One column layout does not use full width of windo

问题:

I would like to create a layout: 2 rows, 1 column. 1st row should occupy 70% height of the window and 2nd row 30% of the window. I achieve this by using weighty attribute of GridBagConstraints.

However I have problem with the width of my component, because when I resize application window the component remain in the center, its width is constant and I get a white spaces in the left and right of the component (even if I set fill to BOTH). This problem does not occur when I change the height of the window (components resize very well and fill full height of the window).

Below my constraints:

firstConstraints.gridx = 0;
firstConstraints.gridy = 0;  
firstConstraints.weighty = 0.7;
firstConstraints.fill = GridBagConstraints.BOTH;

secondConstraints.gridx = 0;
secondConstraints.gridy = 1;  
secondConstraints.weighty = 0.3;
secondConstraints.fill = GridBagConstraints.BOTH;

回答1:

I think you also need:

gbc.weightx = 1.0;

See the secton from the Swing tutorial on How to Use a GrigBagLayout that talks about the weightx, weighty constraints.

回答2:

simple example

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

public class BorderPanels extends JFrame {

    private static final long serialVersionUID = 1L;

    public BorderPanels() {
        getContentPane().setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        JPanel panel1 = new JPanel();
        Border eBorder = BorderFactory.createEtchedBorder();
        panel1.setBorder(BorderFactory.createTitledBorder(eBorder, "70pct"));
        gbc.gridx = gbc.gridy = 0;
        gbc.gridwidth = gbc.gridheight = 1;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.anchor = GridBagConstraints.NORTHWEST;
        gbc.weightx = gbc.weighty = 70;
        getContentPane().add(panel1, gbc);
        JPanel panel2 = new JPanel();
        panel2.setBorder(BorderFactory.createTitledBorder(eBorder, "30pct"));
        gbc.gridy = 1;
        gbc.weightx = 30;
        gbc.weighty = 30;
        gbc.insets = new Insets(2, 2, 2, 2);
        getContentPane().add(panel2, gbc);
        pack();
    }

    public static void main(String[] args) {
        new BorderPanels().setVisible(true);
    }
}