在JApplet中覆盖绘制方法

Question

我正在开发一个项目，使JApplet的内容自动缩放到html中指定的大小。我意识到这就是布局管理器的用途，但由于不允许重新编写整个applet结构，我决定尝试覆盖paint方法并简单地设置Graphics对象的AffineTransform为适当缩放的版本，然后在顶级容器中捕获鼠标事件并使用适当的缩放变换将它们缩小回来。目前我遇到了绘图问题。在Web浏览器中查看时，它会正确地呈现缩放版本一次，然后将图像缩小回其原始大小。此外，似乎JApplet中的paint方法只被调用一次。以下是我的代码剪辑版本，重点关注问题。任何帮助都将不胜感激。谢谢。

import javax.swing.JApplet;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;

public class Test extends JApplet
{
        public static final int ORIGINAL_APPLET_WIDTH = 1024;
        public static final int ORIGINAL_APPLET_HEIGHT = 800;
        private AffineTransform scalingTransform;
        private AffineTransform inverseScalingTransform;
 @Override
 public void init()
 {
            double xFactor = ((double)(this.getWidth()))/((double)(Test.ORIGINAL_APPLET_WIDTH));
            double yFactor = ((double)(this.getHeight()))/((double)(Test.ORIGINAL_APPLET_HEIGHT));
            this.scalingTransform = new AffineTransform();
            this.inverseScalingTransform = new AffineTransform();
            this.scalingTransform.scale(xFactor,yFactor);
            this.inverseScalingTransform.scale(1D/xFactor,1D/yFactor);
 }
    @Override
    public void paint(Graphics g)
    {
        ((Graphics2D)g).setTransform(Test.this.scalingTransform);
        super.paint(g);
    }
}

- user545199

---

虽然问题不完全相同，但是这里提供了一个例子，展示如何保存绘制时使用的变换，并将其用于将鼠标坐标映射到源图像中的像素。 - finnw

Answer 1

经过大量的研究，我发现问题在于JApplet的绘制方法很少被调用。相反，内容面板有自己的绘图表面，所以我只需要替换内容面板就可以上传了。这是我做的方式：

@Override
    public void init()
    {
            double xFactor = ((double)(this.getWidth()))/((double)(qt.ORIGINAL_APPLET_WIDTH));
            double yFactor = ((double)(this.getHeight()))/((double)(qt.ORIGINAL_APPLET_HEIGHT));
            this.scalingTransform = new AffineTransform();
            this.inverseScalingTransform = new AffineTransform();
            this.scalingTransform.scale(xFactor,yFactor);
            this.inverseScalingTransform.scale(1D/xFactor,1D/yFactor);
            JPanel drawScale = new JPanel()
            {
                @Override
                public void paint(Graphics g)
                {
                    ((Graphics2D)g).setTransform(Test.this.scalingTransform);
                    super.paint(g);
                }
                @Override
                public void paintAll(Graphics g)
                {
                    ((Graphics2D)g).setTransform(Test.this.scalingTransform);
                    super.paintAll(g);
                }
                @Override
                public void paintComponents(Graphics g)
                {
                    ((Graphics2D)g).setTransform(Test.this.scalingTransform);
                    super.paintComponents(g);
                }
                @Override
                public void paintComponent(Graphics g)
                {
                    ((Graphics2D)g).setTransform(Test.this.scalingTransform);
                    super.paintComponents(g);
                }
            };
            Container oldPane = this.getContentPane();
            drawScale.setLayout(oldPane.getLayout());

            this.setContentPane(drawScale);
}

当然，这些绘制方法是在小程序中已有的方法之外添加的。

- user545199