仅当在 Java 中按下鼠标时如何让 mouseEntered 执行

Posted 2023-02-22

【中文标题】仅当在 Java 中按下鼠标时如何让 mouseEntered 执行

【英文标题】：How to have mouseEntered execute only if mouse is pressed down in Java

【发布时间】：2012-05-21 02:41:38

【问题描述】：

我只想在当前按下鼠标时执行 mouseEntered，基本上是这样的：

    @Override
    public void mouseEntered(MouseEvent e) 
       if(e.mouseDown())
         //Do stuff
        
    

我可以这样做吗，或者我需要鼠标运动监听器还是什么？

谢谢！

编辑：抱歉应该更清楚地说明这一点，但我需要在它进入组件之前按下鼠标，就像按住鼠标并将鼠标悬停在组件上会激活监听器

【参考方案1】：

您可能想评估 MouseEvent API 以查看可用的方法，因为我认为您会在那里找到您的解决方案：

  myComponent.addMouseListener(new MouseAdapter() 

     @Override
     public void mouseEntered(MouseEvent mEvt) 
        System.out.println("mouse entered");

        if (mEvt.getModifiers() == MouseEvent.BUTTON1_MASK) 
           System.out.println("Mouse dragging as entered");
        

     

  );

例如：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class MouseEnteredPressed extends JPanel 
   private static final int SIDE = 500;

   public MouseEnteredPressed() 
      setLayout(new GridBagLayout());
      JLabel label = new JLabel("Hovercraft Rules The World!");
      label.setFont(label.getFont().deriveFont(Font.BOLD, 24));
      label.setBorder(BorderFactory.createLineBorder(Color.LIGHT_GRAY));
      add(label);

      label.addMouseListener(new MouseAdapter() 
         @Override
         public void mouseEntered(MouseEvent mEvt) 
            System.out.println("mouse entered");

            if (mEvt.getModifiers() == MouseEvent.BUTTON1_MASK) 
               System.out.println("Mouse dragging as entered");
            
         
      );

   

   @Override
   public Dimension getPreferredSize() 
      return new Dimension(SIDE, SIDE);
   

   private static void createAndShowGui() 
      MouseEnteredPressed mainPanel = new MouseEnteredPressed();

      JFrame frame = new JFrame("MouseEnteredPressed");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(mainPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   

   public static void main(String[] args) 
      SwingUtilities.invokeLater(new Runnable() 
         public void run() 
            createAndShowGui();
         
      );
   

【讨论】：

@HovercraftFullOfEels 非常关注修饰符 +1