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Thread: problem with paintComponent

  1. #1
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    Default problem with paintComponent

    import java.awt.Graphics;
     
    import javax.swing.JComponent;
    import javax.swing.JFrame;
    import javax.swing.JPanel;
     
    public class Painting extends JFrame {
    	public Painting() {
    		JPanel panel = new JPanel();
    		this.setSize(333, 200);
    		this.setVisible(true);
     
    		this.add(panel);
     
    		panel.add(new Extra("Jasmin Rahimic"));
    		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    	}
     
    	public static void main(String[] args) {
    		Painting c = new Painting();
    	}
    }
     
    class Extra extends JComponent {
    	String str;
     
    	public Extra(String s) {
    		this.setSize(70, 70);
    		this.str = s;
    	}
     
    	public void paintComponent(Graphics g) {
    		g.drawString(str, 50, 50);
    	}
    }

    Can someone tell me why paintComponent() is not being called.
    Thank you.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: problem with paintComponent

    First thing to check: add an @Override in front of it to be sure you are overriding and not creating a new method.
    Call setVisible() AFTER all your GUI has been put together.

    Override the getPreferredSize() method.
    Last edited by Norm; July 21st, 2011 at 02:51 PM.

  3. #3
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    Default Re: problem with paintComponent

    try to add LayoutManager to your panel GridLayout will be good for this example.
    By the way...u dont have to use "this" into Painting class...Methods like setSize and others refer to your class automatically...(because she inherent from JFrame)
    Last edited by remigio; July 21st, 2011 at 02:49 PM.

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  5. #4
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    Default Re: problem with paintComponent

    Word to the wise, call the super constructor beforehand.

    So put this as the first call in your constructor:
    super();

    If that doesn't work, put the super.paintComponent call in your paintComponent method.
    So have this instead:
    public void paintComponent(Graphics g) {
    super.paintComponent(g);
    		g.drawString(str, 50, 50);
    	}

    The next thing I would do is confirm the JComponent is showing up like you'd expect. The easiest way of doing it would be to create a border around the JComponent. Putting this line in your Extra constructor will handle that for you:
    setBorder(javax.swing.BorderFactory.createLineBorder(java.awt.Color.black));

    If the component does not show up (you won't see a border, or it will be very small), try using the setPreferredSize() method instead of the setSize method.

    If, after you've confirmed the JComponent is showing and you've added the super call in the constructor and the paintComponent, call the repaint method on the created Extra object. If all of that doesn't work, then I'll need more info on the problem.
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    jasox (July 21st, 2011)

  7. #5
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    Default Re: problem with paintComponent

    Thank you guys.

  8. #6
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    Default Re: problem with paintComponent

    You can just call setPreferredSize(..) in the Extra constructor (instead of calling setSize(..) or overriding setPreferredSize(..)). But the width of 70 id unlikely to be big enough to display the whole string you want to use.

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