Android OpenGL ES 3.0开发实战(01)：Android OpenGL ES 3.0 Native开发环境搭建

• 一、前言
• 二、准备工作
• • OpenGL ES 声明
  • Activity
• 三、GLSurfaceView和NativeRender
• • GLSurfaceView
  • Render
• 四、NDK和JNI
• • NativeRenderJNI
  • C++开发环境搭建
  • • 安装NDK
    • 配置
    • CMakeLists.txt
    • JNI

本篇包括：

• 准备工作
• GLSurfaceView和NativeRender
• NDK和JNI

Demo Github:

整个项目目录如下：

1. app 业务上层，简单的界面逻辑
2. basic 一些通用的工具类
3. demos 一些demos存放的地方
4. libmedianative native opengl es代码

注意：一般搭建环境，只需要app和native即可，或直接都放在app里

更详细可参考官方：https://developer.android.com/guide/topics/graphics/opengl#java

final ConfigurationInfo configurationInfo = activityManager.getDeviceConfigurationInfo();
final boolean supportsEs3 = configurationInfo.reqGlEsVersion >= 0x30000

代码层面可根据不同的机型做如上判断

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);
        setContentView(new DefaultGLSurfaceView(this));
    }
}

1. 沉浸式Flag设置
2. new DefaultGLSurfaceView

public class DefaultGLSurfaceView extends GLSurfaceView {
    BaseWrapRender baseWrapRender;
    public DefaultGLSurfaceView(Context context) {
        this(context,null);
    }
    public DefaultGLSurfaceView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }
    private void init() {
        setEGLContextClientVersion(3);
        baseWrapRender = new BaseWrapRender(new NativeRenderV2(IAssignType.LearnOpenGL.ASSIGN_LEARN_OPENGL_SHADER_UNIFORM_SHADER));
        setRenderer(baseWrapRender);
        //RENDERMODE_CONTINUOUSLY 1s 60帧
//        setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);
        setRenderMode(GLSurfaceView.RENDERMODE_CONTINUOUSLY);
    }
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        super.surfaceDestroyed(holder);
        baseWrapRender.onSurfaceDestroyed();
    }
}

注：在源码里详细说明了GLSurfaceView的简单功能和用法
An implementation of SurfaceView that uses the dedicated surface for displaying OpenGL rendering.
A GLSurfaceView provides the following features:

1. Manages a surface, which is a special piece of memory that can be composited into the Android view system.
2. Manages an EGL display, which enables OpenGL to render into a surface.
3. Accepts a user-provided Renderer object that does the actual rendering.
4. Renders on a dedicated thread to decouple rendering performance from the UI thread.
5. Supports both on-demand and continuous rendering.
6. Optionally wraps, traces, and/or error-checks the renderer's OpenGL calls.

这里就不细说GLSurfaceView，感兴趣的可看源码，主要做了如下几件事情

1. setEGLContextClientVersion(3); 设置version 3 EGL Context
2. 设置render -> BaseWrapRender
3. 设置render Mode。
	 RENDERMODE_CONTINUOUSLY为连续请求(经测试1s60帧)
	 RENDERMODE_WHEN_DIRTY surface create / 手动调用requestRender触发

public class NativeRenderV2 implements IRender {
    NativeRenderJni nativeRenderJni;
    private int assignType = IAssignType.LearnOpenGL.ASSIGN_LEARN_OPENGL_TRIANGLE_SIMPLE;

    public NativeRenderV2(int assignType) {
        this.assignType = assignType;
    }

    @Override
    public void init() {
        AssetManager assetManager = AppContext.basicContext.getAssets();
        nativeRenderJni = new NativeRenderJni();
        nativeRenderJni.initV2(assetManager, assignType);
    }

    @Override
    public void onSurfaceCreated() {
        nativeRenderJni.onSurfaceCreated();
    }

    @Override
    public void onSurfaceChanged(int width, int height) {
        nativeRenderJni.onSurfaceChanged(width,height);
    }

    @Override
    public void onDrawFrame() {
        nativeRenderJni.onDrawFrame();

    }

    @Override
    public void onSurfaceDestroyed() {
    }
}

1. BaseWrapRender是实现IRender接口的NativeRender的一层包装
2. IRender定义了调用到Native层面的接口。自己也可直接在GLSurfaceView里设置setRender(new NativeRender())这样实现
3. 该Render最终都调用到NativeRenderJni类

public class NativeRenderJni {
    public native void init(AssetManager assetManager, int assignType, String vertexShaderAssetName, String fragmentShaderAssetName);
    public native void initV2(AssetManager assetManager, int assignType);
    public native void onSurfaceCreated();
    public native void onSurfaceChanged(int width, int height);
    public native void onDrawFrame();
    public native void onDestroy();
}

1. AssetManager用于读取放在asset里的glsl shader
2. assignType用于区分使用哪类demo

project Structure选择对应的NDK；如果没有，则去SDK Manager里下载对应的NDK

buildTypes {
   debug {
       minifyEnabled false
       proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
       externalNativeBuild {
           cmake {
               arguments '-DANDROID_PLATFORM=android-21', '-DANDROID_TOOLCHAIN=clang',
                       '-DANDROID_ARM_NEON=TRUE', '-DANDROID_STL=c++_static'
               cFlags '-O3', '-DGL_GLEXT_PROTOTYPES', '-DEGL_EGLEXT_PROTOTYPES', '-fsigned-char', '-Wformat','-mfpu=neon', '-mfloat-abi=softfp -frtti' // full optimization, char data type is signed
               // 编译优化，设置函式是否能被 inline 的伪指令长度
               cppFlags '-O3', '-fexceptions', '-fsigned-char',
                       "-frtti -std=c++11", '-Wformat'
           }
       }
   }

   release {
       minifyEnabled false
       proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
       externalNativeBuild {
           cmake {
               arguments '-DANDROID_PLATFORM=android-21', '-DANDROID_TOOLCHAIN=clang',
                       '-DANDROID_ARM_NEON=TRUE', '-DANDROID_STL=c++_static'
               cFlags '-O3', '-DGL_GLEXT_PROTOTYPES', '-DEGL_EGLEXT_PROTOTYPES', '-fsigned-char', '-Wformat','-mfpu=neon', '-mfloat-abi=softfp -frtti'
               // full optimization, char data type is signed
               // 编译优化，设置函式是否能被 inline 的伪指令长度
               cppFlags '-O3', '-fexceptions', '-fsigned-char',
                       "-frtti -std=c++11", '-Wformat'
           }
       }
   }
}

externalNativeBuild {
   cmake {
       path "CMakeLists.txt"
       version "3.10.2"
   }
}

compileOptions {
   sourceCompatibility = JavaVersion.VERSION_1_8
   targetCompatibility = JavaVersion.VERSION_1_8
}

1. externalNativeBuild配置

// 版本说明 和build.gradle对应上。具体不同版本号差异可自行查询相关资料
cmake_minimum_required(VERSION 3.10.2)

//设置code目录变量：PATH_TO_CODE_CORE 
set(PATH_TO_CODE_CORE ${CMAKE_SOURCE_DIR}/src/main/cpp)

//文件操作命令设置全局变量
file(GLOB FILES_JNI_LAYER "${PATH_TO_JNI_LAYER}
// 包含用于记录到 logcat 的 API。
find_library(log-lib log)

find_library(android-lib android)
//zlib 压缩
//您可以通过添加  并链接到 libz 来使用
find_library(z-lib z)

find_library(EGL-lib EGL)
//open gl es 头文件
find_library(GLESv3-lib GLESv3)

//设置platform-libs变量
set(platform-libs
        ${log-lib}
        ${android-lib}
        ${EGL-lib}
        ${GLESv3-lib}
        ${z-lib}
        )

//add_library 根据源码文件生成目标库。注意这里需要添加所需要的C++代码。这里只放入了NativeRenderJNI对应的NativeRenderJNI.cpp
add_library(openglnative SHARED
        ${FILES_JNI_LAYER}
        ${FILES_LIB_CORE_CODE}
        ${PATH_TO_CODE_CORE}/jni/NativeRenderJNI.cpp
        )

//link libraries => medianative.so
target_link_libraries(
        openglnative
        ${platform-libs}
        )

CmakeLists.txt里cmake使用语法具体可参考如下记录：
https://github.com/sunquan9301/AndroidLearning/blob/master/OpenGL/learnnote/Cmake%20Develop%20Guide

此时我们把所有相关的cpp代码编译成了名为openglnative库，因此在App启动的时候需要loadLibrary =>

try {
    System.loadLibrary("openglnative");
} catch (Throwable ignore) {
    Log.e(TAG, "loadLibrary Load native library failed : " + ignore.getMessage());
}

这里我们编译好了相关的C++ native开发环境也引入了相关的库，此时NativeRenderJNI.java和NativeRenderJNI.cpp相对应，在NativeRenderJNI.cpp我们通过JNI建立与NativeRenderJNI.java对应的函数。

JNI相关资料可自行查阅，android通过JNI链接上层java开发和下层C++开发。JNI有2种链接函数方式静态链接和动态链接。

1. 静态链接根据函数签名方式在编译时注册，可直接在代码里通过提示创建。
2. 动态链接在JNI_OnLoad方法里通过registerNativeMethods方式注册

最终在NativeRenderJNI.cpp里呈现如下(部分函数)，输出log验证正确性。

JNIEXPORT void JNICALL
Java_com_scott_nativecode_NativeRenderJni_onSurfaceCreated(JNIEnv *env, jobject thiz) {
	__android_log_print(ANDROID_LOG_DEBUG,  "NativeRenderJni", "onSurfaceCreated");
}

JNIEXPORT void JNICALL
Java_com_scott_nativecode_NativeRenderJni_onSurfaceChanged(JNIEnv *env, jobject thiz, jint width,
                                                           jint height) {
}
JNIEXPORT void JNICALL
Java_com_scott_nativecode_NativeRenderJni_onDrawFrame(JNIEnv *env, jobject thiz) {
}