JTextField/JTextComponent 中的选择有限? [英] Limited selection in a JTextField/JTextComponent?

问题描述

考虑一个 JFormattedTextField(或任何 JTextComponent，真的)，其中有一个前缀和一个后缀显示在什么是字段的实际文本"周围.

Consider a JFormattedTextField (or any JTextComponent, really) wherein there is a prefix and a suffix displayed around what is the actual "text" of the field.

例如，双 3.5 将是字符串(通过格式化)3.50"，其周围将是前缀$"和后缀"，用于显示文本$ 3.50".

For instance, the double 3.5 would be the String (via formatting) "3.50" around which would be the prefix "$ " and the suffix "", for a display text of "$ 3.50".

显然，这很容易做到.但是，用户仍然可以选择前缀/后缀中的文本，因此他们可以想象删除部分或全部前缀/后缀.我希望用户受到限制，以至于根本无法选择前缀/后缀(同时仍然是文本字段的一部分，因此没有 JLabels).我几乎可以使用 CaretListener(或通过覆盖 setCaretPosition/moveCaretPosition)来实现这一点，它可以防止 C-a 选择整个字段，并且可以防止使用箭头键移动到前缀/后缀中.但是，鼠标拖动和 shift 箭头键仍然允许选择移动到这些限制区域.

Clearly, this is simple to do. However, the user is still allowed to select text within the prefix/suffix, so they could conceivably delete part or all of the prefix/suffix. I would prefer the user be restricted such that the prefix/suffix cannot be selected at all (while still part of the text field, so no JLabels). I can almost accomplish this with a CaretListener (or by overriding setCaretPosition/moveCaretPosition), which prevents a C-a from selecting the entire field, and it prevents using the arrow keys to move into the prefix/suffix. However, mouse dragging and shift-arrow keys still allows the selection to move into these restricted areas.

有什么想法吗?

推荐答案

您可以为此使用 NavigationFilter.

You can use a NavigationFilter for this.

这是一个让您入门的示例:

Here is an example to get you started:

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);
    }

    public void setDot(NavigationFilter.FilterBypass fb, int dot, Position.Bias bias)
    {
        fb.setDot(Math.max(dot, prefixLength), bias);
    }

    public void moveDot(NavigationFilter.FilterBypass fb, int dot, Position.Bias bias)
    {
        fb.moveDot(Math.max(dot, prefixLength), bias);
    }

    class BackspaceAction extends AbstractAction
    {
        public void actionPerformed(ActionEvent e)
        {
            JTextComponent component = (JTextComponent)e.getSource();

            if (component.getCaretPosition() > prefixLength)
            {
                deletePrevious.actionPerformed( null );
            }
        }
    }

    public static void main(String args[]) throws Exception {

        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);
    }
}

我相信这是 JFormattedTextField 的工作方式.所以我不确定你是否可以将它与格式化的文本字段一起使用，因为它可能会取代默认行为.

I believe this is a how a JFormattedTextField works. So I'm not sure if you can use this with a formatted text field as is may replace the default behaviour.

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