哪个鼠标按钮是中间的？

Question

我目前正在用 Java 开发一个程序，其中只有当用户同时单击一个按钮的左键和右键单击时才能触发某个事件。

由于它有点不合常规，我决定先测试一下。这里是：

import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JLabel;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;

public class GUI
{
    private JFrame mainframe;
    private JButton thebutton;

    private boolean left_is_pressed;
    private boolean right_is_pressed;

    private JLabel notifier;

    public GUI ()
    {
        thebutton = new JButton ("Double Press Me");
        addListen ();
        thebutton.setBounds (20, 20, 150, 40);

        notifier = new JLabel (" ");
        notifier.setBounds (20, 100, 170, 20);

        mainframe = new JFrame ("Double Mouse Tester");
        mainframe.setDefaultCloseOperation (JFrame.DISPOSE_ON_CLOSE);
        mainframe.setResizable (false);
        mainframe.setSize (400, 250);

        mainframe.setLayout (null);

        mainframe.add (thebutton);
        mainframe.add (notifier);

        mainframe.setVisible (true);

        left_is_pressed = right_is_pressed = false;
    }

    private void addListen ()
    {
        thebutton.addMouseListener (new MouseListener ()
        {
            @Override public void mouseClicked (MouseEvent e) { }
            @Override public void mouseEntered (MouseEvent e) { }
            @Override public void mouseExited (MouseEvent e) { }

            @Override public void mousePressed (MouseEvent e)
            {
                //If left button pressed
                if (e.getButton () == MouseEvent.BUTTON1)
                {
                    //Set that it is pressed
                    left_is_pressed = true;

                    if (right_is_pressed)
                    {
                        //Write that both are pressed
                        notifier.setText ("Both pressed");
                    }

                }
                //If right button pressed
                else if (e.getButton () == MouseEvent.BUTTON3)
                {
                    //Set that it is pressed
                    right_is_pressed = true;

                    if (left_is_pressed)
                    {
                        //Write that both are pressed
                        notifier.setText ("Both pressed");
                    }
                }
            }

            @Override public void mouseReleased (MouseEvent e)
            {
                //If left button is released
                if (e.getButton () == MouseEvent.BUTTON1)
                {
                    //Set that it is not pressed
                    left_is_pressed = false;

                    //Remove notification
                    notifier.setText (" ");
                }
                //If right button is released
                else if (e.getButton () == MouseEvent.BUTTON3)
                {
                    //Set that it is not pressed
                    right_is_pressed = false;

                    //Remove notification
                    notifier.setText (" ");
                }
            }
        });
    }
}

我测试了它，它可以工作，但是有一个问题。

如您所见，鼠标左键由MouseEvent.BUTTON1 表示，鼠标右键由MouseEvent.BUTTON3 表示。

如果用户有一个没有滚轮的鼠标（显然这样的鼠标仍然存在），那么在 MouseEvent 中只设置了两个按钮。这是否意味着右键将由MouseEvent.BUTTON2 而不是MouseEvent.BUTTON3 表示？如果是，我该如何更改我的代码以适应这一点？有什么办法可以检测到这样的事情吗？

我在 MouseListener 界面和 MouseEvent 上阅读了我能找到的任何内容，但我找不到关于此的任何内容。

Answer 1

要确定按下了哪个鼠标按钮，SwingUtilities 中的这三种方法可以帮助您：

1. isLeftMouseButton
2. isMiddleMouseButton
3. isRightMouseButton

Answer 2

您可以使用SwingUtilties中的实用程序方法：

SwingUtilities.isLeftMouseButton(MouseEvent anEvent)   
SwingUtilities.isRightMouseButton(MouseEvent anEvent) 
SwingUtilities.isMiddleMouseButton(MouseEvent anEvent)

Answer 3

还有MouseEvent.isPopupTrigger()。如果按下鼠标右键，此方法应返回 true。