vue3 + canvas 实现坦克大战

前言

记得几年前刚做前端开发的时候，跟着师傅用纯 es5 实现了这款坦克大战，可以说我入行前端是从 javaScript 小游戏开始的，时间已匆匆过去了数年，前端发展日新月异，各种新框架、新概念层出不穷，很容易就迷失在对各种新技术的盲目学习和应用中，真正的编程是什么呢？值得思考的问题。

我准备用 vue3 重新实现一下这款游戏，顺便回顾和梳理下自己的知识体系。

W/上 S/下 A/左 D/右 F/射击

让我们开始吧！

架构搭建

项目技术选型为 vue3、vite、less、pnpm、ts，按照vue3 官网文档来新建项目，注意：虽然我用了 vue3 实际上只是强行尝鲜，主体内容都是 js 用到的框架特性有限。

$ pnpm create vite <project-name> -- --template vue$ cd <project-name>$ pnpm install$ pnpm add -D less$ pnpm dev

Canvas 构造函数

游戏的核心为 canvas 画布和坦克元素，我们定义两个构造函数

canvas 构造函数的定义参数、方法：dom、dimension 尺寸、renderTo 渲染函数、drawText 文本绘制函数、drawImageSlice 图片绘制函数

画布绘制

canvas 图层按照一般的游戏设计优化理念，需要为静态背景和动态元素单独用不同的 canvas 图层表示，每次更新时只需要重新绘制动态元素就好了，我抽象出一个渲染函数

// 渲染this.renderTo = function renderTo(container_id) {  if (!is_rendered) {    let container = document.getElementById(container_id)    //画布起始坐标    dom = document.createElement('canvas') // 创造canvas画布    dom.setAttribute('class', 'canvas')    ctx = dom.getContext('2d')    dom.setAttribute('width', container.clientWidth)    dom.setAttribute('height', container.clientHeight)
    // 画布尺寸    dimension = {      x: container.clientWidth,      y: container.clientHeight,    }    container.insertBefore(dom, container.firstChild) // 插入cantainer容器  }}

文本渲染

想要知道画布中的具体位置坐标，可以定义一个函数，当鼠标滑动时候执行来将当前位置坐标绘制出来


this.drawText = function drawText(text, offset_left, offset_top, font) {  ctx.font = font || '25px Calibri'  ctx.fillStyle = '#fff'  ctx.fillText(text, offset_left, offset_top)}

画布重绘前的 clear

每次重绘前需要先擦掉整个画布

this.clear = function clear() {  ctx.clearRect(0, 0, dimension.x, dimension.y)}

核心：绘制函数

坦克、子弹、建筑等元素等绘制都是通过这个函数来完成的，实现远离是利用来雪碧图，通过坐标抓取特定位置的图片元素来获取各种不同坦克等元素的UI；

通过 rotate 旋转元素来实现坦克的转向；

this.drawImageSlice = function drawImage(img_ele, sx, sy, sWidth, sHeight, x, y, rotatation) {  ctx.save()  ctx.translate((2 * x + sWidth) / 2, (2 * y + sHeight) / 2) // 改变起始点坐标  ctx.rotate((Math.PI / 180) * rotatation) // 旋转  x = x || 0  y = y || 0  ctx.drawImage(img_ele, sx, sy, sWidth, sHeight, -sWidth / 2, -sHeight / 2, sWidth, sHeight)  ctx.restore() // 复原}

BattleCity 构造函数

BattleCity 构造函数定义坦克的各种配置信息，和方法函数

let TankConfig = function (cfg) {  this.explosion_count = cfg.explosion_count  this.width = cfg.type.dimension[0]  this.height = cfg.type.dimension[1]  this.missle_type = cfg.missle_type || MISSILE_TYPE.NORMAL  this.x = cfg.x || 0  this.y = cfg.y || 0  this.direction = cfg.direction || DIRECTION.UP  this.is_player = cfg.is_player || 0  this.moving = cfg.moving || 0  this.alive = cfg.alive || 1  this.border_x = cfg.border_x || 0  this.border_y = cfg.border_y || 0  this.speed = cfg.speed || TANK_SPEED  this.direction = cfg.direction || DIRECTION.UP  this.type = cfg.type || TANK_TYPE.PLAYER0}

实现坦克的移动

用键盘的 W、S、A、D、来表示上下左右方向键，按下键盘则会触发对应坦克实例的 move 函数，用于计算移动后的位置坐标信息，注意：对边界条件的判断，不可使其超出战场边界。

  CanvasSprite.prototype.move = function (d, obstacle_sprites) {    this.direction = d
    switch (d) {      case DIRECTION.UP:        if ((obstacle_sprites && !this.checkRangeOverlap(obstacle_sprites)) || !obstacle_sprites) {          this.y -= this.speed
          if (this.y <= 5) {            if (!this.out_of_border_die) {              this.y = 0            } else {              // this.alive = 0;              this.explode()              document.getElementById('steelhit').play()            }          }        }        break      case DIRECTION.DOWN:        if ((obstacle_sprites && !this.checkRangeOverlap(obstacle_sprites)) || !obstacle_sprites) {          this.y += this.speed
          if (this.y + this.height >= this.border_y - 10) {            if (!this.out_of_border_die) {              this.y = this.border_y - this.height            } else {              // this.alive = 0;              this.explode()              document.getElementById('steelhit').play()            }          }        }        break      case DIRECTION.LEFT:        if ((obstacle_sprites && !this.checkRangeOverlap(obstacle_sprites)) || !obstacle_sprites) {          this.x -= this.speed
          if (this.x <= 5) {            if (!this.out_of_border_die) {              this.x = 0            } else {              // this.alive = 0;              this.explode()              document.getElementById('steelhit').play()            }          }        }        break      case DIRECTION.RIGHT:        if ((obstacle_sprites && !this.checkRangeOverlap(obstacle_sprites)) || !obstacle_sprites) {          this.x += this.speed          if (this.x + this.width >= this.border_x - 10) {            if (!this.out_of_border_die) {              this.x = this.border_x - this.width            } else {              // this.alive = 0;              this.explode()              document.getElementById('steelhit').play()            }          }        }        break    }  }

坦克发射子弹的逻辑

首先需要定义子弹的配置信息以及构造函数；

let MissileConfig = function (cfg) {  this.x = cfg.x  this.y = cfg.y  this.type = cfg.type || MISSILE_TYPE.NORMAL  this.width = cfg.width || this.type.dimension[0]  this.height = cfg.height || this.type.dimension[1]  this.direction = cfg.direction || DIRECTION.UP  this.is_from_player = cfg.is_from_player  this.out_of_border_die = cfg.out_of_border_die || 1 // 判断边界类型  this.border_x = cfg.border_x || 0  this.border_y = cfg.border_y || 0  this.speed = cfg.speed || TANK_SPEED  this.alive = cfg.alive || 1}
    var Missile = function (MissileConfig) {      var x = MissileConfig.x      var y = MissileConfig.y      var width = MissileConfig.width      var height = MissileConfig.width      var direction = MissileConfig.direction      this.type = MissileConfig.type      this.is_from_player = MissileConfig.is_from_player || 0      var explosion_count = 0
      CanvasSprite.apply(this, [        {          alive: 1,          out_of_border_die: 1,          border_y: HEIGHT,          border_x: WIDTH,          speed: MISSILE_SPEED,          direction: direction,          x: x,          y: y,          width: width,          height: height,        },      ])
      this.isDestroied = function () {        return explosion_count > 0      }
      this.explode = function () {        if (explosion_count++ === 5) {          this.alive = 0        }      }
      this.getImg = function () {        if (explosion_count > 0) {          return {            width: TANK_EXPLOSION_FRAME[explosion_count].dimension[0],            height: TANK_EXPLOSION_FRAME[explosion_count].dimension[1],            offset_x: TANK_EXPLOSION_FRAME[explosion_count].image_coordinates[0],            offset_y: TANK_EXPLOSION_FRAME[explosion_count].image_coordinates[1],          }        } else {          return {            width: width,            height: height,            offset_x: this.type.image_coordinates[0],            offset_y: this.type.image_coordinates[1],          }        }      }
      this.getHeadCoordinates = function () {        var h_x, h_y
        switch (this.direction) {          case DIRECTION.UP:            h_x = this.x + this.width / 2 - this.type.dimension[0] / 2            h_y = this.y - this.type.dimension[1] / 2            break          case DIRECTION.DOWN:            h_x = this.x + this.width / 2 - this.type.dimension[0] / 2            h_y = this.y + this.height - this.type.dimension[1] / 2            break          case DIRECTION.LEFT:            h_x = this.x            h_y = this.y + this.width / 2 - this.type.dimension[0] / 2            break          case DIRECTION.RIGHT:            h_x = this.x + this.height            h_y = this.y + this.width / 2 - this.type.dimension[0] / 2        }        console.log({          x: h_x,          y: h_y,        })
        return {          x: h_x,          y: h_y,        }      }
      this._generateId = function () {        return uuidv4()      }      sprites[this._generateId()] = this    }

然后再定义一个 fire 开发函数，当开火后，会使用 window.requestAnimationFrame() 来达到循环的效果，每次重绘最新的位置信息

  this.fire = function (boolean_type) {    if (!this.missle || !this.missle.alive) {      var coor = this.getCannonCoordinates()      this.missle = new Missile(        new MissileConfig({          x: coor.x,          y: coor.y,          direction: this.direction,          type: this.miss_type,          is_from_player: boolean_type,        })      )
      if (boolean_type) {        document.getElementById('shoot').play()      }    }  }