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java – 为什么我的Jpanel borderlayout不按预期工作？

2019-06-12 02:02:03 作者：互联网

我在JPanel,JLabel和JButton中添加了2个元素.我希望它们彼此叠加,所以我使用BorderLayout.NORTH和SOUTH添加它们.

我遇到的问题是JLabel JButton并排坐在彼此旁边,而不是像预期的那样彼此叠加.这个问题可能与我使用borderlayout将其他面板添加到框架的事实有关,如下所示.

这是一个SSCE来演示我的问题.您会注意到,如果展开窗口,您将看到JLabel左侧的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);
    }

}

解决方法:

你在哪里设置thePanel JPanel的布局？答：你没有,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());

标签：java,swing,jpanel,layout-manager,border-layout
来源： https://codeday.me/bug/20190612/1222629.html