Graphics error
I am trying to draw a photograph in a JFrame with some other information. I set up and load the Image and draw it to a buffered image. When I go and get the graphics from the panel I want to draw to, I get null back. My code look like:
backbuffer =new BufferedImage(photoPanel.getWidth(), photoPanel.getHeight(), BufferedImage.TYPE_INT_RGB);
g2 = backbuffer.createGraphics();
try{
photo = tk.getImage(photopath);
}catch (Exception e){
photo = tk.getImage("images/null.png");
}
g2.drawImage(photo, 0, 0, photoPanel.getWidth(), photoPanel.getHeight(),null);
if (photoPanel.getGraphics() ==null){
System.out.println("Null Graphics");
}else{
photoPanel.getGraphics().drawImage(backbuffer,640,20,200,200,this);
}
Both the JPanel (photoPanel) and JFrame return nothing. This is the first time I have run into a problem like this. The class file I am writing extends JFrame and the JPanel is a local variable.
I am using Java 1.6 and Net Beans 5.5
[1568 byte] By [
Sideina] at [2007-11-27 8:18:01]
# 1
If the gui is not realized then none of the components such as JFrame and JPanel will have a
non–null graphics context. Using getGraphics is a con anyway. Use a JPanel and
override paintComponent for proper drawing.
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.*;
public class FrameExtension extends JFrame {
BufferedImage backbuffer;
BufferedImage photo;
public FrameExtension() {
loadImage();
getContentPane().add(photoPanel);
setSize(400,400);
System.out.println("graphics context before realization = " +
photoPanel.getGraphics());
setVisible(true);
System.out.println("graphics context after realization = " +
photoPanel.getGraphics());
}
private void loadImage() {
String photopath = "images/cougar.jpg";
boolean groping = true;
while(groping) {
try {
photo = ImageIO.read(new File(photopath));
groping = false;
} catch (Exception e) {
System.out.println("Load error: " + e.getClass().getName() +
" " + e.getMessage());
if(photopath.equals("images/null.png"))
groping = false;
photopath = "images/null.png";
}
}
}
JPanel photoPanel = new JPanel() {
protected void paintComponent(Graphics g) {
if(backbuffer == null) {
backbuffer = new BufferedImage(getWidth(), getHeight(),
BufferedImage.TYPE_INT_RGB);
Graphics2D g2 = backbuffer.createGraphics();
g2.setBackground(getBackground());
g2.clearRect(0, 0, getWidth(), getHeight());
g2.drawImage(photo, 0, 0, null);
g2.dispose();
}
g.drawImage(backbuffer,0,0,this);
}
};
public static void main(String[] args) {
new FrameExtension();
}
}
