尝试在 Java GUI 中更改背景颜色和元素的绝对位置时出错

Question

我正在尝试创建一个JButton (r) 并设置其绝对位置。我也想改变背景颜色。当我像这样插入一个新的FlowLayout 时：setLayout(new FlowLayout()); 背景的颜色不会改变，而绝对位置会改变。

同时删除这个：setLayout(new FlowLayout()); 绝对位置不会改变，而颜色会改变。那么谁能解释一下为什么会发生这种情况以及我如何更改代码以使JButton 的颜色和绝对位置都发生变化？

这是我的代码：

import java.awt.*;
import java.awt.event.*;
import javax.swing.event.*;
import javax.swing.*;
import java.util.Random;

public class Back extends JFrame{

    private JButton r;
    private JButton c;
    private Container container;
    public Back(){
        super("title");
        //setLayout(new FlowLayout());
        ran = new Random();
        value = nextValue();

        r=new JButton("ROLL");
        add(r,BorderLayout.SOUTH);

        thehandler hand=new thehandler(this);//konstruktori i handler merr nje instance te Background
        r.addActionListener(hand);
    }

    private class thehandler implements ActionListener{
        public void actionPerformed(ActionEvent event) {
        }
    }

    public static void main(String[] args) {
         Back  d = new Back() ;

         d.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
         d.getContentPane().setBackground(Color.GREEN);
         d.setSize(700,500);

         d.setVisible(true);    
    }
}

Answer 1

我编辑了你的代码，以便它可以编译：

import java.awt.*;
import java.awt.event.*;
import javax.swing.event.*;
import javax.swing.*;
import java.util.Random;

public class Back extends JFrame {

    private JButton r;
    private Random ran;
    private String position = BorderLayout.NORTH;
    private Container container;

    public Back() {
        super("title");
        ran = new Random();
        int value = ran.nextInt();

        r = new JButton("ROLL");
        thehandler hand = new thehandler(this);//konstruktori i handler merr     nje instance te Background
        r.addActionListener(hand);

        this.change();

    }

    private class thehandler implements ActionListener {
        private final Back back;

        public thehandler(Back back) {
            this.back = back;
        }
        public void actionPerformed(ActionEvent event) {
            back.change();
        }
    }

    private void change() {
        this.remove(r);
        String newPos = null;
        if (position.equals(BorderLayout.NORTH))
            newPos = BorderLayout.SOUTH;
        else 
            newPos = BorderLayout.NORTH;
        this.add(r, newPos);
        this.position = newPos;
        int r = ran.nextInt(255);
        int g = ran.nextInt(255);
        int b = ran.nextInt(255);
        this.getContentPane().setBackground(new Color(r, g, b));
        this.revalidate();
        this.repaint();
    }

    public static void main(String[] args) {
        Back d = new Back();

        d.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        d.setSize(700, 500);
        d.setVisible(true);
    }
}

布局将在您的程序中排列 JComponent：因此注释或取消注释“setLayout(new FlowLayout());”行将移动按钮。有不同的布局，例如 FLowLayout、BorderLayout 或 GridLayout。我强烈建议您使用布局而不是绝对定位！

我无法重现您的问题，即删除该行会改变颜色。相反，我相信颜色在“d.getContentPane().setBackground(Color.GREEN);”行发生了变化如果你想要不同的颜色，你可以在这里设置不同的颜色！

Answer 2

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;

import javax.swing.JButton;
import javax.swing.JFrame;

public class Back extends JFrame{

/**
 * 
 */
private static final long serialVersionUID = 1L;
private JButton r;
public Back(){
    super("title");
    setLayout(null);
    r=new JButton("ROLL");
    r.setBounds(20, 20, 70, 30);
    add(r);

    Thehandler hand=new Thehandler(this);//konstruktori i handler merr nje instance te Background
    r.addActionListener(hand);
}

private class Thehandler implements ActionListener{
    private JFrame frame;
    public Thehandler(JFrame frame) {
        this.frame = frame;
    }
    public void actionPerformed(ActionEvent event) {
        Random ra = new Random();
        int r = ra.nextInt(255);
        int g = ra.nextInt(255);
        int b = ra.nextInt(255);
        Color c = new Color(r, g, b);

        frame.getContentPane().setBackground(c);

    }
}

public static void main(String[] args) {
     Back  d = new Back() ;

     d.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
     d.getContentPane().setBackground(Color.GREEN);
     d.setSize(700,500);

     d.setVisible(true);    
}
}

Answer 3

我知道这可能不是您正在寻找的答案。但是把它当作推荐。如果您想要绝对位置，则需要将布局更改为

setLayout(null);

我会推荐你​​使用 GridBagLayout： Oralce's documentation GridBagLayout

以及对我帮助很大的 youtube 视频： GridBagLayout tutorial