为什么我的 Jpanel borderlayout 没有按预期工作？

Question

我正在向 JPanel、JLabel 和 JButton 添加 2 个元素。我希望它们彼此重叠，所以我使用 BorderLayout.NORTH 和 SOUTH.

添加了它们

我遇到的问题是 JLabel JButton 和 JLabel JButton 彼此水平并排放置，而不是像预期的那样彼此重叠。这个问题可能与我还使用 borderlayout 添加到框架的其他面板有关，如下所示。

这是一个 SSCE 来演示我的问题。您会注意到，如果展开 window，您会在 JLabel 的左侧看到 JButton。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Question {
    /**
     * @param args
     */
    public static void main(String[] args) {
        gui();
    }

    public static void gui() {

        final JFrame theFrame = new JFrame();
        theFrame.setSize(550, 290);

        theFrame.setLocationRelativeTo(null);

        // options for the JComboBox
        String[] options = { ("1"), ("2"), ("3") };

        final JPanel thePanel = new JPanel();
        JLabel aMessage = new JLabel(
                "<html>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus tempus<br> lacus eu ante vestibulum tincidunt. Donec venenatis rhoncus justo sit amet <br>gravida. Pellentesque habitant morbi tristique senectus et netus et malesuada<br>est ac mattis. Donec lobortis rhoncus quam. In at vulputate ipsum<br>to fix. Phasellus tempus lacus eu ante vestibulum tincidunt. Donec venenatis rhoncus<br>turpis quam sagittis arcu, non pulvinar purus leo ege.<br><br><br></html>");
        aMessage.setVisible(true);

        JButton theButton = new JButton();
        theButton
                .setText("<HTML><FONT color=\"#000099\"><U>Click here</U></FONT>"
                        + " if you would like to view some file.</HTML>");

        theButton.setBorderPainted(false);
        theButton.setOpaque(false);
        theButton.setBackground(Color.WHITE);
        theButton.setVisible(true);

        thePanel.add(aMessage, BorderLayout.NORTH);
        thePanel.add(theButton, BorderLayout.SOUTH);

        // create second panel
        final JPanel secondPanel = new JPanel();
        JLabel bMessage = new JLabel("Here's another Jlabel");
        final JComboBox cBox = new JComboBox(options);
        // would be nice to get bmessage + cBox left aligned
        secondPanel.add(bMessage);
        secondPanel.add(cBox);

        // create third panel
        final JPanel thirdPanel = new JPanel();
        JLabel cMessage = new JLabel("Here's a third message");
        String newString = ("Hello");
        JTextField stringInput = new JTextField(newString);
        stringInput.setPreferredSize(new Dimension(250, 20));
        thirdPanel.add(cMessage);
        thirdPanel.add(stringInput);


        JButton lastButton = new JButton("A Button");

        thirdPanel.add(cMessage);
        thirdPanel.add(stringInput);
        thirdPanel.add(lastButton);

        theFrame.add(thePanel, BorderLayout.NORTH);
        theFrame.add(thirdPanel, BorderLayout.SOUTH);
        theFrame.add(secondPanel, BorderLayout.CENTER);

        theFrame.setVisible(true);
    }

}

Answer 1

在哪里设置 thePanel JPanel 的布局？答：你不需要，所以它默认使用 FlowLayout。解决方案：通过 setLayout(...)

将布局设置为您想要的布局

例如，

thePanel.setLayout(new BorderLayout());

为什么我的 Jpanel borderlayout 没有按预期工作？

Why doesn't my Jpanel borderlayout work as expected?

java

swing

jpanel

layout-manager

border-layout