Question

为什么以下代码单独放在JPanel子类的构造函数中，会在split_pane左边但在mQueryField之上生成一个比例空的空格？

mMessageArea = new JTextArea ();
JScrollPane message_pane = new JScrollPane (mMessageArea);

mTableView = new JTable ();
mTableView.setFillsViewportHeight (true);
JScrollPane table_pane = new JScrollPane (mTableView);

JSplitPane split_pane = new JSplitPane (JSplitPane.VERTICAL_SPLIT,
        message_pane, table_pane);

mQueryField = new JTextField ();
mQueryField.setMaximumSize (new Dimension (Short.MAX_VALUE, 20));

setLayout (new BoxLayout (this, BoxLayout.Y_AXIS));
add (split_pane);
add (mQueryField);

编辑 - SSCCE：

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

public class SSCCE extends JPanel
{

    private JTextArea mMessageArea;
    private JTable mTableView;
    private JTextField mQueryField;

    public SSCCE ()
    {
        mMessageArea = new JTextArea ();
        JScrollPane message_pane = new JScrollPane (mMessageArea);

        mTableView = new JTable ();
        mTableView.setFillsViewportHeight (true);
        JScrollPane table_pane = new JScrollPane (mTableView);

        JSplitPane split_pane = new JSplitPane (JSplitPane.VERTICAL_SPLIT,
                message_pane, table_pane);

        mQueryField = new JTextField ();
        mQueryField.setMaximumSize (new Dimension (Short.MAX_VALUE, 20));

        setLayout (new BoxLayout (this, BoxLayout.Y_AXIS));
        add (split_pane);
        add (mQueryField);
    }

    public static void main (String[] args)
    {
        JFrame frame = new JFrame ();
        frame.add (new SSCCE ());
        frame.setVisible (true);
        frame.pack ();
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
    }

}

Answer 1

也许是因为JSplitPane的最大尺寸不够大。您可以将其设置或嵌套在使用BorderLayout的JPanel中：

  JSplitPane split_pane = new JSplitPane(JSplitPane.VERTICAL_SPLIT,
        message_pane, table_pane);
  JPanel splitHolder = new JPanel(new BorderLayout());
  splitHolder.add(split_pane);

  mQueryField = new JTextField();
  mQueryField.setMaximumSize(new Dimension(Short.MAX_VALUE, 20));

  setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));
  add(splitHolder);
  add(mQueryField);

顺便说一句，SSCCE为1+。它使您的问题更多更容易。

修改
我错了，问题只是对齐，因为JTextFields默认为Component.CENTER_ALIGNMENT的x对齐。设置解决方案将X对齐设置为左侧：

JSplitPane split_pane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, message_pane, table_pane); System.out.println("split_pane.getAlignmentX() before:" + split_pane.getAlignmentX()); split_pane.setAlignmentX(LEFT_ALIGNMENT); // NOT REALLY NEEDED System.out.println("split_pane.getAlignmentX() after:" + split_pane.getAlignmentX()); mQueryField = new JTextField(); mQueryField.setMaximumSize(new Dimension(Short.MAX_VALUE, 20)); System.out.println("mQueryField.getAlignmentX() before: " + mQueryField.getAlignmentX()); mQueryField.setAlignmentX(LEFT_ALIGNMENT); System.out.println("mQueryField.getAlignmentX() after: " + mQueryField.getAlignmentX());

Answer 2

JSplitPane在方法pack()后知道自己的大小，使用BorderLayout

可以解决此问题

为什么这段代码会产生比例空的空间？

2 个答案: