自己插入一个LeafElement

Question

我试图在一个覆盖DefaultStyledDocument(也提供自定义EditorKit)为JEditorPane插入一个LeafElement:但我得到一个javax.swing.text.StateInvariantError。因此，按照JGuru论坛主题的指导方针，我添加了writeLock()和writeUnlock()调用，但这次我的JEditorPane仍然是空的。那么，我应该如何重写AbstractDocument的fireXXX()方法，以便通知文档的所有侦听器?

这里是我的主类:MyFrame.java

import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.JScrollPane;

public class MyFrame extends JFrame {
    public MyFrame(){
        setSize(400, 300);
        JEditorPane editorPane = new JEditorPane();
        editorPane.setEditorKit(new MyEditorKit());
        add(new JScrollPane(editorPane));
    }
    public static void main(String[] args) {
        new MyFrame().setVisible(true);
    }
    private static final long serialVersionUID = -2122161377842820073L;
}

这里是我的类MyEditorKit.java

import javax.swing.text.Document;
import javax.swing.text.StyledEditorKit;

public class MyEditorKit extends StyledEditorKit {
    @Override
    public Document createDefaultDocument() {
        return new MyDocument();
    }
    private static final long serialVersionUID = -5973765338689236766L;

}

我的类mydocument。java

import javax.swing.JLabel;
import javax.swing.text.DefaultStyledDocument;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.StyleConstants;

public class MyDocument extends DefaultStyledDocument {
    public MyDocument(){
        BranchElement rootElement = (BranchElement) getDefaultRootElement();
        writeLock();
        LeafElement black10Element = (LeafElement) createLeafElement(rootElement, new SimpleAttributeSet(),0, 1);
        JLabel black10 = new JLabel("10 ...");
        StyleConstants.setComponent(black10Element, black10);
        writeUnlock();
    }
    private static final long serialVersionUID = -7424640574620960694L;
}

这是当我用writeLock()和writeUnlock()注释行时的错误堆栈跟踪:

    Exception in thread "main" javax.swing.text.StateInvariantError: Illegal cast to MutableAttributeSet
    at javax.swing.text.AbstractDocument$AbstractElement.checkForIllegalCast(AbstractDocument.java:2050)
    at javax.swing.text.AbstractDocument$AbstractElement.addAttributes(AbstractDocument.java:1983)
    at javax.swing.text.AbstractDocument$AbstractElement.<init>(AbstractDocument.java:1777)
    at javax.swing.text.AbstractDocument$LeafElement.<init>(AbstractDocument.java:2502)
    at javax.swing.text.AbstractDocument.createLeafElement(AbstractDocument.java:1275)
    at MyDocument.<init>(MyDocument.java:13)
    at MyEditorKit.createDefaultDocument(MyEditorKit.java:9)
    at javax.swing.JEditorPane.setEditorKit(JEditorPane.java:1058)
    at MyFrame.<init>(MyFrame.java:11)
    at MyFrame.main(MyFrame.java:16)

Answer 1

我终于解决了我的问题:

只是把MyDocument.java改成这样:

import javax.swing.JLabel;
import javax.swing.event.DocumentEvent.EventType;
import javax.swing.text.DefaultStyledDocument;
import javax.swing.text.SimpleAttributeSet;
import javax.swing.text.StyleConstants;

public class MyDocument extends DefaultStyledDocument {
    public MyDocument(){
        BranchElement rootElement = (BranchElement) getDefaultRootElement();
        writeLock();
        LeafElement black10Element = (LeafElement) createLeafElement(rootElement, new SimpleAttributeSet(), 0, 1);
        JLabel black10 = new JLabel("10 ...");
        StyleConstants.setComponent(black10Element, black10);
        /////////////////// Added lines
        DefaultDocumentEvent documentEvent = this.new DefaultDocumentEvent(0, 1, EventType.INSERT);
        try {
            getContent().insertString(0, " ");
        } catch(BadLocationException e){
            e.printStackTrace();
        }
        insertUpdate(documentEvent, black10Element);
        documentEvent.end();
        fireInsertUpdate(documentEvent);
        /////////////////////////////////////
        writeUnlock();
    }

    private static final long serialVersionUID = -7424640574620960694L;
}

为什么要添加这些行?

JGuru的主题链接建议应该生成一个新的documenttevent:在我的例子中，它是一个插入事件。所以:

1. 我创建了这个DocumentEvent实例
2. 在插入字符串到文档的内容(否则，它不会增长:所以强制，即使我只是使用一个JComponent) => getContent()。插入字符串(offset, String)
3. 我使用它是为了在文档中应用更改(insertUpdate())
4. 我将其标记为"not in progress any more" (end())
5. 我通知所有的文档监听器(fireInsertUpdate())