全局变量的宣言

全局变量的声明
当一个类中有几个方法中都用到了一个变量名时，把这个变量在这个类的属性部分声明为全局变量，这样在下边的函数方法中就把那个变量的类型去掉。

package mydraw1.copy;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;

/*
 * 自定义鼠标监听类，继承MouseAdapter（或实现了MouseListener、MouseMotionListener）
 */

	public class MyMouseListener extends MouseAdapter{
		private int x1,y1,x2,y2;
		private Graphics g;
		private ToolPanel tool_panel;
		private ColorPanel color_panel;
		private Color color;
		private String command;		//构造方法
		public MyMouseListener(ToolPanel tool_panel,ColorPanel color_panel,DrawPanel draw_panel){
		g=draw_panel.getGraphics();//获取画布
		this.tool_panel=tool_panel;//接收对象
		this.color_panel=color_panel;//接收对象
		
		}
		//按下
		public void mousePressed(MouseEvent e){
			x1=e.getX();
			y1=e.getY();
			command=tool_panel.getCommand();//获取标志
			color=color_panel.getColor();//获取颜色			g.setColor(color);//设置画布的颜色
		
		}
		//释放
		public void mouseReleased(MouseEvent e){
		x2=e.getX();
		y2=e.getY();
		
		if("line".equals(command)){
			Line line=new Line(x1,y1,x2,y2,color);
			line.draw(g);
		
		}
		else if("rect".equals(command)){
			Rect rect=new Rect(x1,y1,x2,y2,color);
			rect.draw(g);
		}
		else if("oval".equals(command)){
			Oval oval=new Oval(x1,y1,x2,y2,color);
			oval.draw(g);
		}
		
		
	}
		//拖拽
		public void mouseDragged(MouseEvent e){
			x2=e.getX();
			y2=e.getY();
			Line line=new Line(x1,y1,x2,y2,color);
			line.draw(g);
			x1=x2;
			y1=y2;
		}

}

全局变量的宣言

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