how change the update images

[mDennis10]

i am writing a program that every time the user selects an item from a combo box the image in a panel changes.The problem im having is that i want to know how to update the image when the person selects the a new item using the paintComponent method. this is the code for the class that draws the image

import java.io.*;
import java.awt.image.*;
import java.awt.*;

import javax.imageio.ImageIO;
import javax.swing.*;

public class DrawImage extends JPanel {

	private String imgUrl;
	
	//constructor
	public DrawImage (String imgUrl)
	{
		setImageUrl (imgUrl);
	}//end constructor
	
	//constructor
	public DrawImage ()
	{
		
	}//end constructor
	
	/**
	 * setImageUrl method
	 * 
	 * this method sets the url of image 
	 * which will be drawn to the screen. */
	public void setImageUrl (String imgUrl)
	{
		this.imgUrl = imgUrl;
	}//end  setImageUrl method
	
	
	
	/**
	 * getImageUrl method
	 * 
	 * gets the url of image */
	public String getImageUrl ()
	{
		return imgUrl;
	}//end getImageUrl method
	
	
	
	//Draws image to panel
	public void paintComponent (Graphics g)
	{
		super.paintComponents (g);
		
		BufferedImage img = null;
		
		try		//creates bufferedImage
		{
			img = ImageIO.read(new File (imgUrl));
		}
		
		catch (IOException e)
		{
			e.printStackTrace ();
		}//end catch
		
		g.drawImage (img,0,0,null);
	}//end paintComponent method
	
}//end DrawImage class

[Fubarable]

Never read in an image or any other type of file from within a paint or paintComponent method as this at best will slow down your application's ability to paint itself or freeze your application at worst. Much better is to read in the BufferedImage from within the setImageUrl method, and then once done, to call repaint.

[mDennis10]

thanks

[mDennis10]

the repaint method which class does that belong or better yet give me example has how to repaint, this were im at now:

public void setImageUrl (String imgUrl)
	{
		this.imgUrl = imgUrl;
		
		BufferedImage img = null;
		try
		{
			img= ImageIO.read(new File (imgUrl));
		}
		catch (IOException e)
		{
			e.printStackTrace();
		}
		
	}//end  setImageUrl method

[Fubarable]

You'll want to repaint object that draws the image, your DrawImage class. You'll need to draw the image in the paintComponent method after checking first that it's not null.

[mDennis10]

wait, so how do i paint it without using the paintComponent method in the first place

[Fubarable]

wait, so how do i paint it without using the paintComponent method in the first place

You use paintComponent, and in fact draw your BufferedImage in this method using the Graphics object, g's, drawImage method, but only first after checking that the image is not null. What you do is make your BufferedImage variable, img, a class field, then read in the BufferedImage into img in your setImageUrl method. Then call repaint(). This will make the JVM call paintComponent and thereby draw your image.

[camickr]

See: How to Use Combo Boxes (The Java™ Tutorials > Creating a GUI With JFC/Swing > Using Swing Components) for a working example.