I created one JFrame with JDesktopPane, in which I am calling JInternalFrame. Now I want to close that internal frame by pressing escape key.
I tried 2-3 ways, but no output.
I did that by using code given below:
public static void closeWindow(JInternalFrame ji){
ActionListener close=New ActionListener(){
public void actionPerformed(ActionEvent e){
ji.dispose();
}
};
When I called above method from my intern frame class constructor by supplying its object , I was able to close it. But when there I write some other lines of code to the constructor. The above method call doesn't work. Please help me. I unable to find the problem in the code.
Also I tried to add KeyListener to internal frame, so I able to work with key strokes,but it also doesn't work.
Again I tried to setMnemonic to button as escape as below:
jButton1.setMnemonic(KeyEvent.VK_ESCAPE);
But also gives no output.
You need to implement the KeyListener interface, or add one that is Anonymous. In this example, I just implemented it.
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
public class JInternalFrame extends JFrame implements KeyListener {
public JInternalFrame()
{
super();
// other stuff to add to frame
this.setSize(400, 400);
this.setVisible(true);
this.addKeyListener( this );
}
#Override
public void keyTyped(KeyEvent e) {
// Don't need to implement this
}
#Override
public void keyPressed(KeyEvent e) {
if( e.getKeyCode() == KeyEvent.VK_ESCAPE ) {
System.exit(0); //Change this to dispose or whatever you want to do with the frame
}
}
#Override
public void keyReleased(KeyEvent e) {
//Dont need to implement anything here
}
public static void main(String[] args)
{
JInternalFrame frame = new JInternalFrame();
}
}
Now if this is an internal jframe as mentioned, it is probably better to implement the keylistener in the JDesktopPane and call the dispose method on the JInternalFrame after pressing escape instead of implementing keylistener in this frame. It all depends on which GUI component has focus of input.
This issue is old now but I recently got stuck on a similar problem. Adding the key listener to the content pane of the internal frame instead of the internal frame itself did the job for me.
this.getContentPane().addKeyListener(this);
Related
I am fairly new to coding and have encountered this issue within my code.
I create a button using the Java AWT import. I then check for a response using a while loop and wish to create another button after, however .add() seems to no longer function.
import java.awt.*;
import java.awt.event.*;
public class Main1
{
public static void main(String[] args)
{
Frame f = new Frame();
f.setSize(500, 500);
f.setVisible(true);
ButtonPanel bp = new ButtonPanel(f);
bp.x = null;
while (bp.x == null)
{
}
System.out.println(bp.x);
//THE ISSUE- THIS WILL NOT APPEAR AFTER BUTTON PRESS
f.add("South", new Button("REEE"));
}
}
class ButtonPanel extends Panel implements ActionListener
{
volatile String x;
public ButtonPanel(Frame f)
{
Button b = new Button("Hi");
b.addActionListener(this);
f.add("North", b);
}
public void actionPerformed(ActionEvent e)
{
x = e.getActionCommand();
}
}
I have been trying solutions for this for the last day or so and nothing seems to be working. I've seen in other posts people have said to use Wait/Notify however I am not too sure how those work and I would like to know explicitly what is going wrong in my program (though I am still open to using Wait/Notify in my solution).
Any help would be appreciated, thank you very much
So, they're a number of issues at play here.
The first is the fact that layout managers are generally lazy. This means that you can add and/or remove a number of components quickly and then do a single layout and paint pass.
To do this, you need to revalidate the Container which was updated.
Next, AWT (and Swing by extension) is based on Model-View-Controller concept, one aspect of this is the "observer pattern". This is basically a callback concept that allows you to be notified when something of interest happens.
Button makes use of an ActionListener to generate events when the button is "actioned". This is the "observer pattern" in action.
Why is this important? You really want to think about what information is needed to be passed where and who's actually responsible for doing what.
For example, is it really the ButtonPanel's responsibility to update the frame? Is giving ButtonPanel unfettered control over the frame really a good idea?
Instead, ButtonPanel "should" be providing some kind of notification when some action has occurred and then any interested parties should be able to do what ever they need to.
As a "basic" example...
import java.awt.Button;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Frame;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.EventListener;
import javax.swing.event.EventListenerList;
public class Test {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new Test();
}
});
}
public Test() {
Frame f = new Frame();
f.setPreferredSize(new Dimension(500, 500));
f.pack();
ButtonPanel bp = new ButtonPanel(f);
bp.addObsever(new Observer() {
#Override
public void hiWasPerformed() {
f.add("South", new Button("REEE"));
f.revalidate();
}
});
f.setVisible(true);
}
public interface Observer extends EventListener {
public void hiWasPerformed();
}
class ButtonPanel extends Panel {
private EventListenerList eventListener = new EventListenerList();
public ButtonPanel(Frame f) {
Button b = new Button("Hi");
b.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
Observer[] listeners = eventListener.getListeners(Observer.class);
for (Observer observer : listeners) {
observer.hiWasPerformed();
}
}
});
f.add("North", b);
}
public void addObsever(Observer observer) {
eventListener.add(Observer.class, observer);
}
public void removeObsever(Observer observer) {
eventListener.remove(Observer.class, observer);
}
}
}
It looks like nothing is happening because the buttons are being added below the bottom of the window. You should consider using a layout manager to solve this issue.
However, in the meantime the simple solution is to move this line f.add("South", new Button("REEE")); inside the action event and to make use of Frame.pack();:
public class Main1
{
public static void main(String[] args)
{
Frame f = new Frame();
//set minimums rather than a fixed size
f.setMinimumSize(new Dimension(500, 500));
f.setVisible(true);
CustomButton b = new CustomButton(f);
//Add this line to update/size/show the UI
f.pack();
//Don't place any more code inside the main method. Future events should be triggered by interacting with the UI/buttons
}
}
Then for the button we don't need to extend Panel, we can do something like this:
class CustomButton implements ActionListener
{
Frame parentFrame;
public CustomButton(Frame f)
{
parentFrame = f;
Button b = new Button("Hi");
b.addActionListener(this);
f.add("North", b);
}
public void actionPerformed(ActionEvent e)
{
//Add button here instead of the main class
parentFrame.add("South", new Button("REEE"));
//The buttons are being added below the bottom of your window, this will force them to be shown.
//Using a layout manager will solve this ploblem and you will not need to do this:
parentFrame.pack();
}
}
Note: clicking on the "Hi" button multiple times will have interesting results of the "REEE" buttons overlapping or doing odd things if you resize the window.
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
I want to call a function when the user pastes text in my JTextArea. Is there any event generated when the text is pasted to the JTextArea and which listener can I use to trigger my function on this event?
One possible solution (and I hope some one has a better one) would be to replace the key binding Action responsible for actually performing the paste operation.
Now, before you do this, the default paste operation is not trivial, instead, I would replace the default paste Action with a proxy, which could call the original, but would allow you to intercept the operation, but not have to re-implement the functionality yourself, for example...
public class ProxyAction extends AbstractAction {
private Action action;
public ProxyAction(Action action) {
this.action = action;
}
#Override
public void actionPerformed(ActionEvent e) {
action.actionPerformed(e);
System.out.println("Paste Occured...");
}
}
Then you would simply need to look up the default Action and replace it...
JTextArea ta = new JTextArea(10, 10);
Action action = ta.getActionMap().get("paste-from-clipboard");
ta.getActionMap().put("paste-from-clipboard", new ProxyAction(action));
The problem here is, this won't tell you if the operation failed or succeeded or what was actually pasted. For that, you could use a DocumentListener, registered before you call the default Action which could record the changes to the document. Obviously, you'd want to deregister this after the default action ;)...
Now, equally, you could just override the paste method of the JTextArea, which equates to about the same thing, but, the first option would be more portable...
As an idea...
Take a look at How to Use Actions and How to Use Key Bindings for more details
you can have something like below, whenever you paste something in the textarea, then 'Pasted!' is printed out on your console. It prints only on paste !
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.*;
public class TextAreaDemo extends JFrame {
JTextArea _resultArea = new JTextArea(6, 20);
public TextAreaDemo() {
_resultArea.setText("");
JScrollPane scrollingArea = new JScrollPane(_resultArea);
JPanel content = new JPanel();
content.setLayout(new BorderLayout());
content.add(scrollingArea, BorderLayout.CENTER);
this.setContentPane(content);
this.setTitle("TextAreaDemo B");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.pack();
_resultArea.addKeyListener(new KeyListener() {
#Override
public void keyTyped(KeyEvent e) {
}
#Override
public void keyPressed(KeyEvent e) {
if ((e.getKeyCode() == KeyEvent.VK_V) && ((e.getModifiers() & KeyEvent.CTRL_MASK) != 0)) {
System.out.println("Pasted!");
}
}
#Override
public void keyReleased(KeyEvent e) {
}
});
}
public static void main(String[] args) {
JFrame win = new TextAreaDemo();
win.setVisible(true);
}
}
You can also check out Wrapping Actions which is basically the same suggestion as MadProgrammer except that the WrapperAction will delegate all the methods of the Action to the original Action. This will allow you to pick up the text and Icons associated with the original Action in case you ever want to add your custom Action to a JMenuItem or JButton.
I don't get how can I employ this code:
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
to close the program with the x button.
You need the line
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
Because the default behaviour for the JFrame when you press the X button is the equivalent to
frame.setDefaultCloseOperation(WindowConstants.HIDE_ON_CLOSE);
So almost all the times you'll need to add that line manually when creating your JFrame
I am currently referring to constants in WindowConstants like WindowConstants.EXIT_ON_CLOSE instead of the same constants declared directly in JFrame as the prior reflect better the intent.
If you don't have it, the JFrame will just be disposed. The frame will close, but the app will continue to run.
Calling setDefaultCloseOperation(EXIT_ON_CLOSE) does exactly this. It causes the application to exit when the application receives a close window event from the operating system. Pressing the close (X) button on your window causes the operating system to generate a close window event and send it to your Java application. The close window event is processed by the AWT event loop in your Java application which will exit the application in response to the event.
If you do not call this method the AWT event loop may not exit the application in response to the close window event but leave it running in the background.
I spent quite a bit of time spelunking through the internet for an elegant solution to this. As is usually the case, I found a lot of conflicting information.
I finally ended with:
Do not use EXIT_ON_CLOSE as this can leave resources behind;
Do use something like the following in the JFrame initialization:
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
The real discovery was how to actually dispatch a window message to the JFrame. As an example, as part of your JMenuItem for exiting the application, use the following, where the function getFrame() returns a reference to the JFrame:
public class AppMenuFileExit extends JMenuItem implements ActionListener
{
// do your normal menu item code here
#Override
public void actionPerformed(ActionEvent e)
{
WindowEvent we;
we = new WindowEvent((Window) App.getFrame(), WindowEvent.WINDOW_CLOSING);
App.getFrame().dispatchEvent(we);
}
}
JFrame is a subclass of Window so may be cast to Window for this purpose.
And, have the following in your JFrame class to handle Window messages:
public class AppFrame extends JFrame implements WindowListener
{
// Do all the things you need to for the class
#Override
public void windowOpened(WindowEvent e)
{}
#Override
public void windowClosing(WindowEvent e)
{/* can do cleanup here if necessary */}
#Override
public void windowClosed(WindowEvent e)
{
dispose();
System.exit(0);
}
#Override
public void windowActivated(WindowEvent e)
{}
#Override
public void windowDeactivated(WindowEvent e)
{}
#Override
public void windowDeiconified(WindowEvent e)
{}
#Override
public void windowIconified(WindowEvent e)
{}
}
If you're using a Frame (Class Extends Frame) you'll not get the
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE)
If you don't extend JFrame and use JFrame itself in variable, you can use:
frame.dispose();
System.exit(0);
The following code works for me:
System.exit(home.EXIT_ON_CLOSE);
this.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
this worked for me in case of Class Extends Frame
What code is called when a JFrame is minimized? Is it hooked up to a listener? I just want to know what happens internally when the frame is minimized.
EDIT:
Im actually looking for the code that is called when the frame is minimized. For example, the code for the actual windowListener. Ive been searching through JFrame, Frame, and Window searching for windowIconified but have been unable to find the actual code.
Reason being, when my program runs, it has a small defect with one of the Panels, but when I minimize and maximize the JFrame, the problem goes away. I wanted to see what was going on so that I can apply whatever is going on to my Panel so it paints right.
you can listening by using WindowListener
for example
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import javax.swing.JFrame;
public class WinStateListener implements WindowListener {
static JFrame window = new JFrame("Window State Listener");
public WinStateListener() {
window.setBounds(30, 30, 300, 300);
window.addWindowListener(this);
window.setVisible(true);
}
public static void main(String[] args) {
WinStateListener winStateListener = new WinStateListener();
}
public void windowClosing(WindowEvent e) {
System.out.println("Closing");
window.dispose();
System.exit(0);
}
public void windowOpened(WindowEvent e) {
System.out.println("Opened");
}
public void windowClosed(WindowEvent e) {
System.out.println("Closed");
}
public void windowIconified(WindowEvent e) {
System.out.println("Iconified");
}
public void windowDeiconified(WindowEvent e) {
System.out.println("Deiconified");
}
public void windowActivated(WindowEvent e) {
System.out.println("Activated");
}
public void windowDeactivated(WindowEvent e) {
System.out.println("Deactivated");
}
}
You want to read about WindowListeners and WindowEvents. The event you are talking about is called Iconifying the window. Read more here:
http://download.oracle.com/javase/tutorial/uiswing/events/windowlistener.html
EDIT:
Use revalidate() then repaint() on the JPanel that is acting up.
When minimizing the JFrame application a window event windowIconified is called. If you want to process such window events by your own then either implement WindowListener interface or use WindowAdapter abstract class.
What code is called when a JFrame is minimized?
As noted in How to Make Frames: Specifying Window Decorations, "window decorations are supplied by the native window system." The article goes on to describe some changes you can make to the host platform's default.
Addendum: Reading your update, note that restoring an iconified window repaints it. As #Andrew Thompson points out, you may need to verify that you're building on the event dispatch thread. You may also need to schedule a repaint(). An sscce might clarify things.