Question

求java图形编译程序

不要用鼠标事件！要求在窗口中出现几个按钮，分别是圆形，矩形，多边形，圆弧，椭圆，直线，三角形等，然后点击其中一个按钮就会出现相应的图形，图形的大小颜色不做具体要求。当所画的图形出来之后，按 保存按钮能吧图形保存下来并且要求格式是JPEG的！

Answer 1

package net.miqiang.gui;

import java.awt.BasicStroke;
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Color;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.Label;
import java.awt.Panel;
import java.awt.RenderingHints;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.BufferedImage;

/**
* 简单画图板程序
* 好久没用 AWT 了，写起来真别扭，如果用 swing 会很舒服，有空再改写吧。
*
* @author 米强
*
*/
public class TestMain extends Frame {
// 画板
private Palette palette = null;

// 显示当前颜色的面板
private Panel nonceColor = null;

// 画笔粗细
private Label drawWidth = null;

// 画笔端点的装饰
private Label drawCap = null;

// 选取颜色按钮的监听事件类
private ButtonColorAction buttonColorAction = null;

// 鼠标进入按钮后光标样式的监听事件类
private ButtonCursor buttonCursor = null;

// 画笔样式的监听事件
private ButtonStrokeAction buttonStrokeAction = null;

/**
* 构造方法
*
*/
public TestMain() {
// 设置标题栏文字
super("简易画图板");

// 构造一个画图板
palette = new Palette();

Panel pane = new Panel(new GridLayout(2, 1));

// 画笔颜色选择器
Panel paneColor = new Panel(new GridLayout(1, 13));

// 12 个颜色选择按钮
Button [] buttonColor = new Button[12];
Color [] color = {Color.black, Color.blue, Color.cyan, Color.darkGray, Color.gray, Color.green, Color.magenta, Color.orange, Color.pink, Color.red, Color.white, Color.yellow};
// 显示当前颜色的面板
nonceColor = new Panel();
nonceColor.setBackground(Color.black);
paneColor.add(nonceColor);
buttonColorAction = new ButtonColorAction();
buttonCursor = new ButtonCursor();
for(int i = 0; i < buttonColor.length; i++){
buttonColor[i] = new Button();
buttonColor[i].setBackground(color[i]);
buttonColor[i].addActionListener(buttonColorAction);
buttonColor[i].addMouseListener(buttonCursor);
paneColor.add(buttonColor[i]);
}
pane.add(paneColor);

// 画笔颜色选择器
Panel paneStroke = new Panel(new GridLayout(1, 13));

// 控制画笔样式
buttonStrokeAction = new ButtonStrokeAction();
Button [] buttonStroke = new Button[11];
buttonStroke[0] = new Button("1");
buttonStroke[1] = new Button("3");
buttonStroke[2] = new Button("5");
buttonStroke[3] = new Button("7");
buttonStroke[4] = new Button("9");
buttonStroke[5] = new Button("11");
buttonStroke[6] = new Button("13");
buttonStroke[7] = new Button("15");
buttonStroke[8] = new Button("17");
buttonStroke[9] = new Button("■");
buttonStroke[10] = new Button("●");
drawWidth = new Label("3", Label.CENTER);
drawCap = new Label("●", Label.CENTER);
drawWidth.setBackground(Color.lightGray);
drawCap.setBackground(Color.lightGray);
paneStroke.add(drawWidth);
for(int i = 0; i < buttonStroke.length; i++){
paneStroke.add(buttonStroke[i]);
buttonStroke[i].addMouseListener(buttonCursor);
buttonStroke[i].addActionListener(buttonStrokeAction);
if(i <= 8){
buttonStroke[i].setName("width");
}else{
buttonStroke[i].setName("cap");
}
if(i == 8){
paneStroke.add(drawCap);
}
}
pane.add(paneStroke);

// 将画笔颜色选择器添加到窗体中
this.add(pane, BorderLayout.NORTH);

// 将画图板添加到窗体中
this.add(palette);

// 添加窗口监听，点击关闭按钮时退出程序
this.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});

// 设置窗体 ICON 图标
this.setIconImage(Toolkit.getDefaultToolkit().createImage("images/palette.png"));

// 设置窗口的大小
this.setSize(new Dimension(400, 430));
// 设置窗口位置，处于屏幕正中央
this.setLocationRelativeTo(null);
// 显示窗口
this.setVisible(true);
}

/**
* 程序入口
*
* @param args
* 字符串数组参数
*/
public static void main(String[] args) {
new TestMain();
}

/**
* 选取颜色按钮的监听事件类
* @author 米强
*
*/
class ButtonColorAction implements ActionListener {

public void actionPerformed(ActionEvent e) {
Color color_temp = ((Button)e.getSource()).getBackground();
nonceColor.setBackground(color_temp);
palette.setColor(color_temp);
}

}

/**
* 鼠标进入按钮变换光标样式监听事件类
* @author 米强
*
*/
class ButtonCursor extends MouseAdapter {

public void mouseEntered(MouseEvent e) {
((Button)e.getSource()).setCursor(new Cursor(Cursor.HAND_CURSOR));
}

public void mouseExited(MouseEvent e) {
((Button)e.getSource()).setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
}

}

/**
* 设置画笔的监听事件类
* @author 米强
*
*/
class ButtonStrokeAction implements ActionListener {

public void actionPerformed(ActionEvent e) {
Button button_temp = (Button) e.getSource();
String name = button_temp.getName();
if(name.equalsIgnoreCase("width")){
drawWidth.setText(button_temp.getLabel());
palette.setStroke(Float.parseFloat(button_temp.getLabel()));
}else if(name.equalsIgnoreCase("cap")){
drawCap.setText(button_temp.getLabel());
if(button_temp.getLabel().equals("■")){
palette.setStroke(BasicStroke.CAP_SQUARE);
}else if(button_temp.getLabel().equals("●")){
palette.setStroke(BasicStroke.CAP_ROUND);
}
}
}

}

}

/**
* 画板类
*
* @author 米强
*
*/
class Palette extends Panel implements MouseListener, MouseMotionListener {
// 鼠标 X 坐标的位置
private int mouseX = 0;

// 上一次 X 坐标位置
private int oldMouseX = 0;

// 鼠标 Y 坐标的位置
private int mouseY = 0;

// 上一次 Y 坐标位置
private int oldMouseY = 0;

// 画图颜色
private Color color = null;

// 画笔样式
private BasicStroke stroke = null;

// 缓存图形
private BufferedImage image = null;

/**
* 构造一个画板类
*
*/
public Palette() {
this.addMouseListener(this);
this.addMouseMotionListener(this);
// 默认黑色画笔
color = new Color(0, 0, 0);
// 设置默认画笔样式
stroke = new BasicStroke(3.0f, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
// 建立 1280 * 1024 的 RGB 缓存图象
image = new BufferedImage(1280, 1024, BufferedImage.TYPE_INT_RGB);
// 设置颜色
image.getGraphics().setColor(Color.white);
// 画背景
image.getGraphics().fillRect(0, 0, 1280, 1024);
}

/**
* 重写 paint 绘图方法
*/
public void paint(Graphics g) {
super.paint(g);

// 转换为 Graphics2D
Graphics2D g2d = (Graphics2D) g;

// 获取缓存图形 Graphics2D
Graphics2D bg = image.createGraphics();

// 图形抗锯齿
bg.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

// 设置绘图颜色
bg.setColor(color);

// 设置画笔样式
bg.setStroke(stroke);

// 画线，从上一个点到新的点
bg.drawLine(oldMouseX, oldMouseY, mouseX, mouseY);

// 将缓存中的图形画到画板上
g2d.drawImage(image, 0, 0, this);
}

/**
* 重写 update 方法
*/
public void update(Graphics g) {
this.paint(g);
}

/**
* @return stroke
*/
public BasicStroke getStroke() {
return stroke;
}

/**
* @param stroke 要设置的 stroke
*/
public void setStroke(BasicStroke stroke) {
this.stroke = stroke;
}

/**
* 设置画笔粗细
* @param width
*/
public void setStroke(float width) {
this.stroke = new BasicStroke(width, stroke.getEndCap(), stroke.getLineJoin());
}

/**
* 设置画笔端点的装饰
* @param cap 参考 java.awt.BasicStroke 类静态字段
*/
public void setStroke(int cap) {
this.stroke = new BasicStroke(stroke.getLineWidth(), cap, stroke.getLineJoin());
}

/**
* @return color
*/
public Color getColor() {
return color;
}

/**
* @param color 要设置的 color
*/
public void setColor(Color color) {
this.color = color;
}

public void mouseClicked(MouseEvent mouseEvent) {
}

/**
* 鼠标按下
*/
public void mousePressed(MouseEvent mouseEvent) {
this.oldMouseX = this.mouseX = mouseEvent.getX();
this.oldMouseY = this.mouseY = mouseEvent.getY();
repaint();
}

public void mouseReleased(MouseEvent mouseEvent) {
}

/**
* 鼠标进入棋盘
*/
public void mouseEntered(MouseEvent mouseEvent) {
this.setCursor(new Cursor(Cursor.CROSSHAIR_CURSOR));
}

/**
* 鼠标退出棋盘
*/
public void mouseExited(MouseEvent mouseEvent) {
this.setCursor(new Cursor(Cursor.DEFAULT_CURSOR));
}

/**
* 鼠标拖动
*/
public void mouseDragged(MouseEvent mouseEvent) {
this.oldMouseX = this.mouseX;
this.oldMouseY = this.mouseY;
this.mouseX = mouseEvent.getX();
this.mouseY = mouseEvent.getY();
repaint();
}

public void mouseMoved(MouseEvent mouseEvent) {
}

}

Answer 2

for (int i = 0; i <= 9; i++) {
jbtNumber[i] = new JButton(""+i);
// jbtNumber[i].setText(""+i); // ""+i 使i转化为字符
}

因为你没new就使用，所以报空指针。改成如上即可。
JButton[] jbtNumber = new JButton[10];
它不会给你实例化数组里面的每个对象的~