java - 创建 VolatileImage 总是返回 null

Question

我在下面的类中创建了一个可变图像，但每次都会遇到 NullPointerException。 createVolatileImage() 返回 null(从其 JavaDoc)的原因是 GraphicsEnvironment.isHeadless() 为真。

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.VolatileImage;
import javax.swing.JPanel;

public class Tube extends JPanel {

    private VolatileImage image;
    private int width, height;

    public Tube() {
        super(true);
    }

    public Tube(int width, int height) {
        this.width = width;
        this.height = height;
        createImage();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        if(image == null)
            createImage();
        if(image.validate(getGraphicsConfiguration()) == VolatileImage.IMAGE_INCOMPATIBLE)
            createImage();
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
                RenderingHints.VALUE_TEXT_ANTIALIAS_LCD_HRGB);
        g2.drawImage(image, 0, 0, this);
    }

    public VolatileImage getBufferedImage() {
        return this.image;
    }

    private void createImage(){
        if(image != null){
            image.flush();
            image = null;
        }
        image = createVolatileImage(width, height);
        image.setAccelerationPriority(1.0f);
    }
}

我怎样才能返回一个非空的 VolatileImage ？？

Answer 1

这将改变 headless 模式:

System.setProperty("java.awt.headless", "false");