小画板与鼠标事件

小画板与鼠标事件

耿祥义

摘要通过一个编写一个“小画板”学习使用MouseAdapter和MouseMotionAdapter处理MouseEvent巩固教材的学习效果。MouseAdapter已经实现了MouseListener接口， 2.MouseMotionAdapter已经实现了MouseMotionListener接口。

一、左键拖动鼠标自由绘制

用户左键拖动鼠标触发MouseEvent，程序处理MouseEvent事件时，绘制鼠标拖动形成的轨迹，如图：

二、右键拖动鼠标清除绘制

用户右键拖动鼠标触发MouseEvent，程序处理MouseEvent事件时，清除左键拖动鼠标绘制的部分图形，如图所示意：

三、click鼠标清除全部绘制

用户click鼠标触发MouseEvent，程序处理MouseEvent事件时，清除左键拖动鼠标绘制的全部图形，如图所示意：

四、视频讲解

https://share.weiyun.com/em6WvGzi

1.PaintPoint类(负责点对象)

public class PaintPoint {

public int x;

public int y;

public boolean isPaint = true;

public PaintPoint(int x,int y){

this.x = x;

this.y = y;

}

public boolean equals(Object object){

PaintPoint p =(PaintPoint)object;

if(Math.abs(x-p.x)+Math.abs(y-p.y)

return true;

else

return false;

}

}

2.FreeDrawingBoard类(负责画板对象)

import java.util.ArrayList;

import javax.swing.JPanel;

import java.awt.Color;

import java.awt.Graphics;

import java.awt.Graphics2D;

import java.awt.BasicStroke;

public class FreeDrawingBoard extends JPanel{

ArrayList

list;//存放被绘制的点

Color c;

BasicStroke bs;//画笔线条的粗细

boolean isClear;

public FreeDrawingBoard(){

list= new ArrayList

();

bs=

new BasicStroke

(3f,BasicStroke.CAP_ROUND,BasicStroke.JOIN_MITER);

c = Color.blue;

addMouseListener(new ListenOne());

addMouseMotionListener(new ListenTwo());

}

public void paint(Graphics g){

super.paint(g);

Graphics2D g_2d=(Graphics2D)g;

g_2d.setStroke(bs);

g_2d.setColor(c);

int i = 0;

if(list.size()==0)

return;

for(i=0;i

if(list.get(i).isPaint){

int xStart = (int)list.get(i).x;

int yStart = (int)list.get(i).y;

int xEnd = (int)list.get(i+1).x;

int yEnd = (int)list.get(i+1).y;

g_2d.drawLine(xStart,yStart,xEnd,yEnd);

}

}

}

class ListenOne extends MouseAdapter {

public void mousePressed(MouseEvent e){

//按下鼠标左键

if(e.getButton()==MouseEvent.BUTTON1){

isClear = false;

}

//按下鼠标右键

else if(e.getButton()==MouseEvent.BUTTON3){

isClear = true;

}

}

public void mouseReleased(MouseEvent e){

//以后不再绘制最后一个点

if(list.size()==0)

return;

list.get(list.size()-1).isPaint = false;

}

public void mouseClicked(MouseEvent e){

if(e.getClickCount()>=2){

for(PaintPoint point:list){

point.isPaint = false;

}

list.clear();

repaint();

}

}

}

class ListenTwo extends MouseMotionAdapter {

public void mouseDragged(MouseEvent e) {

int x = e.getX();

int y = e.getY();

if(isClear == false){

list.add(new PaintPoint(x,y));

repaint();

}

else {

PaintPoint p = new PaintPoint(x,y);

for(PaintPoint point:list){

if(point.equals(p)){

point.isPaint = false;

}

}

repaint();

}

}

}

}

3.FreeDrawingBoard类(主类)

import javax.swing.JFrame;

public class DrawWindow extends JFrame{

FreeDrawingBoard drawer;

public DrawWindow(){

setTitle

("左键拖动鼠标自由绘制，右键拖动鼠标清除绘制，双击鼠标全部清除");

setVisible(true);

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

setBounds(10,10,800,600);

drawer = new FreeDrawingBoard();

add(drawer);

}

public static void main(String args[]){

new DrawWindow();

}

}