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Java Forum / General / December 2005Using self made Component
Hello! I got a bit of an problem using my self-made component. Which is that it won't paint's itself.. I noticed the object is being made, but for some reason the components paint methode isn't executed. Here is the code of the component: public class Peg extends Component { int x,y; public Peg(int x, int y) { super(); this.x = x; this.y = y; } public void paint(Graphics g) { g.setColor(Color.YELLOW); g.fillOval(x,y,100,100); } public Dimension getMinimumSize() { return new Dimension(100,100); } public Dimension getPreferredSize() { return getMinimumSize(); } public Dimension getMaximumSize() { return new Dimension(500,500); } } Its for a school assingment and we need to use Awt and extending it as a Component. I really hope someone has an idear what im doing wrong here, been at for some days now. Thanks in advance! > Hello! > [quoted text clipped - 37 lines] > for some days now. > Thanks in advance! How are you attempting to use it? This codes seems to work fine for me: //Start code import java.awt.BorderLayout; import javax.swing.JFrame; public class Test { public void testPegComponent(){ JFrame f = new JFrame("TEST"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); Peg p = new Peg(4, 4); f.add(p, BorderLayout.CENTER); f.pack(); f.setVisible(true); } public static void main(String[] args){ Test t = new Test(); t.testPegComponent(); } } //End Code Thank you for your reaction! Im using it this way: //Code Public class MyFrame extends Frame implements WindowListener { public MyFrame() { super("MasterMind"); setSize(400,600); setResizable(false); setLayout(new FlowLayout()); addWindowListener(this); Peg test = new Peg(100,100); add(test); show(); } Code// I tried your code aswell, but i got an error: "Exception in thread "main" java.lang.Error: Do not use javax.swing.JFrame.add() use javax.swing.JFrame.getContentPane().add() instead" Could the problem be the version of the SDK that im using ? I got 1.4.2. > Thank you for your reaction! > Im using it this way: [quoted text clipped - 20 lines] > Could the problem be the version of the SDK that im using ? > I got 1.4.2. Yeah, my mistake. That is correct, you should use the getContentPane().add() not the deprecated JFrame.add(). Your error is indeed in your implementation of the Frame component. My suggestion to you would be to remove lines until the problem is revealed, or alternatively to start with a new, minimalist constructor. //CODE public MyFrame(){ super("MasterMind"); setSize(400,600); addWindowListener(this); Peg test = new Peg(100,100); add(test); } //END CODE Also notice that I don't think you should be calling the show() method in the Frame constructor; have the object that created the Frame object decide when to display it. i.e. Frame f = new MyFrame(); f.show(); > Yeah, my mistake. That is correct, you should use the > getContentPane().add() not the deprecated JFrame.add(). Doh!, And I should also point out that the add() method for JFrame is not actually deprecated, and have no idea I phrased it that way. Anyways, you should indeed use the getContentPane().add() when using JFrame and not add() as you would for Frame. This is not really relevant to your project, I just wanted to clear up the mistake in my previous post. Carl. >Anyways, you should indeed use the getContentPane().add() when >using JFrame and not add() as you would for Frame. Last time I looked at http://download.java.net/jdk6/docs/api/javax/swing/JFrame.html , I found no hint in this direction. Instead, "frame.add( child )" is mentioned in a prominent place, right at the start and seems to be quite approved. Quote: As a conveniance add and its variants, remove and setLayout have been overridden to forward to the contentPane as necessary. This means you can write: frame.add( child ); And the child will be added to the contentPane. So, why should I not use this? >>Anyways, you should indeed use the getContentPane().add() when >>using JFrame and not add() as you would for Frame. [quoted text clipped - 19 lines] > > So, why should I not use this? _You_ should use this, however it may be worth mentioning that in 1.5.0, the add() method has "been overridden to forward to the contentPane as necessary". The OP mentioned using 1.4.2, where the documentation states that when "using JFrame you need to add the child to the JFrame's content pane instead: frame.getContentPane().add(child);" See http://java.sun.com/j2se/1.4.2/docs/api/javax/swing/JFrame.html for more details. Maybe I should have made the version bit clearer :) . Cheers, Carl. >>Anyways, you should indeed use the getContentPane().add() when using >>JFrame and not add() as you would for Frame. [quoted text clipped - 19 lines] > > So, why should I not use this? Depends on which JDK you are using. As you might glean from your quote, add() did not always add to the contentPane. In previous versions, you ended up using the inherited Container.add(), which did not do what you want. To clarify, here's what the 1.4.x javadocs say in place of your quote: The content pane provided by the root pane should, as a rule, contain all the non-menu components displayed by the JFrame. This is different from the AWT Frame case. For example, to add a child to an AWT frame you'd write: frame.add(child); However using JFrame you need to add the child to the JFrame's content pane instead: frame.getContentPane().add(child); The same is true for setting layout managers, removing components, listing children, and so on. All these methods should normally be sent to the content pane instead of the JFrame itself.  Signaturemonique Ask smart questions, get good answers: http://www.catb.org/~esr/faqs/smart-questions.html I tried using your minimalist constructor Carl, and that does work! Only when i make another object of Peg the one added first disappears. But that might be normal ? The reason it didn't worked before was maybe because i had a paint methode in MyFrame? Because once i removed that code, the oval was displayed. @Monique Im adding it the same way as in Carl's code. /CODE public MyFrame(){ super("MasterMind"); setSize(400,600); addWindowListener(this); Peg test = new Peg(100,100); add(test); } //END CODE >Yeah, my mistake. That is correct, you should use the >getContentPane().add() not the deprecated JFrame.add(). His assignment is pure AWT, so the prof wants a Frame not a JFrame which does not have the contentPane complication. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > Thank you for your reaction! > Im using it this way: [quoted text clipped - 20 lines] > Could the problem be the version of the SDK that im using ? > I got 1.4.2. The error is telling you not to use the add() method, where you have add(test); You might want to replace that with getContentPane().add(test). - Oliver > Public class MyFrame extends Frame implements WindowListener I haven't looked at your code in detail but here: http://www.segal.org/java/tooltip6/index.html is an example of a working applet with full source code that has a Frame to which is added a custom component. The custom component extends Canvas, not Component, but maybe the example will help answer the question. Hi Neneko, > Thank you for your reaction! > Im using it this way: [quoted text clipped - 14 lines] > } > Code// As Roedy suggested in another part of this thread, you need to validate your Frame. A call to "pack()" should do that. HTH, Piet Sorry for my late reaction But thanks alot for the very usefull information! It works now! ^_^ > Hello! > [quoted text clipped - 37 lines] > for some days now. > Thanks in advance! Can you show the rest of the code? The part where you're adding it to something? Signaturemonique Ask smart questions, get good answers: http://www.catb.org/~esr/faqs/smart-questions.html >I got a bit of an problem using my self-made component. Which is that >it won't paint's itself.. >I noticed the object is being made, but for some reason the components >paint methode isn't executed. >Here is the code of the component: I don't see anything obviously wrong. Perhaps the problem is elsewhere in the code you did not provide. Your component must be added to a container and the whole thing validated and made visible. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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