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Java AWT:如何知道鼠标标记事件后释放了哪个鼠标按钮?

mouse awt events java

Skywarp · 技术社区 · 7 年前

如果我按住两个鼠标按钮,然后拖动鼠标,然后释放其中一个按钮,我如何确定释放了哪个按钮?按下的按钮可以用鼠标按钮取回。getModifiersEx(),但似乎没有任何方法来判断哪个被释放,因为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"
     */

}

1 回复 | 直到 7 年前

Hovercraft Full Of Eels 7 年前

为什么不呢?

如果希望在拖动停止后释放鼠标的状态,可以在MouseAdapter中使用布尔标志,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());
    }
}