可滚动 JTextField 的大小调整问题

Question

我有一个包含大量文本字段的表单，其中一些文本字段可能包含很长的字符串。为了使它工作，我使用以下代码使这些文本字段可滚动：

JScrollPane scroll = new JScrollPane(textField);
scroll.setPreferredSize(new Dimension((int)textField.getPreferredSize().getWidth(), (int)textField.getPreferredSize().getHeight() * 2));

然后我使用 GridBagLayout 将滚动条放入表单中。

我的示例中的第二行是显示滚动条所必需的。但它有缺点。当我调整窗口大小以适应文本字段中的整个文本时，滚动消失让我只比其他文本字段高两倍，这看起来很荒谬。 隐藏滚动条后，如何使这一切正常工作并显示正常大小的文本字段？

编辑：

您可以使用以下演示代码来重现该问题：

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

public class ScrollTextDemo extends JFrame{

public  ScrollTextDemo(){
    super();
    this.setPreferredSize(new Dimension(500, 300));
    JPanel panel = new JPanel();
    panel.setLayout(new GridBagLayout());
    JTextField textField = new JTextField("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
    textField.setCursor(new Cursor(0));
    textField.setEditable(false);
    JScrollPane scroll = new JScrollPane(textField);
    scroll.setPreferredSize(new Dimension(70, 40) );
    GridBagConstraints gbc = new GridBagConstraints();
    gbc.gridx = 1;
    gbc.gridy = 1;
    gbc.fill = GridBagConstraints.HORIZONTAL;
    gbc.weightx = 0.5;
    gbc.insets = new Insets(5, 5, 0, 5);
    panel.add(scroll,gbc);
    //let's add one more text field without scroll bar to compare
    JTextField textField2 = new JTextField("abc");
    gbc = new GridBagConstraints();
    gbc.gridx = 1;
    gbc.gridy = 2;
    gbc.fill = GridBagConstraints.HORIZONTAL;
    gbc.weightx = 0.5;
    gbc.insets = new Insets(5, 5, 0, 5);
    panel.add(textField2,gbc);
    this.add(panel);
} 

public static void main(String args[]){
    ScrollTextDemo demo = new ScrollTextDemo();
    demo.pack();
    demo.setVisible(true);
}
}

Answer 1

为此，在没有好的SSCCE 的情况下，我认为您没有提供任何用于填充的约束，用于

当组件的显示区域大于组件请求的大小时使用，以确定是否以及如何调整组件的大小。有效值（定义为 GridBagConstraints 常量）包括 NONE（默认）、HORIZONTAL（使组件足够宽以水平填充其显示区域，但不改变其高度）、VERTICAL（使组件足够高以垂直填充其显示区域，但不改变其宽度）和 BOTH（使组件完全填满其显示区域）。

所以你必须在你的 GridBagConstraints 中添加这样的东西

constraintsGridBag.fill = GridBagConstraints.HORIZONTAL;

这只允许它横向扩展，而不是双向扩展。

** 编辑：至于添加的代码 **

永远不要为 Swing 中的任何组件指定 setPreferredSize(...)。让您正在使用的布局管理器注意这一点。删除所有 setPreferredSize(...) 事物，使其在调整大小时保持正常大小。

*编辑 2：*

代码告诉你我在说什么：

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;

import java.awt.event.*;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;

public class GridBagTest extends JFrame
{
    private JPanel topPanel;
    private JPanel bottomPanel;

    public GridBagTest()
    {
        setLayout(new GridBagLayout());

        GridBagConstraints gbc = new GridBagConstraints();      
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        //gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.fill = GridBagConstraints.BOTH;
        gbc.weightx = 1.0;
        gbc.weighty = 0.8;

        // Setting TOP PANEL.
        topPanel  = new JPanel();
        topPanel.setLayout(new GridBagLayout());
        GridBagConstraints constraintsTopPanel = new GridBagConstraints();
        constraintsTopPanel.gridwidth = 2; // Specifies that this component will take two columns.
        constraintsTopPanel.gridheight = 1; // specifies that the component will take one row.
        /*
         *  fill with HORIZONTAL, means the component upon resize, will
         * only expand along the X-Axis.
         */
        constraintsTopPanel.fill = GridBagConstraints.NONE;
        constraintsTopPanel.insets = new Insets(5, 5, 5, 5);
        constraintsTopPanel.ipadx = 2;
        constraintsTopPanel.ipady = 2;
        constraintsTopPanel.weightx = 0.3;
        constraintsTopPanel.weighty = 0.2;

        constraintsTopPanel.gridx = 0;
        constraintsTopPanel.gridy = 0;
        JTextField tfield1 = new JTextField("kajslkajfkl dsjlafj lksdj akljsd lfkajflkdj lkaj flkdjalk jflkaj lkfdsj salkj flkaj flkja dslkfjal ksjdflka jlfjd aflsdj", 10);
        topPanel.add(tfield1, constraintsTopPanel);

        constraintsTopPanel.gridx = 2;
        constraintsTopPanel.gridy = 0;
        final JTextField tfield2 = new JTextField("kajslkajfkl dsjlafj lksdj akljsd lfkajflkdj lkaj flkdjalk jflkaj lkfdsj salkj flkaj flkja dslkfjal ksjdflka jlfjd aflsdj", 10);              
        topPanel.add(tfield2, constraintsTopPanel);

        constraintsTopPanel.gridx = 4;
        constraintsTopPanel.gridy = 0;
        JTextField tfield3 = new JTextField("kajslkajfkl dsjlafj lksdj akljsd lfkajflkdj lkaj flkdjalk jflkaj lkfdsj salkj flkaj flkja dslkfjal ksjdflka jlfjd aflsdj", 10);
        topPanel.add(tfield3, constraintsTopPanel);

        topPanel.setBackground(Color.WHITE);
        add(topPanel, gbc);

        constraintsTopPanel.gridx = 0;
        constraintsTopPanel.gridy = 2;
        constraintsTopPanel.gridwidth = 6; // Specifies that this component will take two columns.
        constraintsTopPanel.gridheight = 1; // specifies that the component will take one row.

        JButton button = new JButton("REMOVE");
        button.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ae)
            {
                topPanel.remove(tfield2);
                topPanel.revalidate();
                topPanel.repaint();
            }
        });
        topPanel.add(button, constraintsTopPanel);

        //Setting BOTTOM PANEL.
        bottomPanel = new JPanel();
        bottomPanel.setLayout(new BorderLayout());
        bottomPanel.setBackground(Color.DARK_GRAY);     
        JLabel label3 = new JLabel("I am a new JLABEL for the bottom JPanel", JLabel.CENTER);
        label3.setForeground(Color.WHITE);
        bottomPanel.add(label3, BorderLayout.CENTER);       
        gbc.weighty = 0.2;      
        add(bottomPanel, gbc);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);

        pack();
        setVisible(true);
    }

    public static void main(String... args)
    {
        javax.swing.SwingUtilities.invokeLater(new Runnable()
            {
                public void run()
                {
                    new GridBagTest();
                }
            });
    }
}

Answer 2

嗯，我所拥有的最好的就是在代码中看起来很丑，但正是我需要的 textField。下面是从最初的问题更改的示例代码。如果有任何想法可以使它变得更好，我将不胜感激：

import javax.swing.*;
import java.awt.*;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;

public class ScrollTextDemo extends JFrame{

public  ScrollTextDemo(){
    super();
    this.setPreferredSize(new Dimension(500, 300));
    JPanel panel = new JPanel();
    panel.setLayout(new GridBagLayout());
    JTextField textField = new JTextField("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
    textField.setCursor(new Cursor(0));
    textField.setEditable(false);
    JScrollPane scroll = new JScrollPane(textField, JScrollPane.VERTICAL_SCROLLBAR_NEVER,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
    GridBagConstraints gbc = new GridBagConstraints();
    gbc.gridx = 1;
    gbc.gridy = 1;
    gbc.fill = GridBagConstraints.HORIZONTAL;
    gbc.weightx = 0.5;
    //gbc.ipady = 20;//gives some room for scroll to appear and don't hide text area under the scroll.
    gbc.insets = new Insets(5, 5, 0, 5);
    panel.add(scroll,gbc);
    //let's add one more text field without scroll bar to compare
    JTextField textField2 = new JTextField("bbbbbbbb");
    gbc = new GridBagConstraints();
    gbc.gridx = 1;
    gbc.gridy = 2;
    gbc.fill = GridBagConstraints.HORIZONTAL;
    gbc.weightx = 0.5;
    gbc.insets = new Insets(5, 5, 0, 5);
    panel.add(textField2,gbc);
    scroll.addComponentListener( new ScrollTextComponentListener(scroll, textField2));
    this.add(panel);
}



public static void main(String args[]){
    ScrollTextDemo demo = new ScrollTextDemo();
    demo.pack();

    demo.setVisible(true);
}
}

class ScrollTextComponentListener implements ComponentListener {
private boolean scrollVisible;
private JScrollPane scroll;
private JComponent compareComponent;

public ScrollTextComponentListener(JScrollPane scroll, JComponent compareComponent) {
    this.scroll = scroll;
    this.compareComponent = compareComponent;
}

private boolean isScrollVisible() {
    return scroll.getHorizontalScrollBar().getModel().getExtent() != scroll.getHorizontalScrollBar().getModel().getMaximum();
}

private void setScrollSize(){
    boolean scrollVisible = isScrollVisible();
    if (scrollVisible){
        scroll.setPreferredSize(new Dimension(compareComponent.getWidth(),compareComponent.getHeight()*2));
        //also had to set both min and max sizes, because only preffered size didn't always work
        scroll.setMinimumSize(new Dimension(compareComponent.getWidth(),compareComponent.getHeight()*2));
        scroll.setMaximumSize(new Dimension(compareComponent.getWidth(),compareComponent.getHeight()*2));
    }
    else {
        scroll.setPreferredSize(new Dimension(compareComponent.getWidth(),compareComponent.getHeight()));
        scroll.setMinimumSize(new Dimension(compareComponent.getWidth(),compareComponent.getHeight()));
        scroll.setMaximumSize(new Dimension(compareComponent.getWidth(),compareComponent.getHeight()));
    }
    this.scrollVisible = scrollVisible;
}

@Override
public void componentResized(ComponentEvent e) {
    if (isScrollVisible() != scrollVisible) setScrollSize();
}

@Override
public void componentMoved(ComponentEvent e) {
}

@Override
public void componentShown(ComponentEvent e) {
    setScrollSize();
}

@Override
public void componentHidden(ComponentEvent e) {
}

}