从JTextArea获取密钥 [英] Get a key from JTextArea

问题描述

我想做的一切，如果我在JtextArea.automatically'}'按'{'这个键'这也将打印。

All I want to do, If I'm pressing '{' this key in JtextArea.automatically '}' this will be print also.

 if(evt.KEY_PRESSED == '{')

            System.out.print("}");

这没关系吗？

推荐答案

用于监听对JTextComponent的更改是否存在DocumentListener，如果您需要控制输入的Char，sings，空格字符或单词，则必须实现DocumentFilter

for listening changes into JTextComponent is there DocumentListener, if you have to need control over inputed Char, sings, whitespace chars or word(s) you have to implements DocumentFilter

通过编程语言预留的字符通知你必须使用双重逃脱，

notice for Chars reservated by programing language(s) you have to use double escapes,

\\ （而不是（

或

\\ {而不是 {

否则你得到

Exception in thread "AWT-EventQueue-0" java.util.regex.PatternSyntaxException: 
Illegal repetition

例如

import java.awt.*;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.text.*;

public class TextAreaTest extends JFrame {

    private static final long serialVersionUID = 1L;
    private JTextArea textArea;

    public TextAreaTest() {
        textArea = new JTextArea();
        textArea.setPreferredSize(new Dimension(60, 32));
        textArea.setOpaque(true);
        textArea.setLineWrap(true);
        textArea.setWrapStyleWord(true);
        ((AbstractDocument) textArea.getDocument()).setDocumentFilter(new DocumentFilter() {

            @Override
            public void insertString(FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException {
                string = string.replaceAll("\\{", "\\{}");
                super.insertString(fb, offset, string, attr);
            }

            @Override
            public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
                text = text.replaceAll("\\{", "\\{}");
                //TODO must do something here
                super.replace(fb, offset, length, text, attrs);
            }
        });

        textArea.getDocument().addDocumentListener(new DocumentListener() {

            @Override
            public void changedUpdate(DocumentEvent e) {
                update(e);
            }

            @Override
            public void insertUpdate(DocumentEvent e) {
                update(e);
            }

            @Override
            public void removeUpdate(DocumentEvent e) {
                update(e);
            }

            private void update(DocumentEvent e) {
                List<String> lines = getLines(textArea);
                String lastLine = lines.get(lines.size() - 1);
                int tabbedTextWidth = Utilities.getTabbedTextWidth(new Segment(
                        lastLine.toCharArray(), 0, lastLine.length()), textArea.getFontMetrics(textArea.getFont()), 0, null, 0);
                int lineHeight = getLineHeight(textArea);
                if (lines.size() * lineHeight > textArea.getHeight() || tabbedTextWidth > textArea.getWidth()) {
                    System.out.println("Too big! Should refuse the update!");
                }
            }
        });

        getContentPane().add(textArea);
    }

    private static List<String> getLines(JTextArea textArea) {
        int lineHeight = getLineHeight(textArea);
        List<String> list = new ArrayList<String>();
        for (int num = 0;; num++) {
            int i = textArea.viewToModel(new Point(0, num * lineHeight));
            int j = textArea.viewToModel(new Point(0, (num + 1) * lineHeight));
            if (i == 0 && j == 0) {
                continue;
            }
            if (textArea.getDocument().getLength() == i && i == j) {
                break;
            }
            String s = removeTrailingNewLine(textArea.getText().substring(i, j));
            list.add(s);
            //System.out.println(i + " " + j + " = " + s);
        }
        return list;
    }

    private static int getLineHeight(JTextArea textArea) {
        return textArea.getFontMetrics(textArea.getFont()).getHeight();
    }

    private static String removeTrailingNewLine(String s) {
        if (s.endsWith("\n")) {
            return s.substring(0, s.length() - 1);
        } else {
            return s;
        }
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                TextAreaTest test = new TextAreaTest();
                test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                test.pack();
                test.setVisible(true);
            }
        });
    }
}

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