drawmain.java

是一个简单的绘图源代码程序,可以绘画点,线,圆等图形.

/**************************************************************
班别：04级4班
姓名：吕成宾
学号：20042102083

作业7.8：
    1.请设计一个简单的鼠标绘图程序，要求，能绘制基本图形（自由绘图，直线，椭圆，矩形）
	2.增加图形的重画，存贮与文件操作
我的实现技术:
	1.增加颜色选择框
	2.采用JFileChooser文件保存与打开,文件保存与打开的后缀名为".msd"表示MouseDraw
	3.采用对象串行化保存与加载.把自由绘图,直线,椭圆,矩形封装到一个类
	4.在鼠标移动时进行重画,使画图时出现橡皮筋效果,但画面会出现闪烁
	5.解决闪烁的方法时采用双缓存机制
***************************************************************/

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.util.*;
import java.io.*;
import javax.swing.JFileChooser;

//绘图对象
class DrawObject implements Serializable
{
	int drawType;   //绘图类型
	ArrayList point;  //用来保存直线,椭圆,矩形起点坐标和终点坐标的链表
	                  //用来保存自由绘图的移动过的每一个坐标
	Color color;      //绘图颜色
	public DrawObject(int drawType, ArrayList point, Color color)
	{
		this.drawType = drawType;
		this.point = point;
		this.color = color;
	}
	public int getDrawtype()
	{
		return drawType;
	}
	public Color getColor()
	{
		return color;
	}
	public ArrayList getArrayList()
	{
		return point;
	}
}

// 设置过滤器,文件类型为".msd" 表示:mousedraw
class MyFilter extends javax.swing.filechooser.FileFilter
{
	public boolean accept(File f) 
	{
		if (f.isDirectory())return true;
		return f.getName().endsWith(".msd");
	} 
	public String getDescription()
	{
		return ".msd";
	}
}

// 对象串行化  
class SaveObject implements Serializable
{
	private ArrayList list;
	public SaveObject(ArrayList list)
	{
		this.list = list;
	}
	public ArrayList getArrayList()
	{
		return list;
	}
}

class MouseDraw extends JFrame
{
	private int drawType = 0;  //画图类型 1.自由画图,2.画直线,3.画椭圆,4.画矩形
	private Color color = new Color(255,0,0); //画图颜色
	private int startX, startY;   // 起点坐标
	private int currentX, currentY;  //移动坐标(结束坐标)
	private ArrayList list;        //保存绘图对象链表
	private DrawCanvas bp;
	MouseDraw()
	{
		setTitle("MouseDraw");
		setSize(800, 600);
		setLocation(100, 100);
		insertMenu();
		//添加画布
		bp = new DrawCanvas();
		Container c = getContentPane();
		c.add(bp);
	}
	private void insertMenu()
	{
		MenuBar mb = new MenuBar();
		
		Menu m_File = new Menu("File");
		Menu m_Draw = new Menu("Draw");
		Menu m_Para = new Menu("Parameters");
		
		MenuItem mi_Open = new MenuItem("Open");
		MenuItem mi_Save = new MenuItem("Save");
		MenuItem mi_Exit = new MenuItem("Exit");
		MenuItem mi_Free = new MenuItem("DrawFree");
		MenuItem mi_Line = new MenuItem("DrawLine");
		MenuItem mi_Elli = new MenuItem("DrawElli");
		MenuItem mi_Rect = new MenuItem("DrawRect");
		MenuItem mi_Color = new MenuItem("Color");
		MenuItem mi_Clear = new MenuItem("Clear");
		m_File.add(mi_Open);
		m_File.add(mi_Save);
		m_File.add(mi_Exit);
		m_Draw.add(mi_Free);
		m_Draw.add(mi_Line);
		m_Draw.add(mi_Elli);
		m_Draw.add(mi_Rect);
		
		m_Para.add(mi_Color);
		m_Para.add(mi_Clear);
		
		mb.add(m_File);
		mb.add(m_Draw);
		mb.add(m_Para);
		
		setMenuBar(mb);
		// 添加监听器
		mi_Free.addActionListener(new DrawAction(1));
		mi_Line.addActionListener(new DrawAction(2));
		mi_Elli.addActionListener(new DrawAction(3));
		mi_Rect.addActionListener(new DrawAction(4));
		mi_Clear.addActionListener(new ActionListener()
			{
				public void actionPerformed(ActionEvent event)
				{
					if (list.size()!=0)
					{
						list.clear();
						startX = startY = currentX = currentY = 0;
						drawType = 0;
						bp.repaint(); //重画
						
					}

				}
			});
		mi_Color.addActionListener(new ActionListener()
			{
				public void actionPerformed(ActionEvent event)
				{
					chooseColor();

				}
			});
		mi_Save.addActionListener(new ActionListener()
			{
				public void actionPerformed(ActionEvent event)
				{
					saveFile();
				}
			});
		mi_Open.addActionListener(new ActionListener()
			{
				public void actionPerformed(ActionEvent event)
				{
					openFile();
				}
			});
		mi_Exit.addActionListener(new ActionListener()
			{
				public void actionPerformed(ActionEvent event)
				{
					System.exit(0); // 退出
				}
			});
		
	}
	private void chooseColor()
	{
		// 颜色对话框,选择颜色
		JColorChooser cc = new JColorChooser();
		color = cc.showDialog(this, "调色板", Color.red);
		startX = startY = currentX = currentY = 0;
	}	
	private void saveFile()
	{
		if (list.size()==0)
		{
			JOptionPane.showMessageDialog(null, "Save failed! There is no draw object!", "Result", JOptionPane.INFORMATION_MESSAGE);
			return;
		}
		// 文件保存对话框
		StringBuffer filePath=new StringBuffer(""); // 文件路径
		MyFilter my=new MyFilter();   
		JFileChooser jf=new JFileChooser();
		jf.setFileFilter(my);  // 设置过滤器
		jf.setFileSelectionMode(JFileChooser.FILES_ONLY); 
		int returnVal = jf.showSaveDialog(null);
		
		
		if (returnVal == JFileChooser.APPROVE_OPTION)
		{
			filePath.append(jf.getSelectedFile().getPath());
			// 如果没有后缀名,则加上后缀名
			if ((filePath.lastIndexOf(".")) == -1)
				filePath.append(".msd");

			try
			{
				ObjectOutputStream f = new ObjectOutputStream(new FileOutputStream(
					filePath.toString()));
				SaveObject so = new SaveObject(list);
				f.writeObject(so); //把对象写到文件中
				f.close();
			}
			catch (Exception e)
			{
				JOptionPane.showMessageDialog(null, e.toString(), "Error", JOptionPane.ERROR_MESSAGE);
			}
		}
	}
	private void openFile()
	{
		//文件加载框
		MyFilter my=new MyFilter();
		JFileChooser jf=new JFileChooser();
		jf.setFileFilter(my);  // 设置过滤器
		jf.setFileSelectionMode(JFileChooser.OPEN_DIALOG); 
		int returnVal = jf.showOpenDialog(null);

		if (returnVal == JFileChooser.APPROVE_OPTION) //按保存按钮时...
		{
			try
			{
				// 使用对象串行化读取文件,并绘图
				//JOptionPane.showMessageDialog(null, jf.getSelectedFile(), "Error", JOptionPane.ERROR_MESSAGE);
				ObjectInputStream f = new ObjectInputStream(new FileInputStream(
					jf.getSelectedFile()));
				SaveObject so = (SaveObject)(f.readObject());//读出对象
				f.close();
				list.clear();  // 先清空
				startX = startY = currentX = currentY = 0;
				drawType = 0;
				list = so.getArrayList();
				bp.repaint(); //重画
			}
			catch (Exception e)
			{
				JOptionPane.showMessageDialog(null, e.toString(), "Error", JOptionPane.ERROR_MESSAGE);
			}
		}
		
	}

	
	//为菜单"Draw"下的菜单项重写监听器,由构造函数里的参数传递画图类型到全局变量drawType
	private class DrawAction implements ActionListener
	{
		DrawAction(int type)
		{
			this.type = type;
		}
		public void actionPerformed(ActionEvent event)
		{
			drawType = type;
		}
		private int type;

	}
	//内部类,画布:Canvas
	private class DrawCanvas extends Canvas
	{
		private DrawObject object;
		private ArrayList point;
		private ArrayList free;
		private Image bgImage;
		private Graphics bg;
		DrawCanvas()
		{
			setBackground(Color.white);
			addListener();
			list = new ArrayList();
			free = new ArrayList();
		}
		private void addListener()
		{
			addMouseListener(new MouseAdapter()
			{
				public void mousePressed(MouseEvent e)
				{
					if (drawType != 0)
						setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR)); 
					startX = currentX = e.getX();
					startY = currentY = e.getY();
					point = new ArrayList();
					point.add(new Point(startX, startY));  //添加起始点
				}
				public void mouseReleased(MouseEvent e)  //释放鼠标
				{
					setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR)); 
					currentX = e.getX();
					currentY = e.getY();
					point.add(new Point(currentX, currentY)); //添加结束点
					object = new DrawObject(drawType, point, color);
					list.add(object); //添加画图对象到list中
					free.clear();
				}
			});
		
			addMouseMotionListener(new MouseMotionAdapter()
			{
				public void mouseDragged(MouseEvent e)
				{
					currentX = e.getX();
					currentY = e.getY();
					// 自由画图时,把当前点添加到free链表和point链表中.
					if (drawType == 1)
					{
						free.add(new Point(currentX, currentY));
						point.add(new Point(currentX, currentY));
					}
					repaint();
				}
			});
		}
		//画椭圆
		private void drawElli(Graphics g, int start_x, int start_y, int current_x, int current_y)
		{
			if (current_x > start_x)
			{
				if(current_y > start_y)
					g.drawOval(start_x, start_y, current_x-start_x, current_y-start_y);
				else 
					g.drawOval(start_x, current_y, current_x-start_x, start_y-current_y);
			}
			else
			{
				if(current_y > start_y)
					g.drawOval(current_x, start_y, start_x-current_x, current_y-start_y);
				else
					g.drawOval(current_x, current_y, start_x-current_x, start_y-current_y);
			}
		}
		//画矩形
		private void drawRect(Graphics g, int start_x, int start_y, int current_x, int current_y)
		{
			if (current_x > start_x)
			{
				if(current_y > start_y)
				{
					g.drawRect(start_x, start_y, current_x-start_x, current_y-start_y);
				}
				else
				{
					g.drawRect(start_x, current_y, current_x-start_x, start_y-current_y);
				}
			}
			else
			{
				if(current_y > start_y)
				{
					g.drawRect(current_x, start_y, start_x-current_x, current_y-start_y);
				}
				else
				{
					g.drawRect(current_x, current_y, start_x-current_x, start_y-current_y);
				}
			}		
		}
		/*利用双缓冲机制清除画面闪烁
		具体实现：
　　　  1.首先我们用createImage方法新建一后台图像类变量
　　　  2.然后使用getGraphics()方法得到当前图像的图形关联
　　　  3.在后台处理所有相关的处理，如清除屏幕，后台绘画等等
　　    当完成所有的后台工作后，复制已经绘制好的图像到前台，并覆盖前台的存在图像。
        这样我们的所有操作都是在后台前行，在屏幕显示新的图像前，这些内容都已经存
        在于后台了。所以你也将在任何时刻都看不到空屏幕的存在。也即代表闪烁消除了。

　　	Update()方法要实现下面三个步骤：
　　　	1.清除屏幕上的组件
　　　	2.设置相关联组件的前景色
　　　	3.调用paint方法重画屏幕
		*/
		public void update(Graphics g)
		{
			//super.update(g);
			// 初始化buffer
			if (bgImage == null)
			{
			
			bgImage = createImage (this.getSize().width, this.getSize().height);
			bg = bgImage.getGraphics ();
			
			}
			
			// 后台清屏,即设置组件和后台一样的颜色，大小
			bg.setColor (getBackground ());
			bg.fillRect (0, 0, this.getSize().width, this.getSize().height);
			
			// 绘制相应的元素组件
			bg.setColor (getForeground());
			paint (bg);
			
			// 在屏幕上重画已经绘制好的圆
			g.drawImage (bgImage, 0, 0, this);

		}
		//paint函数
		public void paint(Graphics g)
		{
			ArrayList p;
			//绘制之前保存的对象
			for (int i=0; i<list.size(); i++)
			{
				g.setColor(((DrawObject)list.get(i)).getColor());
				p = ((DrawObject)list.get(i)).getArrayList();
				switch(((DrawObject)list.get(i)).getDrawtype())
				{
					//1.自由画图,2.画直线,3.画椭圆,4.画矩形
					case 1:
					{
						for (int j=0; j<p.size()-1; j++)
						{
							g.drawLine((int)((Point)p.get(j)).getX(), (int)((Point)p.get(j)).getY(), 
							(int)((Point)p.get(j+1)).getX(), (int)((Point)p.get(j+1)).getY());
						}
						break;
					}
					case 2:
					{
						g.drawLine((int)((Point)p.get(0)).getX(), (int)((Point)p.get(0)).getY(), 
							(int)((Point)p.get(1)).getX(), (int)((Point)p.get(1)).getY());
						break;
					}
					case 3:
					{
						drawElli(g, (int)((Point)p.get(0)).getX(), (int)((Point)p.get(0)).getY(), 
							(int)((Point)p.get(1)).getX(), (int)((Point)p.get(1)).getY());
						break;
					}
					case 4:
					{
						drawRect(g, (int)((Point)p.get(0)).getX(), (int)((Point)p.get(0)).getY(), 
							(int)((Point)p.get(1)).getX(), (int)((Point)p.get(1)).getY());
						break;
					}
					default:
					{
						break;
					}
				}
			}
			//对当前的点画图,使效果看起来来像拉动的橡皮筋,free链表在这里起作用,想想为什么不用point链表?
			g.setColor(color);
			switch (drawType)
			{
				case 1:
					for (int j=0; j<free.size()-1; j++)
					{
						g.drawLine((int)((Point)free.get(j)).getX(), (int)((Point)free.get(j)).getY(), 
							(int)((Point)free.get(j+1)).getX(), (int)((Point)free.get(j+1)).getY());
					}
					break;
				case 2:
					g.drawLine(startX, startY, currentX, currentY);
					break;
				case 3:
					drawElli(g, startX, startY, currentX, currentY);
					break;
				case 4:
					drawRect(g, startX, startY, currentX, currentY);
					break;
				default:
					break;
			}
		}
	}
}

public class DrawMain
{
	public static void main(String args[])
	{
		MouseDraw md = new MouseDraw();
		md.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		md.show();
	}
}