[英]How to make part of a JTextField uneditable
I wanted to develop a console-like interface, similar to IDLE. 我想开发一个类似于IDLE的类似于控制台的界面。 That involved determining how to prevent a certain part of the text in a JTextField
from being edited. 这涉及确定如何防止JTextField
中的文本的某些部分被编辑。 For example: 例如:
>>> help
Where the ">>> " is uneditable. “ >>>”不可编辑的地方。 The caret must never move behind a certain position, and the text behind that position cannot be edited in any way. 插入符号绝对不能移到某个位置的后面,并且该位置后面的文本不能以任何方式进行编辑。
I looked at NavigationFilter, but it doesn't seem to prevent keyboard driven manipulation of the caret. 我看了一下NavigationFilter,但它似乎并不能阻止键盘驱动的插入符号操作。
This shows how to do it with a NavigationFilter
: 这显示了如何使用NavigationFilter
做到这一点:
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
public class NavigationFilterPrefixWithBackspace extends NavigationFilter
{
private int prefixLength;
private Action deletePrevious;
public NavigationFilterPrefixWithBackspace(int prefixLength, JTextComponent component)
{
this.prefixLength = prefixLength;
deletePrevious = component.getActionMap().get("delete-previous");
component.getActionMap().put("delete-previous", new BackspaceAction());
component.setCaretPosition(prefixLength);
}
@Override
public void setDot(NavigationFilter.FilterBypass fb, int dot, Position.Bias bias)
{
fb.setDot(Math.max(dot, prefixLength), bias);
}
@Override
public void moveDot(NavigationFilter.FilterBypass fb, int dot, Position.Bias bias)
{
fb.moveDot(Math.max(dot, prefixLength), bias);
}
class BackspaceAction extends AbstractAction
{
@Override
public void actionPerformed(ActionEvent e)
{
JTextComponent component = (JTextComponent)e.getSource();
if (component.getCaretPosition() > prefixLength)
{
deletePrevious.actionPerformed( null );
}
}
}
private static void createAndShowUI()
{
JTextField textField = new JTextField("Prefix_", 20);
textField.setNavigationFilter( new NavigationFilterPrefixWithBackspace(7, textField) );
JFrame frame = new JFrame("Navigation Filter Example");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().add(textField);
frame.pack();
frame.setLocationRelativeTo( null );
frame.setVisible(true);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}
Spent a little while figuring this out, so I thought I would share my solution for anyone else with the same dilemma. 在弄清楚这一点时花了一点时间,所以我想我将与其他遇到同样困境的人分享我的解决方案。 I don't know if it's optimal, but it does seem to work. 我不知道它是否是最佳选择,但它似乎确实有效。
It prevents the user from using backspace behind the postion n
. 它防止用户使用位置n
后面的退格键。 It also moves the caret back to n
for any other events, such as (illegally) changing the caret position with the arrow keys or mouse. 对于任何其他事件,它也会将插入符号移回n
位置,例如(非法)使用箭头键或鼠标更改插入符号的位置。 Finally, it resets the text and caret position after a entry is processed. 最后,它会在处理完条目后重置文本和插入符号的位置。
EDIT: While I'm leaving this answer here for posterity, see the accepted answer for the best way to solve this problem. 编辑:虽然我将这个答案留在后头,但请参阅已接受的答案,以解决该问题的最佳方法。
JTextField in = new JTextField();
final String protectMe = ">>> "; //protect this text
final int n = protectMe.length();
in.setText(protectMe);
in.setCaretPosition(n);
in.addCaretListener(new CaretListener()
{
@Override
public void caretUpdate(CaretEvent e)
{
if (e.getDot() < n)
{
if (!(in.getText().length() < n))
in.getCaret().setDot(n);
}
}
});
in.addKeyListener(new KeyListener()
{
@Override
public void keyPressed(KeyEvent arg0)
{
if (in.getCaret().getDot() <= n)
{
in.setText(protectMe + in.getText().substring(n));
arg0.consume();
}
}
@Override
public void keyReleased(KeyEvent arg0){}
@Override
public void keyTyped(KeyEvent arg0){}
});
in.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent evt)
{
String input = in.getText().substring(n).trim();
//do something
in.setText(protectMe);
in.setCaretPosition(n);
}
});
As usual, let me know if there's anything I missed! 和往常一样,让我知道我是否错过任何事情!
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