多层组件内的paintComponent方法内得到的height和width很小解决方案

import javax.swing.*;import javax.imageio.*;;import java.awt.*;import java.awt.geom.*;import java.io.*;public class TestTh extends JFrame{  public static void main(String[] args){    TestTh t = new TestTh();    t.setSize(600, 400);    t.setVisible(true);    t.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);    t.add(new Thumbnail("G:\\Image\\image.jpg"));  }}class Thumbnail extends JComponent{    private Image img;    double ratio;    String path;    private AffineTransform af = AffineTransform.getScaleInstance(1,1);    public Thumbnail(){        setSize(180, 200);    }    public void setPath(String path){        this.path = path;    }    public Thumbnail(String path){        this.path = path;        setSize(180, 200);        setImage();    }    private void setImage(){        try{            img = ImageIO.read(new File(path));            ratio = culculateRatio(img.getWidth(null),img.getHeight(null));            //paintImmediately(getBounds());        }catch(IOException ex){            System.out.println("Can not find this file!");        }        //paintImmediately(getBounds());        concateZoom(ratio);    }    private void concateZoom(double scale){        if (img==null)return;        af.preConcatenate(AffineTransform.getScaleInstance(scale,scale));        paintImmediately(getBounds());        System.out.println(getWidth() + "&" + getHeight());//此处输出180 & 200    }    @Override    protected void paintComponent(Graphics g) {        System.out.println(getWidth() + "*" + getHeight());//此处输出1 * 1，最终画出的图只有一个点        super.paintComponent(g);        if (img==null) {            g.setColor(Color.BLACK);            g.fillRect(0,0,getWidth(),getHeight());        }        else {            Graphics2D g2d = (Graphics2D)g;            g2d.setTransform(af);            g2d.drawImage(img, (int)(((getWidth()-img.getWidth(null)*ratio)/2)/ratio),                    (int)(((getHeight()-img.getHeight(null)*ratio)/2)/ratio), this);        }    }//paintComponent    final double culculateRatio(int width, int height){//计算缩放比率        //System.out.println(getWidth() + "*" + getHeight());        if(getWidth()>=width && getHeight()>=height)            return 1;        if((double)getWidth()/width > (double)getHeight()/height)            return (double)getHeight() / height;        else return (double)getWidth() / width;    }//culculateRatio}//Thumbnail