vue3 + canvas 实现坦克大战(一)(下)

简介: vue3 + canvas 实现坦克大战(一)(下)

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()
      }
    }
  }



总结


利用 requestAnimationFrame 来实现循环刷新画布,通过修改各元素位置坐标值,在下一次画布重绘时更新视图,这是阶段交互的基本逻辑;

到这里已经实现了坦克移动和发射子弹的效果,下篇将介绍最关键的子弹和物体碰撞的实现逻辑。

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