Why gif animation doesn't animate when using it in paintComponent()?

问题

I'm using paintComponent() to paint a gif animated image at the backgound of JPanel. It shows up the gif but doesn't animate. I use java 1.5 and i know that i can use label with icon.

Does any body know why and how to fix it?

    private static class CirclePanel extends JPanel {

    ImageIcon imageIcon = new ImageIcon(BarcodeModel.class.getResource("verify.gif"));
    Point point = f.getLocation();
    protected void paintComponent(Graphics g) {
        Graphics gc = g.create();
        Graphics2D g2d = (Graphics2D) g.create();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.3f));
        g2d.setColor(Color.BLUE);
        g2d.drawImage(imageIcon.getImage(), getWidth() / 2, getHeight() / 2, null);
        g2d.drawRect(0, 0, getWidth(), getHeight());
        g2d.setStroke(new BasicStroke(10f,BasicStroke.CAP_ROUND,BasicStroke.JOIN_MITER));
        g2d.setFont(g.getFont().deriveFont(Font.BOLD | Font.ITALIC,15f));
        g2d.drawString("Wait Please ...",getWidth()/2-imageIcon.getIconHeight()/3,getHeight()/2+imageIcon.getIconHeight()+15);

        g2d.dispose();

}

This is the gif image.

Edited: just add image observer to the g2d.drawImage() method.

 g2d.drawImage(imageIcon.getImage(), getWidth() / 2, getHeight() / 2, this);

回答1:

The reason is that the standard Java ImageIO API only loads the first image of the gif. How to fix? Google for a Gif Loader for Java, which loads every image of the gif. Then you have to paint the right image at the right time. An alternative way would be to have different png files representing each time one frame of the animation.

Update: Well... Actually, after doing some research, it looks like the way you did it actually loads all the frames of the animated gif. The reason for it is that the ImageIcon's method getImage() always returns the first image.

To fix it, you can try this (I'm not sure if it will work...)

Instead of using Grahpics.drawImage(), use ImageIcon.paintIcon(). Like this:

imageIcon.paintIcon(this, g2d, getWidth() / 2 - imageIcon.getIconWidth() / 2, getHeight() / 2);

回答2:

Image observer will take care of it. You should just pas the observer to the g2d.drawImage(); as below.

g2d.drawImage(imageIcon.getImage(), getWidth() / 2, getHeight() / 2, this);

In my case 'this' refer to CirclePanel which extends JPanel, it can be any thing for example if you are using gif as a icon for a button, you should use button as image observer.

来源：https://stackoverflow.com/questions/11648696/why-gif-animation-doesnt-animate-when-using-it-in-paintcomponent

标签

java

swing

jpanel

animated-gif

paintcomponent