java - 获取 mouseReleased 下的组件

Question

我正在尝试做类似的事情:Swing - Get new component under mouseReleased

在一个窗口中，我有一些按钮，每个按钮上都有一个数字。例如 2 8 5 6。这将显示 4 个 JButton。如果我在 2 上按下鼠标，在 8 上拖动并释放...我希望 firstcomponent 包含 JButton 2，lastcomponent 包含带有 8 的 JButton。

public class Bouton extends JButton implements MouseListener {

String name;
Component firstEntered; 
Component lastEntered;

public Bouton(String str) {
    super(str);
    this.name = str;
    this.addMouseListener(this);
}

@Override
public void mouseClicked(MouseEvent event) { }

 @Override
 public void mouseEntered(MouseEvent event) { 
     lastEntered = event.getComponent();
     String name2 = ((JButton) lastEntered).getName();
     System.out.println("entered : " + name2);
}

@Override
public void mouseExited(MouseEvent event) { 
    firstEntered = event.getComponent();
}

@Override
public void mousePressed(MouseEvent event) { 
    // I tried this didn't work...
    //firstEntered = event.getComponent();
}


@Override
public void mouseReleased(MouseEvent event) { 
    firstEntered.setBackground(Color.RED);
    lastEntered.setBackground(Color.BLUE);

    String name = ((JButton) firstEntered).getName();
    String name2 = ((JButton) lastEntered).getName();
    System.out.println("Release ... first: " + name);
    System.out.println("Release ... last entered: " + name2);
}    

@Override
public String getName() {
    return name;
}

}

输出是:

entered : 2
entered : 8
Release ... first: 2
Release ... last entered: 2

我的问题是我不明白为什么“Release ... last entered: 2”显示 2。为什么不是 8？

谢谢

Answer 1

你添加的每个Bouton都有它自己的firstEntered和lastEntered，因此它只能正确打印出当前按钮(this )。我的建议是只创建一个MouseListener 的新实例，我认为没有必要创建自己的JButton:( mousePressed() 方法现在也可以正常工作了)

import java.awt.Color;
import java.awt.Component;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Example {

    public static void main(String[] args) {

        JFrame frame = new JFrame();

        JPanel p = new JPanel();

        MyMouseListener ml = new MyMouseListener(); // Only one MouseListener
        for (int i = 0; i < 8; i++) {
            JButton b = new JButton(String.valueOf(i));
            b.addMouseListener(ml); // Add the same MouseListener to every
                                    // button
            p.add(b);
        }
        frame.setContentPane(p);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(500, 500);
        frame.setVisible(true);

    }

    public static class MyMouseListener implements MouseListener {

        Component firstEntered;
        Component lastEntered;

        @Override
        public void mouseClicked(MouseEvent event) {

        }

        @Override
        public void mouseEntered(MouseEvent event) {
            lastEntered = event.getComponent();
            System.out.println("entered : " + ((JButton) lastEntered).getText());
        }

        @Override
        public void mouseExited(MouseEvent event) {

        }

        @Override
        public void mousePressed(MouseEvent event) {
            firstEntered = event.getComponent();
            System.out.println("pressed : " + ((JButton) event.getComponent()).getText());
        }

        @Override
        public void mouseReleased(MouseEvent event) {
            firstEntered.setBackground(Color.RED);
            lastEntered.setBackground(Color.BLUE);

            System.out.println("Release ... first: " + ((JButton) firstEntered).getText());
            System.out.println("Release ... last entered: " + ((JButton) lastEntered).getText());
        }
    }

}