HTML5 Canvas 优化动画性能技巧

使用 Konva 创建动画时，需要优化动画以提高性能。 以下是一些主要技巧：

1. 使用 Konva.Animation，而不是直接使用 requestAnimationFrame
2. 仅对需要变化的属性应用动画
3. 考虑为复杂图形使用缓存
4. 尽量减少应用动画的节点数量

以下示例展示了经过优化的动画技巧：

Vanilla

import Konva from 'konva';

const stage = new Konva.Stage({
  container: 'container',
  width: window.innerWidth,
  height: window.innerHeight,
});

const layer = new Konva.Layer();
stage.add(layer);

// Create a complex star shape
const star = new Konva.Star({
  x: stage.width() / 2,
  y: stage.height() / 2,
  numPoints: 6,
  innerRadius: 40,
  outerRadius: 70,
  fill: 'yellow',
  stroke: 'black',
  strokeWidth: 4,
});

// Cache the shape for better performance
star.cache();
layer.add(star);

// Create simple circle that doesn't need caching
const circle = new Konva.Circle({
  x: 100,
  y: 100,
  radius: 20,
  fill: 'red',
});
layer.add(circle);

// Create optimized animation
const anim = new Konva.Animation((frame) => {
  // Rotate star (cached shape)
  star.rotation(frame.time * 0.1);
  
  // Move circle in a circle pattern
  circle.x(100 + Math.cos(frame.time * 0.002) * 50);
  circle.y(100 + Math.sin(frame.time * 0.002) * 50);
}, layer);

// Add start/stop button
const button = document.createElement('button');
button.textContent = 'Toggle Animation';
button.style.position = 'absolute';
button.style.top = '10px';
button.style.left = '10px';
document.body.appendChild(button);

let isPlaying = true;
button.addEventListener('click', () => {
  if (isPlaying) {
    anim.stop();
    button.textContent = 'Start Animation';
  } else {
    anim.start();
    button.textContent = 'Stop Animation';
  }
  isPlaying = !isPlaying;
});

anim.start();

React

import { Stage, Layer, Star, Circle } from 'react-konva';
import { useState, useEffect, useRef } from 'react';

const App = () => {
  const [isPlaying, setIsPlaying] = useState(true);
  const starRef = useRef(null);
  const circleRef = useRef(null);
  const animRef = useRef(null);

  useEffect(() => {
    // Cache the star shape for better performance
    if (starRef.current) {
      starRef.current.cache();
    }

    // Create animation
    const anim = new Konva.Animation((frame) => {
      // Rotate star (cached shape)
      starRef.current.rotation(frame.time * 0.1);
      
      // Move circle in a circle pattern
      circleRef.current.x(100 + Math.cos(frame.time * 0.002) * 50);
      circleRef.current.y(100 + Math.sin(frame.time * 0.002) * 50);
    }, starRef.current.getLayer());

    animRef.current = anim;
    anim.start();

    return () => anim.stop();
  }, []);

  const toggleAnimation = () => {
    if (isPlaying) {
      animRef.current.stop();
    } else {
      animRef.current.start();
    }
    setIsPlaying(!isPlaying);
  };

  return (
    <div>
      <button
        onClick={toggleAnimation}
        style={{ position: 'absolute', top: '10px', left: '10px' }}
      >
        {isPlaying ? 'Stop Animation' : 'Start Animation'}
      </button>
      
      <Stage width={window.innerWidth} height={window.innerHeight}>
        <Layer>
          <Star
            ref={starRef}
            x={window.innerWidth / 2}
            y={window.innerHeight / 2}
            numPoints={6}
            innerRadius={40}
            outerRadius={70}
            fill="yellow"
            stroke="black"
            strokeWidth={4}
          />
          <Circle
            ref={circleRef}
            x={100}
            y={100}
            radius={20}
            fill="red"
          />
        </Layer>
      </Stage>
    </div>
  );
};

export default App;

Vue

<template>
  <div>
    <button
      @click="toggleAnimation"
      style="position: absolute; top: 10px; left: 10px"
    >
      {{ isPlaying ? 'Stop Animation' : 'Start Animation' }}
    </button>
    
    <v-stage :config="stageSize">
      <v-layer ref="layerRef">
        <v-star
          ref="starRef"
          :config="starConfig"
        />
        <v-circle
          ref="circleRef"
          :config="circleConfig"
        />
      </v-layer>
    </v-stage>
  </div>
</template>

<script setup>
import { ref, onMounted, onUnmounted } from 'vue';
import Konva from 'konva';

const stageSize = {
  width: window.innerWidth,
  height: window.innerHeight
};

const starConfig = {
  x: window.innerWidth / 2,
  y: window.innerHeight / 2,
  numPoints: 6,
  innerRadius: 40,
  outerRadius: 70,
  fill: 'yellow',
  stroke: 'black',
  strokeWidth: 4
};

const circleConfig = ref({
  x: 100,
  y: 100,
  radius: 20,
  fill: 'red'
});

const layerRef = ref(null);
const starRef = ref(null);
const circleRef = ref(null);
const isPlaying = ref(true);
let anim = null;

onMounted(() => {
  // Cache the star shape for better performance
  starRef.value.getNode().cache();

  // Create animation
  anim = new Konva.Animation((frame) => {
    // Rotate star (cached shape)
    starRef.value.getNode().rotation(frame.time * 0.1);
    
    // Move circle in a circle pattern
    const circle = circleRef.value.getNode();
    circle.x(100 + Math.cos(frame.time * 0.002) * 50);
    circle.y(100 + Math.sin(frame.time * 0.002) * 50);
  }, layerRef.value.getNode());

  anim.start();
});

onUnmounted(() => {
  if (anim) {
    anim.stop();
  }
});

const toggleAnimation = () => {
  if (isPlaying.value) {
    anim.stop();
  } else {
    anim.start();
  }
  isPlaying.value = !isPlaying.value;
};
</script>