java - 当你有JLabel背景时如何将Jbuttons设置到特定位置: code below

Question

当您有 JLabel 背景时，如何将 Jbuttons 设置到特定位置:代码如下我无法让 jlabel 保持在顶部而按钮保持在南边(底部)？

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

public class ButtonsClass extends JFrame
              implements ActionListener {
    JButton b1 = new JButton("button1");
    JButton b2 = new JButton("button2");
    JButton b3 = new JButton("button3");
    JButton b4 = new JButton("button4");
    JLabel label = new JLabel("buttons:");

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

public Jukebox() {
    setLayout(new BorderLayout());
    setContentPane(new JLabel(new ImageIcon("image.png")));
    setLayout(new FlowLayout());
    setSize(500,150);
    setTitle("Backgroundwithbuttons");
    setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);


   JPanel top = new JPanel();

    top.add(label);
    add("North", top);
    JPanel bottom = new JPanel();
    bottom.add(b1); 
    bottom.add(b2); 
    bottom.add(b3); 
    bottom.add(b4); 
    add("South", bottom); 
    setVisible(true);
}

}

Answer 1

" i can't get the jlabel to stay at the top and the buttons to stay south(bottom)"

• 那是因为您将布局设置为 BorderLayout，然后立即将其设置为 FlowLayout。使用 FlowLayout，您的 BorderLayout 定位将不会执行任何操作。

  setLayout(new BorderLayout());
  setContentPane(new JLabel(new ImageIcon("image.png")));
  setLayout(new FlowLayout());
  

只需摆脱 setLayout(new FlowLayout());

• 你的构造函数也是错误的

  public Jukebox() {
  
  -Should be- 
  
  public ButtonClass() {
  

• 您还需要设置设置为内容 Pane 的 JLabel 的布局。您的构造函数应该如下所示

  public ButtonClass() {
      JLabel background = new JLabel(new ImageIcon("image.png"));
      background.setLayout(new BorderLayout());
      setContentPane(background);
      setTitle("Background with buttons");
      setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
  
      JPanel top = new JPanel();
      top.add(label);
      add(top, BorderLayout.NORTH);
      JPanel bottom = new JPanel();
      bottom.add(b1);
      bottom.add(b2);
      bottom.add(b3);
      bottom.add(b4);
      add(bottom, BorderLayout.SOUTH);
      //pack();
      setVisible(true);
  } 
  

• 此外，add("North", top); 是一个已弃用的方法。而是使用 add(top, BorderLayout.NORTH) 和相同的 add(bottom, BorderLayout.SOUTH)

• 此外，Swing 应用程序应在事件调度线程上运行。您可以通过使用 SwingUtilities.invokeLater...

  将代码包装在 main 中来实现此目的

  public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
          public void run() {
              new ButtonClass();
          }
      });
  }
  

• 此外，如果您希望图像显示在面板后面，则应该将面板的 opaque 属性设置为 false。

  top.setOpaque(false);
  bottom.setOpaque(false);
  

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

public class ButtonClass extends JFrame
        implements ActionListener {

    JButton b1 = new JButton("button1");
    JButton b2 = new JButton("button2");
    JButton b3 = new JButton("button3");
    JButton b4 = new JButton("button4");
    JLabel label = new JLabel("buttons:");

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new ButtonClass();
            }
        });
    }

    public ButtonClass() {
        label.setForeground(Color.WHITE);
        JLabel background = new JLabel(new ImageIcon(getClass().getResource("/resources/space.png")));
        background.setLayout(new BorderLayout());
        setContentPane(background);
        setTitle("Background with buttons");
        setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);

        JPanel top = new JPanel();
        top.setOpaque(false);
        top.add(label);
        add(top, BorderLayout.NORTH);
        JPanel bottom = new JPanel();
        bottom.setOpaque(false);
        bottom.add(b1);
        bottom.add(b2);
        bottom.add(b3);
        bottom.add(b4);
        add(bottom, BorderLayout.SOUTH);
        setSize(400, 300);
        setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent e) {}
}