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jave. Problem with extended class from jframe

I have a problem when i try to create an extended class from jframe. When i add a panel to the created class with a specific dimension and position it will fill all the window. My code is:
package tuto;
import java.awt.Color;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class test extends JFrame{
public test(){
super();
initComponents();
}
private void initComponents() {
setBounds(0, 0, 1000, 618);
panel = new JPanel();
panel.setBounds(10, 10, 100, 100);
panel.setBackground(Color.blue);
add(panel);
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
new test().setVisible(true);
}
});
}
//Components
JPanel panel;
}
After executing the code all the window become blue. Some help please.

JFrame by default, uses a BorderLayout, which is why you component fills the full size of the window. See How to Use BorderLayout for more details.
In fact, I'd recommend also reading through Laying Out Components Within a Container to get a better understanding of how the layout management system.
You should beware that "manual" placement of components is generally discouraged in most cases, instead, you should make use of one or more layout managers.
As a general recommendations, you should also avoid extending from top level containers like JFrame, as it looks you into a single use case, top level containers tend to be complicated, compound components and you're just not adding any new functionality to the class generally. Better to simply create them when you need them and fill them with the components you need.

If you want to use absolute positioning you should set the layout to null.
setLayout(null)
But it’s recommended you have a look at the different layouts. Everything is better than null layouts.
E.g. https://docs.oracle.com/javase/tutorial/uiswing/layout/border.html

JFrame position three buttons one below another in the center

So I would like to have three JButtons all on top of each other, but not to large in width or height either. I am not too familiar with Java's layouts, and to be honest I am not too keen on them. Please view the image a code below to explain to me how, thanks.
package com.aqagame.harrykitchener;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
public class Main
{
private JButton playGame, playerNames, exitGame;
public Main()
{
JPanel mainCard = new JPanel(new BorderLayout(8, 8));
playGame = new JButton("Play Game");
playerNames = new JButton("Player Names");
exitGame = new JButton("Exit Game");
mainCard.add(playGame, BorderLayout.NORTH);
mainCard.add(playerNames, BorderLayout.CENTER);
mainCard.add(exitGame, BorderLayout.SOUTH);
JFrame window = new JFrame("Harry's AQA game");
window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
window.getContentPane().add(mainCard);
window.setSize(900, 800);
window.setLocationRelativeTo(null);
window.setVisible(true);
}
public static void main(String args[])
{
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Main();
}
});
}
}

Check out the Java Documentation for the different layout managers. I know you're not familiar with them, which is why you should probably start. Once you get used to them there is no end to their benefits. There is a lot of excellent information in the documentation and I am sure you will learn a lot. Personally, I recommend looking at the Box Layout:

Create JPanel that uses a GridLayout and add all the buttons to the panel. The GridLayout will automactially size the buttons to be the same size.
Set the layout manager of your main window to use a GridBagLayout.
add the panel to the main window using the default GridBagConststraints. Then the panel will automatically be centered both horizontally and vertically.

To not use Box or GridBag, I think a combination such as this may work out:
Have main panel (let's call it A) have a BorderLayout
Create another panel (let's call it B), with a FlowLayout, with constructor aligning components to the center
Create another panel (let's call it C), with a GridLayout, 1 column 3 rows
Add each button to a new JPanel with a FlowLayout (1 JPanel per button, so buttons are wrapped by a FlowLayout), and then add each of those JPanels to C
Add C to B
Add B to A (center position)
I think this should cause buttons to be on top of each other with small amount of padding while not being stretched widthwise and while appearing in the center of the screen.

Focus on component when a panel is loaded

I have a frame, where i load a panel into. It works fine, but nothing has focus when it loads. Pressing tab doesn't help. I have to use the mouse to press a textfield.
I've tried: jtextfield1.requestFocus(); and jtextfiel1.requestFocusInWindow(); But it doesn't work.
What am I doing wrong?
The constructor in the JPanel:
public OpretOpdater(BrugerHandler brugerHandler, ReklamationHandler reklamationsHandler) {
initComponents();
jTextFieldOrdnr.requestFocusInWindow();
this.brugerHandler = brugerHandler;
this.rekH = reklamationsHandler;
startUp();
}
Putting the panel in the frame in the GUI:
public static void opret(ReklamationHandler reklamationHandler) {
rHandler = reklamationHandler;
SwingUtilities.invokeLater(opret);
}
static Runnable opret = new Runnable() {
#Override
public void run() {
JFrame f = jframe;
f.getContentPane().removeAll();
JPanel opret = new OpretOpdater(bHandler, rHandler);
f.getContentPane().add(opret);
f.pack();
f.setLocationRelativeTo(null);
}
};

You should call requestFocusInWindow() only when components are visible/shown on a container or after pack() has been called and all components are added to the container or else it wont work.
Also please be sure to create Swing components on Event Dispatch Thread. If you haven't already have read on Concurrency in Swing.
The reason I mention the above is not creating and manipulating Swing components on the EDT can cause random artifacts in the code. i.e focus is not being given etc.
This code below was created to show how calling requestFocusInWindow before a component is visible will not work but calling it after its visible works as expected.
Also note that removing the SwingUtilities block will cause the requestFocusInWindow not to work as expected (i.e we might be given focus or not depending on our luck :P):
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class Test {
public Test() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
JTextField f1 = new JTextField(10);
JTextField f2 = new JTextField(10);
//f2.requestFocusInWindow(); //wont work (if uncomment this remember to comment the one after setVisible or you wont see the reults)
JButton b = new JButton("Button");
JPanel p = new JPanel();
p.add(f1);//by default first added component will have focus
p.add(f2);
p.add(b);
frame.add(p);
//f2.requestFocusInWindow();//wont work
frame.pack();//Realize the components.
//f2.requestFocusInWindow();//will work
frame.setVisible(true);
f2.requestFocusInWindow();//will work
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {//if we remove this block it wont work also (no matter when we call requestFocusInWindow)
#Override
public void run() {
new Test();
}
});
}
}
I would suggest a read on How to Use the Focus Subsystem.

Often it is nice to indicate which field you want to have focus when you create the field and not separate the code by adding the request focus when the frame becomes visible.
Take a look at Dialog Focus which has a solution that is also applicable in this case. Using this approach your code would look like:
JTextField f2 = new JTextField(10);
f2.addAncestorListener( new RequestFocusListener() );

I can't see my JPanel and its components in the JApplet

I want to put a JPanel in a JApplet, the problem is that I can't see it :( I've overridden the paintComponent of my JPanel in order to have a background image, but I can't see anything. When I remove the paintComponenet method that I had overriden, and set a color to the background of this panel, it seems that JPanel fills the JApplet and still no component is visible :-S I've tried different layouts. I also put my panel in the center of another panel which fills my JApplet but nothing changed, and still no component and no background image is visible :(
import java.awt.BorderLayout;
import java.awt.Graphics;
import javax.swing.ImageIcon;
import javax.swing.JApplet;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
public class Main extends JApplet implements Runnable{
private JTextArea display;
private Thread outputThread;
JPanel boardPanel;
private ClientViewManager view;
#Override
public void init() {
try {
javax.swing.SwingUtilities.invokeAndWait(new Runnable() {
public void run() {
createGUI();
}
});
} catch (Exception e) {
System.err.println("createGUI didn't successfully complete");
}
}
private void createGUI() {
display = new JTextArea(4, 30);
display.setEditable(false);
getContentPane().add(new JScrollPane(display), BorderLayout.SOUTH);
setFocusable(true);
setVisible(true);
setName("CE Tanks");
setSize(600, 600);
setLocation(100, 100);
boardPanel = new JPanel();
boardPanel.setLayout(null);
boardPanel.setBackground(new java.awt.Color(128, 255, 255));
getContentPane().add(boardPanel, BorderLayout.CENTER);
}
public void start() {
outputThread = new Thread(this);
outputThread.start();
}
public void run() {
view = new ClientViewManager();
boardPanel.add(view);
boardPanel.repaint();
repaint();
}
}
class ClientViewManager extends JPanel {
private int rows=8;
private int columns=8;
public ClientViewManager() {
super(null);
JLabel lb= new JLabel("lb.jpg");
lb.setLocation(10, 10);
lb.setSize(50, 50);
lb.setOpaque(false);
lb.setVisible(true);
this.add(lb);
}
public void paintComponent(Graphics g) {
g.drawImage(new ImageIcon("ground.jpg").getImage(), 0, 0, columns * 50,
rows * 50, this);
}
}
The code above can be compiled. I cant even add Keylistener to neither my JPanel nor to my JApplet. I used java.awt.KeyEventDispatcher and in dispatchKeyEvent(KeyEvent e) I printed something in console but, it was printed 3 times. :(

I've overridden the paintComponent of my JPanel inorder to have a background image,
But you didn't add the custom component to your applet:
//boardPanel = new JPanel();
boardPanel = new ClientViewManager();
Also:
get rid of setVisible(). This is not required for any of the controls in your program. By default all components except top level Container (Jframe, JDialog etc) are already visible. In the case of JApplet, you don't need to make it visible as this is part of the process of displaying an applet.
get rid of setSize() and setLocation() you can't control the position of the applet this way.
Don't read the image file in the paintComponent() method. This is not efficient as this method is invoked whenever Swing determines the component needs to be repainted.
JLabels are opaque by default so there is not need to invoke the setOpaque method.
When doing custom painting you should also override the getPreferredSize() method of the component to return the proper size of the custom painting so layout managers can use this information. It works in this case because you added the panel to the CENTER of the BorderLayout. Try adding the panel to the NORTH to see what happens.
Edit:
Now I see where you are adding the ClientViewManager. I'm not sure why you are trying to do this with a Thread but once again there are several problems.
When you add/remove components from a visble GUI then the basic code is:
panel.add(...);
panel.revalidate();
panel.repaint();
However this still won't work because you are using a null layout and the size of the panel is 0. Use a proper layout manager and implement the getPreferredSize() method as suggest above and the component will be displayed properly.

I recommend you to use the GUI Builder of Netbeans to build a GUI like that, and then compare the generated code to your code. Netbeans results really useful to help you create swing code.

JPanel's child components paint/layout problem

I'm having a problem that when my frame is shown (after a login dialog) the buttons are not on correct position, then in some miliseconds they go to the right position (the center of the panel with border layout).
-- update
In my machine, this SSCCE shows the layout problem in 2 of 10 times I run it:
import java.awt.BorderLayout;
import java.awt.Dimension;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class TEST {
public static void main(String[] args) throws Exception {
SwingUtilities.invokeAndWait(new Runnable() {
public void run() {
System.out.println("Debug test...");
JPanel btnPnl = new JPanel();
btnPnl.add(new JButton("TEST"));
JFrame f = new JFrame("TEST");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().setLayout(new BorderLayout());
f.getContentPane().add(btnPnl);
f.setPreferredSize(new Dimension(800, 600));
f.pack();
f.setExtendedState(JFrame.MAXIMIZED_BOTH);
f.setVisible(true);
System.out.println("End debug test!");
}
});
}
}
The button first appers in the up-left, and then it goes to the center. Is it a java bug?
--update
Looks like the SSCCE don't show the problem for everyone that is trying.
Maybe it's my computer performance problem. I still think Java Swing is creating new threads for make the layout behind the scenes. But I'm not sure.
--update
The problem only occur with the f.setExtendedState(JFrame.MAXIMIZED_BOTH);

Your problem intrigued me. After some investigation I think I confirmed something that I recall about setting the window state (maximized, restored, etc) which is that setting the state is a request to the operating system and is left to the whim of the OS to process the request. This means it is asynchronous, or at least done later, after you set it. I confirmed using logging and adding resize listeners where you can see that the frame is resized after your block of code exits. Because of this, the pack() will layout components to their preferred size. So imagine the frame being sized to 800x600 and components positioned as such (button centered horizontally around 400). Then later, the OS changes the size of the frame to full screen (e.g. 1024x768) - for a moment, you'll see the button still at 400. Then the frame processes the new size and re-lays out components and centers the button at around 512. So you'll see the flicker as it transitions during this process. Perhaps a solution is to NOT pack() - it will remain at a size of zero and user will see minimum flicker.
Try this change first:
// pack()
If that looks good then you might have the next problem...if the user clicks the restore button, the whole frame shrinks into a black hole. So try calling pack AFTER the frame has been predictably resized due to the maximize. Something like this:
f.addComponentListener( new ComponentAdapter( ComponentEvent e ) {
public void componentResized( Component) {
if( f.getSize().getWidth() > 0 ) {
e.getComponent().removeComponentListener( this );
((JFrame)e.getComponent()).pack();
}
}
}
So if the user later clicks restore button the frame will have a nicely packed size ready to go.
--Update
OK, one last attempt. While I think my description of the problem has some truth, my solutions offered did nothing. Here's one last attempt. Remove pack() and setPreferredSize() and replace with setting the size to the screen size. This seems to reduce the flicker greatly on my system. This is because there should be no difference between the initial layout and the maximized layout done later. You can see this if you switch between restore and maximized. Although I still see a very slight flicker when switching the two, at least it seems to look better when first displayed.
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.Toolkit;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class TEST {
public static void main(String[] args) throws Exception {
SwingUtilities.invokeAndWait(new Runnable() {
public void run() {
System.out.println("Debug test...");
JPanel btnPnl = new JPanel();
btnPnl.add(new JButton("TEST"));
JFrame f = new JFrame("TEST");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().setLayout(new BorderLayout());
f.getContentPane().add(btnPnl);
// f.setPreferredSize(new Dimension(800, 600));
// f.pack();
f.setSize( Toolkit.getDefaultToolkit().getScreenSize() );
f.setExtendedState(JFrame.MAXIMIZED_BOTH);
f.setVisible(true);
System.out.println("End debug test!");
}
});
-Mike

Maybe you are missing a frameThatContainsCentralPanel.pack()?

Well, if it works with a SSCCE, then you've proven the problem isn't with the basic logic. There must be something different between the SSCCE and your real code. Since we don't have access to your real code you need to do the debugging yourself to see what the difference is.
However, in this case a better solution is to use a CardLayout, which is designed to let you swap panels easily. Read the Swing tutorial for a working example.
Or anther approach is to use a "login dialog". Once the login is successfull, you display your main frame with the panel for your application.

I would guess that you need to call pack() before making your frame visible.
If you are calling the above code not on the event thread then you have a race condition and all bets are off - you can only manipulate the GUI from the EDT (event dispatch thread).
EDIT: I tried your SSCCE on my system and it is not exhibiting the behavior you are seeing. I tried it about 50 times, and also tried creating 10 windows by looping your code. I am running 1.6.0_18 on Windows XP SP3.

The "then in some milliseconds" part sounds to me like you need to call validate() on your frame. Also, if you use f.pack(), your panel needs a preferred size, because pack() gives the parent's components their preferred sizes and resizes based on them.

If I copied your code, I had the same problem, but not so heavy.
I solved it by setting a preferred size for your frame before packing. So:
import java.awt.Dimension;
System.out.println("Debug test...");
JPanel btnPnl = new JPanel();
btnPnl.add(new JButton("TEST"));
JFrame f = new JFrame("TEST");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().setLayout(new BorderLayout());
f.getContentPane().add(btnPnl);
f.setPreferredSize(new Dimension(800, 600));
f.pack();
f.setVisible(true);
System.out.println("End debug test!");
I'm running on Linux.
It is indeed strange... I'm sure it is something about the size of all the containers in the swing tree.

I would expect the frame to be maximised both before it is shown, but after checking this I'm sure that on linux frame is maximised after it has been displayed. You can make the frame size equal to a Screen size before calling setVisible, or you can make the components invisible until you know that the it's got preferred initial size. Here is modified sample which shows the elements after the frame has been activated (on linux activated event comes late enough to not show the "jumping button"):
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class TEST {
public static void main(String[] args) throws Exception {
SwingUtilities.invokeAndWait(new Runnable() {
public void run() {
final JPanel btnPnl = new JPanel();
btnPnl.add(new JButton("TEST"));
final JFrame f = new JFrame("TEST");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setContentPane(btnPnl);
// calculate preferred size for TEST frame
// f.isDisplayable() will become true
f.pack();
// extended state, if can be applied, needs to be called after f.isDisplayable()
WindowListener maxBoth = new WindowAdapter() {
#Override
public void windowOpened(WindowEvent e) {
f.setExtendedState(Frame.MAXIMIZED_BOTH);
}
};
// after windows has been opened - maximize both
f.addWindowListener(maxBoth);
// initially hide the elements
// after maximized state has been applied show them
f.getContentPane().setVisible(false);
f.addWindowListener(new WindowAdapter() {
#Override
public void windowActivated(WindowEvent e) {
f.getContentPane().setVisible(true);
// remove this listener
f.removeWindowStateListener(this);
}
});
// set the frame visible
f.setVisible(true);
}
});
}
}

Looks like a java bug. I've reported it (but for some reason it still not show on the bugs reports).