53 lines
951 B
JavaScript
53 lines
951 B
JavaScript
import Sprite from '../base/sprite';
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import { SCREEN_WIDTH, SCREEN_HEIGHT } from '../render';
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const BACKGROUND_IMAGE_SRC = 'images/bg.jpg';
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const BACKGROUND_WIDTH = 512;
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const BACKGROUND_HEIGHT = 512;
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const BACKGROUND_SPEED = 2;
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/**
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* 游戏背景类
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* 提供 update 和 render 函数实现无限滚动的背景功能
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*/
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export default class BackGround extends Sprite {
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constructor() {
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super(BACKGROUND_IMAGE_SRC, SCREEN_WIDTH, SCREEN_HEIGHT);
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}
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update() {
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// 背景不再滚动
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}
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/**
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* 背景图重绘函数
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* 绘制一张静态图片
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*/
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render(ctx) {
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ctx.drawImage(
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this.img,
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0,
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0,
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this.width,
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this.height,
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0,
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0,
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SCREEN_WIDTH,
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SCREEN_HEIGHT
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);
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// 绘制第二张背景
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ctx.drawImage(
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this.img,
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0,
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0,
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this.width,
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this.height,
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0,
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BACKGROUND_HEIGHT,
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SCREEN_WIDTH,
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SCREEN_HEIGHT
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);
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}
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}
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