程式語言 - Java - Android - OpenGL ES - Draw Triangle

settings.gradle

pluginManagement {
    repositories {
        google()
        mavenCentral()
        gradlePluginPortal()
    }
}
dependencyResolutionManagement {
    repositories {
        google()
        mavenCentral()
    }
}
rootProject.name = "hello-android"
include(":app")

build.gradle

buildscript {
    repositories {
        google()
        mavenCentral()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:8.2.2"
    }
}

執行如下命令：

$ gradle wrapper
$ ./gradlew
$ mkdir -p app/src/main/java/com/example/hello
$ mkdir -p app/src/main/res

app/build.gradle

plugins {
    id "com.android.application"
}

android {
    namespace "com.example.hello"
    compileSdk 34

    defaultConfig {
        applicationId "com.example.hello"
        minSdk 21
        targetSdk 34
        versionCode 1
        versionName "1.0"
    }
}

app/src/main/AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android">
    <application
        android:label="HelloApp">
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>
</manifest>

app/src/main/java/com/example/hello/MainActivity.java

package com.example.hello;
 
import android.app.Activity;
import android.opengl.GLES20;
import android.opengl.GLSurfaceView;
import android.os.Bundle;
 
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
 
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;
 
public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
 
        GLSurfaceView glView = new GLSurfaceView(this);
        glView.setEGLContextClientVersion(2);
        glView.setRenderer(new TriangleRenderer());
 
        setContentView(glView);
    }
 
    static class TriangleRenderer implements GLSurfaceView.Renderer {
        private final float[] triangleCoords = {
             0.0f,  0.5f, 0.0f,
            -0.5f, -0.5f, 0.0f,
             0.5f, -0.5f, 0.0f
        };
 
        private int pos;
        private int program;
        private FloatBuffer vertexBuffer;
 
        private final String vertexShaderCode =
            "attribute vec4 vPosition;" +
            "void main() {" +
            "    gl_Position = vPosition;" +
            "}";
 
        private final String fragmentShaderCode =
            "precision mediump float;" +
            "void main() {" +
            "    gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);" +
            "}";
 
        @Override
        public void onSurfaceCreated(GL10 gl, EGLConfig config) {
            GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
 
            ByteBuffer bb = ByteBuffer.allocateDirect(triangleCoords.length * 4);
            bb.order(ByteOrder.nativeOrder());
            vertexBuffer = bb.asFloatBuffer();
            vertexBuffer.put(triangleCoords);
            vertexBuffer.position(0);
 
            int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode);
            int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode);
 
            program = GLES20.glCreateProgram();
            GLES20.glAttachShader(program, vertexShader);
            GLES20.glAttachShader(program, fragmentShader);
            GLES20.glLinkProgram(program);
            GLES20.glUseProgram(program);

            pos = GLES20.glGetAttribLocation(program, "vPosition");
        }
 
        @Override
        public void onSurfaceChanged(GL10 gl, int width, int height) {
            GLES20.glViewport(0, 0, width, height);
        }
 
        @Override
        public void onDrawFrame(GL10 gl) {
            GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);

            GLES20.glEnableVertexAttribArray(pos);
            GLES20.glVertexAttribPointer(pos, 3, GLES20.GL_FLOAT, false, 3 * 4, vertexBuffer);
            GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3);
            GLES20.glDisableVertexAttribArray(pos);
        }
 
        private int loadShader(int type, String shaderCode) {
            int shader = GLES20.glCreateShader(type);
            GLES20.glShaderSource(shader, shaderCode);
            GLES20.glCompileShader(shader);
            return shader;
        }
    }
}

編譯

$ ./gradlew assembleDebug
$ file app/build/outputs/apk/debug/app-debug.apk
    app/build/outputs/apk/debug/app-debug.apk: Android package (APK), with gradle app-metadata.properties, with APK Signing Block

完成