如何使 JPanel 中的组件尽可能伸展？

Posted 2023-02-23

【中文标题】如何使 JPanel 中的组件尽可能伸展？

【英文标题】：How to make components in a JPanel stretch as far as possible?

【发布时间】：2015-07-08 16:15:57

【问题描述】：

我正在尝试创建一个简单的挥杆程序，让用户玩一个圆圈。

这是我的代码：

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JButton;
import javax.swing.border.Border;
import javax.swing.BorderFactory;

import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.FlowLayout;
import java.awt.BorderLayout;

public class SixthProgram

    public static void main(String[] args)
    
        GUI prog=new GUI("SixthProgram");
        prog.setBounds(350,250,500,250);
        prog.setVisible(true);
    


class GUI extends JFrame implements MouseListener, MouseMotionListener

    JPanel colorPan, color1, color2, color3 ,color4 ,color5;

    int x=3,y=30; // Position of circle

    public GUI(String header)
    
        super(header);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        maker();

        addMouseListener(this);
        addMouseMotionListener(this);

        add(colorPan, BorderLayout.SOUTH);
    

    public void maker()
    
        colorPan = new JPanel();

        Border raisedbevel = BorderFactory.createRaisedBevelBorder();
        Border loweredbevel = BorderFactory.createLoweredBevelBorder();
        Border compound = BorderFactory.createCompoundBorder(raisedbevel, loweredbevel);
        colorPan.setBorder(compound);

        colorPan.setLayout(new FlowLayout(FlowLayout.CENTER));

        color1 = new JPanel();
        color2 = new JPanel();
        color3 = new JPanel();
        color4 = new JPanel();
        color5 = new JPanel();

        color1.setBackground(Color.WHITE);
        color2.setBackground(Color.GREEN);
        color3.setBackground(Color.RED);
        color4.setBackground(Color.BLUE);
        color5.setBackground(Color.BLACK);

        colorPan.add(color1);
        colorPan.add(color2);
        colorPan.add(color3);
        colorPan.add(color4);
        colorPan.add(color5);

    

    @Override
    public void paint(Graphics g)
    
        //g.setColor(Color.WHITE);
        //g.fillRect(0,0,getWidth(),getHeight());
        super.paint(g); //Do the same thing as above(Clear jframe)

        g.setColor(Color.RED);
        g.fillOval(x,y,50,50);
    

    public void mouseExited(MouseEvent e) //MouseListener overrided methods
    
        System.out.println("Exit");
    

    public void mouseEntered(MouseEvent e)
    
        System.out.println("Enter");
    

    public void mouseReleased(MouseEvent e)
    
        System.out.println("Release");
    

    public void mousePressed(MouseEvent e)
    
        System.out.println("Press");    
        x=e.getX();
        y=e.getY();
        if(x+50<getWidth() && y+50<getHeight()) // Preventing out of bounds
            repaint();
    

    public void mouseClicked(MouseEvent e) //Press+Release=Click
    
        System.out.println("Click");
        System.err.println(((JPanel)e.getSource()).getName());
    

    public void mouseDragged(MouseEvent e) //MouseMotionListener overrided methods
    
        System.out.println("Dragged to ("+ e.getX() +","+ e.getY() +")");
        x=e.getX();
        y=e.getY();
        if((x>=3 && y>=30) && (x+50<getWidth() && y+50<getHeight())) // Preventing out of bounds
            repaint();
    

    public void mouseMoved(MouseEvent e)
    
        System.out.println("Moved to ("+ e.getX() +","+ e.getY() +")");
    

我正在尝试创建具有不同颜色的 JPanel。单击颜色时，圆圈的颜色会发生变化。我还没有实现这部分。

我的问题是，当我运行上面的程序时，我得到的输出是：

但我希望输出是

我试过删除

colorPan.setLayout(new FlowLayout(FlowLayout.CENTER));

这导致了相同的输出。

如何拉伸colorPan 中的组件，以获得预期的输出？

【参考方案1】：

您可以使用GridLayout 而不是FlowLayout，如下所示：

colorPan.setLayout(new GridLayout(1, 5));

这将元素的宽度分为 1 行和 5 列，每种颜色一个。

【讨论】：

谢谢。我可能会添加更多颜色。所以，我将使用colorPan.setLayout(new GridLayout(1, 0));

【参考方案2】：

更改以下内容：

colorPan.setLayout(new FlowLayout(FlowLayout.CENTER));

到将内容拉伸以适应的布局，例如GridLayout：E.G.

colorPan.setLayout(new GridLayout(1,0));

【参考方案3】：

试试：

colorPan.setLayout(new BoxLayout(colorPan,BoxLayout.LINE_AXIS));