📜  ES6动画(1)

📅  最后修改于: 2023-12-03 15:00:37.412000             🧑  作者: Mango

ES6动画

ES6动画是指使用ES6语法实现的动画效果。ES6在语言层面上提供了更加丰富和灵活的方式来实现动画效果,相较于传统的jQuery动画,ES6动画更加简洁易懂,且动画效果更加流畅自然。本文将介绍ES6动画的实现原理及示例。

实现原理

ES6动画的实现依赖于requestAnimationFrame函数,这个函数是浏览器提供的一个方法,用于循环执行指定的动画操作。使用requestAnimationFrame函数来执行动画操作具有以下优点:

  • 浏览器会在每帧渲染之前执行该函数,确保动画效果更加流畅。
  • 使用该函数执行动画能够占用更少的系统资源,不会造成浏览器卡顿。

以下是一个基于ES6的动画示例,使用requestAnimationFrame函数来实现动画效果。

class Animation {
  constructor({ duration = 1000, onStart, onProgress, onEnd }) {
    this.startTime = null;
    this.endTime = null;
    this.duration = duration;
    this.onStart = onStart;
    this.onProgress = onProgress;
    this.onEnd = onEnd;
    this.requestId = null;
  }

  start() {
    this.startTime = performance.now();
    this.endTime = this.startTime + this.duration;

    if (typeof this.onStart === "function") {
      this.onStart();
    }

    this.requestId = requestAnimationFrame((timestamp) => {
      this.tick(timestamp);
    });
  }

  tick(timestamp) {
    const progress = (timestamp - this.startTime) / this.duration;

    if (progress >= 1) {
      if (typeof this.onProgress === "function") {
        this.onProgress(1);
      }
      if (typeof this.onEnd === "function") {
        this.onEnd();
      }
    } else {
      if (typeof this.onProgress === "function") {
        this.onProgress(progress);
      }
      this.requestId = requestAnimationFrame((timestamp) => {
        this.tick(timestamp);
      });
    }
  }

  stop() {
    cancelAnimationFrame(this.requestId);
  }

  reset() {
    this.startTime = null;
    this.endTime = null;
    this.requestId = null;
  }
}

以上示例中定义了一个Animation类,该类接收一个配置对象,其中包含了动画的时间长度、开始、进行中和结束时的回调函数,以及如何更新动画状态的方法等。类中的start方法用于启动动画,stop方法用于停止动画,reset方法用于重置动画状态。

示例

下面是一个基于ES6的圆形旋转动画示例,代码解释在注释中。

const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");

class Circle {
  constructor({ x, y, radius, color }) {
    this.x = x;
    this.y = y;
    this.radius = radius;
    this.color = color;
  }

  draw() {
    ctx.beginPath();
    ctx.arc(this.x, this.y, this.radius, 0, Math.PI * 2, true);
    ctx.closePath();
    ctx.fillStyle = this.color;
    ctx.fill();
  }
}

class Animation {
  constructor({ duration = 1000, onStart, onProgress, onEnd }) {
    this.startTime = null;
    this.endTime = null;
    this.duration = duration;
    this.onStart = onStart;
    this.onProgress = onProgress;
    this.onEnd = onEnd;
    this.requestId = null;
  }

  start() {
    this.startTime = performance.now();
    this.endTime = this.startTime + this.duration;

    if (typeof this.onStart === "function") {
      this.onStart();
    }

    this.requestId = requestAnimationFrame((timestamp) => {
      this.tick(timestamp);
    });
  }

  tick(timestamp) {
    const progress = (timestamp - this.startTime) / this.duration;

    if (progress >= 1) {
      if (typeof this.onProgress === "function") {
        this.onProgress(1);
      }
      if (typeof this.onEnd === "function") {
        this.onEnd();
      }
    } else {
      if (typeof this.onProgress === "function") {
        this.onProgress(progress);
      }
      this.requestId = requestAnimationFrame((timestamp) => {
        this.tick(timestamp);
      });
    }
  }

  stop() {
    cancelAnimationFrame(this.requestId);
  }

  reset() {
    this.startTime = null;
    this.endTime = null;
    this.requestId = null;
  }
}

const circle = new Circle({
  x: canvas.width / 2,
  y: canvas.height / 2,
  radius: 50,
  color: "#3498db",
});

const animation = new Animation({
  duration: 3000,
  onProgress: (progress) => {
    // 更新圆的位置和状态
    const angle = progress * Math.PI * 2;
    const x = canvas.width / 2 + 60 * Math.cos(angle);
    const y = canvas.height / 2 + 60 * Math.sin(angle);
    circle.x = x;
    circle.y = y;
    circle.radius = 50 - progress * 20;

    // 刷新画布
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    circle.draw();
  },
});

animation.start();
结语

ES6动画为我们提供了更加灵活和方便的动画效果实现方式,能够让我们在动画效果的设计和开发中更加得心应手。同时,ES6动画还能够提升动画效果的性能和流畅度,让我们的应用程序更加出色。