鼠标自由画线趣味程序检验

鼠标自由画线趣味程序检验
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Container;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;//它包含鼠标的点击\按下\松开\进入\离开事件
import java.awt.event.MouseMotionListener;//它包含鼠标的移动\拖动
import javax.swing.JFrame;
public class DrawingBoard extends JFrame implements MouseMotionListener {
private int x1, y1;
private int x2, y2;
private Graphics2D g2;
public DrawingBoard() {
super( "画图板" );
//1 调用方法获取一个容器
Container c = this.getContentPane();
//设置容器的布局方式为null(即:取消容器的默认布局方式)
c.setLayout( null );
//设置容器的背景色为白色
c.setBackground( Color.white );
//2 点击窗口的关闭按钮时, 会实现窗口的关闭.
this.setDefaultCloseOperation( JFrame.EXIT_ON_CL OSE );
//3 为当前窗口添加一个鼠标移动\拖动的监听
this.addMouseMotionListener( this );
//4
this.setSize( 500, 400 );
this.setVisible( true );
}
@Override
public void mouseMoved(MouseEvent e) {
//获取鼠标移动时的第一个坐标
x1 = e.getX();
y1 = e.getY();
}
@Override
public void mouseDragged(MouseEvent e) { //获取鼠标拖动时的第二个坐标
x2 = e.getX();
y2 = e.getY();
//获得一个图形对象
Graphics g = this.getGraphics();
g2 = (Graphics2D)g; //强制转换成二维模式
//设置画图的颜色
g2.setColor( Color.blue );
//设置线条的宽度
g2.setStroke( new BasicStroke(3.0f) );
//画线条
g2.drawLine(x1, y1, x2, y2);
//之后,将第二个点坐标变为第一个点坐标; 便于继续画线
//思考: 关闭此项会这样?
x1 = x2;
y1 = y2;
}
public static void main(String[] args) { new DrawingBoard();
}
}。