初学者一个简单程序的问题！有分
左边是绘图面板，右边有一个滑杆用来控制角度！使一个点围绕另一个点画直线！怎么就有问题呢？！本人使初学者，这个问题可能比较弱，还望大家不要笑话：）
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;
import javax.swing.event.*;
class myPane
extends JPanel {
int x1 = 300;
int y1 = 300;
int x2;
int y2;
int Angle;
public myPane() {
x2 = (int) (x1 + 200 * Math.cos(this.getAngle()));
y2 = (int) (y1 + 200 * Math.sin(this.getAngle()));
}
public void setAngle(int a) {
Angle = a;
}
public int getAngle() {
return Angle;
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawLine(x1, y1, x2, y2);
}
}
public class Applet1
extends JApplet {
private boolean isStandalone = false;
myPane p = new myPane();
JPanel control = new JPanel();
JSlider slider = new JSlider(0, 360, 30);
//Get a parameter value
public String getParameter(String key, String def) {
return isStandalone ? System.getProperty(key, def) :
(getParameter(key) != null ? getParameter(key) : def);
}
//Construct the applet
public Applet1() {
}
//Initialize the applet
public void init() {
try {
jbInit();
}
catch (Exception e) {
e.printStackTrace();
}
}
//Component initialization
private void jbInit() throws Exception {
this.setSize(new Dimension(800, 600));
Container contentPane = getContentPane();
contentPane.setLayout(new BorderLayout());
contentPane.add(p, BorderLayout.CENTER);
contentPane.add(control, BorderLayout.EAST);
control.add(slider);
slider.setMajorTickSpacing(90);
slider.setMinorTickSpacing(30);
slider.setPaintLabels(true);
slider.setPaintLabels(true);
slider.addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent e) {
p.setAngle(slider.getValue());
p.repaint();
}
}
);
}
//Get Applet information
public String getAppletInfo() {
return "Applet Information";
}
//Get parameter info
public String[][] getParameterInfo() {
return null;
}
//static initializer for setting look & feel
static {
try {
//UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
//UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
}
catch (Exception e) {
}
}
}
问题点数：10、回复次数：7Top
1 楼aico（aico）回复于 2005-07-29 13:03:52 得分 0
1、x2,y2的计算应放在paintComponent方法中，而不是在构造方法中。
2、Math.sin和Math.cos的参数都是弧度而不是角度。因此你必须把slider上的数值换算成弧度。Top
2 楼aico（aico）回复于 2005-07-29 13:06:51 得分 0
3、myPane的构造方法中，指定自己的Size，否则不能显示。Top
3 楼aico（aico）回复于 2005-07-29 13:09:48 得分 0
4、弧度＝角度×Math.PI/180Top
4 楼huangdeji（活着就是等死）回复于 2005-07-29 13:18:12 得分 0
鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎鼎 鼎鼎鼎
鼎鼎鼎
鼎鼎鼎Top
5 楼aico（aico）回复于 2005-07-29 13:20:45 得分 10
//修改后代码
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;
import javax.swing.event.*;
class myPane
extends JPanel {
int x1 = 300;
int y1 = 300;
int x2;
int y2;
int Angle;
public myPane() {
setPreferredSize(new Dimension(800,600)); //此处设Size
}
public void setAngle(int a) {
Angle = a;
}
public int getAngle() {
return Angle;
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
x2 = (int) (x1 + 200 * Math.cos(this.getAngle()*Math.PI/180)); //此处计算
y2 = (int) (y1 + 200 * Math.sin(this.getAngle()*Math.PI/180));
g.drawLine(x1, y1, x2, y2);
}
}
public class Applet1
extends JApplet {
private boolean isStandalone = false;
myPane p = new myPane();
JPanel control = new JPanel();
JSlider slider = new JSlider(0, 360, 30);
//Get a parameter value
public String getParameter(String key, String def) {
return isStandalone ? System.getProperty(key, def) :
(getParameter(key) != null ? getParameter(key) : def);
}
//Construct the applet
public Applet1() {
}
//Initialize the applet
public void init() {
try {
jbInit();
}
catch (Exception e) {
e.printStackTrace();
}
}
//Component initialization
private void jbInit() throws Exception {
this.setSize(new Dimension(800, 600));
Container contentPane = getContentPane();
contentPane.setLayout(new BorderLayout());
contentPane.add(p, BorderLayout.CENTER);
contentPane.add(control, BorderLayout.EAST);
control.add(slider);
slider.setMajorTickSpacing(90);
slider.setMinorTickSpacing(30);
slider.setPaintLabels(true);
slider.setPaintLabels(true);
slider.addChangeListener(new ChangeListener() {
public void stateChanged(ChangeEvent e) {
p.setAngle(slider.getValue());
p.repaint();
System.out.println("changed");
}
}
);
}
//Get Applet information
public String getAppletInfo() {
return "Applet Information";
}
//Get parameter info
public String[][] getParameterInfo() {
return null;
}
//static initializer for setting look & feel
static {
try {
//UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
//UIManager.setLookAndFeel(UIManager.getCrossPlatformLookAndFeelClassName());
}
catch (Exception e) {
}
}
}
Top
6 楼aico（aico）回复于 2005-07-29 13:22:01 得分 0
//测试HTML代码
<applet code=Applet1.class codebase=. width=1000 height=600></applet>Top
7 楼secondflying（金乌贼）回复于 2005-07-29 15:21:36 得分 0
谢谢aico(aico)，第一次发贴，就得到了这么详细的指导，多谢了！！Top
