调整JLabel的大小以适应调整后的主JPanel的大小

问题描述

我有两个子面板和一个父面板（​​背景）。我的目标是在JLabel icon面板调整大小后在firstPanel中调整main的大小。我尝试使用StretchIcon，但仅在将JLabel icon添加到main时有效。 现在我的代码：

    import darrylbu.icon.StretchIcon;
    import javax.imageio.ImageIO;
    import javax.swing.*;
    import java.awt.*;
    import java.awt.image.BufferedImage;
    import java.io.IOException;
    import java.net.URL;

public class Task {
JFrame frame;
JPanel main;

public static void main(String args[]) {
    new Task();
}

public Task() {
    frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setPreferredSize(new Dimension(600,400));
    main = mainPanel();
    frame.add(main);
    main.add(firstPanel());
    main.add(secondPanel());
    frame.pack();
    frame.setVisible(true);
}

private JPanel mainPanel(){
    JPanel main_panel = new JPanel() {
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            BufferedImage background = null;
            try {
                background  = ImageIO.read(new URL("https://jpegshare.net/images/17/b0/17b0bad019ea5e37c84a5147a33b0ce7.jpg"));
            } catch (IOException e) {
                e.printStackTrace();
            }
            g.drawImage(background,this.getWidth(),this.getHeight(),this);
        }
    };
    main_panel.setLayout(new OverlayLayout(main_panel));
    main_panel.setLayout(new GridLayout(1,2));
    return main_panel;
}

private JPanel firstPanel() {
    JPanel first_panel = new JPanel();
    first_panel.setOpaque(false);
    BufferedImage image = null;
    try {
        image = ImageIO.read(new URL("https://jpegshare.net/images/7a/f3/7af3bfc51cb1170be9f5655d643147d7.png"));
    } catch (IOException e) {
        e.printStackTrace();
    }
    StretchIcon img = new StretchIcon(image);
    JLabel icon = new JLabel(img);
    first_panel.add(icon);
    first_panel.setLayout(getLayout());
    return first_panel;
}

private JPanel secondPanel(){
    JPanel second_panel = new JPanel() {
        @Override
        public Dimension getMaximumSize() {
            return new Dimension(300,400);
        }
        @Override
        public void paintComponent(Graphics g) {
            BufferedImage image = null;
            try {
                image = ImageIO.read(new URL("https://jpegshare.net/images/17/bc/17bc21f519133ca31f857a65c897925a.jpg"));
            } catch (IOException e) {
                e.printStackTrace();
            }
            g.drawImage(image,getWidth() / 2,getHeight() / 2,this);
        }
    };
    second_panel.setLayout(new BoxLayout(second_panel,BoxLayout.Y_AXIS));

    String [] resources = {"flowers","nyanko","tutturu~"};
    for(String s : resources){
        JLabel label = new JLabel(0 + " " + s);
        label.setFont(new Font("Serif",Font.BOLD,18));
        second_panel.add(label);
    }

    return second_panel;
}

private GridBagLayout getLayout() {
    GridBagLayout gridBagLayout = new GridBagLayout();
    gridBagLayout.rowHeights = new int[]{0,0};
    gridBagLayout.rowWeights = new double[]{0.0,0.0,1.0,1.0};
    gridBagLayout.columnWidths = new int[]{0,0};
    gridBagLayout.columnWeights = new double[]{0.0,1.0};
    return gridBagLayout;
}

}
    

解决方法

您可以通过将一个大小调整侦听器附加到主面板来解决此问题。我假设您想精确调整JLabel的大小，您调整了主面板的大小。这是您可以实现的方法：

private Dimension main_size = null; //Inital Dimension of main JPanel
main.addComponentListener(new ComponentAdapter() {
              @Override
              public void componentResized(ComponentEvent e) {
                //This method is called everytime main panel is resized
                  if((main_size==null) ||
                     (main_size.width==0 && main_size.height==0)) {
                      main_size=main.getSize();
                  }
                  updateJLabelSize(icon,e.getComponent().getSize());
              }
            });       

//Method for updating JLabel size
private void updateJLabelSize(JLabel icon,Dimension newSize) {
        int heightDifference = newSize.height - main_size.height;
        int widthDifference = newSize.width - main_size.width;
        icon.setSize(new Dimension(icon.getWidth() + widthDifference,icon.getHeight()+heightDifference));
        main_size = newSize;
    }