java - 在 Java Swing 中，我可以实时接收 Caret 事件吗？

Question

我正在编写一个类似于十六进制编辑器的 View ，它由两个 JTextComponents(十六进制和 ASCII)组成。我想同步两个 View 之间的选择，所以我为这两个组件实现了 CaretListener。这适用于响应用户长按、拖动和释放鼠标的选择事件。当用户释放鼠标时，组件会收到 caretUpdate。

当用户按下鼠标并在不释放鼠标的情况下四处拖动鼠标时，组件如何接收增量的 caretUpdate 事件？

Answer 1

不幸的是，JTextArea 没有选择模型，否则这会非常简单...

相反，我不得不向每个文本区域的 Caret 添加一个 ChangeListener。这使我能够实时查看插入符号位置何时更改。

当我意识到只有当前文本区域会实际显示它的选择突出显示时，下一个问题出现了....(nb 这很容易纠正，检查下一次更新)

然后我不得不在未聚焦的文本区域应用荧光笔...

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;
import java.io.File;
import java.io.FileReader;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.text.BadLocationException;
import javax.swing.text.DefaultHighlighter;

public class CaretTest {

    public static void main(String[] args) {
        new CaretTest();
    }

    public CaretTest() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridLayout(1, 2));

            JTextArea left = new JTextArea(10, 20);
            JTextArea right = new JTextArea(10, 20);

            left.setEditable(false);
            right.setEditable(false);

            left.getCaret().addChangeListener(new ChangeHandler(left, right));
            right.getCaret().addChangeListener(new ChangeHandler(right, left));

            left.addFocusListener(new FocusHandler(left, right));
            right.addFocusListener(new FocusHandler(right, left));

            JScrollPane leftSP = new JScrollPane(left);
            JScrollPane rightSP = new JScrollPane(right);

            leftSP.getHorizontalScrollBar().setModel(rightSP.getHorizontalScrollBar().getModel());
            leftSP.getVerticalScrollBar().setModel(rightSP.getVerticalScrollBar().getModel());

            add(leftSP);
            add(rightSP);

            FileReader reader = null;
            try {

                reader = new FileReader(new File("Ni.txt"));
                left.read(reader, null);
                reader.close();
                reader = new FileReader(new File("Ni.txt"));
                right.read(reader, null);

            } catch (Exception exp) {
                exp.printStackTrace();
            } finally {
                try {
                    reader.close();
                } catch (Exception e) {
                }
            }
        }

        protected void updateHighlighting(JTextArea source, JTextArea target) {
            DefaultHighlighter.DefaultHighlightPainter painter = new DefaultHighlighter.DefaultHighlightPainter(target.getSelectionColor());
            int start = source.getSelectionStart();
            int end = source.getSelectionEnd();
            try {
                target.getHighlighter().addHighlight(start, end, painter);
            } catch (BadLocationException ex) {
                ex.printStackTrace();
            }
        }

        public class ChangeHandler implements ChangeListener {

            private final JTextArea source;
            private final JTextArea target;

            public ChangeHandler(JTextArea source, JTextArea target) {
                this.source = source;
                this.target = target;
            }

            @Override
            public void stateChanged(ChangeEvent e) {
                if (e.getSource() == source.getCaret()) {
                    target.getHighlighter().removeAllHighlights();
                    updateHighlighting(source, target);
                }
            }
        }

        public class FocusHandler extends FocusAdapter {

            private final JTextArea source;
            private final JTextArea target;

            public FocusHandler(JTextArea source, JTextArea target) {
                this.source = source;
                this.target = target;
            }

            @Override
            public void focusGained(FocusEvent e) {
                source.getHighlighter().removeAllHighlights();
                target.getHighlighter().removeAllHighlights();
                updateHighlighting(source, target);
            }

        }
    }

}

ps- 您需要提供自己的文本 ;)

使用“非荧光笔”示例更新

感谢 StanislavL 指出您可以使用 JTextComponent#getCaret()#setSelectionVisible(true) 使非焦点文本组件显示它的选定文本。

我确实发现焦点更改再次使此 false，因此我在更改处理程序中更新为始终为 true

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;
import java.io.File;
import java.io.FileReader;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.text.BadLocationException;
import javax.swing.text.DefaultHighlighter;

public class CaretTest {

    public static void main(String[] args) {
        new CaretTest();
    }

    public CaretTest() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        public TestPane() {
            setLayout(new GridLayout(1, 2));

            JTextArea left = new JTextArea(10, 20);
            JTextArea right = new JTextArea(10, 20);

            left.setEditable(false);
            right.setEditable(false);

            left.getCaret().setSelectionVisible(true);
            right.getCaret().setSelectionVisible(true);

            left.getCaret().addChangeListener(new ChangeHandler(left, right));
            right.getCaret().addChangeListener(new ChangeHandler(right, left));

            JScrollPane leftSP = new JScrollPane(left);
            JScrollPane rightSP = new JScrollPane(right);

            leftSP.getHorizontalScrollBar().setModel(rightSP.getHorizontalScrollBar().getModel());
            leftSP.getVerticalScrollBar().setModel(rightSP.getVerticalScrollBar().getModel());

            add(leftSP);
            add(rightSP);

            FileReader reader = null;
            try {

                reader = new FileReader(new File("Ni.txt"));
                left.read(reader, null);
                reader.close();
                reader = new FileReader(new File("Ni.txt"));
                right.read(reader, null);

            } catch (Exception exp) {
                exp.printStackTrace();
            } finally {
                try {
                    reader.close();
                } catch (Exception e) {
                }
            }
        }
    }

    public static class ChangeHandler implements ChangeListener {

        private static boolean ignoreUpdates = false;

        private final JTextArea source;
        private final JTextArea target;

        public ChangeHandler(JTextArea source, JTextArea target) {
            this.source = source;
            this.target = target;
        }

        @Override
        public void stateChanged(ChangeEvent e) {
            if (e.getSource() == source.getCaret()) {
                if (!ignoreUpdates) {
                    ignoreUpdates = true;
                    try {
                        target.getCaret().setSelectionVisible(true);
                        source.getCaret().setSelectionVisible(true);
                        target.setSelectionStart(source.getSelectionStart());
                        target.setSelectionEnd(source.getSelectionEnd());
                    } finally {
                        ignoreUpdates = false;
                    }
                }
            }
        }
    }

}