如何一個ActionListener添加到這個類實現了JTextField

Question

您好我有這個類實現一個JTextField：

其中也應該有一個addActoinListener方法，這我不知道該怎麼寫......

package gui; 

import gui.control.ExpressionListener; 
import gui.control.NewListener; 

import javax.swing.JTextField; 

public final class ExpressionView 
    extends JTextField { 

public String text; 

public static final long serialVersionUID = 1L; 

public static final ExpressionView instance = new ExpressionView(); 

private ExpressionView() { 
    super("ExpressionView"); 

    // This is a singleton. 
} 

@Override 
private void addActionListener { 
    ExpressionView.addActionListener(ExpressionListener.instance); 
} 


} 

哪一種執行該操作的ExpressionListener類看起來是這樣的：

package gui.control; 

import gui.ExpressionView; 

import java.awt.event.ActionListener; 
import java.awt.event.ActionEvent; 
import java.util.Scanner; 

import spreadsheet.Application; 
import spreadsheet.Expression; 
import spreadsheet.exception.NoSuchSpreadsheetException; 
import ui.ExpressionInterpreter; 
import ui.exception.IllegalStartOfExpression; 
import ui.exception.InvalidExpression; 
import ui.exception.InvalidPositionException; 

public final class ExpressionListener 
    implements ActionListener { 

    public static final ExpressionListener instance = new ExpressionListener(); 

    private ExpressionListener() { 
    // This is a singleton. 
    } 
    @Override 
    public void actionPerformed(ActionEvent event) { 
    try { 
     Scanner scanner = new Scanner(ExpressionView.instance.getText()); 
     Expression expression = ExpressionInterpreter.interpret(scanner); 
     Application.instance.set(expression); 
    } catch (InvalidPositionException e) { 
     // TODO Auto-generated catch block 
     e.printStackTrace(); 
    } catch (NoSuchSpreadsheetException e) { 
     // TODO Auto-generated catch block 
     e.printStackTrace(); 
    } catch (IllegalStartOfExpression e) { 
     // TODO Auto-generated catch block 
     e.printStackTrace(); 
    } catch (InvalidExpression e) { 
     // TODO Auto-generated catch block 
     e.printStackTrace(); 
    } 


    } 

} 

所以，請你幫助我，告訴我怎麼這樣的ActionListener添加到ExpressionView類？ :)

Answer 1

我想這就夠了：

ExpressionView.instance.addActionListener(ExpressionListener.instance); 

，因爲它們都是單班，爲什麼你會需要一個靜態addActionListener到ExpressionView類？您已經可以從ExpressionView單身實例上的JTextField繼承。