【libGDX】初识libGDX

1 前言

        libGDX 是一个开源且跨平台的 Java 游戏开发框架，于 2010 年 3 月 11 日推出 0.1 版本，它通过 OpenGL ES 2.0/3.0 渲染图像，支持 Windows、Linux、macOS、Android、iOS、Web 等平台，提供了统一的 API，用户只需要写一套代码就可以在多个平台上运行，官方介绍见 → Features。

        libGDX 相关链接如下：

• libGDX 官网：https://libgdx.com
• libGDX 官方文档：https://libgdx.com/dev
• libGDX 启动简介：https://libgdx.com/wiki/start/setup
• libGDX 工具下载：https://libgdx.com/dev/tools
• libGDX GitHub：https://github.com/libgdx/libgdx

2 libGDX 环境搭建

        1）下载 gdx-setup

        官方下载链接：gdx-setup.jar，如果网速较慢，用户也可以从这里下载：libGDX全套工具包。

        2）生成项目

        双击 gdx-setup.jar 文件，填写 Project name、Package name、Game Class、Output folder、Android SDK、Supported Platforms 等信息，点击 Generate 生成项目。官方介绍见 → Generate a Project。

        注意：JDK 最低版为 11，见官方说明 → Set Up a Dev Environment。

        3）打开项目

        使用 Android Studio 打开生成的 Drop 项目，等待自动下载依赖，项目结构如下。

        注意：如果选择了 Android 启动，需要在 gradle.properties 文件中添加 AndroidX 支持，如下。

android.useAndroidX=true

        DesktopLauncher.java

package com.zhyan8.drop;import com.badlogic.gdx.backends.lwjgl3.Lwjgl3Application;
import com.badlogic.gdx.backends.lwjgl3.Lwjgl3ApplicationConfiguration;public class DesktopLauncher {public static void main (String[] arg) {Lwjgl3ApplicationConfiguration config = new Lwjgl3ApplicationConfiguration();config.setForegroundFPS(60);config.setTitle("Drop");new Lwjgl3Application(new Drop(), config);}
}

        AndroidLauncher.java

package com.zhyan8.drop;import android.os.Bundle;import com.badlogic.gdx.backends.android.AndroidApplication;
import com.badlogic.gdx.backends.android.AndroidApplicationConfiguration;public class AndroidLauncher extends AndroidApplication {@Overrideprotected void onCreate (Bundle savedInstanceState) {super.onCreate(savedInstanceState);AndroidApplicationConfiguration config = new AndroidApplicationConfiguration();initialize(new Drop(), config);}
}

        Drop.java

package com.zhyan8.drop;import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.utils.ScreenUtils;public class Drop extends ApplicationAdapter {SpriteBatch batch;Texture img;@Overridepublic void create () {batch = new SpriteBatch();img = new Texture("badlogic.jpg");}@Overridepublic void render () {ScreenUtils.clear(1, 0, 0, 1);batch.begin();batch.draw(img, 0, 0);batch.end();}@Overridepublic void dispose () {batch.dispose();img.dispose();}
}

        4）运行项目（点击操作）

        Desktop：

        Android：

        运行效果如下。

        5）运行项目（通过命令）

        可以通过在 Terminal 中运行以下命令来运行项目，见官方介绍 → Importing & Running。

        Desktop：

./gradlew desktop:run

        Android：

./gradlew android:installDebug android:run

        iOS：

./gradlew ios:launchIPhoneSimulator

        HTML：

./gradlew html:superDev

3 libGDX 官方案例

        官方接水游戏见 → A Simple Game。

        在第二节的基础上，修改 Drop.java，如下。

        Drop.java

package com.zhyan8.drop;import java.util.Iterator;import com.badlogic.gdx.ApplicationAdapter;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Input.Keys;
import com.badlogic.gdx.audio.Music;
import com.badlogic.gdx.audio.Sound;
import com.badlogic.gdx.graphics.OrthographicCamera;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.math.MathUtils;
import com.badlogic.gdx.math.Rectangle;
import com.badlogic.gdx.math.Vector3;
import com.badlogic.gdx.utils.Array;
import com.badlogic.gdx.utils.ScreenUtils;
import com.badlogic.gdx.utils.TimeUtils;public class Drop extends ApplicationAdapter {private Texture dropImage;private Texture bucketImage;private Sound dropSound;private Music rainMusic;private SpriteBatch batch;private OrthographicCamera camera;private Rectangle bucket;private Array<Rectangle> raindrops;private long lastDropTime;@Overridepublic void create() {// load the images for the droplet and the bucket, 64x64 pixels eachdropImage = new Texture(Gdx.files.internal("droplet.png"));bucketImage = new Texture(Gdx.files.internal("bucket.png"));// load the drop sound effect and the rain background "music"dropSound = Gdx.audio.newSound(Gdx.files.internal("drop.mp3"));rainMusic = Gdx.audio.newMusic(Gdx.files.internal("rain.mp3"));// start the playback of the background music immediatelyrainMusic.setLooping(true);rainMusic.play();// create the camera and the SpriteBatchcamera = new OrthographicCamera();camera.setToOrtho(false, 800, 480);batch = new SpriteBatch();// create a Rectangle to logically represent the bucketbucket = new Rectangle();bucket.x = 800 / 2 - 64 / 2; // center the bucket horizontallybucket.y = 20; // bottom left corner of the bucket is 20 pixels above the bottom screen edgebucket.width = 64;bucket.height = 64;// create the raindrops array and spawn the first raindropraindrops = new Array<Rectangle>();spawnRaindrop();}private void spawnRaindrop() {Rectangle raindrop = new Rectangle();raindrop.x = MathUtils.random(0, 800-64);raindrop.y = 480;raindrop.width = 64;raindrop.height = 64;raindrops.add(raindrop);lastDropTime = TimeUtils.nanoTime();}@Overridepublic void render() {// clear the screen with a dark blue color. The// arguments to clear are the red, green// blue and alpha component in the range [0,1]// of the color to be used to clear the screen.ScreenUtils.clear(0, 0, 0.2f, 1);// tell the camera to update its matrices.camera.update();// tell the SpriteBatch to render in the// coordinate system specified by the camera.batch.setProjectionMatrix(camera.combined);// begin a new batch and draw the bucket and// all dropsbatch.begin();batch.draw(bucketImage, bucket.x, bucket.y);for(Rectangle raindrop: raindrops) {batch.draw(dropImage, raindrop.x, raindrop.y);}batch.end();// process user inputif(Gdx.input.isTouched()) {Vector3 touchPos = new Vector3();touchPos.set(Gdx.input.getX(), Gdx.input.getY(), 0);camera.unproject(touchPos);bucket.x = touchPos.x - 64 / 2;}if(Gdx.input.isKeyPressed(Keys.LEFT)) bucket.x -= 200 * Gdx.graphics.getDeltaTime();if(Gdx.input.isKeyPressed(Keys.RIGHT)) bucket.x += 200 * Gdx.graphics.getDeltaTime();// make sure the bucket stays within the screen boundsif(bucket.x < 0) bucket.x = 0;if(bucket.x > 800 - 64) bucket.x = 800 - 64;// check if we need to create a new raindropif(TimeUtils.nanoTime() - lastDropTime > 1000000000) spawnRaindrop();// move the raindrops, remove any that are beneath the bottom edge of// the screen or that hit the bucket. In the latter case we play back// a sound effect as well.for (Iterator<Rectangle> iter = raindrops.iterator(); iter.hasNext(); ) {Rectangle raindrop = iter.next();raindrop.y -= 200 * Gdx.graphics.getDeltaTime();if(raindrop.y + 64 < 0) iter.remove();if(raindrop.overlaps(bucket)) {dropSound.play();iter.remove();}}}@Overridepublic void dispose() {// dispose of all the native resourcesdropImage.dispose();bucketImage.dispose();dropSound.dispose();rainMusic.dispose();batch.dispose();}
}

        音频和图片资源放在 assets 目录下面，如下。

        Desktop 运行效果如下：

        Android 运行效果如下：