android c++ OpenGLES Egl 环境搭建

android搭建opengles 的egl环境之前使用java已经写过，但是一般实际开发opengles的相关代码都在native层，因为native的话效率会比java高很多，步骤都是一致的，只是换一种语言写而已。之前使用java写的opengles egl环境搭建点击下面链接:
https://www.jianshu.com/p/ce3496ab9e02

本文demo下载地址:
https://github.com/ChinaZeng/NativeEglDemo

步骤都是一样的：

1、得到Egl实例
2、得到默认的显示设备（就是窗口）
3、初始化默认显示设备
4、设置显示设备的属性
5、从系统中获取对应属性的配置
6、创建EglContext
7、创建渲染的Surface
8、绑定EglContext和Surface到显示设备中
9、刷新数据，显示渲染场景

代码目录:

代码目录

1. 首先配置android ndk开发环境，我使用的是cmake

cmake_minimum_required(VERSION 3.4.1)

add_library( # Sets the name of the library.
        native-lib
        SHARED
        native-lib.cpp
        egl/EglHelper.cpp
        )

target_link_libraries(
        native-lib
        EGL
        GLESv2
        android
        log
)

2. 书写EglHelper，这个类主要负责egl的环境初始化，绘制和销毁

//环境搭建初始化
int EglHelper::initEgl(EGLNativeWindowType window) {
    //1.得到默认的显示设备（就是窗口） -- eglGetDisplay
    mEglDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
    if (mEglDisplay == EGL_NO_DISPLAY) {
        LOGE("eglGetDisplay error");
        return -1;
    }

    //2. 初始化默认显示设备 -- eglInitialize
    EGLint *version = new EGLint[2];
    if (!eglInitialize(mEglDisplay, &version[0], &version[1])) {
        LOGE("eglInitialize error");
        return -1;
    }

    //3. 设置显示设备的属性
    const EGLint attrib_config_list[] = {
            EGL_RED_SIZE, 8,
            EGL_GREEN_SIZE, 8,
            EGL_BLUE_SIZE, 8,
            EGL_ALPHA_SIZE, 8,
            EGL_DEPTH_SIZE, 8,
            EGL_STENCIL_SIZE, 8,// 眼睛屏幕的距离
            EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,//版本号
            EGL_NONE
    };

    //3.1 根据所需的参数获取符合该参数的config_size，主要是解决有些手机eglChooseConfig失败的兼容性问题
    EGLint num_config;

    if (!eglChooseConfig(mEglDisplay, attrib_config_list, NULL, 1, &num_config)) {
        LOGE("eglChooseConfig error");
        return -1;
    }
    //3.2 根据获取到的config_size得到eglConfig
    EGLConfig eglConfig;
    if (!eglChooseConfig(mEglDisplay, attrib_config_list, &eglConfig, num_config, &num_config)) {
        LOGE("eglChooseConfig error");
        return -1;
    }

    //4. 创建egl上下文 eglCreateContext
    const EGLint attrib_ctx_list[] = {
            EGL_CONTEXT_CLIENT_VERSION, 2,
            EGL_NONE
    };
    mEglContext = eglCreateContext(mEglDisplay, eglConfig, NULL, attrib_ctx_list);
    if (mEglContext == EGL_NO_CONTEXT) {
        LOGE("eglCreateContext  error");
        return -1;
    }
    //5.创建渲染的surface
    mEglSurface = eglCreateWindowSurface(mEglDisplay, eglConfig, window, NULL);
    if (mEglSurface == EGL_NO_SURFACE) {
        LOGE("eglCreateWindowSurface  error");
        return -1;
    }
    //6. 绑定eglContext和surface到display
    if (!eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext)) {
        LOGE("eglMakeCurrent  error");
        return -1;
    }

    //7. 刷新数据，显示渲染场景 -- eglSwapBuffers

    return 0;
}

//交换缓冲 绘制
int EglHelper::swapBuffers() {
    if (mEglDisplay != EGL_NO_DISPLAY && mEglSurface != EGL_NO_SURFACE &&
        eglSwapBuffers(mEglDisplay, mEglSurface)) {
        return 0;
    }
    return -1;
}
//销毁
void EglHelper::destroyEgl() {
    if (mEglDisplay != EGL_NO_DISPLAY) {
        //解绑display上的eglContext和surface
        eglMakeCurrent(mEglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);

        //销毁surface 和 eglContext
        if (mEglSurface != EGL_NO_SURFACE) {
            eglDestroySurface(mEglDisplay, mEglSurface);
            mEglSurface = EGL_NO_SURFACE;
        }

        if (mEglContext != EGL_NO_CONTEXT) {
            eglDestroyContext(mEglDisplay, mEglContext);
            mEglContext = EGL_NO_CONTEXT;
        }

        if (mEglDisplay != EGL_NO_DISPLAY) {
            eglTerminate(mEglDisplay);
            mEglDisplay = EGL_NO_DISPLAY;
        }
    }
}

书写EglThread，顾名思义，这个类主要负责开启一个线程然后根据外部的生命周期调用EglHelper完成egl的环境搭建，并且和外部交互。

EglThread::EglThread() {
    pthread_mutex_init(&pthread_mutex, NULL);
    pthread_cond_init(&pthread_cond, NULL);
}

EglThread::~EglThread() {
    pthread_mutex_destroy(&pthread_mutex);
    pthread_cond_destroy(&pthread_cond);
}


void *eglThreadImpl(void *context) {
    EglThread *eglThread = static_cast<EglThread *>(context);
    if (!eglThread) {
        LOGE("eglThreadImpl eglThread is null");
        return 0;
    }

    EglHelper *eglHelper = new EglHelper();

    if (eglHelper->initEgl(eglThread->mANativeWindow) != 0) {
        LOGE("eglHelper initEgl error");
        return 0;
    }
    eglThread->isExit = false;
    while (!eglThread->isExit) {

        if (eglThread->isCreate) {
            eglThread->isCreate = false;
            eglThread->onCreate();
        }

        if (eglThread->isChange) {
            eglThread->isChange = false;
            eglThread->isStart = true;
            eglThread->onChange(eglThread->surfaceWidth, eglThread->surfaceHeight);
        }

        if (eglThread->isStart) {
            eglThread->onDraw();
            //切换缓冲区，显示
            eglHelper->swapBuffers();

            if (eglThread->mRenderType == RENDER_MODULE_AUTO) {
                usleep(1000000 / 60);
            } else {
                pthread_mutex_lock(&eglThread->pthread_mutex);
                pthread_cond_wait(&eglThread->pthread_cond, &eglThread->pthread_mutex);
                pthread_mutex_unlock(&eglThread->pthread_mutex);
            }
        }

    }

    eglHelper->destroyEgl();
    delete eglHelper;
    eglHelper = NULL;
    //return 0表示线程结束
    return 0;

}


void EglThread::onSurfaceCreate(EGLNativeWindowType window) {
    if (mEglThread == -1) {
        isCreate = true;
        mANativeWindow = window;
        pthread_create(&mEglThread, NULL, eglThreadImpl, this);
    }
}


void EglThread::onSurfaceChange(int width, int height) {
    if (mEglThread != -1) {
        surfaceWidth = width;
        surfaceHeight = height;
        isChange = true;

        notifyRender();
    }
}

void EglThread::setRenderModule(int renderType) {
    mRenderType = renderType;
    notifyRender();
}

void EglThread::notifyRender() {
    pthread_mutex_lock(&pthread_mutex);
    pthread_cond_signal(&pthread_cond);
    pthread_mutex_unlock(&pthread_mutex);
}


void EglThread::callBackOnCreate(EglThread::OnCreate onCreate) {
    this->onCreate = onCreate;
}

void EglThread::callBackOnChange(EglThread::OnChange onChange) {
    this->onChange = onChange;
}

void EglThread::callBackOnDraw(EglThread::OnDraw onDraw) {
    this->onDraw = onDraw;
}

3. 书写java层和native层交互，对应生命周期回调即可
   NationOpenGL.java

public class NationOpenGL {

    static {
        System.loadLibrary("native-lib");
    }

    public native void nativeSurfaceCreate(Surface surface);

    public native void nativeSurfaceChanged(int width, int height);

    public native void nativeSurfaceDestroyed();

}

NativeGLSurfaceView.java

public class NativeGLSurfaceView extends SurfaceView implements SurfaceHolder.Callback {
    private NationOpenGL mNationOpenGL;

    public NativeGLSurfaceView(Context context) {
        this(context, null);
    }

    public NativeGLSurfaceView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public NativeGLSurfaceView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mNationOpenGL = new NationOpenGL();
        getHolder().addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mNationOpenGL.nativeSurfaceCreate(holder.getSurface());
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        mNationOpenGL.nativeSurfaceChanged(width, height);
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mNationOpenGL.nativeSurfaceDestroyed();
    }
}

native-lib.cpp

EglThread *eglThread = NULL;


void callBackOnCreate() {
    LOGE("callBackOnCreate");
}

void callBackOnChange(int width, int height) {
    glViewport(0, 0, width, height);
    LOGE("callBackOnChange");
}

void callBackOnDraw() {
    glClearColor(0.0f, 1.0f, 1.0f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    LOGE("callBackOnDraw");
}

extern "C"
JNIEXPORT void JNICALL
Java_com_zzw_nativeopnegldemo_opengl_NationOpenGL_nativeSurfaceCreate(JNIEnv *env, jobject instance,
                                                                      jobject surface) {

    eglThread = new EglThread();
    eglThread->callBackOnCreate(callBackOnCreate);
    eglThread->callBackOnChange(callBackOnChange);
    eglThread->callBackOnDraw(callBackOnDraw);
    eglThread->setRenderModule(RENDER_MODULE_MANUAL);


    ANativeWindow *nativeWindow = ANativeWindow_fromSurface(env, surface);
    eglThread->onSurfaceCreate(nativeWindow);
}

extern "C"
JNIEXPORT void JNICALL
Java_com_zzw_nativeopnegldemo_opengl_NationOpenGL_nativeSurfaceChanged(JNIEnv *env,
                                                                       jobject instance, jint width,
                                                                       jint height) {
    if (eglThread) {
        eglThread->onSurfaceChange(width, height);
    }
}


extern "C"
JNIEXPORT void JNICALL
Java_com_zzw_nativeopnegldemo_opengl_NationOpenGL_nativeSurfaceDestroyed(JNIEnv *env,
                                                                         jobject instance) {
    if (eglThread) {
        eglThread->isExit = true;
        //等待线程结束
        pthread_join(eglThread, NULL);
        delete (eglThread);
        eglThread = NULL;
    }

}