Java AWT：如何知道在 mouseDragged 事件后释放了哪个鼠标按钮？

Question

如果我按住了两个鼠标按钮，然后拖动鼠标，然后松开其中一个按钮，如何确定松开的是哪个按钮？按住的按钮可以使用 MouseEvent.getModifiersEx() 检索，但似乎没有任何方法可以判断哪个按钮被释放，因为在释放事件触发器之前按下的所有按钮都存储在该掩码中：

public void mouseReleased(MouseEvent e) {

    int b1 = MouseEvent.BUTTON1_DOWN_MASK;
    int b2 = MouseEvent.BUTTON2_DOWN_MASK;

    System.out.println(e.getButton()) // prints "0" when the mousereleased
                                      // event follows a mouseDragged
                                      // event

    if ((mouseEvent.getModifiersEx() & b1) == b1) {
      System.out.println("button 1 released");
    } else if ((mouseEvent.getModifiersEx() & b2) == b2) {
      System.out.println("button 2 released");
    }

    /* 
       Following a mouseDragged event, assuming button 1 and button 2 
       were pressed before either was released, the first if clause 
       evaluates to true regardless of which button was actually released.
       In other words, releasing button 2 in this scenario will print
       "button 1 released"
     */

}

如果 mouseReleased 事件前面有 mousePressed 事件就很容易，但是当它前面有 mouseDragged 时，我不能简单地调用 getButton()...

Answer 1

but when it is preceded by mouseDragged, I can't simply call getButton()...

为什么不呢？

如果你想要在拖动停止后鼠标释放的状态，也许在你的 MouseAdapter 中使用一个布尔标志，并在拖动时将其设置为 true。类似于：

import java.awt.Dimension;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

import javax.swing.*;

public class MouseButtons extends JPanel {
    private static final int PREF_W = 800;
    private static final int PREF_H = 650;

    public MouseButtons() {
        MyMouseAdapter myMouse = new MyMouseAdapter();
        addMouseListener(myMouse);
        addMouseMotionListener(myMouse);
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }

    private class MyMouseAdapter extends MouseAdapter {
        private boolean dragging = false;

        @Override
        public void mousePressed(MouseEvent e) {
        }

        @Override
        public void mouseReleased(MouseEvent e) {
            String text = "";
            int button = e.getButton();
            if (button == MouseEvent.BUTTON1) {
                text = "Button 1";
            } else if (button == MouseEvent.BUTTON2) {
                text = "Button 2";
            } else if (button == MouseEvent.BUTTON3) {
                text = "Button 3";
            }

            if (dragging) {
                System.out.println(text + " just finished dragging");
            } else {
                System.out.println(text + " not recently dragging");
            }
            dragging = false;
        }

        @Override
        public void mouseDragged(MouseEvent e) {
            dragging = true;
        }
    }

    private static void createAndShowGui() {
        JFrame frame = new JFrame("MouseButtons");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new MouseButtons());
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}

除非我完全误解了你的问题，如果是这样，那么我请你澄清一下。

Java AWT：如何知道在 mouseDragged 事件后释放了哪个鼠标按钮？

Java AWT: How to know which mouse button was released after a mouseDragged event?

java

mouse

events

awt