我对 java OO 有点陌生。使用 Java 的经典过程方面相当简单，包括事件处理甚至 Swing。但是我在处理对象时遇到了一些问题。我在 Eclipse 中编写了一个小程序，它使用事件处理来检测小程序查看器中的鼠标移动和点击。我什至通过鼠标点击在查看器中绘制一张脸。面部绘制代码是在程序中包含的方法中完成的，该方法在调用“drawFace()”方法时将绘制的面部作为图形对象“g”作为参数传递。'drawFace()' 方法返回一个 Graphics 类型并且程序运行良好！然后，我尝试在 Eclipse 中创建一个单独的类，以在单击鼠标时创建一个新的“drawFace”对象，就像前面的代码一样，并通过“new”实例化它。脸没有画出来。我确定我没有正确定义 Face 构造函数类或正确调用它。我首先使用方法（'DrawFaceMethod'）附加工作代码，使用主代码和第二个构造函数类（'DrawFaceObject'）附加非工作代码。两个代码都相当短且相似。任何帮助表示赞赏。
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class AppletDrawFaceMethod extends Applet implements MouseListener ,
MouseMotionListener{
int mouseX = 0, mouseY = 30; // display area where coordinates of mouse displayed
int width = 0, height = 0; // size of applet viewing area
String msg = "";
boolean mouseclick = false; //need to test for mouse click on TRUE
Font font = new Font("Serif", Font.BOLD, 36);
public void init() {
width = getSize().width; //get applet viewing size
height = getSize().height;
System.out.println("Applet dimensions: " + width + " , " + height);
//addMouseListeners
addMouseListener(this);
addMouseMotionListener(this);
} // end init()
// paint method executed on every event
public void paint(Graphics g) {
//need to associate font with paint method
g.setFont(font);
//test mouseclick and set boolean
if (mouseclick == true){
//calls method 'drawFace', passes mouseclick x,y coordinates
// and Graphics object 'g'
//the 'drawFace' method returns a Graphic object of a face drawn
drawFace(mouseX, mouseY, g);
msg = "Face drawn at mouse click " + mouseX + ", " + mouseY;
//re-initialize variables
mouseclick = false;
mouseX = 0;
mouseY = 30;
} // end of 'if mouseclick == true' face drawing code
g.drawString(msg, mouseX, mouseY);
} // end of paint method
// Following methods are mouse 'Listener' methods to detect mouse events
// Handle mouse moved.
public void mouseMoved(MouseEvent me) {
// show status
msg = "Moving mouse at " + me.getX() + ", " + me.getY();
//showStatus("Moving mouse at " + me.getX() + ", " + me.getY());
repaint();
}
// Handle mouse clicked.
public void mouseClicked(MouseEvent me) {
mouseclick = true; //set boolean 'mouseclick' to TRUE
//save coordinates
mouseX = me.getX();
mouseY = me.getY();
repaint();
}
// Handle mouse entered.
public void mouseEntered(MouseEvent me) {
// save coordinates
//mouseX = 0;
//mouseY = 30;
msg = "Mouse entered.";
repaint();
}
// Handle mouse exited.
public void mouseExited(MouseEvent me) {
// save coordinates
//mouseX = 0;
//mouseY = 30;
msg = "Mouse exited applet viewer.";
repaint();
}
//Other method mouse event methods required even if not used
// Handle button pressed.
public void mousePressed(MouseEvent me) {}
// Handle button released.
public void mouseReleased(MouseEvent me) {}
// Handle mouse dragged.
public void mouseDragged(MouseEvent me) {}
///////////////////////////////////////////////////////////
//
// 'drawFace method' receive a Graphics object parameter g'
// it must return a Graphics object which the method draws
//
///////////////////////////////////////////////////////////
public Graphics drawFace(int xStart,int yStart, Graphics g) {
g.drawOval (mouseX, mouseY, 120, 150); // Head.
g.drawOval ((mouseX + 45), (mouseY + 60), 30, 30); // nose
g.fillArc((mouseX + 20), (mouseY + 85), 80, 40, 180, 180); //mouth.
g.drawOval ((mouseX + 17),(mouseY + 35), 30, 20); //Left eye.
g.drawOval ((mouseX + 70),(mouseY + 35), 30, 20); //Right eye.
g.fillOval ((mouseX + 28), (mouseY + 41), 10, 10); //Left pupil.
g.fillOval ((mouseX + 81), (mouseY + 41), 10, 10); //Right pupil.
g.drawOval ((mouseX - 15), (mouseY + 52), 15, 30); //Left ear.
g.drawOval ((mouseX + 120), (mouseY + 52), 15, 30); //Right ear.
g.drawArc ((mouseX + 15), (mouseY + 25),35,15,0,180);//Left brow.
g.drawArc ((mouseX + 67), (mouseY + 25), 35, 15, 0, 180);//Right.
return g; //returns pointer to drawn graphics face
} //end of drawFace method
} // End of class
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
//
//
// 'drawFaceObject' Applet code , followed by 'drawFace' constructor class
//
//
//////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class DrawFaceObject extends Applet implements MouseListener ,
MouseMotionListener{
int mouseX = 0, mouseY = 30; // display mouse coordinates
int width = 0, height = 0; // size of applet viewing area
String msg = "";
boolean mouseclick = false; //need to test for mouse click on TRUE
Font font = new Font("Serif", Font.BOLD, 36);
public void init() {
width = getSize().width; //get applet viewing size
height = getSize().height;
System.out.println("Applet dimensions: " + width + " , " + height);
//addMouseListeners
addMouseListener(this);
addMouseMotionListener(this);
} // end init()
// paint method executed on every event
public void paint(Graphics g) {
//need to associate font with paint method
g.setFont(font);
//test mouseclick and set boolean
if (mouseclick == true){
//creates object'drawFace', passes mouseclick x,y coordinates
// and Graphics object 'g'
Class_DrawFace face = new Class_DrawFace(g);
msg = "Face drawn at mouse click " + mouseX + ", " + mouseY;
//re-initialize variables
mouseclick = false;
mouseX = 0;
mouseY = 30;
} // end of 'if mouseclick == true' face drawing code
g.drawString(msg, mouseX, mouseY);
} // end of paint method
// Following are mouse 'Listener' methods to detect mouse events
// Handle mouse moved.
public void mouseMoved(MouseEvent me) {
// show status
msg = "Moving mouse at " + me.getX() + ", " + me.getY();
//showStatus("Moving mouse at " + me.getX() + ", " + me.getY());
repaint();
}
// Handle mouse clicked.
public void mouseClicked(MouseEvent me) {
mouseclick = true; //set boolean 'mouseclick' to TRUE
//save coordinates
mouseX = me.getX();
mouseY = me.getY();
repaint();
}
// Handle mouse entered.
public void mouseEntered(MouseEvent me) {
// save coordinates
//mouseX = 0;
//mouseY = 30;
msg = "Mouse entered.";
repaint();
}
// Handle mouse exited.
public void mouseExited(MouseEvent me) {
// save coordinates
//mouseX = 0;
//mouseY = 30;
msg = "Mouse exited applet viewer.";
repaint();
}
//Other method mouse event methods required even if not used
// Handle button pressed.
public void mousePressed(MouseEvent me) {}
// Handle button released.
public void mouseReleased(MouseEvent me) {}
// Handle mouse dragged.
public void mouseDragged(MouseEvent me) {}
} // End of class
/////////////////////////////////////////////////////////////
//
// 'drawFace' Constructor
////////////////////////////////////////////////////////////
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
public class Class_DrawFace extends Applet{
//instance variables
public Graphics g;
public int x, y;
Class_DrawFace(Graphics g) {
int x = 0;
int y = 0;
}
Class_DrawFace(int mouseX, int mouseY, Graphics g) {
int x = mouseX;
int y = mouseY;
}
public Graphics drawFace(int x, int y, Graphics g) {
g.drawOval (x, y, 120, 150); // Head.
g.drawOval ((x + 45), (y + 60), 30, 30); // nose
g.fillArc ((x + 20), (y + 85),80,40,180, 180);//mouth.
g.drawOval ((x + 17),(y + 35), 30, 20);//Left eye.
g.drawOval ((x + 70),(y + 35), 30, 20);//Right eye.
g.fillOval ((x + 28), (y + 41),10,10);//Left pupil.
g.fillOval ((x + 81), (y + 41),10,10);//Right pupil.
g.drawOval ((x - 15), (y + 52), 15, 30);//Left ear.
g.drawOval ((x + 120), (y + 52), 15, 30);//Right ear.
g.drawArc ((x + 15), (y + 25),35,15,0,180);//Left eyebrow.
g.drawArc ((x + 67), (y + 25),35,15,0,180);//Right eyebrow.
return g; //return drawnFace Graphics object
} //end of drawFace class constructor
}//end of class