I'm trying to paint component inside paint(Graphics) method of JPanel.
The following code snippet works just fine, a JButton is painted nicely in my JPanel:
#Override
public void paint(Graphics g) {
super.paint(g);
JButton btn = new JButton("hello");
Dimension dim = btn.getPreferredSize();
btn.setSize(dim.width, dim.height);
btn.paint(g); // paint the button
}
The code snippet works perfectly also for other components (JLabel, JTree, ...) except JPanel.
The following code will cause very strange NullPointerException at java.awt.Window.access$700(Window.java:132).
#Override
public void paint(Graphics g) {
super.paint(g);
JPanel panel = new JPanel();
panel.setSize(10, 10);
panel.paint(g); // paint the panel
}
Here the full stacktrace:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.awt.Window.access$700(Window.java:132)
at java.awt.Window$1.isOpaque(Window.java:3458)
at javax.swing.RepaintManager.getVolatileOffscreenBuffer(RepaintManager.java:983)
at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1395)
at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:294)
at javax.swing.RepaintManager.paint(RepaintManager.java:1224)
at javax.swing.JComponent.paint(JComponent.java:1015)
at test.paintcontainer.TestPaintContainerMain$TestContentPane.paint(TestPaintContainerMain.java:48)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paint(JComponent.java:1038)
at javax.swing.JLayeredPane.paint(JLayeredPane.java:567)
at javax.swing.JComponent.paintChildren(JComponent.java:862)
at javax.swing.JComponent.paintToOffscreen(JComponent.java:5131)
at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:278)
at javax.swing.RepaintManager.paint(RepaintManager.java:1224)
at javax.swing.JComponent.paint(JComponent.java:1015)
at java.awt.GraphicsCallback$PaintCallback.run(GraphicsCallback.java:21)
at sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:60)
at sun.awt.SunGraphicsCallback.runComponents(SunGraphicsCallback.java:97)
at java.awt.Container.paint(Container.java:1780)
at java.awt.Window.paint(Window.java:3375)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:796)
at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:713)
at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:693)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:125)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:641)
at java.awt.EventQueue.access$000(EventQueue.java:84)
at java.awt.EventQueue$1.run(EventQueue.java:602)
at java.awt.EventQueue$1.run(EventQueue.java:600)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:611)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Any idea how to solve this problem? I need to paint JPanel inside paint(Graphics) method.
I wrote a simple test application which you can copy-paste to reproduce the aforementioned exception:
package test.paintcontainer;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
public class TestPaintContainerMain extends JFrame {
public static void main(String[] args) {
TestPaintContainerMain test = new TestPaintContainerMain();
test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
test.setBounds(0, 0, 300, 200);
test.setContentPane(new TestContentPane());
test.setVisible(true);
}
static class TestContentPane extends JPanel {
JRadioButton paintButtonCheck;
JRadioButton paintPanelCheck;
public TestContentPane() {
paintButtonCheck = createRadioButton("paint button", true);
paintPanelCheck = createRadioButton("paint panel", false);
ButtonGroup buttonGroup = new ButtonGroup();
buttonGroup.add(paintButtonCheck);
buttonGroup.add(paintPanelCheck);
add(paintButtonCheck);
add(paintPanelCheck);
}
#Override
public void paint(Graphics g) {
super.paint(g);
g.translate(100, 100);
if (paintButtonCheck.isSelected()) {
createButton().paint(g);
} else {
createPanel().paint(g);
}
}
private JButton createButton() {
JButton button = new JButton("button");
button.setSize(button.getPreferredSize().width, button.getPreferredSize().height);
return button;
}
private JPanel createPanel() {
JPanel panel = new JPanel();
panel.setBackground(Color.GREEN);
panel.add(createButton());
panel.setSize(panel.getPreferredSize().width, panel.getPreferredSize().height);
return panel;
}
private JRadioButton createRadioButton(String title, boolean selected) {
JRadioButton radio = new JRadioButton(title, selected);
radio.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
TestContentPane.this.repaint();
}
});
return radio;
}
}
}
This is most likely not a bug in Swing, but more of a problem because you are trying to paint a component which has not yet been realized, meaning it has no active graphic context. You can realize a component by adding it to already realized component like your JFrame - which itself gets realized by setVisible(true).
Also one should probably never call JComponent.paint(Graphics) manually, because this is the job of Swing (more precisely the Event Dispatcher Thread) - it even says so in the documentation of the paint method:
Applications should not invoke paint directly, but should instead use the repaint method to schedule the component for redrawing.
What you can call is the method printAll(Graphics g), which paints the component and all its subcomponents. Also in Swing one should also not override paint but paintComponent.
So here is a test code:
JButton button = createButton();
JPanel panel = createPanel();
public TestContentPane() {
paintButtonCheck = createRadioButton("paint button", true);
paintPanelCheck = createRadioButton("paint panel", false);
ButtonGroup buttonGroup = new ButtonGroup();
buttonGroup.add(paintButtonCheck);
buttonGroup.add(paintPanelCheck);
add(paintButtonCheck);
add(paintPanelCheck);
//Hack, just prove something (realize both components)
add(panel);
add(button);
}
...
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.translate(100, 100);
if (paintButtonCheck.isSelected()) {
button.paintAll(g);
} else {
panel.paintAll(g);
}
g.translate(-100, -100);
}
This should work (although you will obviously have two components on the screen you don't want). Also note "reset" the graphics object, because it will still be used afterwards by Swing.
So this is the theory, but it's not yet an actual solution.
My solution to your problem is: "Don't do it like this"!
Components are not like images, in the sense that they don't look the same everywhere. The output of the paintAll call will be different, depending on how (or where) the components were realized.
So one suggestion is to show actual components. Create your tooltip box, add your panel and your button and let them draw themselves. You can even subclass these components and override their paintComponent() methods, add transparency and all. It will require some work, but Swing was never known to be easy.
I just found a solution.
The only modification of a sample code from my question is that called panel.setDoubleBuffered(false) on JPanel I was trying to paint.
However, I would still consider the exeption to be a Swing bug. If double buffering should be turned off by design you shouldn't get NullPointerException but some other, more meaningful exception which explains the condition.
Here is a fixed sample application:
package test.paintcontainer;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
public class TestPaintContainerMain extends JFrame {
public static void main(String[] args) {
TestPaintContainerMain test = new TestPaintContainerMain();
test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
test.setBounds(0, 0, 300, 200);
test.setContentPane(new TestContentPane());
test.setVisible(true);
}
static class TestContentPane extends JPanel {
JRadioButton paintButtonCheck;
JRadioButton paintPanelCheck;
public TestContentPane() {
paintButtonCheck = createRadioButton("paint button", false);
paintPanelCheck = createRadioButton("paint panel", true);
ButtonGroup buttonGroup = new ButtonGroup();
buttonGroup.add(paintButtonCheck);
buttonGroup.add(paintPanelCheck);
add(paintButtonCheck);
add(paintPanelCheck);
}
#Override
public void paint(Graphics g) {
super.paint(g);
g.translate(100, 100);
if (paintButtonCheck.isSelected()) {
createButton().paint(g);
} else {
createPanel().paint(g);
}
}
private JButton createButton() {
JButton button = new JButton("button");
button.setSize(button.getPreferredSize().width, button.getPreferredSize().height);
return button;
}
private JPanel createPanel() {
JPanel panel = new JPanel();
panel.setBackground(Color.GREEN);
panel.add(createButton());
// --------------------------------
panel.setDoubleBuffered(false); // <-- TURN OFF DOUBLE BUFFERING
// --------------------------------
panel.setSize(panel.getPreferredSize().width, panel.getPreferredSize().height);
return panel;
}
private JRadioButton createRadioButton(String title, boolean selected) {
JRadioButton radio = new JRadioButton(title, selected);
radio.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
TestContentPane.this.repaint();
}
});
return radio;
}
}
}
Related
So, I'm developing a program using the Swing library and I obviously have buttons and menu items. Some of these are supposed to do the same stuff, and I thought using the Command Pattern should be the way to do it, e.g. I have a "save" button and a "save" menu item and they have to implement the same saving algorithm.
Command Pattern seems to be ok but I can't get who's the receiver in all that. Isn't a comand supposed to work on an object which implements some sort of "receiver interface", so that you can use different commands on different receivers coupling them aribtrarily? It looks like there's no "receiver" in my implementation of the pattern.
Another doubt i have is should a command be implemented as a singleton, since you could potentially call its functions from differents parts of the same project, and it would be handly to instantiate it only once and make it statically invokable?
Thank you.
" I obviously have buttons and menu items. Some of these are supposed to do the same stuff,"
As #nIcEcOw noted, that's what Actions are for. This Answer Shows exactly this.
As stated in the How to use Actions :
An Action can be used to separate functionality and state from a component. For example, if you have two or more components that perform the same function, consider using an Action object to implement the function. An Action object is an action listener that provides not only action-event handling, but also centralized handling of the state of action-event-firing components such as tool bar buttons, menu items, common buttons, and text fields. The state that an action can handle includes text, icon, mnemonic, enabled, and selected status.
An There only three Actions. Ont to open, save, and new. Each Action has an ActionCommand, and icon, and and action to perform. Both the JMenuItem and JToolBar button share the same Action and do the same thing. Here is the code you can run.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.Box;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JToolBar;
import javax.swing.SwingUtilities;
import javax.swing.border.LineBorder;
public class ActionTest {
public ActionTest() {
ImageIcon openIcon = new ImageIcon(
ActionTest.class.getResource("/resources/image/open.gif"));
ImageIcon saveIcon = new ImageIcon(
ActionTest.class.getResource("/resources/image/save.gif"));
ImageIcon newIcon = new ImageIcon(
ActionTest.class.getResource("/resources/image/new.gif"));
Action openAction = new AbstractAction("Open", openIcon) {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("Open File");
}
};
Action saveAction = new AbstractAction("Save", saveIcon) {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("Save File");
}
};
Action newAction = new AbstractAction("New", newIcon) {
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("New File");
}
};
JMenuItem openMenuItem = new JMenuItem(openAction);
JMenuItem saveMenuItem = new JMenuItem(saveAction);
JMenuItem newMenuItem = new JMenuItem(newAction);
JMenuBar menuBar = new JMenuBar();
JMenu fileMenu = new JMenu("File");
fileMenu.add(openMenuItem);
fileMenu.add(saveMenuItem);
fileMenu.add(newMenuItem);
menuBar.add(fileMenu);
JToolBar toolBar = new JToolBar();
toolBar.add(Box.createHorizontalGlue());
toolBar.setBorder(new LineBorder(Color.LIGHT_GRAY, 1));
toolBar.add(newAction);
toolBar.add(openAction);
toolBar.add(saveAction);
JFrame frame = new JFrame("Toolbar and Menu Test");
frame.setJMenuBar(menuBar);
frame.add(toolBar, BorderLayout.PAGE_START);
frame.pack();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new ActionTest();
}
});
}
}
As stated in the quote from the above mentioned tutorial, you can do more than just add an image and an action command to the Action. You can use it to set mnemonics and accelorators. Here is a custom Action class that takes
An action command String
an icon
a description for tooltips
a mnemonic
and a key accelorator.
private class MyAction extends AbstractAction {
String name;
public MyAction(String name, Icon icon) {
super(name, icon);
this.name = name;
}
public MyAction(String name, Icon icon, String desc,
Integer mnemonic, KeyStroke accelorator) {
super(name, icon);
putValue(Action.SHORT_DESCRIPTION, desc);
putValue(Action.MNEMONIC_KEY, mnemonic);
putValue(Action.ACCELERATOR_KEY, accelorator);
this.name = name;
}
#Override
public void actionPerformed(ActionEvent e) {
switch (name) {
case "Open":
System.out.println("Open");
break;
case "New":
System.out.println("New");
break;
case "Save":
System.out.println("Save");
break;
}
}
}
Here's an instantiation of this Action
Action newAction = new MyAction("New", newIcon,
"Creates a new file",
new Integer(KeyEvent.VK_N),
KeyStroke.getKeyStroke(KeyEvent.VK_N, ActionEvent.CTRL_MASK));
And here's the new result. You will see the actionCommand in the menu, along with the key mnemonics and accelerators, tooltips, and you will see the jtoolbar buttons share the same traits. You will also see in the final code, that never once once a component created. All you do is add the Action to the JToolBar and the JMenu and let them work their magic.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class ActionInterfaceDemo extends JFrame {
public ActionInterfaceDemo() {
ImageIcon openIcon = new ImageIcon(ActionInterfaceDemo.class.getResource("/resources/image/open.gif"));
ImageIcon saveIcon = new ImageIcon(ActionInterfaceDemo.class.getResource("/resources/image/save.gif"));
ImageIcon newIcon = new ImageIcon(ActionInterfaceDemo.class.getResource("/resources/image/new.gif"));
Action openAction = new MyAction("Open", openIcon,
"Opens a file",
new Integer(KeyEvent.VK_O),
KeyStroke.getKeyStroke(KeyEvent.VK_O, ActionEvent.CTRL_MASK));
Action saveAction = new MyAction("Save", saveIcon,
"Saves a file",
new Integer(KeyEvent.VK_S),
KeyStroke.getKeyStroke(KeyEvent.VK_S, ActionEvent.CTRL_MASK));
Action newAction = new MyAction("New", newIcon,
"Creates a new file",
new Integer(KeyEvent.VK_N),
KeyStroke.getKeyStroke(KeyEvent.VK_N, ActionEvent.CTRL_MASK));
JMenuBar menuBar = new JMenuBar();
JMenu fileMenu = new JMenu("File");
setJMenuBar(menuBar);
menuBar.add(fileMenu);
fileMenu.add(newAction);
fileMenu.add(openAction);
fileMenu.add(saveAction);
JToolBar toolBar = new JToolBar("Alignment");
toolBar.setBorder(BorderFactory.createLineBorder(Color.BLUE));
toolBar.add(Box.createHorizontalGlue());
toolBar.add(newAction);
toolBar.add(openAction);
toolBar.add(saveAction);
add(toolBar, BorderLayout.PAGE_START);
add(new JScrollPane(new TextArea(10, 40)), BorderLayout.CENTER);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setTitle("Action Interface Demo");
pack();
setLocationByPlatform(true);
setVisible(true);
}
private class MyAction extends AbstractAction {
String name;
public MyAction(String name, Icon icon) {
super(name, icon);
this.name = name;
}
public MyAction(String name, Icon icon, String desc,
Integer mnemonic, KeyStroke accelorator) {
super(name, icon);
putValue(Action.SHORT_DESCRIPTION, desc);
putValue(Action.MNEMONIC_KEY, mnemonic);
putValue(Action.ACCELERATOR_KEY, accelorator);
this.name = name;
}
#Override
public void actionPerformed(ActionEvent e) {
switch (name) {
case "Open":
System.out.println("Open");
break;
case "New":
System.out.println("New");
break;
case "Save":
System.out.println("Save");
break;
}
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable(){
public void run() {
new ActionInterfaceDemo();
}
});
}
}
UPDATE
The better explain the relationship of Action and Command Patterns
As noted in Command Pattern
The command pattern is a commonly used pattern which encapsulates a method call or action-like code into a single class. The advantages of being able to package a method (or methods) into a class become evident when you have multiple invokers for a single action (for example a button and a menu item may perform the same action).
In Swing and Borland Delphi programming, an Action is a command object. In addition to the ability to perform the desired command, an Action may have an associated icon, keyboard shortcut, tooltip text, and so on. A toolbar button or menu item component may be completely initialized using only the Action object.
So basically Swing uses the concept of the command pattern through the use of Actions
As for OP's question
"Command Pattern seems to be ok but I can't get who's the receiver in all that."
As for the receiver, the wiki uses a text editor as an example and defines the receiver as such
Receiver, Target Object: the object that is about to be copied, pasted, moved, etc. The receiver object owns the method that is called by the command's execute method. The receiver is typically also the target object. For example, if the receiver object is a cursor and the method is called moveUp, then one would expect that the cursor is the target of the moveUp action. On the other hand, if the code is defined by the command object itself, the target object will be a different object entirely.
The main more components of a Command Pattern are stated as follows
Four terms always associated with the command pattern are command, receiver, invoker and client.
Client, Source, Invoker: the button, toolbar button, or menu item clicked, the shortcut key pressed by the user.
So to put it all together:
The MenuItem (client) invokes it
Action (command object) which calls it actionPerformed which in turn
Invokes an method on the receiver.
The wiki article is good read with a Java example
When two or more components are mean to do exactly the same thingy, one should look at Action, which reduces the duplicate code.
Small example for further help :
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ActionExample {
private JFrame frame;
private JButton button;
private JMenuItem exitItem;
private Action commonActions;
private class CommonActions extends AbstractAction {
public CommonActions(String title, String desc) {
super(title);
putValue(SHORT_DESCRIPTION, desc);
}
#Override
public void actionPerformed(ActionEvent ae) {
JOptionPane.showMessageDialog(frame,
"Closing Frame", "Information", JOptionPane.INFORMATION_MESSAGE);
frame.dispose();
}
};
private void displayGUI() {
frame = new JFrame("Action Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
commonActions = new CommonActions("Exit", "To Exit the Application");
JPanel contentPane = new JPanel();
button = new JButton();
button.setAction(commonActions);
contentPane.add(button);
frame.setJMenuBar(getMenuBar());
frame.setContentPane(contentPane);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JMenuBar getMenuBar() {
JMenuBar menuBar = new JMenuBar();
JMenu fileMenu = new JMenu("File");
exitItem = new JMenuItem(commonActions);
fileMenu.add(exitItem);
menuBar.add(fileMenu);
return menuBar;
}
public static void main(String[] args) {
Runnable runnable = new Runnable() {
#Override
public void run() {
new ActionExample().displayGUI();
}
};
EventQueue.invokeLater(runnable);
}
}
ADDED an example with SINGLETON PATTERN (though I am not sure of this approach(about how good this approach is))
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ActionExample {
private JFrame frame;
private JButton button;
private JMenuItem exitItem;
private void displayGUI() {
frame = new JFrame("Action Example");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
CommonActions.setValues(frame);
JPanel contentPane = new JPanel();
button = new JButton();
button.setAction(CommonActions.getInstance());
contentPane.add(button);
frame.setJMenuBar(getMenuBar());
frame.setContentPane(contentPane);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JMenuBar getMenuBar() {
JMenuBar menuBar = new JMenuBar();
JMenu fileMenu = new JMenu("File");
exitItem = new JMenuItem(CommonActions.getInstance());
fileMenu.add(exitItem);
menuBar.add(fileMenu);
return menuBar;
}
public static void main(String[] args) {
Runnable runnable = new Runnable() {
#Override
public void run() {
new ActionExample().displayGUI();
}
};
EventQueue.invokeLater(runnable);
}
}
class CommonActions extends AbstractAction {
private static CommonActions commonActions = null;
private static JFrame frame = null;
static {
try {
commonActions = new CommonActions("Exit", "To Exit the Application");
} catch (Exception e) {
throw new RuntimeException("BINGO, an error");
}
}
private CommonActions(String title, String desc) {
super(title);
putValue(SHORT_DESCRIPTION, desc);
}
public static CommonActions getInstance() {
return commonActions;
}
public static void setValues(JFrame f) {
frame = f;
}
#Override
public void actionPerformed(ActionEvent ae) {
JOptionPane.showMessageDialog(frame,
"Closing Frame", "Information", JOptionPane.INFORMATION_MESSAGE);
frame.dispose();
}
}
I am trying to implement action listener on two buttons in JFrame, but the issue is one of the two button is performing both the functions; but i've not configured it to do so. Please find the sample code:-
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class MyChangingCirlce implements ActionListener{
JButton colorButton, labelButton;
JLabel myLabel;
MyDrawPanel mdp;
JFrame frame;
public static void main(String [] args)
{
MyChangingCirlce mcc = new MyChangingCirlce();
mcc.createFrame();
}
public void createFrame()
{
frame = new JFrame();
colorButton = new JButton("Changing Colors");
labelButton = new JButton("Change Label");
myLabel = new JLabel("BA");
mdp = new MyDrawPanel();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(BorderLayout.CENTER, mdp);
frame.getContentPane().add(BorderLayout.SOUTH,colorButton);
frame.getContentPane().add(BorderLayout.EAST,labelButton);
frame.getContentPane().add(BorderLayout.WEST,myLabel);
colorButton.addActionListener(this);
labelButton.addActionListener(this);
frame.setSize(300,300);
frame.setVisible(true);
} // end of createFrame Method
public void actionPerformed(ActionEvent e)
{
if(e.getSource()== colorButton)
{
frame.repaint();
}
else
{
myLabel.setText("AB");
}
} //end of interface method...
}
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MyDrawPanel extends JPanel{
public void paintComponent(Graphics g)
{
int red = (int) (Math.random() * 255);
int green = (int) (Math.random() * 255);
int blue= (int) (Math.random() * 255);
Color randomColor = new Color(red,green,blue);
g.setColor(randomColor);
g.fillOval(20,70,100,100);
}
}
You think the button triggers both the if and else statement but that is not the case. If you would adjust your code in the following way:
add a setColor, changeColor or something similar to your MyDrawPanel class
adjust the MyDrawPanel#paintComponent method to use a fixed color instead of a random color, and only adjust the color through the method created in the first step
your color change button should use the method created in the first step to adjust the color of the MyDrawPanel
The thing is that paintComponent can be called by Swing itself. It is not only called when you call repaint (which is a good thing, or all code you write for Swing components would be filled with repaint calls).
Side note: when overriding the paintComponent method I would recommended to call super.paintComponent as well
I've been working on this for some time, and I'd really appreciate some help right now.
I'm trying to get the JFrame containing the text input fields to close from my actionPerformed method, but I can't seem to get anything to work. JFrame.dispose wont let me access the right Jframe, and setVisible(false) is equally useless, unless I'm doing this completely wrong.
//halp
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
class PersonInput extends JPanel
implements ActionListener {
//Fields for data entry
private JFormattedTextField firstField, lastField, dateField;
public String x[] = new String[3];
public PersonInput() {
//Values for the fields
String first = "First Name";
String last = "Last Name";
String date = "MM/DD/YYYY";
//Create the text fields and set them up.
firstField = new JFormattedTextField();
firstField.setValue(new String(first));
lastField = new JFormattedTextField();
lastField.setValue(new String(last));
dateField = new JFormattedTextField();
dateField.setValue(new String(date));
dateField.setColumns(10);
JButton ok = new JButton("OK");
ok.setVerticalTextPosition(AbstractButton.BOTTOM);
ok.setHorizontalTextPosition(AbstractButton.CENTER);
ok.setActionCommand("ok");
ok.addActionListener(this);
ok.setToolTipText("Confirms user input and continues with the program.");
JPanel buttons = new JPanel(new GridLayout(0,1));
buttons.add(ok);
//Layout the text fields in a panel.
JPanel fieldPane = new JPanel(new GridLayout(0,1));
fieldPane.add(firstField);
fieldPane.add(lastField);
fieldPane.add(dateField);
//Put the panels in this panel, labels on left,
//text fields on right.
setBorder(BorderFactory.createEmptyBorder(20, 20, 20, 20));
add(fieldPane, BorderLayout.CENTER);
add(buttons, BorderLayout.LINE_END);
}
public void actionPerformed(ActionEvent e) {
if ("ok".equals(e.getActionCommand()))
{
JFrame frame1 = new JFrame("People Sorter");
x[0] = firstField.getText();
x[1] = lastField.getText();
x[2] = dateField.getText();
JOptionPane.showMessageDialog(frame1, "Person has been added.");
dispPerson();
frame.setVisible(false);
}
}
public void dispPerson()
{
System.out.println(x[0] + x[1] + x[2]);
}
public static void createAndShowGUI() {
//Create and set up the window.
JFrame frame = new JFrame("Person Input");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Add contents to the window.
frame.add(new PersonInput());
//Display the window.
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
//Turn off metal's use of bold fonts
UIManager.put("swing.boldMetal", Boolean.FALSE);
createAndShowGUI();
}
});
}
}
I'm all ears if anyone has any ideas; I've been stressed over this all day. Thanks much for lending me your time!
EDIT: Just for clarification, the frame I'm trying to close is the one instantiated in the createAndShowGUI method.
it seems that the problem is that we are trying to merge both static and non static contents. For a short explanation static contents can be referred without need of creating an instance (object) of that class. Which means that createAndShowGUI can be called:
inside another static method (like main)
From class reference PersonInput.createAndShowGUI()
or from an object, but that method or attribute will be always the same, static attributes are shared.
I can suggest 2 ways to solve your problem.
One is pass the object frame to PersonInput
//halp
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
class PersonInput extends JPanel
implements ActionListener {
//Fields for data entry
private JFormattedTextField firstField, lastField, dateField;
public String x[] = new String[3];
JFrame frame;
public PersonInput(JFrame frame) {
this.frame = frame;
//the rest of your code
}
The other way is to have the frame object outside the method and declare it static.
static JFrame frame = new JFrame("Person Input");;
public static void createAndShowGUI() {
//Create and set up the window.
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//Add contents to the window.
frame.add(new PersonInput());
//Display the window.
frame.pack();
frame.setVisible(true);
}
Remember that static variable cannot be referenced from a static context
I'm having some bother understanding why I cannot get a TreeModelChanged listener to respond to changes in the model which it subscribes to.
I have managed to reproduce the problem in a small example.
The SysOut message does not print to the console whenever a new node is added to the tree.
I intend to replace the SysOut message with some commands to redraw the tree. At the moment I am using a SysOut message just to prove that the listener is not being fired.
Am I missing something fundamental?
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.event.TreeModelEvent;
import javax.swing.event.TreeModelListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
public class TreeTest {
private JTree t;
private DefaultTreeModel m ;
public static void main(String[] args) {
new TreeTest();
}
public TreeTest() {
//Draw Frame & Panel - set dimensions
JFrame f = new JFrame();
f.setSize(new Dimension(800,600));
JPanel p = new JPanel();
p.setSize(new Dimension(800,600));
//Create a Tree Model. Give it a String at the root.
m = new DefaultTreeModel(new DefaultMutableTreeNode("Root"));
//Create a tree and add the Model to it
t = new JTree();
t.setModel(m);
//Try a Tree Model Listener
m.addTreeModelListener(new TreeModelListener() {
private void doSomething() {
//Should fire whenever a node is added to the model
System.out.println("Responding to TreeModelListener");
}
#Override
public void treeStructureChanged(TreeModelEvent e) {
doSomething();
}
#Override
public void treeNodesRemoved(TreeModelEvent e) {
doSomething();
}
#Override
public void treeNodesInserted(TreeModelEvent e) {
doSomething();
}
#Override
public void treeNodesChanged(TreeModelEvent e) {
doSomething();
}
});
//Add listener to a button which adds nodes to the tree when clicked
JButton addNode = new JButton("Add node");
addNode.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
DefaultMutableTreeNode newNode = new DefaultMutableTreeNode("New Node");
DefaultMutableTreeNode root = (DefaultMutableTreeNode) m.getRoot();
root.add(newNode);
}
});
JScrollPane s = new JScrollPane(t);
p.add(s);
p.add(addNode);
p.setVisible(true);
f.add(p);
f.setVisible(true);
}
}
that's because the model doesn't know about the addition, it happens under its feet. Use the methods on DefaultTreeModel to do the insertion:
model.insertNodeInto(newNode, root, root.getChildCount())
Edit
a TreeNode is just a (more or less) dumb data structure. As you can see in the api, it's not an Observable, so there is no way for the model which uses that data structure to detect if anything changed on the node. To make it aware of the change, you have to do one of two things
use the node manipulation methods of the model
update the node and notify the model manually (calling nodesWereInserted)
The first is the preferable way (keeps control where it belongs), the second might be needed in more complex contexts (though I would strongly recommend to never do it, that's why SwingX DefaultTreeTableModel doesn't have them exposed :)
The basic setup is this: I have a vertical JSplitPane that I want to have a fixed-size bottom component and a resizing top component, which I accomplished by calling setResizeWeight(1.0). In this application there is a button to restore the "default" window configuration. The default height of the window is the desktop height, and the default divider location is 100 pixels from the bottom of the split pane.
To set the divider location to 100px, I take the JSplitPane height - 100. The problem is, just before this I resize the JFrame, and since the code is in a button callback, the JSplitPane has been invalidated but not yet resized. So the divider location is set incorrectly.
Here is a SSCCE. Click the button twice to see the problem. The first click will resize the window, but the divider location remains the same (relative to the bottom of the window). The second click properly moves the divider, since the window size didn't change.
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GraphicsConfiguration;
import java.awt.Insets;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JSplitPane;
public class SSCCE {
/**
* #param args unused
*/
public static void main(String[] args) {
new SSCCE();
}
private final JFrame f = new JFrame("JSplitPane SSCE");
private final JSplitPane sp = new JSplitPane(JSplitPane.VERTICAL_SPLIT,true);
public SSCCE() {
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
sp.add(new JLabel("top"));
sp.add(new JLabel("bottom"));
sp.setResizeWeight(1.0);
f.getContentPane().add(sp);
f.getContentPane().add(new JButton(new AbstractAction("Resize to Default") {
#Override
public void actionPerformed(ActionEvent e) {
restoreDefaults();
}
}),BorderLayout.PAGE_END);
f.setSize(400,300);
f.setVisible(true);
}
void restoreDefaults() {
f.setSize(f.getWidth(), getDesktopRect(f.getGraphicsConfiguration()).height);
sp.setDividerLocation(sp.getSize().height - 100); // Does not work on first button press
}
Rectangle getDesktopRect(GraphicsConfiguration gc) {
Toolkit toolkit = Toolkit.getDefaultToolkit();
Dimension size = toolkit.getScreenSize();
Insets insets = toolkit.getScreenInsets(gc);
return new Rectangle(insets.left, insets.top, size.width - (insets.left + insets.right), size.height - (insets.top + insets.bottom));
}
}
I have thought of a few ways I might get around this, but they all seem sort of hackish. So far the best idea I've had has been to call f.validate() in between setting the frame size and setting the divider location, but I'm concerned there might be side effects to forcing validation early.
The other option I thought of is to use EventQueue.invokeLater() to put the call to set the divider location at the end of the event queue. But that seems risky to me - I'm assuming the JSplitPane will have been validated at that point, and I'm concerned that may be a faulty assumption to make.
Is there a better way?
Took a while (probably due to being early morning here :-) to understand the problem, so just to make sure I got it:
the size of the bottom component can be whatever the user decides at all times
when resizing the frame all height change should happen to the top component
there's an option to restore to default sizes, independent of any setting before
"default" means the bottom component must have a fixed height of xx
If so, the solution is to separate the frame resizing from the sizing the bottom component. Your second option is dead on: resize the frame and wrap the bottom comp resize into a invokeLater (EventQueue or SwingUtilities, doesn't matter).
void restoreDefaults() {
f.setSize(f.getWidth(), getDesktopRect(f.getGraphicsConfiguration()).height);
SwingUtilities.invokeLater(new Runnable() {
public void run() {
sp.setDividerLocation(sp.getSize().height - 100);
}
});
}
That's guaranteed to work as expected, because the invokeLater puts the request as last after all already queued events:
/**
* Causes <i>doRun.run()</i> to be executed asynchronously on the
* AWT event dispatching thread. This will happen after all
* pending AWT events have been processed. [...]
* If invokeLater is called from the event dispatching thread --
* for example, from a JButton's ActionListener -- the <i>doRun.run()</i> will
* still be deferred until all pending events have been processed.
You could create a custom action class that handles the button click and the resize event. This approach would look like this:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.GraphicsConfiguration;
import java.awt.Insets;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JSplitPane;
public class SSCCE {
/**
* #param args unused
*/
public static void main(String[] args) {
new SSCCE();
}
private final JFrame f = new JFrame("JSplitPane SSCE");
private final JSplitPane sp = new JSplitPane(JSplitPane.VERTICAL_SPLIT,true);
public SSCCE() {
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
sp.add(new JLabel("top"));
sp.add(new JLabel("bottom"));
sp.setResizeWeight(1.0);
f.getContentPane().add(sp);
CustomListener resizeViaButtonListener = new CustomListener("Resize to Default");
f.getContentPane().add(new JButton(resizeViaButtonListener), BorderLayout.PAGE_END);
f.addComponentListener(resizeViaButtonListener);
f.setSize(400,300);
f.setVisible(true);
}
void restoreDefaults() {
f.setSize(f.getWidth(), getDesktopRect(f.getGraphicsConfiguration()).height);
sp.setDividerLocation(sp.getSize().height - 100); // Does not work on first button press
}
Rectangle getDesktopRect(GraphicsConfiguration gc) {
Toolkit toolkit = Toolkit.getDefaultToolkit();
Dimension size = toolkit.getScreenSize();
Insets insets = toolkit.getScreenInsets(gc);
return new Rectangle(insets.left, insets.top, size.width - (insets.left + insets.right), size.height - (insets.top + insets.bottom));
}
class CustomListener extends AbstractAction implements ComponentListener {
CustomListener(String actionDescription) {
super(actionDescription);
}
private boolean resizedViaButtonClick = false;
#Override
public void actionPerformed(ActionEvent arg0) {
resizedViaButtonClick = true;
f.setSize(f.getWidth(), getDesktopRect(f.getGraphicsConfiguration()).height);
sp.setDividerLocation(sp.getSize().height - 100);
// you need this also here because if the component is not resized when clicking the button
// it is possible that the divider location must be changed. This happens when the user clicks
// the button after changing the divider but not resizing the frame.
}
#Override
public void componentResized(ComponentEvent e) {
if ( resizedViaButtonClick ) {
resizedViaButtonClick = false;
sp.setDividerLocation(sp.getSize().height - 100);
}
}
#Override
public void componentHidden(ComponentEvent e) { /* do nothing */ }
#Override
public void componentMoved(ComponentEvent e) { /* do nothing */ }
#Override
public void componentShown(ComponentEvent e) { /* do nothing */ }
}
}
This way the code that is responsible for handling the logical task of setting the standard size will be in one single and easy to understand class.
nothing complicated, basic Swing Rules
import java.awt.*;
import java.awt.event.ActionEvent;
import javax.swing.*;
public class SSCCE {
/**
* #param args unused
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
SSCCE sSCCE = new SSCCE();
}
});
}
private final JFrame f = new JFrame("JSplitPane SSCE");
private final JSplitPane sp = new JSplitPane(JSplitPane.VERTICAL_SPLIT,
true);
public SSCCE() {
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
sp.add(new JLabel("top"));
sp.add(new JLabel("bottom"));
sp.setResizeWeight(1.0);
f.getContentPane().add(sp);
f.getContentPane().add(new JButton(new AbstractAction(
"Resize to Default") {
private static final long serialVersionUID = 1L;
#Override
public void actionPerformed(ActionEvent e) {
System.out.println(sp.getLastDividerLocation());
restoreDefaults();
}
}), BorderLayout.PAGE_END);
f.setPreferredSize(new Dimension(400, 300));
f.pack();
f.setVisible(true);
}
void restoreDefaults() {
//EventQueue.invokeLater(new Runnable() {
// #Override
// public void run() {
f.setPreferredSize(new Dimension(f.getWidth(),
getDesktopRect(f.getGraphicsConfiguration()).height));
f.pack();
sp.setDividerLocation(sp.getSize().height - 100);
// Does not work on first button press
// }
//});
}
Rectangle getDesktopRect(GraphicsConfiguration gc) {
Toolkit toolkit = Toolkit.getDefaultToolkit();
Dimension size = toolkit.getScreenSize();
Insets insets = toolkit.getScreenInsets(gc);
return new Rectangle(insets.left, insets.top,
size.width - (insets.left + insets.right),
size.height - (insets.top + insets.bottom));
}
}
but I think pack() may be better than validate()
I generally try to avoid invoking setPreferredSize() on any component. I would rather let the layout manager do its job. In this case this would mean setting the size of the frame and let the BorderLayout take all the available space.
void restoreDefaults() {
// f.setSize(f.getWidth(), getDesktopRect(f.getGraphicsConfiguration()).height);
GraphicsEnvironment env = GraphicsEnvironment.getLocalGraphicsEnvironment();
Rectangle bounds = env.getMaximumWindowBounds();
f.setSize(f.getWidth(), bounds.height);
f.validate();
sp.setDividerLocation(sp.getSize().height - 100); // Does not work on first button press
}