java - PaintComponent() 的问题

Question

public class ImagePreview extends JPanel {

    private static final long serialVersionUID = 1L;
    final float ratio = 1.0f;
    private RenderedImage image;

    public ImagePreview (int imgWidth, int imgHeight) {

        this.setPreferredSize(new Dimension((int) (ratio * imgWidth) + 5, (int) (ratio * imgHeight) + 5));
    }

    public ImagePreview (int imgWidth, int imgHeight, final RenderedImage image) {
        super();
        this.setPreferredSize(new Dimension((int) (ratio * imgWidth) + 5, (int) (ratio * imgHeight) + 5));
        this.image = image; 
        repaint();
    }

    @Override
    public synchronized void paintComponent(Graphics g) {
        super.paintComponent(g);
        VectorGraphics g2 = VectorGraphics.create(g);
        if (image != null) {
            g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            g2.drawRenderedImage(image, AffineTransform.getScaleInstance(ratio, ratio));
        }
    }
}

单击按钮时调用此方法 //调用这个方法 ImagePreview 购物车 = new ImagePreview(imgWidth, imgHeight, image);

我正在获取图像，但它没有在面板上重新绘制。我无法确定背后的原因

Answer 1

But i just want to create a preview panel for the image

当你进行自定义绘画时，你需要重写面板的getPreferredSize()方法来返回图像的大小，否则大小为(0, 0)，所以没有什么可画的.

VectorGraphics g2 = VectorGraphics.create(g);

不要使用第 3 方类发布代码。我们不知道问题是出在您的代码还是类上。

如果您需要更多帮助，请发布适当的SSCCE这说明了问题。