Question

import java.awt.*;
import java.awt.event.*;
import javax.swing.*; 
public class test extends JFrame implements MouseListener
{
JFrame f;
JPanel p;
JButton b;
test()
{
    f=new JFrame("My Frame");
    p=new JPanel();
    f.add(p);
    b=new JButton("Button");
    p.add(b);
    f.setSize(100,100);
    f.setVisible(true);
    b.addMouseListener(new MouseListener()
    {
        public void mouseClicked(MouseEvent ae)
        {
            System.out.print("mouse clicked");
        }
    });
    b.addMouseListener(new MouseListener()
    {
        public void mouseEntered(MouseEvent ae)
        {
            System.out.print("mouse Entered");
        }
    });
    b.addMouseListener(new MouseListener()
    {
        public void mouseExited(MouseEvent ae)
        {
            System.out.print("mouse Exited");
        }
    });
    b.addMouseListener(new MouseListener()
    {
        public void mousePressed(MouseEvent ae)
        {
            System.out.print("mouse Pressed");
        }
    });
    b.addMouseListener(new MouseListener()
    {
        public void mouseReleased(MouseEvent ae)
        {
            System.out.print("mouse Released");
        }
    });
}
public static void main(String args[])
{
    new test();
}
}

错误如下：

--------------------Configuration: <Default>--------------------
C:\Users\SHUBHENDU\Documents\test.java:19: <anonymous test$1> is not abstract and      does not override abstract method mouseExited(java.awt.event.MouseEvent) in        java.awt.event.MouseListener
        {
        ^
C:\Users\SHUBHENDU\Documents\test.java:26: <anonymous test$2> is not abstract and does not override abstract method mouseExited(java.awt.event.MouseEvent) in java.awt.event.MouseListener
        {
        ^
C:\Users\SHUBHENDU\Documents\test.java:33: <anonymous test$3> is not abstract and does not override abstract method mouseEntered(java.awt.event.MouseEvent) in java.awt.event.MouseListener
        {
        ^
C:\Users\SHUBHENDU\Documents\test.java:40: <anonymous test$4> is not abstract and does not override abstract method mouseExited(java.awt.event.MouseEvent) in java.awt.event.MouseListener
        {
        ^
C:\Users\SHUBHENDU\Documents\test.java:47: <anonymous test$5> is not abstract and does not override abstract method mouseExited(java.awt.event.MouseEvent) in java.awt.event.MouseListener
        {
        ^
5 errors

Answer 1

如果您有一个具体的Java类（非抽象类），您必须实现接口所具有的所有方法，当然，如果您的类实现了该接口。因此将MouseListener接口的未实现方法添加到您的代码中。但是每次都在同一个按钮上添加一个新的MouseListener。这不是它的使用方式。您可以/应该在同一代码体中实现所有MouseListener方法。删除多余的MouseListener个JButton b。

Answer 2

我对AWT并不熟悉，但看起来你有一个非抽象类（test），它没有实现接口的抽象方法（MouseListener）。

http://docs.oracle.com/javase/tutorial/uiswing/events/mouselistener.html

您需要实施：

mouseClicked(MouseEvent)    
mouseEntered(MouseEvent)
mouseExited(MouseEvent) 
mousePressed(MouseEvent)    
mouseReleased(MouseEvent)

如果您的类是抽象的，那么您将不需要实现这些方法（onus将在下一个非抽象子类上执行）。

Answer 3

如果您只想覆盖MouseListener界面的一种方法，可以使用MouseAdapter，如下所示：

JButton button = new JButton("Click");
button.addMouseListener(new MouseAdapter() {
    @Override
    public void mouseClicked(MouseEvent e) {
        System.out.println("mouse was clicked");
    }
});

Answer 4

修复这些错误......

1) Remove "implements MouseListener"

2) Change MouseListener to MouseAdapter

无法理解和解决方法覆盖此程序的错误

4 个答案: