libgdx ashley框架的讲解

本文主要是介绍libgdx ashley框架的讲解，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

官网：https://github.com/libgdx/ashley

我的libgdx学习代码：nanshaws/LibgdxTutorial: libgdx 教程项目 本项目旨在提供完整的libgdx桌面教程，帮助开发者快速掌握libgdx游戏开发框架的使用。成功的将gdx-ai和ashley的tests从官网剥离出来,并成功运行。libgdx tutorial project This project aims to provide a complete libgdx desktop tutorial to help developers quickly master the use of libgdx game development framework. Successfully separated GDX-AI and Ashley's tests from the official website and ran them (github.com)

引入依赖：

allprojects {apply plugin: "eclipse"version = '1.0'ext {appName = "My GDX Game"gdxVersion = '1.12.1'roboVMVersion = '2.3.21'box2DLightsVersion = '1.5'ashleyVersion = '1.7.4'aiVersion = '1.8.2'gdxControllersVersion = '2.2.1'}repositories {mavenLocal()mavenCentral()google()gradlePluginPortal()maven { url "https://oss.sonatype.org/content/repositories/snapshots/" }maven { url "https://oss.sonatype.org/content/repositories/releases/" }maven { url "https://jitpack.io" }}
}dependencies {implementation "com.badlogicgames.gdx:gdx:$gdxVersion"implementation "com.badlogicgames.gdx:gdx-backend-lwjgl:$gdxVersion"implementation "com.badlogicgames.gdx:gdx-platform:$gdxVersion:natives-desktop"implementation "com.badlogicgames.ashley:ashley:$ashleyVersion"testImplementation "junit:junit:4.12"
}

在这个ashley框架中，分为

Component

EntitySystem

PooledEngine

EntityListener

好理解吧。以下我用代码来演示

PooledEngine engine = new PooledEngine();MovementSystem movementSystem = new MovementSystem();PositionSystem positionSystem = new PositionSystem();engine.addSystem(movementSystem);engine.addSystem(positionSystem);Listener listener = new Listener();engine.addEntityListener(listener);Entity entity = engine.createEntity();entity.add(new PositionComponent(10, 0));

1. PooledEngine engine = new PooledEngine();
   这行代码创建了一个 PooledEngine 的实例。PooledEngine 是 Engine 的一个子类，它可以重用实体和组件，从而减少内存分配和垃圾回收，提高性能。

2. MovementSystem movementSystem = new MovementSystem();
   创建了一个 MovementSystem 的实例，这是一个自定义的系统，用于处理实体的移动逻辑。

3. PositionSystem positionSystem = new PositionSystem();
   创建了一个 PositionSystem 的实例，这是另一个自定义的系统，用于处理实体的位置更新。

4. engine.addSystem(movementSystem);
engine.addSystem(positionSystem);
   这两行代码将 MovementSystem 和 PositionSystem 添加到 PooledEngine 中。这样，当引擎更新时，这些系统也会被更新。

5. Listener listener = new Listener();
   创建了一个 Listener 的实例，这是一个实体监听器，它会在实体被添加或移除时收到通知。

6. engine.addEntityListener(listener);
   将 Listener 添加到 PooledEngine 中，使其成为实体事件的监听器。

7. Entity entity = engine.createEntity();
   创建了一个新的 Entity 实例。在Ashley中，实体是组件的容器，组件用于存储数据。

8. entity.add(new PositionComponent(10, 0));
   向刚创建的实体添加了一个 PositionComponent 实例，初始化位置为 (10, 0)。PositionComponent 是一个自定义的组件，用于存储实体的位置信息。

每个人物或者标签都可以称之为实体，比如说一个马里奥游戏，马里奥、乌龟和金币都可以被视为实体。每个实体都可以拥有一组组件，这些组件定义了实体的数据和状态。例如，马里奥可能有位置组件（PositionComponent）、移动组件（MovementComponent）和图形组件（GraphicsComponent）等。

这里的实体就是Entity entity = engine.createEntity(); 实体添加组件就是entity.add(new PositionComponent(10, 0)); 而PositionSystem就是各个组件合在一起的逻辑原理

1. private ComponentMapper<PositionComponent> pm = ComponentMapper.getFor(PositionComponent.class);
   这行代码创建了一个 ComponentMapper 对象，专门用于 PositionComponent 类型的组件。这意味着你可以通过这个映射器快速访问任何实体的 PositionComponent。

2. private ComponentMapper<MovementComponent> mm = ComponentMapper.getFor(MovementComponent.class);
   类似地，这行代码创建了一个 ComponentMapper 对象，专门用于 MovementComponent 类型的组件。这使得你可以快速访问任何实体的 MovementComponent。

在MovementSystem里面的两行代码，将每个实体里面的MovementComponent和PositionComponent组件都进行移动。这样的例子在我的libgdx学习代码的

gdx-ashley-tests

 

里面的RenderSystemTest文件，运行起来会让一百个硬币移动

@Overridepublic void update (float deltaTime) {for (int i = 0; i < entities.size(); ++i) {Entity e = entities.get(i);PositionComponent p = pm.get(e);MovementComponent m = mm.get(e);p.x += m.velocityX * deltaTime;p.y += m.velocityY * deltaTime;}log(entities.size() + " Entities updated in MovementSystem.");}

演示一个简单案例吧

MovementComponent

package com.badlogic.ashley.tests.components;import com.badlogic.ashley.core.Component;public class MovementComponent implements Component {public float velocityX;public float velocityY;public MovementComponent (float velocityX, float velocityY) {this.velocityX = velocityX;this.velocityY = velocityY;}
}

PositionComponent

package com.badlogic.ashley.tests.components;import com.badlogic.ashley.core.Component;public class PositionComponent implements Component {public float x, y;public PositionComponent (float x, float y) {this.x = x;this.y = y;}
}

MovementSystem

public static class MovementSystem extends EntitySystem {public ImmutableArray<Entity> entities;private ComponentMapper<PositionComponent> pm = ComponentMapper.getFor(PositionComponent.class);private ComponentMapper<MovementComponent> mm = ComponentMapper.getFor(MovementComponent.class);@Overridepublic void addedToEngine (Engine engine) {entities = engine.getEntitiesFor(Family.all(PositionComponent.class, MovementComponent.class).get());log("MovementSystem added to engine.");}@Overridepublic void removedFromEngine (Engine engine) {log("MovementSystem removed from engine.");entities = null;}@Overridepublic void update (float deltaTime) {for (int i = 0; i < entities.size(); ++i) {Entity e = entities.get(i);PositionComponent p = pm.get(e);MovementComponent m = mm.get(e);p.x += m.velocityX * deltaTime;p.y += m.velocityY * deltaTime;}log(entities.size() + " Entities updated in MovementSystem.");}}

PositionSystem

public static class PositionSystem extends EntitySystem {public ImmutableArray<Entity> entities;@Overridepublic void addedToEngine (Engine engine) {entities = engine.getEntitiesFor(Family.all(PositionComponent.class).get());log("PositionSystem added to engine.");}@Overridepublic void removedFromEngine (Engine engine) {log("PositionSystem removed from engine.");entities = null;}}

Listener

public static class Listener implements EntityListener {@Overridepublic void entityAdded (Entity entity) {log("Entity added " + entity);}@Overridepublic void entityRemoved (Entity entity) {log("Entity removed " + entity);}}public static void log (String string) {System.out.println(string);}

主类：

public static void main (String[] args) {PooledEngine engine = new PooledEngine();MovementSystem movementSystem = new MovementSystem();PositionSystem positionSystem = new PositionSystem();engine.addSystem(movementSystem);engine.addSystem(positionSystem);Listener listener = new Listener();engine.addEntityListener(listener);for (int i = 0; i < 10; i++) {Entity entity = engine.createEntity();entity.add(new PositionComponent(10, 0));if (i > 5) entity.add(new MovementComponent(10, 2));engine.addEntity(entity);}log("MovementSystem has: " + movementSystem.entities.size() + " entities.");log("PositionSystem has: " + positionSystem.entities.size() + " entities.");for (int i = 0; i < 10; i++) {engine.update(0.25f);if (i > 5) engine.removeSystem(movementSystem);}engine.removeEntityListener(listener);}

具体代码可以看：

nanshaws/LibgdxTutorial: libgdx 教程项目 本项目旨在提供完整的libgdx桌面教程，帮助开发者快速掌握libgdx游戏开发框架的使用。成功的将gdx-ai和ashley的tests从官网剥离出来,并成功运行。libgdx tutorial project This project aims to provide a complete libgdx desktop tutorial to help developers quickly master the use of libgdx game development framework. Successfully separated GDX-AI and Ashley's tests from the official website and ran them (github.com)

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