Path: csiph.com!x330-a1.tempe.blueboxinc.net!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder1.hal-mli.net!npeer02.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail From: Lew Newsgroups: comp.lang.java.gui Subject: Re: How do I paint on an existing Panel? Date: Thu, 16 Feb 2012 13:28:04 -0800 (PST) Organization: http://groups.google.com Lines: 168 Message-ID: <800725.801.1329427684213.JavaMail.geo-discussion-forums@pbbpk4> References: <4f16f997$0$2957$fa0fcedb@news.zen.co.uk> <4f3d6f9c$0$2500$da0feed9@news.zen.co.uk> NNTP-Posting-Host: 173.164.137.214 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 X-Trace: posting.google.com 1329429119 27095 127.0.0.1 (16 Feb 2012 21:51:59 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Thu, 16 Feb 2012 21:51:59 +0000 (UTC) In-Reply-To: <4f3d6f9c$0$2500$da0feed9@news.zen.co.uk> Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=173.164.137.214; posting-account=CP-lKQoAAAAGtB5diOuGlDQk0jIwmH0T User-Agent: G2/1.0 X-Google-Web-Client: true X-Received-Bytes: 6516 Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.gui:5029 On Thursday, February 16, 2012 1:05:25 PM UTC-8, A B wrote: > Sorry, I'm stumped, again. I really have been trying to sort it out myself, > but no luck. I've done it by adapting Knute Johnson's code (which works > fine in itself). Mine now defines a line and calls repaint() as nice as you > like, but there's no answer. Note that you did not start the GUI on the Event Dispatch Thread (EDT). I don't know if this causes your problem, but it's a mistake. > I've chopped the code back to just the bits directly involved with the > drawing and sprinkled debugging statements everywhere, which established > that the bit that calls paintComponent() (via repaint() - that's right isn't > it?) is firing but paintComponent() itself isn't. Here's what's left, if > you're interested. Sorry if anyone finds it hard to read, I don't know how > you like it formatted. We like it formatted according to the well-established Java Coding Conventions or a slight variation thereof. > ------------------------ > import java.awt.*; > import java.awt.event.*; > import java.awt.geom.*; > import java.util.*; > import javax.swing.*; > > public class Vectorine extends JFrame implements MouseListener "Favor composition over inheritance". http://java.sun.com/docs/books/effective/ > { > private static final long serialVersionUID = 159L; indent 2 (or 3 or 4) spaces per level, no TABs. Why did you pick '159L'? Just use '1L'. What is up with 159? > // List to contain all the lines generated > private final java.util.List lineList = new > java.util.ArrayList(); Why do you import java.util.* and still use FQNs? > public static void main() {Vectorine v = new Vectorine();} Start GUIs on the EDT! Golly! > public Vectorine() > { > super("Vectorine"); > setSize(200, 200); Use 'setPreferredSize()'. > setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); You forgot 'pack()'. > setVisible(true); > > // Set up window's initial contents > Container contentArea = getContentPane(); > FlowLayout layout = new FlowLayout(); > contentArea.setLayout(layout); > JPanel panelA = new JPanel(); > panelA.addMouseListener(this); > contentArea.add(panelA); > setContentPane(contentArea); > > System.out.println("If you click anywhere in the box, 3 random lines should > appear in it."); Don't use 'System.out.println()' in a GUI, nor for logging. > } > > public void paintComponent(Graphics g2d) > { > Graphics2D g = (Graphics2D)g2d; Your naming is backwards. > System.out.println("Painting..."); Don't use 'System.out.println()' in a GUI, nor for logging. > for (ColoredLine hand : lineList) > { > System.out.println("Drawing line..."); > BasicStroke pen = new BasicStroke(hand.getThickness()); > g.setStroke(pen); > g.setColor(hand.getColor()); > g.draw(hand); > } > } Shouldn't you be painting these lines into a component contained within the JFrame and not the JFrame itself? > > public void mouseClicked(MouseEvent event) > { > System.out.println("Mouse clicked"); > double xcoord = 0, ycoord = 0; > for (int count=0; count<3; count++) > { > xcoord = 100 * Math.random(); > ycoord = 100 * Math.random(); > System.out.println("xcoord="+xcoord+", ycoord="+ycoord); > ColoredLine hand = new ColoredLine(0F, 0F, (float)xcoord, (float)ycoord, > Color.red, 2); > lineList.add(hand); > System.out.println("Calling repaint()..."); > repaint(); I'm less familiar with idioms that interfere with the repainting loops, but shouldn't you be invalidating? Do you actually have to repaint? It's hard to reason about this because the other errors complicate the analysis. > } > } > > /** Blank methods to keep MouseListener happy. */ You could have just inherited the listener from > public void mousePressed(MouseEvent event) {} > public void mouseReleased(MouseEvent event) {} > public void mouseEntered(MouseEvent event) {} > public void mouseExited(MouseEvent event) {} > } > > /** The actual lines drawn are instances of the ColoredLine class. */ > class ColoredLine extends Line2D.Double > { private static final long serialVersionUID = 149L; > private final Color color; > private final int thickness; > public ColoredLine(double x,double y,double w,double h,Color color,int > thickness) > { > super(x,y,w,h); > this.color = color; > this.thickness = thickness; > } > > public Color getColor() {return color;} > public int getThickness() {return thickness;} > } I cannot be sure without putting far too much time into it, but I think the problem stems from a combination of factors: - not running the GUI on the EDT; - drawing on the JFrame itself rather than a contained component, leading to components drawing themselves over your graphic; - failure to pack(); - omission of 'setPreferredSize()'; I promise that I have not analyzed your program in the depth needed to properly suss out your problem. I do know that it helps to eliminate even potentially complicating factors, particularly the failure to use the EDT. Most of those factors won't impinge on the immediate question, but the effort to fix bad code is never wasted. -- Lew