画图板

沐刃青蛟

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java、基础

Java 监听事件 swing组件



先看下实现后的效果：

要完成这东西，首先界面的东西是不能少的

public class DrawBorder extends JFrame{
	
	public static void main(String [] args)
	{
		DrawBorder db=new DrawBorder();
		db.initUI();
	}
	public void initUI()
	{
		this.setTitle("画图板");
		this.setSize(600,500);
		//居中
		this.setLocationRelativeTo(null);
		//不可调大小
		this.setResizable(false);
		//创建监听对象
		DrawListener dl=new DrawListener();

到此停顿一下下，这里DrawBorder继承了JFrame，所以this就是指DrawBorder窗体了。

接着往下，用JPanel组件将整个窗体瓜分为三部分：西边（功能区）、南边（颜色区）、中间（画图区）

		//西边
		JPanel westPanel=new JPanel();
		westPanel.setBackground(Color.GRAY);
		westPanel.setPreferredSize(new Dimension(65,0));
		//一个字符串数组来保存图片名
		String []shapeType={
				"pencil","eraser","line","oval","rect","roundrect","five-pointed star","polygon","立体棋"
		};
		//遍历数组，将图片添加到按钮上
		for (int i=0;i<shapeType.length;i++)
		{
			ImageIcon im=new ImageIcon("image/"+shapeType[i]+".png");
			JButton jb=new JButton(im);
			jb.setPreferredSize(new Dimension(24, 24));
			//按钮动作命令值
			jb.setActionCommand(shapeType[i]);
			jb.addActionListener(dl);
			westPanel.add(jb);		
		}

		this.add(westPanel,BorderLayout.WEST);
		
		//南边(颜色)
		//与西边的差不多
		JPanel southPanel=new JPanel();
		southPanel.setPreferredSize(new  Dimension(0, 100));
		southPanel.setBackground(Color.CYAN);
		southPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
		this.add(southPanel,BorderLayout.SOUTH);
		
		Color[]colorType={
				Color.BLACK,Color.RED,Color.BLUE,Color.GREEN,new Color(12,23,34)	
		};
		for (int i=0;i<colorType.length;i++)
		{
			JButton jb=new JButton();
			jb.setPreferredSize(new Dimension(24, 24));
			jb.setBackground(colorType[i]);
			//给按钮添加监听器
			jb.addActionListener(dl);
			southPanel.add(jb);
		}

		
		//中间
		JPanel centerPanel=new JPanel();
		centerPanel.setBackground(Color.WHITE);
		this.add(centerPanel);
		
		this.setDefaultCloseOperation(3);
		this.setVisible(true);	
		//可见之后获取画笔，否则空指针异常	
		Graphics g=centerPanel.getGraphics();
		//调用set函数，将画笔传到监听器中
		dl.setG(g);
		//添加监听器
		centerPanel.addMouseListener(dl);
		centerPanel.addMouseMotionListener(dl);
	}

接下来就是监听器里的内容了，大概是以下内容：

	//获取传来的画笔之用
          public void setG(Graphics g)
	{
		this.g=g;
		g.setColor(color);
	}
	
	public void actionPerformed(ActionEvent e) {
		if(e.getActionCommand()!=null&&!e.getActionCommand().equals(""))
		{
			shapetype=e.getActionCommand();
		}else
		{
			JButton jb=(JButton)e.getSource();
			color=jb.getBackground();
		}
			
	}
	public void mouseClicked(MouseEvent e) {
		//
		if(flag==1)
		{
			x2=e.getX();
			y2=e.getY();
			g.drawLine(x1, y1, x2, y2);
			x1=x2;
			y1=y2;
		}
		int count=e.getClickCount();
		if(count==2)
		{
			g.drawLine(x0, y0, x1, y1);
			flag=0;
		}
		
	}
	
	public void mousePressed(MouseEvent e) {
		
		if(flag!=1)
		{	
			x1=e.getX();
			y1=e.getY();
			x0=x1;
			y0=y1;
		}
		g.setColor(color);
	}

	public void mouseReleased(MouseEvent e) {
		
		x2=e.getX();
		y2=e.getY();
		if(shapetype.equals("line"))
		{
			//画直线
			g.drawLine(x1, y1, x2, y2);
		}
		else if(shapetype.equalsIgnoreCase("rect"))
		{
			//画矩形
			g.drawRect(x1, y1, Math.abs(x2-x1),Math.abs(y2-y1));
		}
		else if(shapetype.equals("oval"))
		{
			//画椭圆或者圆
			g.drawOval(x1, y1, Math.abs(x1-x2), Math.abs(y1-y2));
		}
		else if (shapetype.equals("roundrect"))
		{
			//画圆角矩形
			g.drawRoundRect(x1, y1, Math.abs(x1-x2),Math.abs(y1-y2) , 20,20);
		}
		else if(shapetype.equals("five-pointed star"))
		{
			//画简陋的五角星
			int width=Math.abs(x1-x2);
			int height=Math.abs(y1-y2);
			g.drawLine(x1+width/2, y1-height/5, x1+(2*width)/5, y1+height/5);
			g.drawLine(x1+(2*width)/5, y1+height/5, x1, y1+height/5);
			g.drawLine(x1, y1+height/5, x1+width/3, y1+(4*height)/9);
			g.drawLine(x1+width/3, y1+(4*height)/9, x1+width/5, y1+height);
			g.drawLine(x1+width/5, y1+height, x1+width/2, y1+(4*height)/5);
			g.drawLine(x1+width/2, y1+(4*height)/5, x1+(4*width)/5, y1+height);
			g.drawLine(x1+(4*width)/5, y1+height, x1+(2*width)/3, y1+(3*height)/5);
			g.drawLine(x1+(2*width)/3, y1+(3*height)/5, x1+width, y1+height/5);
			g.drawLine(x1+width, y1+height/5, x1+(3*width)/5, y1+height/5);
			g.drawLine(x1+(3*width)/5, y1+height/5,x1+width/2, y1-height/5);
		}
		else if(shapetype.equals("polygon"))
		{
                            //多边形
			flag=1;
			g.drawLine(x1, y1, x2, y2);
			x1=x2;
			y1=y2;
			
		}
		else if (shapetype.equals("立体棋"))
		{	//画出多个圆，使其产生立体感
			for(int i=0;i<50;i++)
			{
				Color c=new Color(200+i,200+i, 200+i);
				g.setColor(c);
				g.fillOval(x2+i, y2+i, 100-2*i, 100-2*i);
			}
		}
		
	}

	public void mouseDragged(MouseEvent e) {
		
		x2=e.getX();
		y2=e.getY();
		if(shapetype.equals("eraser"))
		{
			//橡皮的实现
			//与铅笔一样，只不过这是与背景颜色相同，且更粗的铅笔
			g2=(Graphics2D)g;
			g2.setColor(Color.WHITE);
			g2.setStroke(new BasicStroke(10));
			g.drawLine(x1, y1, x2, y2);
			x1=x2;
			y1=y2;
			g2=(Graphics2D)g;
			g2.setColor(Color.BLACK);
			g2.setStroke(new BasicStroke(1));
			
		}else if(shapetype.equals("pencil"))
		{
			//铅笔的实现
			g.drawLine(x1, y1, x2, y2);
			x1=x2;
			y1=y2;
		}	
	}

总而言之，引用胡哥的话，技术是很好学的（虽然我现在感觉不到）。我想慢慢的我会感觉到的