I have this piece of code and read that validate can refer to laying out a container's subcomponents. "Layout-related changes, such as setting the bounds of a component, or adding a component to the container, invalidate the container automatically." (source: javadoc).
However, I see no difference whatsoever between keeping validate() or removing it from this little piece of code.
Can you show me a convincing example where you can see distinct behaviour in two cases (with or without validate) to prove a point? Any other comments/advice appreciated.
public class Sw1
extends JApplet
{
JLabel lbl;
public void init()
{
lbl = new JLabel ("a label");
JPanel pan = (JPanel) getContentPane ();
pan.add(lbl);
validate();
}
}
Here is the program after I intended the push of a button to add a label. It renders an exception when I push the button:
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
public class Sw_test
extends JApplet
implements ActionListener
{
JLabel lbl;
JButton bt ;
JPanel pan ;
JLabel l;
public void init()
{
lbl = new JLabel ("label 1");
bt = new JButton ("go ahead, press me");
bt.addActionListener(this);
JPanel pan = (JPanel) getContentPane ();
pan.setLayout(new FlowLayout());
pan.add(lbl);
pan.add(bt);
validate();
}
public void actionPerformed(ActionEvent ev)
{
l = new JLabel("new label");
pan.add(l);
}
}
You would need to call it if you add a component to a panel after it has been initialized and made visible.
Try adding a button to your applet, and on the click of the button, add a new label to the applet.
i will quote the API:
The validate method is used to cause a container to lay out its subcomponents again. It should be invoked when this container's subcomponents are modified (added to or removed from the container, or layout-related information changed) after the container has been displayed.
so as you see, it is important if you modify your layout, AFTER it has been initialized.
That is the reason why you don´t see any difference
btw: here is your example :
public class TestFrame extends JFrame{
private JButton b = new JButton();
public TestFrame() {
this.setLayout(new GridLayout(5,5));
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.add(b);
b.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
TestFrame.this.add(new JLabel("whatever"));
//try it with and without
//validate();
}
});
this.setSize(300, 300);
this.setVisible(true);
}
public static void main(String[] args) {
new TestFrame();
}
}
Related
I'm trying to make a little game that will first show the player a simple login screen where they can enter their name (I will need it later to store their game state info), let them pick a difficulty level etc, and will only show the main game screen once the player has clicked the play button. I'd also like to allow the player to navigate to a (hopefully for them rather large) trophy collection, likewise in what will appear to them to be a new screen.
So far I have a main game window with a grid layout and a game in it that works (Yay for me!). Now I want to add the above functionality.
How do I go about doing this? I don't think I want to go the multiple JFrame route as I only want one icon visible in the taskbar at a time (or would setting their visibility to false effect the icon too?) Do I instead make and destroy layouts or panels or something like that?
What are my options? How can I control what content is being displayed? Especially given my newbie skills?
A simple modal dialog such as a JDialog should work well here. The main GUI which will likely be a JFrame can be invisible when the dialog is called, and then set to visible (assuming that the log-on was successful) once the dialog completes. If the dialog is modal, you'll know exactly when the user has closed the dialog as the code will continue right after the line where you call setVisible(true) on the dialog. Note that the GUI held by a JDialog can be every bit as complex and rich as that held by a JFrame.
Another option is to use one GUI/JFrame but swap views (JPanels) in the main GUI via a CardLayout. This could work quite well and is easy to implement. Check out the CardLayout tutorial for more.
Oh, and welcome to stackoverflow.com!
Here is an example of a Login Dialog as #HovercraftFullOfEels suggested.
Username: stackoverflow Password: stackoverflow
import java.awt.*;
import java.awt.event.*;
import java.util.Arrays;
import javax.swing.*;
public class TestFrame extends JFrame {
private PassWordDialog passDialog;
public TestFrame() {
passDialog = new PassWordDialog(this, true);
passDialog.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new TestFrame();
frame.getContentPane().setBackground(Color.BLACK);
frame.setTitle("Logged In");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
}
});
}
}
class PassWordDialog extends JDialog {
private final JLabel jlblUsername = new JLabel("Username");
private final JLabel jlblPassword = new JLabel("Password");
private final JTextField jtfUsername = new JTextField(15);
private final JPasswordField jpfPassword = new JPasswordField();
private final JButton jbtOk = new JButton("Login");
private final JButton jbtCancel = new JButton("Cancel");
private final JLabel jlblStatus = new JLabel(" ");
public PassWordDialog() {
this(null, true);
}
public PassWordDialog(final JFrame parent, boolean modal) {
super(parent, modal);
JPanel p3 = new JPanel(new GridLayout(2, 1));
p3.add(jlblUsername);
p3.add(jlblPassword);
JPanel p4 = new JPanel(new GridLayout(2, 1));
p4.add(jtfUsername);
p4.add(jpfPassword);
JPanel p1 = new JPanel();
p1.add(p3);
p1.add(p4);
JPanel p2 = new JPanel();
p2.add(jbtOk);
p2.add(jbtCancel);
JPanel p5 = new JPanel(new BorderLayout());
p5.add(p2, BorderLayout.CENTER);
p5.add(jlblStatus, BorderLayout.NORTH);
jlblStatus.setForeground(Color.RED);
jlblStatus.setHorizontalAlignment(SwingConstants.CENTER);
setLayout(new BorderLayout());
add(p1, BorderLayout.CENTER);
add(p5, BorderLayout.SOUTH);
pack();
setLocationRelativeTo(null);
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
addWindowListener(new WindowAdapter() {
#Override
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
jbtOk.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (Arrays.equals("stackoverflow".toCharArray(), jpfPassword.getPassword())
&& "stackoverflow".equals(jtfUsername.getText())) {
parent.setVisible(true);
setVisible(false);
} else {
jlblStatus.setText("Invalid username or password");
}
}
});
jbtCancel.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
setVisible(false);
parent.dispose();
System.exit(0);
}
});
}
}
I suggest you insert the following code:
JFrame f = new JFrame();
JTextField text = new JTextField(15); //the 15 sets the size of the text field
JPanel p = new JPanel();
JButton b = new JButton("Login");
f.add(p); //so you can add more stuff to the JFrame
f.setSize(250,150);
f.setVisible(true);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Insert that when you want to add the stuff in. Next we will add all the stuff to the JPanel:
p.add(text);
p.add(b);
Now we add the ActionListeners to make the JButtons to work:
b.addActionListener(this);
public void actionPerforemed(ActionEvent e)
{
//Get the text of the JTextField
String TEXT = text.getText();
}
Don't forget to import the following if you haven't already:
import java.awt.event*;
import java.awt.*; //Just in case we need it
import java.x.swing.*;
I hope everything i said makes sense, because sometimes i don't (especially when I'm talking coding/Java) All the importing (if you didn't know) goes at the top of your code.
Instead of adding the game directly to JFrame, you can add your content to JPanel (let's call it GamePanel) and add this panel to the frame. Do the same thing for login screen: add all content to JPanel (LoginPanel) and add it to frame. When your game will start, you should do the following:
Add LoginPanel to frame
Get user input and load it's details
Add GamePanel and destroy LoginPanel (since it will be quite fast to re-create new one, so you don't need to keep it memory).
I have a simple task.
There is a frame. There are two panel in that frame. In second panel there is a button. When user click that button first panel must change its content.
Here is a code:
package test;
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.*;
class MyJPanel1 extends JPanel {
MyJPanel1() {
this.add(new JButton("MyJPanel1"));
}
}
class MyJPanel2 extends JPanel {
MyJPanel2() {
this.add(new JButton("MyJPanel2"));
}
}
class MyFrame extends JFrame {
JPanel topPanel = null;
MyFrame() {
super("Test");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLayout(new GridLayout(0, 1, 20, 20));
topPanel = new MyJPanel1();
this.add(topPanel);
JPanel bottomPanel = new JPanel();
this.add(bottomPanel);
JButton button = new JButton("switch");
button.addMouseListener(new MouseClickListener());
bottomPanel.add(button);
this.pack();
this.setVisible(true);
}
class MouseClickListener extends MouseAdapter {
#Override
public void mouseClicked(MouseEvent e) {
topPanel = new MyJPanel2();
System.out.println("switch");
topPanel.invalidate();
topPanel.validate();
topPanel.repaint();
MyFrame.this.invalidate();
MyFrame.this.validate();
MyFrame.this.repaint();
}
}
}
public class Test {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new MyFrame();
}
});
}
}
But that don't work. After I click on button I see text in console, but first panel remain the same. I read that I must use invalidate() validate() and repaint() methods and I did, but it isn't help.
Any help would be appreciated.
If you want to "switch" panels then you should be using a CardLayout. The CardLayout allows 2 (or more) components to share the same space in a container but only one is ever visible at a time.
Read the section from the Swing tutorial on How to Use CardLayout for more information and working examples.
In your mouseClicked() method you create a new topPanel, but you don't do anything with it. Perhaps you meant to remove the original topPanel from myFrame, create a new topPanel, and then add the new toipPanel to myFrame.
Note that this may not be the best strategy (creating a new topPanel).
I'm trying to add a JPanel to another JPanel from another class. The program does not longer throw an error and all methods have been run, but the new panel just has a black screen. A basic version of the program looks as follows:
package ninjadragon;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class NinjaDragon extends JFrame implements ActionListener{
public JPanel panelMain;
public JPanel panelTurnBase;
public static void main(String[] args) {
NinjaDragon();
}
public static void NinjaDragon() {
NinjaDragon frame;
frame = new NinjaDragon();
frame.CreateMenuScreen();
JFrame.setDefaultLookAndFeelDecorated(true);
frame.setSize(750, 750);
frame.show();
frame.setResizable(false);
frame.pack();
}
private void CreateMenuScreen() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container window = getContentPane();
panelMain =new JPanel();
panelMain.setPreferredSize(new Dimension(750,750));
panelMain.setBackground(Color.BLACK);
panelMain.setLayout (new FlowLayout());
window.add(panelMain);
PanelTop();
PanelButtons();
PanelIcon();
}
#Override
public void actionPerformed(ActionEvent event) {
Object eventSource = event.getSource();
if (eventSource == buttonStart) {
panelMain.removeAll();
TurnBase TB = new TurnBase();
TB.CreateTurnBase();
}
}
The other class looks something like this:
public void CreateTurnBase() {
panelMain=new JPanel();
panelTurnBase =new JPanel();
setLayout(new FlowLayout());
setPreferredSize(new Dimension(750,750));
setBackground(Color.BLUE);
panelTurnBase.setLayout (new FlowLayout());
panelMain.add(panelTurnBase);
System.out.println("1");
PanelTurnBaseTop();
PanelGameScreen();
PanelTurnBaseBottom();
repaint();
revalidate();
buttonAttack = new JButton("Attack");
buttonAttack.addActionListener(this);
panelTurnBase.add(buttonAttack);
System.out.println("2");
}
The reason the panel has "just a black screen" is because you dont add anything to it, and you tell it to have a black screen.
i.e
panel.setBackground(Color.BLACK);
You never actually do anything to that first panel inside of any of those methods, which I can assume based on your representation of your second "class" (it's a method). Hence why it stays black.
You say:
panelMain=new JPanel();
panelTurnBase =new JPanel();
You're creating new JPanels every time and just call them panelMain and they just sit inside of that method, never leaving. You either need to return a JPanel or give it a JPanel as an argument.
The program is doing exactly what you tell it to do.
Also, do not compare Objects like this:
eventSource == buttonStart
You should use:
eventSource.equals(buttonStart);
I am new to swing, can anyone help me out with this...
It is not showing my "label" , instead it shows me only components which are in the "panel" class.
One more question, can anyone clarify me about LayoutManagers ?
Can 2 or more LayoutManagers be used in a frame ? like for the frame i will be using FlowLayout and i have a JPanel added to the frame for which i will be using BoxLayout ... is it possible in the first place ??
import javax.swing.*;
import java.awt.event.*;
import java.awt.Graphics;
public class JForm1 extends JFrame
{
public JForm1()
{
init();
}
public static void main(String[] args)
{
JForm1 form = new JForm1();
}
public void init()
{
JFrame frame = new JFrame("My Form 1");
frame.setSize(500,500);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
getContentPane().setLayout(new BoxLayout(this,BoxLayout.PAGE_AXIS));
JLabel label = new JLabel("Enter your Name : ");
panel MyPanel = new panel();
frame.getContentPane().add(label);
frame.getContentPane().add(MyPanel);
frame.setVisible(true);
}
}
class panel extends JPanel implements ActionListener
{
JButton submitButton;
JTextField text;
panel()
{
this.setLayout(new BoxLayout(this,BoxLayout.Y_AXIS));
}
public void paintComponent(Graphics g)
{
text = new JTextField("Enter Name here");
text.setSize(100,25);
submitButton = new JButton("Submit");
submitButton.setSize(50,90);
submitButton.setBounds(200, 0, 80, 80);
submitButton.addActionListener(this);
this.add(text);
this.add(submitButton);
}
public void actionPerformed(ActionEvent event)
{
if(event.getSource()==submitButton)
{
System.out.println("The Entered Name is : "+text.getText());
}
}
}
What is this ?:
public void paintComponent(Graphics g)
{
text = new JTextField("Enter Name here");
text.setSize(100,25);
submitButton = new JButton("Submit");
submitButton.setSize(50,90);
submitButton.setBounds(200, 0, 80, 80);
submitButton.addActionListener(this);
this.add(text);
this.add(submitButton);
}
This code has nothing to do in paintComponent. paintComponent is about "painting a component", ie, paint a rectangle, draw a line, fill an oval, etc... This is absolutely not the place where to add your components. Instead, call that code in your constructor.
Additionally, if you are using LayoutManager's (which you should), calling setSize/setBounds/setLocation is useless (dimply remove those calls).
A few more things:
If you override paintComponent, make sure to invoke the super-method
Don't extends JFrame if not needed (here it is clearly not needed)
Follow Java naming conventions (class names should start with an UpperCase letter, variables and methods with a lowerCase letter)
All Swing-related code must be called on the EDT. Start your UI within a SwingUtilities.invokeLater() block.
Try by changing layout to FlowLayout for mypanel.
mypanel.setLayout(new FlowLayout());
I am new to Java and was trying to develop a basic swing application. I wanted to set the location of the button on the JFrame. I tried to do this but was unable to do this this is my code. I am using eclipse for development
public class MyUI extends JFrame {
JButton button1 = new JButton("Click");
JTextField tb1 = new JTextField(5);
JPanel panel1 = new JPanel();
public MyUI() {
super("Test");
setVisible(true);
this.setLayout(null);
panel1.setLayout(null);
panel1.setVisible(true);
button1.setVisible(true);
panel1.add(button1);
add(panel1);
panel1.setLocation(10, 10);
button1.setLocation(10, 10);
setDefaultCloseOperation(EXIT_ON_CLOSE);
button1.addActionListener(this);
}
public static void main(String[] args) {
MyUI gui = new MyUI();
gui.setSize(400, 300);
}
}
1.why you put two JComponents to the same Bounds
panel1.setLocation(10, 10);
button1.setLocation(10, 10);
2.have look at Initials Thread
3.public class MyUI extends JFrame {
should be
public class MyUI extends JFrame implements ActionListener{
4.don't extend JFrame, create a local variable
5.setVisible(true); should be (in this form) only last code line into MyUI() constructor
6.setVisible(true); is important issue, you visibled JFrame and then to add JComponent(s)
7.don't use NullLayout, use proper LayoutManager, in the case that you remove this.setLayout(null); and panel1.setLayout(null); added JComponents could be visible
8.use pack() before setVisible(true) as last two code lines in constructor
EDIT (by using built_in LayoutManagers, BorderLayout for JFrame and FlowLayout for JPanel)
import java.awt.event.*;
import javax.swing.*;
public class MyUI extends JFrame implements ActionListener {
private static final long serialVersionUID = 1L;
private JButton button1 = new JButton("Click");
private JTextField tb1 = new JTextField(5);
private JPanel panel1 = new JPanel();
public MyUI() {
super("Test");
panel1.add(tb1);
panel1.add(button1);
add(panel1);
setDefaultCloseOperation(EXIT_ON_CLOSE);
button1.addActionListener(this);
pack();
setVisible(true);
}
public void actionPerformed(ActionEvent e) {
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
MyUI testing = new MyUI();
}
});
}
}
Your panel and button are not seen because they have zero size. Add something like:
panel1.setSize(100, 100);
button1.setSize(80, 30);
or use the setBounds method which is more convenient to set location and size simultaneously:
panel1.setBounds(10, 10, 100, 100);
button1.setBounds(10, 10, 80, 30);
Would like to suggest something, though its not the direct immediate answer to your question, but still its important from my point of view....
You can use Group Layout which was developed by NetBeans team back in 2005, its awesome to work with.... Try using the Windows Builder Pro which is provided by Google for free now... You can get your application up and running in no time......