Develop Reference

JFrame doesn't update its content

I've been struggling to get my JFrame to repaint its content. I've tried using both the revaluate() and repaint() methods together after I add the new components into the JFrame but I'm not seeing the frame change.
Here's the simple GUI of a minesweeper game I'm trying to make.
When a user clicks on either of the top 3 buttons, they enter the following code block
private void drawGrid()
{
removeAll();
setLayout(new GridLayout(2,1));
add(new JButton("button"));
setVisible(true);
revalidate();
repaint();
setVisible(false);
setVisible(true);
}
When clicking a button, the whole application turns white, but I can't see the new button I added. When I remove the two setVisible() method lines, then clicking a button definitely removes the components since I can't click on any of them now, but the 4 initial buttons are still visible. Removing the revalidate or repaint methods has no effect on the application.
What else can I try to get the application to refresh and display its new content.

Calling removeAll on a JFrame is dangerous and can produce unexpected results, another reason why it's discouraged to extend from or manage UI's directly on top level containers.
Start by using a JPanel as you base UI component, then use a CardLayout to manage switching between the views.
Separate each view into it's own class (extending from JPanel or something simular) for easier management

Maybe it would work better if you used this
easyBtn.setVisible( false );
medBtn.setVisible( false );
hardBtn.setVisible( false );
customBtn.setVisible( false );
newBtn.setVisible( true );
If that does not work, try putting it into a SwingWorker.

Getting text from a JTextArea using a JButton and a JTabbedPane

Newbie here trying to make a simple GUI with JTabbedPane. I've looked through a lot of examples but have been unable to find a solution. Basically, I'm trying to print out a String to a JTextArea. While it seems very simple, I have been unable to get everything to work together. I understand the difference between local and global variables, but I think that is where my problem lies. Any guidance would be greatly appreciated. *Please note that we are unable to use a layout manager for this project.
The code below represents part of the tab that has the JButton and JTextArea.
//Text area that shows details. Scrolls.
JTextArea areaDeets = new JTextArea();
areaDeets.setBounds(65, 300, 250, 300 );
areaDeets.setText("");
JScrollPane scroll = new JScrollPane (areaDeets);
scroll.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED);
panel2.add(areaDeets);
panel2.add(scroll);
areaDeets.addActionListener(new StopTest());
//Stop button--stops tests when pressed.
JButton stop = new JButton("Stop");
stop.setBounds(215, 650, 100, 40);
panel2.add(stop);
stop.addActionListener(new StopTest());
The code below is the method that calls the ActionListener.
//Panel 1 - Stop, shows that the test has been stopped
static class StopTest implements ActionListener{
public void actionPerformed(ActionEvent e){
String stop = "The test has been stopped";
areaDeets.setText(stop);
panel2.repaint();
}
}
Edit: Code does not compile. Eclipse says that I cannot call addActionListener on a JTextField.

You can pass the reference of the JTextArea to the constructor of the ActionListener:
public class StopTest implements ActionListener {
private JTextArea area;
public StopTest(JTextArea area) {
this.area = area;
}
public void actionPerformed(ActionEvent e) {
String stop = "The test has been stopped";
area.setText(stop);
}
}

One possible solution (guessing here due to limited information): don't make the StopTest class static. Rather make it a private inner non-static class or a stand-alone class. This will allow it access to non-static fields of your outer class.
Don't add an ActionListener to your JTextArea as this is not allowed and has no real meaning, since JTextAreas allow returns to be entered, and use this to start a new line in the JTextArea.
Other unrelated recommendations:
Also, as a general rule, you should avoid use of null layout as this makes for very inflexible GUI's that while they might look good on one platform look terrible on most other platforms or screen resolutions and that are very difficult to update and maintain.
Much better would be to use nested JPanels, each using its own layout manager, and then calling pack() on your JFrame after adding all components but prior to displaying it.
Never call setBounds(), setSize(), setPreferredSize() or any similar call on a JTextArea that goes inside of a JScrollPane as it will prevent the JScrollPane from working correctly within your JScrollPane due to your setting bounds. This will prevent the JTextArea from expanding when more lines are added, sometimes preventing display of the scrollbars, or if their displayed, preventing them from working properly. Better to set the JTextArea's viewable columns and rows via one of its constructors that has int parameters.
There's no need to call repaint() after setting the text of a JTextComponent such as a JTextArea, since the textarea's model will notify its view (the part that is rendered on the GUI) of changes, and the view will then automatically call repaint itself.

Why isn't this gui updating?

I have a Gui and a Game class, and I'm unable to update the gui from the game. I'm not using threads, but I've seen it update before, so that isn't the problem. The game logic is really simple, there is no need for threads. No matter how furiously I call repaint() and revalidate(), it doesn't work now, no matter where I put it.
class Gui {
//...
public Gui(Game game) {
this.game = game;
initialize();
}
private void initialize() {
//...
okButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent arg0) {
okAction(textField.getText());
textField.setVisible(false);
okButton.setVisible(false);
textField.setText("");
}
});
}
private void okAction(String input) {
game.receiveInput(input);
}
public void output(String msg) {
textArea.append(msg + "\n");
}
public void getInput() {
textField.setVisible(true);
okButton.setVisible(true);
textField.setText("");
}
}
Also I want to be able to pass a String back to the game instance. I thought I'd call getInput() from the game, which will show a JTextField to type in, and a JButton to submit. In the actionPerformed() method I would just get the text entered, and call a method back in the game class. I don't know if this would work, since the gui is not updating, and I never had the input field and button appear. Is this right?
This would be the method which the gui "calls back":
class Game {
//...
public void receiveInput(String input) {
int n = Integer.parseInt(input);
if ( validInput(input, actualDecision.choices.size()) ) {
parser.setAction(actualDecision.choices.get(n-1).action);
}
}
}
From the game class, I just want to call gui.output() and gui.getInput() a few times.
Where is my problem? Why isn't it updating, nor freezing? If I use the debugger, the both output() and getInput() is executed, but nothing happens...
EDIT:
Ok I see a problem myself, with the getting input part... Since it returns quickly, it can never receive an input. But that doesn't explain why aren't the input field and the button, or any text is showing up
EDIT 2:
Oh god, sorry, I really don't know how to make it shorter, but you only ever need to look at the Game and the Gui, others are just there to compile.
The code: https://gist.github.com/anonymous/53bad714592792316b4d
An xml to test against: https://gist.github.com/anonymous/30b56facb78fe6ecd482

Honestly I have just taken a look to Gui class code and don't know why it doesn't update properly when it interacts with Game class. BUT I have several remarks on your code and I hope these can lead you in the right way by making this class simpler and then you can focus on the interaction with Game class.
Menu bar
You're adding the JMenuBar to a JPanel instead of setting it to the JFrame:
panel.add(menuBar, gbc);
//frame.setJMenuBar(menuBar); Use this instead
As JFrame is a top level container prepared to handle a menu bar you should consider make the suggested change.
Saving validate() call
As the JFrame is initialized at the start of initialize() method and the JPanel is added after making the frame visible then you have to call frame.revalidate() method to revalidate the components hierarchy. If you just initialize the panel before make the frame visible then you don't need to call revalidate() method. Take a look to this answer for further details.
Missing pack() call
There's no call to frame.pack() method to lay out the frame's subcomponents. Take a look to Window.pack().
Missing GridBagConstraints when adding okButton
There's no GridBagConstraints as argument when adding okButton to panel:
panel.add(okButton);
//panel.add(okButton, gbc); This is the correct way.
Use of setSize()
In this line:
frame.setSize(800, 600);
We should avoid using set(Preferred | Minimum | Maximum)Size() because of reasons discussed in this topic: Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing?
Use of GridBagLayout
This is just a suggestion there's nothing wrong on how you are using GridBagLayout. As probably you have noted this layout manager is a little hard to use (and I really don't like it by the way :) You can use a Nested Layout approach to make the components layout easier and your code more readable. Maybe this approach is good enough:
Set the JMenuBar to the JFrame. It's one less component to lay out
;)
Add the scroll pane with the text area directly to the frame's
content pane using
BorderLayout
constraints: frame.getContentPane().add(scrollPane,
BorderLayout.CENTER);
Create a new JPanel to hold the text field and the button used to
ask for user's input and add it to the frame's content pane.
Translated to code:
JPanel usersInput = new JPanel(new FlowLayout(FlowLayout.CENTER));
usersInput.add(textField);
usersInput.add(okButton);
frame = new JFrame();
frame.setJMenuBar(menuBar);
frame.getContentPane().add(scrollPane, BorderLayout.CENTER);
frame.getContentPane().add(usersInput, BorderLayout.SOUTH);
frame.setTitle("Choose your own adventure");
frame.pack();
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); // It's better practice DISPOSE_ON_CLOSE ;)
frame.setVisible(true);
Update
Well I'm curious and I really want to test your game (quite nice work by the way :) The thing is I have found at least two problems in the logic:
Use of == to compare strings
In Parser class there are several string comparisons using == but this is not the proper way to compare strings. We must use .equals() method to compare strings equality. Take a look to this topic: How do I compare strings in Java?
Game.processStory() has an endless loop
This method has an endless loop here:
while ( !end() ) { // this condition never is false so the loop is infinite
...
}
Looking closer to Game.end() method I have found an incorrect string comparison:
private boolean end() {
return ( parser.getAction() == "end" );
//It should be: return parser.getAction().equals("end");
}
But fixing that doesn't solve the problem either: it turns parser.getAction() always returns "d1" and consequently it will never be equal to "end".
Having said this as Game.play() is executed in the Event Dispatching Thread (a.k.a. EDT) triggered by newGameItem menu item and Game.processStory() has this endless loop, then the EDT is getting blocked and Gui is never updated.
In this case I would suggest you take a look to Concurrency in Swing trail to learn about how to avoid blocking the EDT.

JFrame whose content changes as we click on the different buttons

I am using Java's Swing here to make a UI application. I have a created a JFrame, with some buttons. When I click on this button, I want a new JFrame with some different content at this place. However, I do not want a new JFrame to load here.
One approach, I know is of setting the visbility of the second JFrame to be True in the actionPerformed(ActionEvent obj) method of the button in the first JFrame. But it again loads a new JFrame and I don't want that.
public class FirstUI extends JFrame {
JButton but1;
public FirstUI(){
but1= new JButton("Click here");
add(but1);
XYZ obj= new XYZ():
but1.addActionListener(obj);
}
public class XYZ implements ActionListener{
public void actionPerformed(ActionEvent obj1){
// WHAT TO DO HERE
}
}
}
I only want a single JFrame whose content changes as we click on different buttons. How can I achieve that ?

Have a look at CardLayout, this would allow to switch the content of your frame:
A CardLayout object is a layout manager for a container. It treats each component in the container as a card. Only one card is visible at a time, and the container acts as a stack of cards. The first component added to a CardLayout object is the visible component when the container is first displayed.
See How to Use CardLayout for an example.

You can also dynamically manipulate the contents of your JFrame at runtime. You can use add(...), remove(...), removeAll(...) methods to add and remove the contents as you do before showing the frame. After you're done you need to call revalidate() and repaint() methods of the modified container to make everything settle down and displayed properly.
However I think the right solution depends on the actual concept you are trying to implement. If you want to add or remove a couple of GUI elements to emphasize a functionality, then the correct way is to manipulate the container as I outlined. But if you want slightly different GUI depending on system state (not more then 2-3) then CardLayout would be a better suited choice

You can set visibility of parent class false.
Then you get only one Frame at a time with your required content.
You have to create static object of the frame and setVisible(fase) at the click event of the Button.
Ex.
public class demo {
static JFrame jf;
public static void main(String a[])
{
JButton b=new JButton("OK");
JPanel jp=new JPanel();
jf=new JFrame();
jf.setVisible(true);
jf.setSize(200,200);
jf.add(jp);
jp.add(b);
b.addActionListener( new ActionListener(){
public void actionPerformed(ActionEvent e)
{
jf.setVisible(false);
JFrame f= new JFrame();
f.setSize(200,200);
f.setVisible(true);
}
});
}
}
It will help you.
you got my point?

One approach is to change the JFrame's Content Pane. which is basically a JPanel. You can do that byframe.setContentPane( <your new panel> );
The Second approach is to do what #Peter Lang did. and that is to use a Layout Manager which could change different content groups.

Image not getting displayed on a JPanel

class Deal implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
dl.setDeck();
dl.shuffle();
dl.firstDraw(pl);
for(Card c:pl.showHand())
panelplay.add(new JLabel(c.getImageIcon()));
panelplay.validate();
}
}
This is an event handler for a Jbutton. The method pl.showHand() returns a ArrayList of a user defined class 'Card'. Inserting a println() inside the loop shows the print, so the code is being executed but the Panel panelplay isnt showing card Images.

What about the existing labels on the panel? You don't remove them. I'm guessing you are using a FlowLayout and the labels just get added to the end of the panel so you don't see them.
So one solution is to use panel.removeAll() before adding the labels back to the panel. I then use:
panel.revalidate();
panel.repaint();
Or the better option as suggested earlier is to not replace the labels but just replace the Icons using the setIcon() method.

Do as Gilbert says, look at the Swing Tutorial part that concerns Labels.
JLabel has the following methods...
void setIcon(Icon)
Icon getIcon()
Also look at the SplitPaneDemo It does exactly what you want, you can even run it with JNLP to see.

You don't want to add the JLabel in the ActionListener.
You want to use an already added JLabel setText() method in the ActionListener.
You define all the Swing components once, when you create the GUI.