前言
最近小程序的游戏挺火的，本节呢就用小程序做一个简单的大转盘
效果图
设计思路
大转盘转动，指针不动
要在小程序里面新建一个画布，并且铺满屏幕
画两个圆，一个绘制大转盘，一个绘制指针
获取用户点击的坐标，看是否点击到了指针
随机一个奖励，真正业务中应该是后端随机一个结果告诉前端
计算奖励的角度
旋转大转盘
计算角度减速大转盘
旋转完回调函数处理
完整代码
pages/main/main.js
const utils = require('utils.js');const Animation = require('Animation.js');const Circle = require('Circle.js');
Page({ /** * 页面的初始数据 */
data: { wheelImg: 'assets/wheel.png', pointImg: 'assets/point.png', touch: { x: 0, y: 0, isPressed: false }
}, touchMove: function (event) {
}, canvasTouchStart: function (event) { var touch = event.changedTouches[0];
touch.isPressed = true; this.setData({ touch: touch
})
}, canvasTouchEnd: function (event) { var touch = event.changedTouches[0];
touch.isPressed = false; this.setData({ touch: touch
})
}, /** * 生命周期函数--监听页面加载 */
onLoad: function (options) { var that = this; // 把设备的尺寸赋值给画布，以做到全屏效果
wx.getSystemInfo({ success: function (res) {
that.setData({ windowWidth: res.windowWidth, windowHeight: res.windowHeight
});
},
})
}, /** * 生命周期函数--监听页面初次渲染完成 */
onReady: function () { var that = this,
fps = 100,
slicePrizes = ["恭喜中了大奖", "50 积分", "500 积分",
"谢谢参与", "200 积分", "100 积分", "150 积分", "谢谢参与"],
w = this.data.windowWidth,
h = this.data.windowHeight,
context = wx.createCanvasContext('canvas'),
wheel = new Circle(w / 2, h / 2.5, 229),
point = new Circle(w / 2, h / 2.5, 37.5),
animation = new Animation(wheel)
;
wheel.img = that.data.wheelImg;
wheel.width = 458;
wheel.height = 458;
point.img = that.data.pointImg;
point.width = 150;
point.height = 150; // 缩小比例
wheel.scale(0.6, 0.6);
point.scale(0.6, 0.6); // 启用事件
point.inputEvent = true;
point.onInputDown = run; // 更新动画
var update = function () { // 清空
context.clearRect(0, 0, w, h); // 画转盘
wheel.draw(context); // 画指针
point.draw(context); // 更新数据
animation.update(); // 获取手指点击
var touch = that.data.touch; if (point.inputEvent && touch.isPressed && point.onInputDown) { // 如果点击到了指针
if (point.contains(touch)) { // 调用点击回调方法
point.onInputDown();
}
} // 绘图
context.draw();
};
setInterval(update, 1000 / fps, 1000 / fps); // 开始转
function run() { // 避免重复调用
if (animation.isRun) return; // 随机一个奖品
var prizeIndex = utils.getRandom(slicePrizes.length - 1); var prize = slicePrizes[prizeIndex]; // 计算奖品角度
var degrees = utils.getRandom(prizeIndex * 45 + 45, prizeIndex * 45); // 当动画完成时
animation.onComplete = function () {
wx.showToast({ title: prize
})
setTimeout(function () {
wx.hideToast()
}, 1000)
};
animation.tween(5, degrees);
}
}
})pages/main/Animation.js
/** * 动画 * @author qiao * @version 2017/12/30 */function Animation(circle) { this.circle = circle; // 角速度
this.speed = 0; // 最大速度
this.maxSpeed = 10; // 摩擦力
this.friction = 0.98; // 加速度
this.acceleration = 0.1; // 是否开始运行
this.isRun = false; // 圈数
this.rounds = 0; //角度
this.degrees = 0; // 当前角度
this.angle = 0; // 开始减速
this.speedDown = false; // 开始加速
this.speedUp = true; // 顺时针还是逆时针
this.anticlockwise = false; // 完成
this.onComplete = null;
}
Animation.prototype.tween = function (rounds, degrees) { this.circle.rotation = 0; this.angle = 0; this.speedDown = false; this.speedUp = true; this.rounds = rounds; this.degrees = degrees; this.isRun = true; this.speed = 0;
};
Animation.prototype.update = function () { if (this.isRun) { // 是否要减速
if (this.angle >= (this.rounds * 360 + this.degrees)) { this.speedDown = true; this.angle = 0;
} // 是否要停止加速
if (this.speed >= this.maxSpeed) { this.speedUp = false;
} // 转动角度
this.angle += this.speed; // 加速
if (this.speedUp) { this.speed += this.acceleration;
} // 减速
if (this.speedDown) { if (Math.abs(this.angle) >= 360) { this.isRun = false; this.speed = 0; if (this.onComplete) this.onComplete();
} else { this.speed *= this.friction;
}
} // 旋转方向
if (this.anticlockwise) { this.circle.rotation += (Math.PI / 180) * this.speed;
} else { this.circle.rotation -= (Math.PI / 180) * this.speed;
}
}
};module.exports = Animation;pages/main/Circle.js
/** * 大转盘 * @author qiao * @version 2017/12/30 */function Circle(x, y, radius) { this.x = x; this.y = y; this.width = 0; this.height = 0; this.radius = radius; this.rotation = 0; this.img = null; this.scaleX = 1; this.scaleY = 1; this.inputEvent = false; this.onInputDown = null;
}
Circle.prototype.draw = function (context) { // 保存
context.save(); // 移动到圆心
context.translate(this.x, this.y); // 旋转
context.rotate(this.rotation); // 缩放
context.scale(this.scaleX, this.scaleY); if (this.img) { var imgX = -this.width / 2; var imgY = -this.height / 2;
context.drawImage(this.img, imgX, imgY);
} // 还原
context.restore();
};
Circle.prototype.scale = function (x, y) { this.scaleX = x; this.scaleY = y;
};
Circle.prototype.contains = function (obj) { return Circle.contains(this, obj.x, obj.y);
};
Circle.contains = function (a, x, y) { // Check if x/y are within the bounds first
if (a.radius > 0 && x >= a.left && x <= a.right && y >= a.top && y <= a.bottom) { var dx = (a.x - x) * (a.x - x); var dy = (a.y - y) * (a.y - y); return (dx + dy) <= (a.radius * a.radius);
} else { return false;
}
};Object.defineProperty(Circle.prototype, "left", { get: function () { return this.x - this.radius;
}, set: function (value) { if (value > this.x) { this.radius = 0;
} else { this.radius = this.x - value;
}
}
});Object.defineProperty(Circle.prototype, "right", { get: function () { return this.x + this.radius;
}, set: function (value) { if (value < this.x) { this.radius = 0;
} else { this.radius = value - this.x;
}
}
});Object.defineProperty(Circle.prototype, "top", { get: function () { return this.y - this.radius;
}, set: function (value) { if (value > this.y) { this.radius = 0;
} else { this.radius = this.y - value;
}
}
});Object.defineProperty(Circle.prototype, "bottom", { get: function () { return this.y + this.radius;
}, set: function (value) { if (value < this.y) { this.radius = 0;
} else { this.radius = value - this.y;
}
}
});module.exports = Circle;pages/main/main.wxml
<canvas
style='width: {{windowWidth}}px; height: {{windowHeight}}px' disable-scroll="true" bindtouchstart="canvasTouchStart" bindtouchmove="touchMove" bindtouchend="canvasTouchEnd" canvas-id="canvas"></canvas>pages/main/main.wxss
page{ height: 100%;
}pages/main/utils.js
var utils = {};
utils.getRandom = function (max, min) {
min = arguments[1] || 0; return Math.floor(Math.random() * (max - min + 1) + min);
};
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