错误MouseMotionListener，MouseListener

Question

我收到一个错误：

AniWorld is not abstract and does not override abstract method mouseMoved(MouseEvent) in MouseMotionListener
public class AniWorld extends  Applet implements MouseMotionListener, MouseListener

代码是：

 import java.awt.*;
import java.lang.*;
import java.applet.*;
import java.net.*;
import java.net.MalformedURLException;
import java.applet.Applet.*;
import java.io.IOException;
import java.awt.event.*;

public class AniWorld extends  Applet implements MouseMotionListener, MouseListener
{
public Stage      stage;
GridBagLayout     layout;
public void init()
{
    addMouseMotionListener(this);
    addMouseListener(this);
    setBackground( Color.white );
    layout = new GridBagLayout();
    setLayout( layout );
    int width = Integer.parseInt( getParameter( "width" ).trim() );
    int height = Integer.parseInt( getParameter( "height" ).trim() );
    stage = new Stage( width-10,height-10);
    constrain( stage,this,layout,1,0,1,6,
               GridBagConstraints.NONE,
               GridBagConstraints.CENTER,0,0 );

    stage.addBall();
    stage.addRect();
    stage.addArc();
    stage.start();
}
public void start()
{
    stage.start();
} // end of start()



public static void constrain(
                 Component     component,
                 Container     container,
                 GridBagLayout layout,
                 int           gridx,
                 int           gridy,
                 int           gridwidth,
                 int           gridheight,
                 int           fill,
                 int           anchor,
                 double        weightx,
                 double        weighty
                 ) {

    GridBagConstraints gbc = new GridBagConstraints();

    gbc.gridx      = gridx;
    gbc.gridy      = gridy;
    gbc.gridwidth  = gridwidth;
    gbc.gridheight = gridheight;
    gbc.fill       = fill;
    gbc.anchor     = anchor;
    gbc.weightx    = weightx;
    gbc.weighty    = weighty;

    layout.setConstraints( component,gbc );

    container.add( component );

    } // end of constrain()

public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
public void mousePressed(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
}

Answer 1

因为要实现MouseMotionListener接口，所以必须实现(或者至少为方法MouseDragged(MouseEvent e)和MouseMoved(MouseEvent e)保留一个空白实现)。

这里是MouseMotionListener的文档

Answer 2

不让GUI类实现侦听器接口的另一个原因。最好的解决方案不是这样做，而是使用扩展MouseAdapter的匿名内部类或执行相同操作的私有内部类。否则，您会要求您的GUI做太多的事情，并为将来可能出现的调试问题做好准备。

Answer 3

您需要添加

public void mouseMoved(MouseEvent) 

设置为AniWorld，或从已实现的接口列表中删除“MouseMotionListener”。

出现该错误的原因是，当您说实现一个接口时，您必须为该接口中的所有方法提供实现，或者您的类需要是抽象的。