Java Swing - JTabbedframe 左上角的位置面板

Question

由于工作变动，我不得不从 Python TKinter 迁移到 Java Swing。

我遇到的问题是：

如何在JTabbedFrame 的左上角定位包含标签和文本字段等对象的面板。

如果 frame 本身比 panel 大，JPanel 在页面上默认居中。

到目前为止，这是我的代码：

public class GUI {

    //Constructor
    GUI(){
        //Craete a new frame
        //borderlayout
        JFrame jfrm = new JFrame("Tabbed Demo");            
        //Intialize size
        jfrm.setSize(500, 250);         
        //Terminate program 
        jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);            
        //Create Tabbed Frame
        JTabbedPane jtp = new JTabbedPane(JTabbedPane.TOP);         
        //Create a panel to place on tabbed page
        JPanel jpnl = new JPanel();
        jpnl.setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.fill=GridBagConstraints.HORIZONTAL;
        gbc.insets = new Insets(5,5,5,5);           
        jpnl.setOpaque(true);
        jpnl.setComponentOrientation(ComponentOrientation.LEFT_TO_RIGHT);
        //create a 3 labels horizontally            
        gbc.gridx=1;
        gbc.gridy=0;
        JLabel title= new JLabel(" Tracking System   ");
        title.setFont(new Font("Serif", Font.PLAIN, 40));
        jpnl.add(title,gbc);
        gbc.gridx=0;
        gbc.gridy=1;    
        JLabel subtitle= new JLabel("First");
        subtitle.setFont(new Font("Serif", Font.PLAIN, 18));
        jpnl.add(subtitle,gbc);
        gbc.gridx=1;
        gbc.gridy=1;
        JTextArea firstText = new JTextArea("Type Here!");
        firstText.setFont(new Font("Serif", Font.PLAIN, 18));
        jpnl.add(firstText,gbc);            
        gbc.gridx=0;
        gbc.gridy=2;            
        JLabel subtitle2= new JLabel("Last");
        jpnl.add(subtitle2,gbc);
        subtitle2.setFont(new Font("Serif", Font.PLAIN, 18));           
        //add to Tab
        jtp.addTab("Demo", jpnl);           
        //make visible
        jfrm.getContentPane().add(jtp);         
        jfrm.setVisible(true);
    }

    public static void main(String[] args) {
        // launch app

        //create the frame on the event dispaytching thread
        SwingUtilities.invokeLater(new Runnable(){
            public void run(){
                new GUI();
            }
        });
    }    
}

结果如下图

我想要做的是将JPanel的位置移动到左上角，无论框架有多大，例如标签页的位置0,0。覆盖JPanel的居中。

我正在使用GridBaglayout 经理。

Answer 1

不要低估 MigLayout 之类的功能，但如果您被困在一个限制第三方库的项目上，那么知道如何操作默认布局管理器是您可以培养的最重要的技能之一

您可以简单地在布局中添加一个“填充”组件，将其设置为 weightx 和 weighty 属性以填充可用空间

import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestLayout {

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

    public TestLayout() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.gridwidth = 2; //GridBagConstraints.REMAINDER;
            gbc.insets = new Insets(4, 4, 4, 4);

            JLabel title = new JLabel("Tracking System");
            title.setFont(title.getFont().deriveFont(40f));
            add(title, gbc);

            gbc.gridy++;
            gbc.gridwidth = 1;
            gbc.anchor = GridBagConstraints.WEST;
            add(new JLabel("First: "), gbc);
            gbc.gridy++;
            add(new JLabel("First: "), gbc);

            gbc.gridx++;
            gbc.gridy = 1;
            gbc.gridwidth = 1;
            gbc.anchor = GridBagConstraints.WEST;
            gbc.fill = GridBagConstraints.HORIZONTAL;
            add(new JTextField(10), gbc);
            gbc.gridy++;
            add(new JTextField(10), gbc);

            gbc.gridx++;
            gbc.gridy++;
            gbc.weightx = 1;
            gbc.weighty = 1;
            // Blank/filler component
            add(new JLabel(), gbc);
        }

    }

}

通过改变

gbc.gridwidth = 2; //GridBagConstraints.REMAINDER;

到

gbc.gridwidth = GridBagConstraints.REMAINDER;

我也可以影响title的位置

但您也可以使用anchor 属性来实现它。您使用的将取决于您的需求

查看How to Use GridBagLayout了解更多详情