize().width/2, getHeight()/2-button.getSize().height/2);
container.add(button);
button.addActionListener(this);
}
public void actionPerformed(ActionEvent e) {
int width = (button.getSize().width == getWidth()/2) ? getWidth()/4 : getWidth()/2;
int height = button.getSize().height;
button.setSize(width,height);
button.setLocation(getWidth()/2-width/2, getHeight()/2-height/2);
}
}
To re-size a button in JFrame:
public class Button extends JFrame implements ActionListener {
private JButton button;
public Button(String title) {
Container container = getContentPane();
container.setLayout(null);
container.setBackground(Color.white);
setTitle(title);
setSize(400,400);
button = new JButton("Press Me");
button.setSize(getWidth()/2,20);
button.setLocation(getWidth()/2-button.getSize().width/2,
getHeight()/2-button.getSize().height/2);
container.add(button);
button.addActionListener(this);
}
public void actionPerformed(ActionEvent e) {
int width = (button.getSize().width == getWidth()/2) ? getWidth()/4 : getWidth()/2;
int height = button.getSize().height;
button.setSize(width,height);
button.setLocation(getWidth()/2-width/2, getHeight()/2-height/2);
}
public static void main(String[] args) {
Button button = new Button("Test");
button.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
button.setVisible(true);
}
}

Have you declared the repaint method...???
You are using swing. It needs to have declared a repaint.
Please define a custom repaint mwthod

Using an ActionListener in one class to start a timer in another class

I have a class (simulation) which creates an instance of another class (GUI). Inside the class GUI there is a button (start) which has an actionlistener attached to it.
I need this actionlistener to start a timer in simulation but I can't figure out how to do it.
Code in Class Simulation:
public class Simulation{
private static JFrame frame;
private static GUI control;
public static Integer xcontrol = 100, ycontrol = 100;
public Timer timer;
public int steps;
public static void main(String[] args) {
Simulation sim = new Simulation ();
}
public Simulation() {
frame = new JFrame("Action Listener Test");
frame.setLayout(new BorderLayout(1,0));
control = new GUI (xcontrol, ycontrol);
frame.getContentPane().add(control , BorderLayout.CENTER);
frame.setResizable(false);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
public void StartTimer() {
timer.start();
System.out.println("It worked!");
}
Code in Class GUI:
panel1.add(button1a);
button1a.addActionListener(new ActionListener() {
public void actionPerformed (ActionEvent event) {
Simulation.StartTimer();
}
} );
The error Eclipse tells me there is, is that for "Simulation.timer.start();" :
Cannot make a static reference to the non-static method StartTimer() from the type Simulation.
However the method StartTimer() cannot be static as this seems to break the timer...
Any help would be very appreciated.

Pass this as an argument to the GUI constructor.
In general it is best to avoid such cyclic references. Both the GUI and Simulator become dependent upon one another. The essence of the solution is to separate out the GUI from the interesting domain-specific behaviour.
(BTW: I would strongly avoid using static variables for anything other than constants. Also avoid non-private instance variables. But point for not extending JFrame!)
There is some hideous boilerplate that you should add to prevent multithreading.
public static void main(final String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() { public void run() {
Simulation sim = new Simulation();
}});
}

What I would do is have your GUI class expose the button via a getButton() method, then after creating the GUI object, your Simulation class can add its own ActionListener to the button, e.g. control.getButton().addActionListener(new ActionListener()... etc.