【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 {
    @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 > 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();
            }
        }
    }

    @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：

声明：本文转自【libGDX】初识libGDX。