I'm working with a JFrame adding JPanel instances dynamically in the following way:
private void addBox(int x, int y){
JPanel panel = new JPanel();
panel.setBackground(Color.RED);
panel.setSize(10, 10);
panel.setVisible(true);
panel.setLocation(x, y);
this.getContentPane().add(panel);
}
The problem is, when I use addBox method, the JPanel instance does not appear in the JFrame. The only way I can see the box I need to manualy resize the window.
Note: I tried using this.pack();, but this did not work.
You need to call revalidate() and repaint() after such structural changes to the GUI.
Note that setSize and setLocation should preferrably be handled by the layout manager.
Related link:
jGuru: What is the difference between repaint() and revalidate() in Swing components?
What are the purpose of the boxes?
If they are purely visual, and you don't intend to add components to them, it would be better to define a Box class (or use a Rectangle2D) and draw or fill them at time of paintComponent().
Alternately, draw them to the Graphics object of a BufferedImage and add the image to a JLabel, as shown here.
This example showing add/remove/pack may help.
private void addBox(int x, int y){
JPanel panel = new JPanel();
panel.setBackground(Color.RED);
add(panel);
//If there isn't another JPanel, then this way you'll occupy
//the whole JFrame area; by defalut, JFrame has BorderLayout,
//and only one JComponent can occupy the central area
revalidate();
repaint();
}
Related
I'm pretty new to GUI and Java as a whole so I hope that I can explain this well enough and understand people's answers.
For a school project, I need to put a bunch of stuff on some rectangles but I'm having issues even adding one rectangle properly.
From researching online, this is what I have (the JPanel and GridBagConstraints are just there to show what I'd like to use):
public class GUI extends JPanel
{
public static void main (String [] args)
{
GUI g = new GUI();
JFrame window = new JFrame("Java Window");
window.setSize(1280, 960);
window.add(g);
window.setVisible(true);
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel layout = new JPanel(new GridBagLayout());
GridBagConstraints constraints = new GridBagConstraints();
}
#Override
public void paintComponent(Graphics g)
{
Color boxColour = new Color(194, 190, 190);
super.paintComponent(g);
g.setColor(boxColour);
g.fillRect(10, 10, 100, 100);
}
}
So right now, the rectangle appears in the window. But how can I add constraints to it? Is that possible? I would think that I should use JPanel to keep everything more organized since there will be many components so I tried adding this:
layout.add(g);
window.add(layout);
window.setVisible(true);
However, the rectangle no longer appeared. What am I doing wrong and how can I fix it and add constraints to my shapes? Thanks!
In your first scenario, the default layout manager of the frame is the BorderLayout and you are adding your "g" panel to the BorderLayout.CENTER. So based on the rules of the BorderLayout your "g" panel will take up all the space available in the frame. So you have plenty of space to paint your rectangle.
However, in your second scenario, your "layout" panel is using the default layout manager of a JPanel which is a FlowLayout which respects the preferred size of any component added to it.
The preferred size of the "g" panel is 10 x 10. So, when you add the "g" panel to the "layout" panel there is nothing to see because all you custom painting is done outside the bounds of the panel.
You need to override the getPreferredSize() method of your GUI panel to return a preferred size of (120, 120) so you can see your rectangle painted with a 10 pixel border around all the edges.
Read the section from the Swing tutorial on Custom Painting for more information and working examples demonstrating how to override the `getPreferredSize() method.
You will also need to read the Swing tutorial on How to Use GridBagLayout for example of using the constraints to add multiple components.
I would like to be able to have a JPanel within my JFrame of a fixed size 400x400.
I would also like the to be a 20px wide border all around it.
The main problem is the following code doesnt stick it its size.` JScrollPane runningAni = new JScrollPane(new views.cRunningAnimation(
model));
runningAni.setMaximumSize(new Dimension(400,400));
this.setSize(new Dimension(600,600));
this.add(runningAni,BorderLayout.CENTER);`
When doing this the runningAni panel just strethces accross the whole frame.
public void paint(Graphics g) {
this.setBackground(new Color(0,255,0));
}
I know this because my full frame paints itself green rather than just the JPanel (The above paint code is for my panel not the frame)
How would i create the panel so it always stays the same size and so there is always a 20px colored border around it?
BorderLayout ignores the size. You need to set a LayoutManager that either allows you to set the size to a fixed size or one that cares for the sizes set. There are different layout managers that allow this (e.g. GrindBagLayout or no layout manager at all). Some are not that easy to use (e.g. GridBagLayout). What to use depends on the rest of the layout.
You could probably use a layout panel that contains your custom panel. The layout panel needs an appropriate layout manager and could be put into the center of the BorderLayout. This would mean nearly no modifications to existing layout code.
The whole point of BorderLayout is to fill the center with the center component.
Don't override the paint() method to set the color of the panel. Use:
panel.setBackground(...);
When you create the panel.
How would i be able to set a border around my Jpanel
See How to Use Borders.
Just set your layout to null, to what ever class your adding your JPanel.
Then use the setBounds() method to set your location and size!
For example:
public class Main extends JFrame{
YourPanelClass panel = new YourPanelClass();
public Main(){
// I didn't want to put all the, everyday JFrame methods...
setLayout(null);
/*
First two coordinates indicate the location of JPanel inside JFrame.
The seconds set of coordinates set the size of your JPanel.
(The first two coordinates, 0 and 0, tell the JPanel to start at the
top left of your JFrame.)
*/
panel.setBounds(0, 0, 100, 100);
add(panel);
}
}
And i would GREATLY recommend using the paintComponent() method.
For instance:
(Obviously you put this in your JPanel's class.)
public void paintComponent(Graphics g){
super.paintComponent(g); // don't forget this if you are going to use this method.
//Basically this makes your JPanel's background green(I did it this way because I like doing it this way better.)
g.setColor(new Color(0, 255, 0));
g.fillRect(0, 0, getWidth(), getHeight());
}
Please don't forget to thumbs up if this helped!
setPreferredSize()
setMinimumSize()
setMaximumSize()
should do the trick
I am writing a simple game withing which I am using a JFrame which contains a grid and a JPanel.
Here is my pseudo code:
void MyJframeConstructor()
{
// some basic bootstrap logic
// calling repaint to draw grid
repaint();
// Grid is drawn fine.
// Showing user a confirm dialog box on which I add below JPanel.
if(confirmed)
{
// GameInfoPanel extends JPanel.
infoPanel = new GameInfoPanel(new FlowLayout(FlowLayout.LEFT));
infoPanel.setPreferredSize(new Dimension(400, 100));
infoPanel.setLocation(500, 50);
this.add(infoPanel);
infoPanel.validate();
}
}
My problem here is my JFrame or window is 480 x 680.
Within this I am drawing a grid in 480 x 480 area.
Below which I want the JPanel to be located at 500,50 with dimension 400, 100.
However, when I run this code, once the user confirms with OK, the JPanel fills up the entire JFrame.
How can I keep the panel in its location and consistent in size through out the life of the app ?
Any help is highly appreciated and thanks in advance.
Within this I am drawing a grid in 480 x 480 area.
override PreferredSize for JPanel
then call JFrame.pack() and JFrame.setVisible(true) as last code lines
have to read InitialThread
if is there only one JPanel (JPanel filling entire JFrame) then to use built_in BorderLayout in JFrame f.e. myFrame.add(infoPanel, BorderLayout.CENTER) not FlowLayout
don't to extend JFrame create this Object as local variable
I want to be able to set a JFrame's contentpane after a button inside one of that frame's JPanels has been clicked.
My architecture consists of a controller which creates the JFrame and the first JPanel inside of it. From within the first JPanel I'm calling a method: setcontentpane(JPanel jpanel) on the controller. However, instead of loading the passed JPanel it does nothing but removing all Panels (see code below)
ActionListener inside of the first JPanel:
public void actionPerformed(ActionEvent arg0) {
controller.setpanel(new CustomPanel(string1, string2));
}
Controller:
JFrame frame;
public void setpanel(JPanel panel)
{
frame.getContentPane().removeAll();
frame.getContentPane().add(panel);
frame.repaint();
}
public Controller(JFrame frame)
{
this.frame=frame;
}
Can anyone tell me what I'm doing wrong? Thanks :)
Call revalidate, then repaint. This tells the layout managers to do their layouts of their components:
JPanel contentPane = (JPanel) frame.getContentPane();
contentPane.removeAll();
contentPane.add(panel);
contentPane.revalidate();
contentPane.repaint();
Better though if you just want to swap JPanels is to use a CardLayout and have it do the dirty work.
I found a way to do what I outlined above.
Implementing the setpanel method like this:
public void setpanel(JPanel panel)
{
frame.setContentPane(panel);
frame.validate();
}
did the trick in my case.
I'm sure that I still need to fix something within my code, since pack() still shrinks the window, but at least the method posted above works.
Whenever you change a frame's containment hierarchy, you have to call pack().
From the docs:
Causes this Window to be sized to fit
the preferred size and layouts of its
subcomponents. [...] The Window will
be validated after the preferredSize
is calculated.
I have a JPanel sitting inside the center position of a BorderLayout of a JFrame. How can I swap out the current JPanel for a new one?
Did you try something on the lines of:
void swapCenterPanel(JFrame frame, JPanel oldPanel, JPanel newPanel) {
frame.getContentPane().remove(oldPanel);
frame.getContentPane().add(newPanel, BorderLayout.CENTER);
}
Use a Card Layout which manages this for you.
I got this to work with no z index issues through trial and error.
lets call x the JPanel which has the BorderLayout
lets call y the Component which is currently occupying BorderLayout.Center
lets call z the JPanel to replace in the center position.
x.remove(y);
x.add(z);
x.repaint();
x.revalidate();
I found if I tried to remove the existing JPanel through the LayoutManager itself, it doesn't work. Instead if you use the remove method of the JPanel the java doc says it notifies the layouts removeLayoutComponent method and seems to do the trick.
Just add the component to center and revalidate() the parent container
container.add(BorderLayout.CENTER, newPanel);
container.revalidate();