【libGDX】初识libGDX

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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 { @Override protected 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; @Override public void create () { batch = new SpriteBatch(); img = new Texture("badlogic.jpg"); } @Override public void render () { ScreenUtils.clear(1, 0, 0, 1); batch.begin(); batch.draw(img, 0, 0); batch.end(); } @Override public 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，本节完整代码资源见 → 基于libGDX实现接水游戏。

        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; @Override public void create() { // load the images for the droplet and the bucket, 64x64 pixels each dropImage = 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 immediately rainMusic.setLooping(true); rainMusic.play(); // create the camera and the SpriteBatch camera = new OrthographicCamera(); camera.setToOrtho(false, 800, 480); batch = new SpriteBatch(); // create a Rectangle to logically represent the bucket bucket = new Rectangle(); bucket.x = 800 / 2 - 64 / 2; // center the bucket horizontally bucket.y = 20; // bottom left corner of the bucket is 20 pixels above the bottom screen edge bucket.width = 64; bucket.height = 64; // create the raindrops array and spawn the first raindrop raindrops = 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(); } @Override public 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 drops batch.begin(); batch.draw(bucketImage, bucket.x, bucket.y); for(Rectangle raindrop: raindrops) { batch.draw(dropImage, raindrop.x, raindrop.y); } batch.end(); // process user input if(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 bounds if(bucket.x < 0) bucket.x = 0; if(bucket.x > 800 - 64) bucket.x = 800 - 64; // check if we need to create a new raindrop if(TimeUtils.nanoTime() - lastDropTime > ) 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(); } } } @Override public void dispose() { // dispose of all the native resources dropImage.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：