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将滚动放入我的表单。
我的示例中的第二行是滚动条显示所必需的。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，只留下两倍高于其他文本字段，这看起来很荒谬。 如何隐藏卷轴后，如何使这一切工作并显示正常大小的文本字段？
修改：
您可以使用以下作为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);
}
}
答案 0 :(得分：4)
为此，在没有好SSCCE的情况下，我认为你没有提供任何填充的约束，用于
当组件的显示区域大于组件的请求大小时使用，以确定是否以及如何调整组件大小。有效值（定义为GridBagConstraints常量）包括NONE（默认值），HORIZONTAL（使组件足够宽以水平填充其显示区域，但不更改其高度），VERTICAL（使组件足够高以垂直填充其显示区域） ，但不要改变它的宽度）和BOTH（使组件完全填满其显示区域）。
所以你必须在GridBagConstraints
中添加这样的东西 constraintsGridBag.fill = GridBagConstraints.HORIZONTAL;
这只允许它不是双向扩展HORIZONTALLY。
**编辑：至于添加的代码**
永远不要为Swing中的任何组件指定setPreferredSize（...）。让您使用布局管理器，注意这一点。删除所有setPreferredSize（...）的东西，在调整大小时让它保持正常大小。
* 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();
}
});
}
}
答案 1 :(得分：0)
我所拥有的最好的东西在代码中看起来很丑陋，但确实完全符合我对textField的要求。以下是从初始问题更改的示例代码。我会感谢任何想法如何让它变得更好：
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) {
}
}