Java - 如何防止BorderLayout EAST拥抱屏幕的一侧？

Question

If I add components like JButton s on the East or West side, how do I prevent it from hugging the side of the screen? I want some space between the JButton s and the edge of the screen.

Answer 1

call setBorder on your JButton like this:

setBorder( new EmptyBorder( 3, 3, 3, 3 ) )

From the JavaDoc, an EmptyBorder is a "transparent border which takes up space but does no drawing". In my example it shall take 3 pixels respectively top, left, bottom and right.

Complete code whose purpose is only to show how to use EmptyBorder:

import java.awt.BorderLayout;
import java.awt.Container;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.border.EmptyBorder;

public class ALineBorder {

    public static void main(String args[]) {
        JFrame frame = new JFrame("Line Borders");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        JButton button1 = new JButton("Button1");
        button1.setBorder( new EmptyBorder( 8, 8, 8, 8 ) );
        JButton button2 = new JButton("Button2");
        JButton button3 = new JButton("Button3");
        button3.setBorder( new EmptyBorder( 16, 16, 16, 16 ) );
        Container contentPane = frame.getContentPane();
        contentPane.add(button1, BorderLayout.WEST);
        contentPane.add(button2, BorderLayout.CENTER);
        contentPane.add(button3, BorderLayout.EAST);
        frame.pack();
        frame.setSize(300, frame.getHeight());
        frame.setVisible(true);
    }

}

Answer 2

Most likely you have (or soon will have) more than one button in the container, and want to align them horizontally. So consider putting the buttons within in a nested JPanel with a GridBagLayout :

class ButtonPanel extends JPanel {
    ButtonPanel() {
        setLayout(new GridBagLayout());
    }

    @Override
    public Component add(Component button) {
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridy = nextGridY++;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.insets = new Insets(3, 3, 3, 3);
        super.add(button, gbc);
        return button;
    }

    int nextGridY;
}

Then add this panel to the parent frame or panel (with a BorderLayout .)

Answer 3

BorderLayout goes as the name says to the border. You can however nest things inside, so you could insert a JPanel with a border and then put your button in that.

You may also want to experiment with the GUI designer in Netbeans. It is really quite nice, and give a lot of help to things you usually want to do (like have a margin to the border, etc).