Develop Reference

Calling #Override on paintComponent() when state changes

How do I override a paintComponent method with response to a state change?
Error message: void is an invalid type for the variable paintComponent
public class MyContainer extends Container {
public void paintComponent(Graphics m){
m.drawArc(100,100,100,100,100,100);
m.setColor(Color.green);
m.fillArc(100,100,100,100,100,100);
}
public static void main(String[] args){
Container y = new Container();
JFrame x = new JFrame();
JPanel gg = new JPanel();
x.add(y);
x.setTitle(" Shape Changer");
x.setBounds(100,50,500,300);
x.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
x.getContentPane().add(new ContentPanel());
x.getContentPane().add(new ContnetPanel());
x.setContentPane(new ContnetPanel());
x.setVisible(true);
}
static class ContentPanel extends JPanel{
private Graphics g;
private JPanel ss;
public void paint(Graphics g){
g.drawArc(100,100,100,100,100,100);
g.fillRect(100, 100,100,100);
}
public ContentPanel(){
}
}
static class ContnetPanel extends JPanel implements ActionListener, ChangeListener{
JComboBox comboerbox;
class appres {
public void paint(Graphics h){
h.drawRect(100,100,100,100);
h.setColor(Color.red);
h.fillRect(100,100,100,100);
}
}
public ContnetPanel(){
comboerbox = new JComboBox();
comboerbox.addItem("Red Square");
comboerbox.addItem("Blue Square");
comboerbox.addItem("Green Square");
comboerbox.setSelectedIndex(1);
add(comboerbox);
setLayout(new GridLayout(2,1));
}
#Override
protected void paintComponent(Graphics h){
super.paintComponent(h);
h.drawArc(100,100,100,100,100,100);
h.setColor(Color.blue);
h.fillArc(100,100,100,100,100,100);
repaint();
}
int yy = 0;
public void actionPerformed(ActionEvent evt){
switch(comboerbox.getSelectedIndex()){
case 0:yy=0;
case 1: yy=1;
case 2: yy=2;
}
}
//evt.getSource()==comboerbox
public void stateChanged(ChangeEvent evt){
if(evt.getSource()==comboerbox){
#Override
protected void paintComponent(Graphics h){
super.paintComponent(h);
h.drawArc(100,100,100,100,100,100);
h.setColor(Color.blue);
h.fillArc(100,100,100,100,100,100);
repaint();
}
}
else
{
System.out.println("DONE");
}
}
}
}
Of course, the paintComponent method isn't a variable. How would I override paintComponent here? Or is a better way to change the shape with response to state change? That would be great too!
Thanks in advance, love you guys!

In your last question: How do I make the superclass go beyond just the content pane? you were given a link to the Swing tutorial for some Swing basics.
Well there is also a section on Custom Painting for you to read. You can then download the example and play with it to understand how painting works.
Basically the Container class doesn't have a paintComponent() method so you should not be trying to do custom painting in that class.
If you want to change a painting property, then you need to add a method to your class to change the state of the property and then invoke repaint() on itself.
So from the tutorial example in Step 3 you can see how the moveSquare(...) method changes the state of the class and then invokes repaint().
Note you should never invoke repaint() in the paintComponent() method since this will cause the painting to be continually rescheduled.

Click Button to Open Another Applet

I want to call another applet by clicking a button; the old applet will then be closed or reloaded to the new applet.
My Action Listener doesn't have anything yet.
public class ConImage extends JApplet implements ActionListener {
Button btn;
Applet second;
public void init()
{
setSize(1600,900);
setLayout(null);
btn=new Button("Replace with other applet");
add(btn);
btn.addActionListener(this);
}
public void paint(Graphics g)
{
super.paint(g);
btn.setLocation(100, 100);
btn.setSize(100, 50);
}
public void actionPerformed(ActionEvent e)
{ second=null;
second= getAppletContext().getApplet("SecondClass");
if (second!=null)
{
if(e.getSource()==Time)
{
SecondClass ma= (SecondClass) second;
}
}
}
}

I'm pretty sure this isn't possible because of Java's security system. The best way to so it is to have a master class, which has an array of JApplet. On that master applet I would create a method that sets the visible applet from the array, calls init() and when a render is requested call paint() of that applet.
Like so:
public class MasterApplet extends JApplet {
private int index = 0;
private JApplet[] applets;
public void init(){
JApplet appletA = new AppletA();
JApplet appletB = new AppletB();
applets = new JApplet[]{appletA, appletB};
setViewing(index);
}
public void paint(Graphics g){
applets[index].paint(g);
}
public void setViewing(int idex){
index = idex;
applets[idex].init();
revalidate();
repaint();
}
Pretty much if you want to change the applet add it to the array of applets, and then call setViewing() with the index of that applet.

How to pass the instance of the actual jFrame to other jFrame

I have two classes, and from the first jFrame1 (CotizacionGUI) I instantiate and make visible the other one (jFrame2), and I want to pass the instance of this jFrame1 (CotizacionGUI), to the other, in the constructor, to dispose it in an action triggered by the button at any moment...
public class CotizacionGUI extends javax.swing.JFrame{
public CotizacionGUI() {
initComponents();
}
private void buttonCallFrame2ActionPerformed(java.awt.event.ActionEvent evt) {
BuscarCotizacionGUI bC = new BuscarCotizacionGUI(thisjFrameinstance);
bC.setVisible();
}
}
And this is the Frame2 (BuscarCotizacionGUI), here is where I want to dispose the previous jFrame, triggered by the action performed event:
public class BuscarCotizacionGUI extends javax.swing.JFrame {
public BuscarCotizacionGUI(final JFrame otherFrame) {
initComponents();
this.setLocationRelativeTo(null);
button.addActionListener(new ActionListener(){
#Override
public void actionPerformed(ActionEvent e){
otherFrame.dispose();
}
});
}
}
Can you help me guys please, I don't want to do it using other class, i want to pass the reference in the jFrame1, Thanks!

The instance of first JFrame is always available to you in the same class as this
public class CotizacionGUI extends javax.swing.JFrame{
public CotizacionGUI() {
initComponents();
}
private void buttonCallFrame2ActionPerformed(java.awt.event.ActionEvent evt) {
BuscarCotizacionGUI bC = new BuscarCotizacionGUI(this);
bC.setVisible();
}
}
Hope this is what you are looking for.
Good luck.

JFrame displays content only after resizing (Xuggler)

I Have written a listener for an IMediaReader from Xuggler.
It should show a video in a JPanel what i can add to a JFrame.
I have created this JFrame in the class main:
class Window extends JFrame {
static IMediaReader reader;
static Window main;
public static void main(String[] args) {
new Thread() {
public void run() {
reader = ToolFactory.makeReader("C:/Users/André/Desktop/Detail.wmv");
reader.addListener(new Player(IMediaViewer.Mode.AUDIO_VIDEO, main));
while (reader.readPacket() == null)
do {} while(false);
}
}.start();
SwingUtilities.invokeLater(new Runnable() {
public void run() {
main = new Window();
}
});
}
private Window() {
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
SwingUtilities.invokeLater(new Runnable() {
public void run() {
setVisible(true);
setSize(700, 700);
}
});
}
// invoked by Player with the video panel
public void add(final JPanel videoPanel) {
add(videoPanel, BorderLayout.CENTER);
}
}
It shows the video but it only works when i resize the window manually and that is my problem. Else, it shows a small black square.
Using pack() instead of setSize() or invoke repaint doesn't help.
The Code of class Player isn't just from me. I've just changed some things:
public class Player extends MediaListenerAdapter implements IMediaListener, IMediaViewer {
private static Main main;
Player(Mode mode, Main main) {
setMode(mode);
Player.main = main;
}
#Override
public void onAddStream(IAddStreamEvent event)
{
[...]
MediaFrame frame = new MediaFrame(stream, this, main);
[...]
}
#Override
public void onVideoPicture(IVideoPictureEvent event)
{
MediaFrame frame = mFrames.get(event.getStreamIndex());
frame.setVideoImage(event.getPicture(), event.getImage());
}
static class PositionFrame extends JPanel
{
public PositionFrame(Player viewer, Main main)
{
main.add(this);
mFrames.add(this);
}
protected void adjustSize()
{
invalidate();
}
}
private class MediaFrame extends PositionFrame
{
// the video image
private BufferedImage mImage;
// the video panel
private final JPanel mVideoPanel;
// the stream
private final IStream mStream;
// the index of the stream (incase it's closed)
private final int mStreamIndex;
/**
* Construct a media frame.
*
* #param defaultCloseOperation what should Swing do if the window
* is closed. See the {#link javax.swing.WindowConstants}
* documentation for valid values.
* #param stream the stream which will appear in this frame
* #param viewer containing media viewer
*/
public MediaFrame(IStream stream,
Player viewer, Main main)
{
super(viewer, main);
// get stream and set title based it, establish a copy of the
// stream since it lives in a separate thread
mStream = stream.copyReference();
mStreamIndex = mStream.getIndex();
// the panel which shows the video image
mVideoPanel = new JPanel()
{
public void paint(Graphics graphics)
{
paintPanel((Graphics2D) graphics);
}
};
// add the videoPanel
add(mVideoPanel);
// show the frame
setVisible(true);
}
// set the video image
protected void setVideoImage(IVideoPicture picture, BufferedImage image)
{
[...]
}
protected void paintPanel(Graphics2D graphics)
{
if (mImage != null)
graphics.drawImage(mImage, 0, 0, null);
}
}
}
It is made up from the class MediaViewer
http://code.google.com/p/xuggle/source/browse/trunk/java/xuggle-xuggler/src/com/xuggle/mediatool/MediaViewer.java?r=644
EDIT: If I do it like this, it doesn't work without resizing manually.
I'm not shure if I have unterstood you right.

You have this code in two places.
pack();
setSize(700, 700);
The pack() class is wasteful since you are setting the size immediately afterwards. Also, the first time you call in your constructor you haven't even added anything yet.
Try setting the size or calling pack after you have added the video component and after you have made the frame visible.
Based on your edits, I believe the issue is that you are setting the frame visible before the component is in place. Move your setVisible and pack() calls to the end of your constructor for the Main class instead of the add() method.
Based on more edits to your question: As I mentioned in the comments, make sure you separate off the GUI code in a separate call to invokeLater to get things happening on the EDT. Therefore you need to move your IMediaReader creation and thread starting into your main() method, then after that create a new call to SwingUtilities.invokeLater that creates a new Main, class. By the way, Main is a confusing name for a class.

how to suspend Applet in browser when tab is unselected

I'm making my first Applet. I have a JPanel which creates a Swing GUI and performs CPU intensive tasks (repainting a Component 60Hz). My Applet displays this JPanel on event dispatching thread. here is an abstraction of the problem. Normally I would launch the applet from an html document instead of having a main method. This program puts about a 40% load on my CPU.
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
import java.awt.event.*;
public class TestApplet extends JApplet {
TestPanel tp;
public void init() {
try {
SwingUtilities.invokeAndWait(new Runnable() {
public void run() {
createGUI();
}
});
} catch (Exception e) {
System.err.println("createGUI didn't complete successfully");
}
}
private void createGUI() {
//Create and set up the content pane.
tp = new TestPanel();
tp.setOpaque(true);
setContentPane(tp);
}
public static void main(String[] args) {
JFrame f = new JFrame("Fish Tank");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JApplet ap = new TestApplet();
ap.init();
f.add("Center", ap);
f.pack();
f.setVisible(true);
}
}
class TestPanel extends JPanel{
public TestTank tt = new TestTank();
public TestPanel() {add(tt);}
public void stop() {tt.stop();}
public void start() {tt.start();}
}
class TestTank extends Component implements ActionListener{
private javax.swing.Timer timer;
TestTank(){
timer = new javax.swing.Timer(17, this);
timer.setCoalesce(true);
timer.start();
}
public Dimension getPreferredSize(){
return new Dimension(900, 700);
}
public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
Dimension size = getSize();
g2.setPaint(new GradientPaint(0,0,Color.RED,900, 0,Color.WHITE));
g2.fill(new Rectangle2D.Float(0,0,size.width,size.height));
}
public void actionPerformed(ActionEvent e) {
repaint();
}
public void stop(){timer.stop();}
public void start(){timer.start();}
}
My question: How do I suspend and resume execution of the JPanel (FishTankPanel) when the user switches tabs or minimizes the browser? I want the Applet to stop using the CPU when the user can't see what it is doing. I need to capture browser events in order to execute tp.stop() in the applet. I have tried to execute them with window event listeners in the JPanel, and by overriding the start() and stop() methods in the Applet. I have been unsuccessful. Any suggestions or solutions would be appreciated.

I would do as Dave said and use the JApplet override start and stop methods to call your GUI methods. For instance, see changes in code:
public class TestApplet extends JApplet {
TestPanel tp;
public void init() {
// ... no change
}
private void createGUI() {
// ... no change
}
#Override
public void stop() {
if (tp != null) {
tp.stop();
}
}
#Override
public void start() {
if (tp != null) {
tp.start();
}
}
}
class TestTank extends Component implements ActionListener {
private javax.swing.Timer timer;
// ... no change
public void stop() {
timer.stop();
System.out.println("stop");
}
public void start() {
timer.start();
System.out.println("start");
}
}

It seems you might need to leverage some JS for this. E.G. use the JS shown in this answer to explicitly call the applet start() & stop() methods on focus & blur detection respectively.

The solution for my problem was to use javascript to implement the Page Visibility API. I then called the appropriate Java methods from within the javascript script.