Physics.js

import Matter from "matter-js";
import { useState, useEffect } from 'react';
import { Accelerometer } from 'expo-sensors';
// 创建引擎
const engine = Matter.Engine.create({ enableSleeping: false });
const world = engine.world;
// 引擎对象
export const physicsEntity = {
  engine: engine,
  world: world
};

// 更新引擎
export const Physics = (entities, { time }) => {
  let engine = entities["physics"].engine;
  Matter.Engine.update(engine, time.delta);
  return entities;
};

// 点击创建球
let ballIndex = 0;
const ballColors = [ "#f93", "#f39", "#9f3", "#3f9", "#93f", "#39f"];
export const CreateBalls = (renderer)=> (entities, { touches, screen }) => {
  const ballSize = Math.trunc(Math.max(screen.width, screen.height) * 0.075);
  
  touches.filter(t => t.type === "press").forEach(t => {
    entities[++ballIndex] = {
      body: createBall(t.event.pageX, t.event.pageY, ballSize / 2),
      size: [ballSize, ballSize],
      color: ballColors[ballIndex % ballColors.length],
      renderer: renderer
    };
  });
  return entities;
};

//创建墙
export const createWall = (x, y, w, h) => {
  const wall = Matter.Bodies.rectangle(x, y, w, h, { isStatic: true })
  Matter.World.add(world, wall);
  return wall;
};

//创建球
export const createBall = (x, y, r) => {
  const ball = Matter.Bodies.circle(x, y, r, { frictionAir: 0.021 });
  Matter.World.add(world, [ball]);
  return ball;

}


export const useAccelerometer = () => {
  const [subscription, setSubscription] = useState(null);
  const subscribeAccelerometer = () => {
    setSubscription(
      Accelerometer.addListener(accelerometerData => {
        const { x, y, z } = accelerometerData;
        world.gravity.x = -x;
        world.gravity.y = y;
      })
    );
  };

  const unsubscribeAccelerometer = () => {
    subscription && subscription.remove();
    setSubscription(null);
  };

  useEffect(() => {
    subscribeAccelerometer();
    return () => unsubscribeAccelerometer();
  }, []);
}