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[Java] Loading Images

Started by monp Sep 30, 2010 at 1:33 PM 8 replies 1.9k views

Original Post

Sep 30, 2010 at 1:33 PM

I am trying to load an image but I am receiving two errors, cannot find symbol on Class URL, also cannot find symbol variable image.

import javax.swing.*;import java.awt.*;import java.awt.Toolkit;import java.awt.Image;class ImageLoader extends JComponent{	public void ImageLoader()	{		Toolkit toolkit = Toolkit.getDefaultToolkit();		URL file = getClass().getResource("test.jpeg");		Image image = toolkit.getImage(file);			}		public void paintComponent(Graphics g)	{		int x = 0;		int y = 0;		g.drawImage(image,x,y,this);	}}

Erik Rufelt

Sep 30, 2010 at 1:45 PM

import java.net.URL and move Image image outside of the constructor, making it a class member variable.

rip-off

Sep 30, 2010 at 1:45 PM

Can you post the full compiler output? You will need to make "Image image" a field, otherwise it will not work, and you should delete the "void" return type in the constructor definition, constructors do not have a return type. But the compiler should be able to parse that...

monp

Sep 30, 2010 at 1:49 PM

Alright I got that working, but when I load the program the image does not show up.

Here is the main part.

import javax.swing.*;import java.awt.*;import java.awt.event.*;public class Paravola{	public static void main(String[] args)	{		JFrame frame = new JFrame("Paravola Outbreak");		frame.add(new ImageLoader2());		frame.setSize(640,480);		frame.setResizable(false);		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);		frame.setVisible(true);	}}

and here is the fixed code.

import javax.swing.*;import java.awt.*;import java.awt.Toolkit;import java.awt.Image;import java.net.*;class ImageLoader2 extends JComponent{	URL file;	Image image;	public void ImageLoader2()	{		Toolkit toolkit = Toolkit.getDefaultToolkit();		file = getClass().getResource("test.jpg");		image = toolkit.getImage(file);			}		public void paintComponent(Graphics g)	{		int x = 0;		int y = 0;		g.drawImage(image,x,y,this);	}}

Gage64

Sep 30, 2010 at 1:52 PM

Like rip-off said, remove the 'void' before the constructor.

monp

Sep 30, 2010 at 1:55 PM

Ok. Thanks for all of your help.

monp

Sep 30, 2010 at 4:36 PM

Now with this how would I go about loading an image then having repaint load a different image?

rip-off

Sep 30, 2010 at 5:23 PM

Are you trying to display an animation? Loading an image during repaint will be non-deterministic as swing will take efforts to avoid needlessly repainting the screen.

Anyway, in general you want to avoid image loading at runtime as it is slow. Instead load any images you need at the start - unless there are too many of them, or they are extremely large.

monp

Sep 30, 2010 at 5:36 PM

Yes, right now I am trying to load a small animation into my application.

rip-off

Sep 30, 2010 at 5:42 PM

Searching Google for animations in swing gives several promising results.

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