I've searched and could not find the answer I need to do the following: I have two java files: one JFrame, one JPanel. I configured a button in the JFrame to open up the JPanel from within the main frame with a new size of 800,800. Now, I want to close the JPanel and go back to the original JFrame (the one that originally was at size 500,500 with an image). It seems simply straightforward, but I've created an instance of the main frame from within the JPanel and set the jPanel to (this.setVisible(false)). I created a new jFrame object and set its visibility to true. What happens is, a new instance of the JFrame appears alright, but the JFrame at 800,800 with no image still appears as well. I've tried several configurations of getContentPane(), setContentPane() and even tried passing a JFrame parameter to the constructor of the JPanel. I'm not sure where I am going wrong with this, but any help would be much appreciated. All I want is the original JFrame with the original size and image displayed. Thank you in advance.
private void jButton_closeActionPerformed(java.awt.event.ActionEvent evt) {
this.setVisible(false);
mainMenuFrame = new MainMenuFrame();
mainMenuFrame.setVisible(true);
invalidate(); validate();
repaint();
}
you could open and close the jpanel from within your JFrame. the button would be also added to the jframe instead of the jpanel. for easier accessing use the jpanel as member variable
Related
I am working with a JFrame Gui, and I have not found a way to change the background of a JLabel using the event handler actionlistener. The main problem is that I have a JPanel created with 4 JLabels inside. I am unsure why I'm not able to use the JLabel variables that are inside the JPanel container. I've tried creating a field for the JLabel, but it returns null when I try to use the .getBackground() method. I've also tried getting the components of the JPanel using a for loop, and changing the labels through that. So far nothing, hopefully this question makes sense, please help me understand this.
https://i.stack.imgur.com/Hnoj5.png
This image shows the refactored method that has my JPanel container with its 4 JLabel components.
https://i.stack.imgur.com/Gw7Xs.png
This image shows the actionlistener part of my code.
why don't you declare a jframe first? Example
JFrame frame = new JFrame();
and then you create a JPanel after that.
JPanel panel = new JPanel();
and then add your jlabel and stuff in the jpanel and then that is when you call your jframe.
example
frame.add(panel);
i have the same project before the only difference about our problem is that I forgot to use the JPanel, but I have a JFrame. Create a JFrame first.
I have a Java Swing GUI and everything in my JFrame is offset by a few pixels. On MacOS, I had to offset everything by 12 pixels downward to account for it. On Windows, everything is shifted to the left and downward as well. I discovered that
setUndecorated(true);
removes the JFrame border (which I suspect is the cause of my problems) but it also removes the title bar.
Is there a way I can remove the JFrame border (or some other alternative to make sure everything is centered) and still keep the title bar? I need the title bar so that I can move the JFrame around and have the maximize/minimize/close functions.
Also, the layout is set to null in case that matters. (Everything I'm doing is pixel - based so I cannot set it to anything else).
Thanks.
I found a solution after Googling a bit more. Calling
getContentPane().setPreferredSize(...)
pack();
inside the JFrame constructor will adjust everything so that the titlebar and borders will not impact the view of the content pane.
For anyone else that may need this, you have to set the preferred size of the content pane specifically as that is what you want to appear correctly.
This way you can keep the titlebar and all the normal functionality of a JFrame window that you would otherwise lose with setUndecorated(true);.
The reason why you are adding 12px is because this is consume by the Title and border.
If you use setUndecorated(true) You will loose the title bar and you have to implement the addWindowListener to add a location changing of of an application.
The best way to do is:
Class Main{
public static void main(String[] args){
//JFrame
JFrame frame = new JFrame();
//Create a Main Panel and setPreferred Size and not set Size or set Bound
JPanel mainPanel = new JPanel(); //You value down
mainPanel.setPrefferedSize(new Dimension(x, y));
frame.add(mainPanel);
//and then in last add
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//the pack method help you to setSize of the JFrame According to the
//Component size
frame.pack();
frame.setVisible(true);
}
}
To put it simple, there's a simple java swing app that consists of JFrame with some components in it. One of the components is a JPanel that is meant to be replaced by another JPanel on user action.
So, what's the correct way of doing such a thing? I've tried
panel = new CustomJPanelWithComponentsOnIt();
parentFrameJPanelBelongsTo.pack();
but this won't work. What would you suggest?
Your use case, seems perfect for CardLayout.
In card layout you can add multiple panels in the same place, but then show or hide, one panel at a time.
1) Setting the first Panel:
JFrame frame=new JFrame();
frame.getContentPane().add(new JPanel());
2)Replacing the panel:
frame.getContentPane().removeAll();
frame.getContentPane().add(new JPanel());
Also notice that you must do this in the Event's Thread, to ensure this use the SwingUtilities.invokeLater or the SwingWorker
frame.setContentPane(newContents());
frame.revalidate(); // frame.pack() if you want to resize.
Remember, Java use 'copy reference by value' argument passing. So changing a variable wont change copies of the reference passed to other methods.
Also note JFrame is very confusing in the name of usability. Adding a component or setting a layout (usually) performs the operation on the content pane. Oddly enough, getting the layout really does give you the frame's layout manager.
Hope this piece of code give you an idea of changing jPanels inside a JFrame.
public class PanelTest extends JFrame {
Container contentPane;
public PanelTest() {
super("Changing JPanel inside a JFrame");
contentPane=getContentPane();
}
public void createChangePanel() {
contentPane.removeAll();
JPanel newPanel=new JPanel();
contentPane.add(newPanel);
System.out.println("new panel created");//for debugging purposes
validate();
setVisible(true);
}
}
On the user action:
// you have to do something along the lines of
myJFrame.getContentPane().removeAll()
myJFrame.getContentPane().invalidate()
myJFrame.getContentPane().add(newContentPanel)
myJFrame.getContentPane().revalidate()
Then you can resize your wndow as needed.
Game game = new Game();
getContentPane().removeAll();
setContentPane(game);
getContentPane().revalidate(); //IMPORTANT
getContentPane().repaint(); //IMPORTANT
It all depends on how its going to be used. If you will want to switch back and forth between these two panels then use a CardLayout. If you are only switching from the first to the second once and (and not going back) then I would use telcontars suggestion and just replace it. Though if the JPanel isn't the only thing in your frame I would use
remove(java.awt.Component) instead of removeAll.
If you are somewhere in between these two cases its basically a time-space tradeoff. The CardLayout will save you time but take up more memory by having to keep this whole other panel in memory at all times. But if you just replace the panel when needed and construct it on demand, you don't have to keep that meory around but it takes more time to switch.
Also you can try a JTabbedPane to use tabs instead (its even easier than CardLayout because it handles the showing/hiding automitically)
The other individuals answered the question. I want to suggest you use a JTabbedPane instead of replacing content. As a general rule, it is bad to have visual elements of your application disappear or be replaced by other content. Certainly there are exceptions to every rule, and only you and your user community can decide the best approach.
Problem: My component does not appear after I have added it to the container.
You need to invoke revalidate and repaint after adding a component before it will show up in your container.
Source: http://docs.oracle.com/javase/tutorial/uiswing/layout/problems.html
I was having exactly the same problem!! Increadible!! The solution I found was:
Adding all the components (JPanels) to the container;
Using the setVisible(false) method to all of them;
On user action, setting setVisible(true) to the panel I wanted to
show.
// Hiding all components (JPanels) added to a container (ex: another JPanel)
for (Component component : this.container.getComponents()) {
component.setVisible(false);
}
// Showing only the selected JPanel, the one user wants to see
panel.setVisible(true);
No revalidate(), no validate(), no CardLayout needed.
The layout.replace() answer only exists/works on the GroupLayout Manager.
Other LayoutManagers (CardLayout, BoxLayout etc) do NOT support this feature, but require you to first RemoveLayoutComponent( and then AddLayoutComponent( back again. :-) [Just setting the record straight]
I suggest you to add both panel at frame creation, then change the visible panel by calling setVisible(true/false) on both.
When calling setVisible, the parent will be notified and asked to repaint itself.
class Frame1 extends javax.swing.JFrame {
remove(previouspanel); //or getContentPane().removeAll();
add(newpanel); //or setContentPane(newpanel);
invalidate(); validate(); // or ((JComponent) getContentPane()).revalidate();
repaint(); //DO NOT FORGET REPAINT
}
Sometimes you can do the work without using the revalidation and sometimes without using the repaint.My advise use both.
Just call the method pack() after setting the ContentPane, (java 1.7, maybe older) like this:
JFrame frame = new JFrame();
JPanel panel1 = new JPanel();
JPanel panel2 = new JPanel();
....
frame.setContentPane(panel1);
frame.pack();
...
frame.setContentPane(panel2);
frame.pack();
...
To put it simple, there's a simple java swing app that consists of JFrame with some components in it. One of the components is a JPanel that is meant to be replaced by another JPanel on user action.
So, what's the correct way of doing such a thing? I've tried
panel = new CustomJPanelWithComponentsOnIt();
parentFrameJPanelBelongsTo.pack();
but this won't work. What would you suggest?
Your use case, seems perfect for CardLayout.
In card layout you can add multiple panels in the same place, but then show or hide, one panel at a time.
1) Setting the first Panel:
JFrame frame=new JFrame();
frame.getContentPane().add(new JPanel());
2)Replacing the panel:
frame.getContentPane().removeAll();
frame.getContentPane().add(new JPanel());
Also notice that you must do this in the Event's Thread, to ensure this use the SwingUtilities.invokeLater or the SwingWorker
frame.setContentPane(newContents());
frame.revalidate(); // frame.pack() if you want to resize.
Remember, Java use 'copy reference by value' argument passing. So changing a variable wont change copies of the reference passed to other methods.
Also note JFrame is very confusing in the name of usability. Adding a component or setting a layout (usually) performs the operation on the content pane. Oddly enough, getting the layout really does give you the frame's layout manager.
Hope this piece of code give you an idea of changing jPanels inside a JFrame.
public class PanelTest extends JFrame {
Container contentPane;
public PanelTest() {
super("Changing JPanel inside a JFrame");
contentPane=getContentPane();
}
public void createChangePanel() {
contentPane.removeAll();
JPanel newPanel=new JPanel();
contentPane.add(newPanel);
System.out.println("new panel created");//for debugging purposes
validate();
setVisible(true);
}
}
On the user action:
// you have to do something along the lines of
myJFrame.getContentPane().removeAll()
myJFrame.getContentPane().invalidate()
myJFrame.getContentPane().add(newContentPanel)
myJFrame.getContentPane().revalidate()
Then you can resize your wndow as needed.
Game game = new Game();
getContentPane().removeAll();
setContentPane(game);
getContentPane().revalidate(); //IMPORTANT
getContentPane().repaint(); //IMPORTANT
It all depends on how its going to be used. If you will want to switch back and forth between these two panels then use a CardLayout. If you are only switching from the first to the second once and (and not going back) then I would use telcontars suggestion and just replace it. Though if the JPanel isn't the only thing in your frame I would use
remove(java.awt.Component) instead of removeAll.
If you are somewhere in between these two cases its basically a time-space tradeoff. The CardLayout will save you time but take up more memory by having to keep this whole other panel in memory at all times. But if you just replace the panel when needed and construct it on demand, you don't have to keep that meory around but it takes more time to switch.
Also you can try a JTabbedPane to use tabs instead (its even easier than CardLayout because it handles the showing/hiding automitically)
The other individuals answered the question. I want to suggest you use a JTabbedPane instead of replacing content. As a general rule, it is bad to have visual elements of your application disappear or be replaced by other content. Certainly there are exceptions to every rule, and only you and your user community can decide the best approach.
Problem: My component does not appear after I have added it to the container.
You need to invoke revalidate and repaint after adding a component before it will show up in your container.
Source: http://docs.oracle.com/javase/tutorial/uiswing/layout/problems.html
I was having exactly the same problem!! Increadible!! The solution I found was:
Adding all the components (JPanels) to the container;
Using the setVisible(false) method to all of them;
On user action, setting setVisible(true) to the panel I wanted to
show.
// Hiding all components (JPanels) added to a container (ex: another JPanel)
for (Component component : this.container.getComponents()) {
component.setVisible(false);
}
// Showing only the selected JPanel, the one user wants to see
panel.setVisible(true);
No revalidate(), no validate(), no CardLayout needed.
The layout.replace() answer only exists/works on the GroupLayout Manager.
Other LayoutManagers (CardLayout, BoxLayout etc) do NOT support this feature, but require you to first RemoveLayoutComponent( and then AddLayoutComponent( back again. :-) [Just setting the record straight]
I suggest you to add both panel at frame creation, then change the visible panel by calling setVisible(true/false) on both.
When calling setVisible, the parent will be notified and asked to repaint itself.
class Frame1 extends javax.swing.JFrame {
remove(previouspanel); //or getContentPane().removeAll();
add(newpanel); //or setContentPane(newpanel);
invalidate(); validate(); // or ((JComponent) getContentPane()).revalidate();
repaint(); //DO NOT FORGET REPAINT
}
Sometimes you can do the work without using the revalidation and sometimes without using the repaint.My advise use both.
Just call the method pack() after setting the ContentPane, (java 1.7, maybe older) like this:
JFrame frame = new JFrame();
JPanel panel1 = new JPanel();
JPanel panel2 = new JPanel();
....
frame.setContentPane(panel1);
frame.pack();
...
frame.setContentPane(panel2);
frame.pack();
...
I'm making a program for fun, it's basically a computer navigation GUI, details not required :)
Anyway, so far, I have a button called "new button" that, when clicked, it creates a new button named "test", to an infinite amount. Right now, i have my GUI set up like this:
Class Main extends JPanel (the main panel that holds everything in it, size set as)
Dimension size = new Dimension(300, 200);
setPreferredSize(size);
JFrame holding the Main JPanel, called like:
panel.frame = new JFrame();
panel.frame.setResizable(false);
panel.frame.setTitle(panel.title);
panel.frame.add(panel);
panel.frame.pack();
panel.frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel.frame.setLocationRelativeTo(null);
panel.frame.setVisible(true);
So, how would i have the JFrame/JPanel set their size based on the components inside it? I've tried to use panel.frame.pack(); but i get an error most of the time, and the other times it doesnt wrap, it is just a staight line. I want it to resize in the form of a square. Any ideas? Sorry if my question isnt clear/poorly phrased, i've always had issues articulating questions online, much better in person cause i can use my hands! :) Thanks in advance!
Class Main extends JPanel (the main panel that holds everything in it, size set as) Dimension size = new Dimension(300, 200); setPreferredSize(size);
Don't set the preferred size of the panel. The layout manager will determine the preferred size based on the components that you add to the panel.
and the other times it doesnt wrap,
The default layout manager for a JPanel is a FlowLayout. It is not designed to wrap automatically. Maybe use a different layout manager. Or you can try the Wrap Layout which extends FlowLayout to provide dynamic wrapping.
I've tried to use panel.frame.pack(); but i get an error most of the time
What error. I've never seen an error when using the pack() method.
Post a proper SSCCE if you need more help.