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Passing an object from one JFrame to another [duplicate]

I have two Jframes where frame1 has some text fields and when a button on frame1 is clicked, I open another JFrame which contains a search box and a JTable containing search results.
When I click on a result row on JTable, I want that particular values to be reflected in the frame1 text fields.
I tried passing the JFrame1's object as a parameter but I have no clear idea on how to achieve this.
Any help would be highly appreciated.
Thanks

First of all, your program design seems a bit off, as if you are using a JFrame for one of your windows where you should in fact be using a JDialog since it sounds as if one window should be dependent upon the other.
But regardless, you pass references of GUI objects the same as you would standard non-GUI Java code. If one window opens the other (the second often being the dialog), then the first window usually already holds a reference to the second window and can call methods off of it. The key often is when to have the first window call the second's methods to get its state. If the second is a modal dialog, then the when is easy -- immediately after the dialog returns which will be in the code immediately after you set the second dialog visible. If it is not a modal dialog, then you probably want to use a listener of some sort to know when to extract the information.
Having said this, the details will all depend on your program structure, and you'll need to tell us more about this if you want more specific help.
For a simple example that has one window open another, allows the user to enter text into the dialog windows JTextField, and then places the text in the first window's JTextField, please have a look at this:
import java.awt.Window;
import java.awt.Dialog.ModalityType;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class WindowCommunication {
private static void createAndShowUI() {
JFrame frame = new JFrame("WindowCommunication");
frame.getContentPane().add(new MyFramePanel());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
// let's be sure to start Swing on the Swing event thread
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
createAndShowUI();
}
});
}
}
class MyFramePanel extends JPanel {
private JTextField field = new JTextField(10);
private JButton openDialogeBtn = new JButton("Open Dialog");
// here my main gui has a reference to the JDialog and to the
// MyDialogPanel which is displayed in the JDialog
private MyDialogPanel dialogPanel = new MyDialogPanel();
private JDialog dialog;
public MyFramePanel() {
openDialogeBtn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
openTableAction();
}
});
field.setEditable(false);
field.setFocusable(false);
add(field);
add(openDialogeBtn);
}
private void openTableAction() {
// lazy creation of the JDialog
if (dialog == null) {
Window win = SwingUtilities.getWindowAncestor(this);
if (win != null) {
dialog = new JDialog(win, "My Dialog",
ModalityType.APPLICATION_MODAL);
dialog.getContentPane().add(dialogPanel);
dialog.pack();
dialog.setLocationRelativeTo(null);
}
}
dialog.setVisible(true); // here the modal dialog takes over
// this line starts *after* the modal dialog has been disposed
// **** here's the key where I get the String from JTextField in the GUI held
// by the JDialog and put it into this GUI's JTextField.
field.setText(dialogPanel.getFieldText());
}
}
class MyDialogPanel extends JPanel {
private JTextField field = new JTextField(10);
private JButton okButton = new JButton("OK");
public MyDialogPanel() {
okButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
okButtonAction();
}
});
add(field);
add(okButton);
}
// to allow outside classes to get the text held by the JTextField
public String getFieldText() {
return field.getText();
}
// This button's action is simply to dispose of the JDialog.
private void okButtonAction() {
// win is here the JDialog that holds this JPanel, but it could be a JFrame or
// any other top-level container that is holding this JPanel
Window win = SwingUtilities.getWindowAncestor(this);
if (win != null) {
win.dispose();
}
}
}
You'd do a very similar technique to get information out of a JTable.
And again, if this information doesn't help you, then please tell us more about your program including showing us some of your code. The best code to show is a small compilable example, an SSCCE similar to what I've posted above.

How to transfer an answer to another jframe? [duplicate]

I have two Jframes where frame1 has some text fields and when a button on frame1 is clicked, I open another JFrame which contains a search box and a JTable containing search results.
When I click on a result row on JTable, I want that particular values to be reflected in the frame1 text fields.
I tried passing the JFrame1's object as a parameter but I have no clear idea on how to achieve this.
Any help would be highly appreciated.
Thanks

First of all, your program design seems a bit off, as if you are using a JFrame for one of your windows where you should in fact be using a JDialog since it sounds as if one window should be dependent upon the other.
But regardless, you pass references of GUI objects the same as you would standard non-GUI Java code. If one window opens the other (the second often being the dialog), then the first window usually already holds a reference to the second window and can call methods off of it. The key often is when to have the first window call the second's methods to get its state. If the second is a modal dialog, then the when is easy -- immediately after the dialog returns which will be in the code immediately after you set the second dialog visible. If it is not a modal dialog, then you probably want to use a listener of some sort to know when to extract the information.
Having said this, the details will all depend on your program structure, and you'll need to tell us more about this if you want more specific help.
For a simple example that has one window open another, allows the user to enter text into the dialog windows JTextField, and then places the text in the first window's JTextField, please have a look at this:
import java.awt.Window;
import java.awt.Dialog.ModalityType;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class WindowCommunication {
private static void createAndShowUI() {
JFrame frame = new JFrame("WindowCommunication");
frame.getContentPane().add(new MyFramePanel());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
// let's be sure to start Swing on the Swing event thread
public static void main(String[] args) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
createAndShowUI();
}
});
}
}
class MyFramePanel extends JPanel {
private JTextField field = new JTextField(10);
private JButton openDialogeBtn = new JButton("Open Dialog");
// here my main gui has a reference to the JDialog and to the
// MyDialogPanel which is displayed in the JDialog
private MyDialogPanel dialogPanel = new MyDialogPanel();
private JDialog dialog;
public MyFramePanel() {
openDialogeBtn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
openTableAction();
}
});
field.setEditable(false);
field.setFocusable(false);
add(field);
add(openDialogeBtn);
}
private void openTableAction() {
// lazy creation of the JDialog
if (dialog == null) {
Window win = SwingUtilities.getWindowAncestor(this);
if (win != null) {
dialog = new JDialog(win, "My Dialog",
ModalityType.APPLICATION_MODAL);
dialog.getContentPane().add(dialogPanel);
dialog.pack();
dialog.setLocationRelativeTo(null);
}
}
dialog.setVisible(true); // here the modal dialog takes over
// this line starts *after* the modal dialog has been disposed
// **** here's the key where I get the String from JTextField in the GUI held
// by the JDialog and put it into this GUI's JTextField.
field.setText(dialogPanel.getFieldText());
}
}
class MyDialogPanel extends JPanel {
private JTextField field = new JTextField(10);
private JButton okButton = new JButton("OK");
public MyDialogPanel() {
okButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
okButtonAction();
}
});
add(field);
add(okButton);
}
// to allow outside classes to get the text held by the JTextField
public String getFieldText() {
return field.getText();
}
// This button's action is simply to dispose of the JDialog.
private void okButtonAction() {
// win is here the JDialog that holds this JPanel, but it could be a JFrame or
// any other top-level container that is holding this JPanel
Window win = SwingUtilities.getWindowAncestor(this);
if (win != null) {
win.dispose();
}
}
}
You'd do a very similar technique to get information out of a JTable.
And again, if this information doesn't help you, then please tell us more about your program including showing us some of your code. The best code to show is a small compilable example, an SSCCE similar to what I've posted above.

How to perform action after JFrame is closed?

I need to perform an action after the JFrame is closed and I have this part of code for it, but this doesn't work.
Could anyone please advise what should be change here?
private void changeDefaults(){
Thread changeDefaultsThread = new Thread(new Runnable(){
public void run(){
Change ch = new Change();
ch.setVisible(true);
ch.setListeners();
ch.defaultInput();
while(ch.isActive()){
System.out.println("active");
}
updateDefaults();
}
});
changeDefaultsThread.start();
}
Change is the JFrame I am opening for another action.

You can add listener to your JFrame
frame.addWindowListener (new java.awt.event.WindowAdapter)
and override the windowClosing
#Override
public void windowClosing
frame.addWindowListener(new java.awt.event.WindowAdapter() {
#Override
public void windowClosing(java.awt.event.WindowEvent windowEvent) {
//do something
}
});

I'm surprised no one has mentioned the simplest solution: don't use a JFrame. The best tool for this behavior -- displaying a child window and doing something immediately after it has closed -- is to use a modal dialog window such as a JDialog or JOptionPane. The JDialog set up code is very similar to that of the JFrame, with an exception being that it uses different constructors, and should have the parent window passed into it, and it uses a subset of the default close operations.
If you use a modal dialog, then program flow is halted in the calling code immediately after the dialog has been displayed (think of how a JOptionPane operates), and then immediately resumes from the spot after calling setVisible(true) on the dialog once the dialog has been closed.
The only bugaboo is that if you don't want modal behavior -- if you don't want the parent/calling window to be disabled while the child window is displayed -- then you'll have to use a non-modal JDialog window with a WindowListener.

If you want to perform an action when closing a JFrame, you just need to attach a WindowListener (extending WindowAdapter so that you do not need to implement all WindowListener methods):
import javax.swing.*;
public class AfterJFrameClose {
public static void main(String[] args) {
JFrame frame = new JFrame("My frame");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.setAlwaysOnTop(true);
frame.addWindowListener(new java.awt.event.WindowAdapter() {
#Override
public void windowClosing(java.awt.event.WindowEvent windowEvent) {
System.out.println("Frame closing");
}
});
}
}
Instead of the System.out.println, just write the code you want to have executed.
Update: If you want to access another frame, you either should pass it as a parameter as suggested above or you can also iterate through active frames using something like this:
Frame[] frames = Frame.getFrames();
for (Frame frame: frames) {
System.out.println(frame.getTitle());
}

Java how to make JFrames maximised but not resizable

Originally (See my previous question "Java how to make JFrames start off as a maximised window") I wanted to make a window which starts out maximised.
This code accomplishes this:
public static void main(String[] args) {
JFrame frame = new JFrame();
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
frame.setVisible(true);
}
However, if this window is restored down it becomes a practically non-existent bar. To solve this I set a size for the window using setSize(). This works but presents another problem, the window can still be resized.
To solve this problem I set setResizable(false); and this is my code so far:
public static void main(String[] args) {
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
JFrame frame = new JFrame("Jedia");
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
frame.setSize(screenSize);
frame.setResizable(false);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
However, now the window starts out at its specified size (rather than maximised) and cannot be restored up.
So, my question is, how can I either make the window start out maximised, give it a size for when it is restored down and make resizing it impossible? Or make a window that starts out maximised and cannot be restored down?

There is a simple fix that works almost all the time: make your frame not resizable after having set visible. So only modifies your code this way:
public static void main(String[] args) {
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
JFrame frame = new JFrame("Jedia");
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
frame.setSize(screenSize);
frame.setVisible(true); // FIRST visible = true
frame.setResizable(false); // THEN resizable = false
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
This way, the frame will start maximized and the maximize button will be greyed out, preventing user to use it. (I don't really know why you have to do this. I suppose the maximized state is really applied only when the window becomes visible, and if you make it unresizable before, it will not apply.)
It works almost all the time because on Windows 7 at least you can make the window goes out of the maximized state by clicking the title bar and dragging it. But it will be at the size you have set it earlier. Problem is that your user will not be able to maximize it again, and I haven't found the way with listeners to make the window back to maximized state. ( Edit: #David Kroukamp shows in the last part of his answer that it is possible to force the maximized state by using a ComponentListener. Therefore you don't have to use setResizable(false) This way you still have a problem with Windows 7 because the dragging action is not catched by this event for whatever reason but users will be able to use the maximized button to put it back where it should be.)
Now, there is almost never a reason to do this kind of things. Users don't really like when you prevent them to manipulate their windows (maximized windows can not be moved, for example, and that can be annoying when you have multiple screens). An exception is if you are making a game, which is typically full-screen. But then you wouldn't want a JFrame because you don't want all the decoration, but a Window.
If your problem is that the default window size is very small, it's normal. You have to put something in your frame first (some controls, buttons, what you want in your application), using layouts (that's important) then call the method pack() on your frame. It will chose a nice default size for your window.
Finally, a last word. I've put my example code in a main method as a shortcut, but you should always do Swing stuff in the Swing EDT by using SwingUtils.invokeLater().

Sometimes, you have to be careful about the order you set JFrame parameters.
Also, you should be using Swing components on the event dispatch thread.
Try this and see if it helps.
public static void main(String[] args) {
final Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame("Jedia");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(screenSize);
frame.setResizable(false);
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
frame.setVisible(true);
}
});
}

What environment are you running on? I tried this with JDK1.6 / JDK1.7 under Win7 and it works as expected (window starts maximized, minimizes to task bar).

I have kind of a hack for you that might work.
Try this code (it worked for me):
public static void main(String[] args) {
final JFrame frame = new JFrame("Jedia");
frame.setMinimumSize(new Dimension(600, 400));
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
frame.setVisible(true);
frame.addComponentListener(new ComponentListener(){
#Override
public void componentHidden(ComponentEvent e) {
// TODO Auto-generated method stub
}
#Override
public void componentMoved(ComponentEvent e) {
// TODO Auto-generated method stub
}
#Override
public void componentResized(ComponentEvent e) {
if (!e.paramString().startsWith("COMPONENT_RESIZED (-8,-8"))
frame.setSize(new Dimension(600, 400));
}
#Override
public void componentShown(ComponentEvent e) {
// TODO Auto-generated method stub
}
});
}
e.paramString() returns a String that looks like "COMPONENT_RESIZED (-8,-8, [screensize])" when a restore action takes place.

Swing getHeight() value changing from 0 to 16

I am trying to make a box in Swing that has a label of "user", a text field for the username, and a button "sign in". This is my code
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;
import java.util.*;
public class Engine
{
JFrame frame;
public void go()
{
setUpGui();
userNameScreen();
}
public void setUpGui()
{
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
public void userNameScreen()
{
JPanel background = new JPanel();
frame.getContentPane().add(background);
JLabel labelUserName = new JLabel("User:");
background.add(labelUserName);
System.out.println(labelUserName.getHeight()); // 0
JTextField textFieldUserName = new JTextField();
System.out.println(labelUserName.getHeight()); // 16
textFieldUserName.setPreferredSize(new Dimension(110,labelUserName.getHeight()));
background.add(textFieldUserName);
JButton buttonSignIn = new JButton("Sign In");
background.add(buttonSignIn);
/*
background.add(labelUserName);
background.add(textFieldUserName);
background.add(buttonSignIn);
frame.getContentPane().add(background);
*/
frame.pack();
}
}
My driver class just creates an instance of engine, then runs the method go().
I read that Swing components do not have attributes of height/width until they are added (because that is for the layout manager to decide how much room they have), so it makes sense that in the method userNameScreen(), adding in all components at the end* (commented out here) makes the textFieldUserName variable have no height.
However, you can see in that same method userNameScreen(), I have it do
System.out.println(labelUserName.getHeight());
twice. The first time, it is 0. The second, it is 16. I don't understand why the first time, it would register it as 0. It has already been added to the panel (in the line before), and there doesn't seem to be anything that would change its height between that first println() and the next. So why is the value 0 in the first one, and why does it change to 16 almost immediately after?
*I should note, when I say adding in all the stuff commented out at the end, it also includes removing/commenting out all the same commands done elsewhere in the code.

It is a side effect from not creating/modifying your Swing components on the EDT. Now the EDT is busy doing the layout while you are adding components in another thread.
Your main method should look like:
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new Engine().go();
}
});
}

I'm not sure why this is happening but may be because the addition of the component maybe on a background thread and might not have been updated till the next statement is called and its updated a few millisecs later and appears when you call it second time.