Event listeners and Mouse listeners

问题

I was wondering if it is possible to check if a JButton is double clicked using an event Listener instead of a mouse listener. Consider the following code;

public void actionPerformed(ActionEvent arg0){
    if (arg0.getClickCount() == 2){
        System.out.println("You Doubled clicked");
    }
}

I get an error saying getClickCount() is undefined for the type ActionEvent. Is the click or doubleclick of a mouse not also considered as an event? Thoughts.

回答1:

You want to use a MouseAdapter. It permits you to don't clutter your code with unecessary methods (mouseDragged, mouseEntered etc).

public class MyClass extends MouseAdapter {
    @Override
    public void mouseClicked(MouseEvent e) {
        if (e.getClickCount() == 2) {
            // Double click
        } else {
           // Simple click
        }
    }     
}

Alternatively, if your class already extends another class, try this code:

public class MyClass extends MyBaseClass {
    private MouseAdapter ma;

    public MyClass () {
        final MyClass that = this;
        ma = new MouseAdapter() {

            @Override
            public void mouseClicked(MouseEvent e) {
                that.myMouseClickedHandler(e);
            }
        };
    }

    public void myMouseClickedHandler(MouseEvent e) {
        if (e.getClickCount() == 2) {
            // Double click
        } else {
           // Simple click
        }        
    }
 }

回答2:

You can't. Read the documentation if you are unsure. Method OnClickCount is not present in Action Event class, It is only available in MouseEvent class. If you want then write your own method.

See the following documentation for reference

http://docs.oracle.com/javase/7/docs/api/java/awt/event/ActionEvent.html

http://docs.oracle.com/javase/7/docs/api/java/awt/event/MouseEvent.html

回答3:

ActionEvent does not have a "getClickCount()" method.
See the documentation:ActionEvent API Doc

You could define a variable "numClicks" in the actionPerformed method:

public void actionPerformed(ActionEvent e) {
     numClicks++;

Then if "numClicks" equals '2', a double click of the mouse has occurred, then you can set it back to zero, etc...

回答4:

The answer depends. Do you only want to know when the button is "clicked" twice or when it is "pressed" twice?

It's generally discouraged to attach a MouseListener to a button, as the button can be triggered in a variety of ways, including programmatically

What you need to be able to do, is not only count the number of times actionPerformed is called, but also know the time between the clicks.

You could record the last click time and compare that with the current time and make determinations that way, or you could simply use a javax.swing.Timer which will do it for you.

The following example also checks to see if the last source of the ActionEvent is the same as the current source and resets the counter if it's not...

This also allows for mouse clicks, key presses and programmatic triggers...

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TimerButton {

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

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

                JButton btn = new JButton("Testing");
                btn.addActionListener(new ActionHandler());

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new GridBagLayout());
                frame.add(btn);
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class ActionHandler implements ActionListener {

        private Timer timer;
        private int count;
        private ActionEvent lastEvent;

        public ActionHandler() {
            timer = new Timer(250, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    System.out.println("Tick " + count);
                    if (count == 2) {
                        doubleActionPerformed();
                    }
                    count = 0;
                }
            });
            timer.setRepeats(false);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            if (lastEvent != null && lastEvent.getSource() != e.getSource()) {
                System.out.println("Reset");
                count = 0;
            }
            lastEvent = e;
            ((JButton)e.getSource()).setText("Testing");
            count++;
            System.out.println(count);
            timer.restart();
        }

        protected void doubleActionPerformed() {
            Object source = lastEvent.getSource();
            if (source instanceof JButton) {
                ((JButton)source).setText("Double tapped");
            }
        }


    }

}

来源：https://stackoverflow.com/questions/21441243/event-listeners-and-mouse-listeners

标签

java

swing

awt

actionlistener

mouse-listeners