Android EGL + C/C++ 编写OpenGLES程序
2018-04-07 本文已影响164人
cain_huang
本人在编写基于FFmpeg的播放器时，需要将解码后的视频帧数据upload到GPU进行渲染输出，方便给视频添加滤镜之类的。输出部分有两种方案，一种是使用GLSurfaceView，就是将Native解码得到的数据回到到Java层进行渲染。第二种是使用EGL + ANativeWindow 直接在Native层利用GPU进行渲染。第一种方案需要在Native层与Java层之间不断进行数据交换，这方的方式其实并不太好，如果遇到多线程处理，由于Java层与Native层之间各自线程空间的不同，个人不太推荐这样的方式。下面来讲解一下如何在Native层使用EGL进行渲染。如果不了解什么是EGL的话，建议先看看本人的文章EGL简介以及窗口初始化了解一下。另外，大家有兴趣的话，可以看下GLSurfaceView的源码，GLSurfaceView也是通过开辟一个Looper线程GLThread来封装EGL来实现的。我们接下来实现一个Native层封装EGL + ANativeWindow的项目，项目的Github地址如下：
EGLNativeRender
EGL的封装
由于EGL的API使用起来比较复杂，为了方便使用，我们需要将EGL做一层封装。关于EGL的API使用方式，可以参考Grafika项目中的EglCore.java、EglSurfaceBase.java、WindowSurface.java和OffscreenSurface.java，我的CainCamera 项目中也用到了Grafika的EGL封装类，使用方便。由于Grafika的EglCore是用Java层封装的，我们现在需要在Native层实现类似的EglCore、EglSurfaceBase、WindowSurface和OffscreenSurface类。废话不多数，直接上源码：
EglCore.h:
#ifndef CAINCAMERA_EGLCORE_H
#define CAINCAMERA_EGLCORE_H
#include <android/native_window.h>
#include <EGL/egl.h>
#include <EGL/eglext.h>
#include <EGL/eglplatform.h>
/**
* Constructor flag: surface must be recordable. This discourages EGL from using a
* pixel format that cannot be converted efficiently to something usable by the video
* encoder.
*/
#define FLAG_RECORDABLE 0x01
/**
* Constructor flag: ask for GLES3, fall back to GLES2 if not available. Without this
* flag, GLES2 is used.
*/
#define FLAG_TRY_GLES3 002
// Android-specific extension
#define EGL_RECORDABLE_ANDROID 0x3142
typedef EGLBoolean (EGLAPIENTRYP EGL_PRESENTATION_TIME_ANDROIDPROC)(EGLDisplay display, EGLSurface surface, khronos_stime_nanoseconds_t time);
class EglCore {
private:
EGLDisplay mEGLDisplay = EGL_NO_DISPLAY;
EGLConfig mEGLConfig = NULL;
EGLContext mEGLContext = EGL_NO_CONTEXT;
// 设置时间戳方法
EGL_PRESENTATION_TIME_ANDROIDPROC eglPresentationTimeANDROID = NULL;
int mGlVersion = -1;
// 查找合适的EGLConfig
EGLConfig getConfig(int flags, int version);
public:
EglCore();
~EglCore();
EglCore(EGLContext sharedContext, int flags);
bool init(EGLContext sharedContext, int flags);
// 释放资源
void release();
// 获取EglContext
EGLContext getEGLContext();
// 销毁Surface
void releaseSurface(EGLSurface eglSurface);
// 创建EGLSurface
EGLSurface createWindowSurface(ANativeWindow *surface);
// 创建离屏EGLSurface
EGLSurface createOffscreenSurface(int width, int height);
// 切换到当前上下文
void makeCurrent(EGLSurface eglSurface);
// 切换到某个上下文
void makeCurrent(EGLSurface drawSurface, EGLSurface readSurface);
// 没有上下文
void makeNothingCurrent();
// 交换显示
bool swapBuffers(EGLSurface eglSurface);
// 设置pts
void setPresentationTime(EGLSurface eglSurface, long nsecs);
// 判断是否属于当前上下文
bool isCurrent(EGLSurface eglSurface);
// 执行查询
int querySurface(EGLSurface eglSurface, int what);
// 查询字符串
const char *queryString(int what);
// 获取当前的GLES 版本号
int getGlVersion();
// 检查是否出错
void checkEglError(const char *msg);
};
#endif //CAINCAMERA_EGLCORE_H
EglCore.cpp:
#include "../common/native_log.h"
#include "EglCore.h"
#include <assert.h>
EglCore::EglCore() {
init(NULL, 0);
}
EglCore::~EglCore() {
release();
}
/**
* 构造方法
* @param sharedContext
* @param flags
*/
EglCore::EglCore(EGLContext sharedContext, int flags) {
init(sharedContext, flags);
}
/**
* 初始化
* @param sharedContext
* @param flags
* @return
*/
bool EglCore::init(EGLContext sharedContext, int flags) {
assert(mEGLDisplay == EGL_NO_DISPLAY);
if (mEGLDisplay != EGL_NO_DISPLAY) {
ALOGE("EGL already set up");
return false;
}
if (sharedContext == NULL) {
sharedContext = EGL_NO_CONTEXT;
}
mEGLDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
assert(mEGLDisplay != EGL_NO_DISPLAY);
if (mEGLDisplay == EGL_NO_DISPLAY) {
ALOGE("unable to get EGL14 display.\n");
return false;
}
if (!eglInitialize(mEGLDisplay, 0, 0)) {
mEGLDisplay = EGL_NO_DISPLAY;
ALOGE("unable to initialize EGL14");
return false;
}
// 尝试使用GLES3
if ((flags & FLAG_TRY_GLES3) != 0) {
EGLConfig config = getConfig(flags, 3);
if (config != NULL) {
int attrib3_list[] = {
EGL_CONTEXT_CLIENT_VERSION, 3,
EGL_NONE
};
EGLContext context = eglCreateContext(mEGLDisplay, config,
sharedContext, attrib3_list);
checkEglError("eglCreateContext");
if (eglGetError() == EGL_SUCCESS) {
mEGLConfig = config;
mEGLContext = context;
mGlVersion = 3;
}
}
}
// 如果GLES3没有获取到，则尝试使用GLES2
if (mEGLContext == EGL_NO_CONTEXT) {
EGLConfig config = getConfig(flags, 2);
assert(config != NULL);
int attrib2_list[] = {
EGL_CONTEXT_CLIENT_VERSION, 2,
EGL_NONE
};
EGLContext context = eglCreateContext(mEGLDisplay, config,
sharedContext, attrib2_list);
checkEglError("eglCreateContext");
if (eglGetError() == EGL_SUCCESS) {
mEGLConfig = config;
mEGLContext = context;
mGlVersion = 2;
}
}
// 获取eglPresentationTimeANDROID方法的地址
eglPresentationTimeANDROID = (EGL_PRESENTATION_TIME_ANDROIDPROC)
eglGetProcAddress("eglPresentationTimeANDROID");
if (!eglPresentationTimeANDROID) {
ALOGE("eglPresentationTimeANDROID is not available!");
}
int values[1] = {0};
eglQueryContext(mEGLDisplay, mEGLContext, EGL_CONTEXT_CLIENT_VERSION, values);
ALOGD("EGLContext created, client version %d", values[0]);
return true;
}
/**
* 获取合适的EGLConfig
* @param flags
* @param version
* @return
*/
EGLConfig EglCore::getConfig(int flags, int version) {
int renderableType = EGL_OPENGL_ES2_BIT;
if (version >= 3) {
renderableType |= EGL_OPENGL_ES3_BIT_KHR;
}
int attribList[] = {
EGL_RED_SIZE, 8,
EGL_GREEN_SIZE, 8,
EGL_BLUE_SIZE, 8,
EGL_ALPHA_SIZE, 8,
//EGL_DEPTH_SIZE, 16,
//EGL_STENCIL_SIZE, 8,
EGL_RENDERABLE_TYPE, renderableType,
EGL_NONE, 0, // placeholder for recordable [@-3]
EGL_NONE
};
int length = sizeof(attribList) / sizeof(attribList[0]);
if ((flags & FLAG_RECORDABLE) != 0) {
attribList[length - 3] = EGL_RECORDABLE_ANDROID;
attribList[length - 2] = 1;
}
EGLConfig configs = NULL;
int numConfigs;
if (!eglChooseConfig(mEGLDisplay, attribList, &configs, 1, &numConfigs)) {
ALOGW("unable to find RGB8888 / %d EGLConfig", version);
return NULL;
}
return configs;
}
/**
* 释放资源
*/
void EglCore::release() {
if (mEGLDisplay != EGL_NO_DISPLAY) {
eglMakeCurrent(mEGLDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
eglDestroyContext(mEGLDisplay, mEGLContext);
eglReleaseThread();
eglTerminate(mEGLDisplay);
}
mEGLDisplay = EGL_NO_DISPLAY;
mEGLContext = EGL_NO_CONTEXT;
mEGLConfig = NULL;
}
/**
* 获取EGLContext
* @return
*/
EGLContext EglCore::getEGLContext() {
return mEGLContext;
}
/**
* 销毁EGLSurface
* @param eglSurface
*/
void EglCore::releaseSurface(EGLSurface eglSurface) {
eglDestroySurface(mEGLDisplay, eglSurface);
}
/**
* 创建EGLSurface
* @param surface
* @return
*/
EGLSurface EglCore::createWindowSurface(ANativeWindow *surface) {
assert(surface != NULL);
if (surface == NULL) {
ALOGE("ANativeWindow is NULL!");
return NULL;
}
int surfaceAttribs[] = {
EGL_NONE
};
ALOGD("eglCreateWindowSurface start");
EGLSurface eglSurface = eglCreateWindowSurface(mEGLDisplay, mEGLConfig, surface, surfaceAttribs);
checkEglError("eglCreateWindowSurface");
assert(eglSurface != NULL);
if (eglSurface == NULL) {
ALOGE("EGLSurface is NULL!");
return NULL;
}
return eglSurface;
}
/**
* 创建离屏渲染的EGLSurface
* @param width
* @param height
* @return
*/
EGLSurface EglCore::createOffscreenSurface(int width, int height) {
int surfaceAttribs[] = {
EGL_WIDTH, width,
EGL_HEIGHT, height,
EGL_NONE
};
EGLSurface eglSurface = eglCreatePbufferSurface(mEGLDisplay, mEGLConfig, surfaceAttribs);
assert(eglSurface != NULL);
if (eglSurface == NULL) {
ALOGE("Surface was null");
return NULL;
}
return eglSurface;
}
/**
* 切换到当前的上下文
* @param eglSurface
*/
void EglCore::makeCurrent(EGLSurface eglSurface) {
if (mEGLDisplay == EGL_NO_DISPLAY) {
ALOGD("Note: makeCurrent w/o display.\n");
}
if (!eglMakeCurrent(mEGLDisplay, eglSurface, eglSurface, mEGLContext)) {
// TODO 抛出异常
}
}
/**
* 切换到某个上下文
* @param drawSurface
* @param readSurface
*/
void EglCore::makeCurrent(EGLSurface drawSurface, EGLSurface readSurface) {
if (mEGLDisplay == EGL_NO_DISPLAY) {
ALOGD("Note: makeCurrent w/o display.\n");
}
if (!eglMakeCurrent(mEGLDisplay, drawSurface, readSurface, mEGLContext)) {
// TODO 抛出异常
}
}
/**
*
*/
void EglCore::makeNothingCurrent() {
if (!eglMakeCurrent(mEGLDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT)) {
// TODO 抛出异常
}
}
/**
* 交换显示
* @param eglSurface
* @return
*/
bool EglCore::swapBuffers(EGLSurface eglSurface) {
return eglSwapBuffers(mEGLDisplay, eglSurface);
}
/**
* 设置显示时间戳pts
* @param eglSurface
* @param nsecs
*/
void EglCore::setPresentationTime(EGLSurface eglSurface, long nsecs) {
eglPresentationTimeANDROID(mEGLDisplay, eglSurface, nsecs);
}
/**
* 是否处于当前上下文
* @param eglSurface
* @return
*/
bool EglCore::isCurrent(EGLSurface eglSurface) {
return mEGLContext == eglGetCurrentContext() &&
eglSurface == eglGetCurrentSurface(EGL_DRAW);
}
/**
* 查询surface
* @param eglSurface
* @param what
* @return
*/
int EglCore::querySurface(EGLSurface eglSurface, int what) {
int value;
eglQuerySurface(mEGLContext, eglSurface, what, &value);
return value;
}
/**
* 查询字符串
* @param what
* @return
*/
const char* EglCore::queryString(int what) {
return eglQueryString(mEGLDisplay, what);
}
/**
* 获取GLES版本号
* @return
*/
int EglCore::getGlVersion() {
return mGlVersion;
}
/**
* 检查是否出错
* @param msg
*/
void EglCore::checkEglError(const char *msg) {
int error;
if ((error = eglGetError()) != EGL_SUCCESS) {
// TODO 抛出异常
ALOGE("%s: EGL error: %x", msg, error);
}
}
到这里，我们就封装好了EglCore核心，那么接下来我们需要对EGLSurface进行封装处理：
EglSurfaceBase.h:
#ifndef CAINCAMERA_EGLSURFACEBASE_H
#define CAINCAMERA_EGLSURFACEBASE_H
#include "EglCore.h"
#include "../common/native_log.h"
class EglSurfaceBase {
public:
EglSurfaceBase(EglCore *eglCore);
// 创建窗口Surface
void createWindowSurface(ANativeWindow *nativeWindow);
// 创建离屏Surface
void createOffscreenSurface(int width, int height);
// 获取宽度
int getWidth();
// 获取高度
int getHeight();
// 释放EGLSurface
void releaseEglSurface();
// 切换到当前上下文
void makeCurrent();
// 交换缓冲区，显示图像
bool swapBuffers();
// 设置显示时间戳
void setPresentationTime(long nsecs);
// 获取当前帧缓冲
char *getCurrentFrame();
protected:
EglCore *mEglCore;
EGLSurface mEglSurface;
int mWidth;
int mHeight;
};
#endif //CAINCAMERA_EGLSURFACEBASE_H
EglSurfaceBase.cpp:
#include <assert.h>
#include <GLES2/gl2.h>
#include "EglSurfaceBase.h"
EglSurfaceBase::EglSurfaceBase(EglCore *eglCore) : mEglCore(eglCore) {
mEglSurface = EGL_NO_SURFACE;
}
/**
* 创建显示的Surface
* @param nativeWindow
*/
void EglSurfaceBase::createWindowSurface(ANativeWindow *nativeWindow) {
assert(mEglSurface == EGL_NO_SURFACE);
if (mEglSurface != EGL_NO_SURFACE) {
ALOGE("surface already created\n");
return;
}
mEglSurface = mEglCore->createWindowSurface(nativeWindow);
}
/**
* 创建离屏surface
* @param width
* @param height
*/
void EglSurfaceBase::createOffscreenSurface(int width, int height) {
assert(mEglSurface == EGL_NO_SURFACE);
if (mEglSurface != EGL_NO_SURFACE) {
ALOGE("surface already created\n");
return;
}
mEglSurface = mEglCore->createOffscreenSurface(width, height);
mWidth = width;
mHeight = height;
}
/**
* 获取宽度
* @return
*/
int EglSurfaceBase::getWidth() {
if (mWidth < 0) {
return mEglCore->querySurface(mEglSurface, EGL_WIDTH);
} else {
return mWidth;
}
}
/**
* 获取高度
* @return
*/
int EglSurfaceBase::getHeight() {
if (mHeight < 0) {
return mEglCore->querySurface(mEglSurface, EGL_HEIGHT);
} else {
return mHeight;
}
}
/**
* 释放EGLSurface
*/
void EglSurfaceBase::releaseEglSurface() {
mEglCore->releaseSurface(mEglSurface);
mEglSurface = EGL_NO_SURFACE;
mWidth = mHeight = -1;
}
/**
* 切换到当前EGLContext
*/
void EglSurfaceBase::makeCurrent() {
mEglCore->makeCurrent(mEglSurface);
}
/**
* 交换到前台显示
* @return
*/
bool EglSurfaceBase::swapBuffers() {
bool result = mEglCore->swapBuffers(mEglSurface);
if (!result) {
ALOGD("WARNING: swapBuffers() failed");
}
return result;
}
/**
* 设置当前时间戳
* @param nsecs
*/
void EglSurfaceBase::setPresentationTime(long nsecs) {
mEglCore->setPresentationTime(mEglSurface, nsecs);
}
/**
* 获取当前像素
* @return
*/
char* EglSurfaceBase::getCurrentFrame() {
char *pixels = NULL;
glReadPixels(0, 0, getWidth(), getHeight(), GL_RGBA, GL_UNSIGNED_BYTE, pixels);
return pixels;
}
好了，我们封装好了EGLSurface的基类，接下来我们需要实现一个用于显示的WindowSurface 和 用于离屏渲染的OffscreenSurface，实现如下：
WindowSurface.h:
#ifndef CAINCAMERA_WINDOWSURFACE_H
#define CAINCAMERA_WINDOWSURFACE_H
#include "EglSurfaceBase.h"
class WindowSurface : public EglSurfaceBase {
public:
WindowSurface(EglCore *eglCore, ANativeWindow *window, bool releaseSurface);
WindowSurface(EglCore *eglCore, ANativeWindow *window);
// 释放资源
void release();
// 重新创建
void recreate(EglCore *eglCore);
private:
ANativeWindow *mSurface;
bool mReleaseSurface;
};
#endif //CAINCAMERA_WINDOWSURFACE_H
WindowSurface.cpp:
#include <assert.h>
#include "WindowSurface.h"
WindowSurface::WindowSurface(EglCore *eglCore, ANativeWindow *window, bool releaseSurface)
: EglSurfaceBase(eglCore) {
mSurface = window;
createWindowSurface(mSurface);
mReleaseSurface = releaseSurface;
}
WindowSurface::WindowSurface(EglCore *eglCore, ANativeWindow *window)
: EglSurfaceBase(eglCore) {
createWindowSurface(window);
mSurface = window;
}
void WindowSurface::release() {
releaseEglSurface();
if (mSurface != NULL) {
ANativeWindow_release(mSurface);
mSurface = NULL;
}
}
void WindowSurface::recreate(EglCore *eglCore) {
assert(mSurface != NULL);
if (mSurface == NULL) {
ALOGE("not yet implemented ANativeWindow");
return;
}
mEglCore = eglCore;
createWindowSurface(mSurface);
}
OffscreenSurface.h:
#ifndef CAINCAMERA_OFFSCREENSURFACE_H
#define CAINCAMERA_OFFSCREENSURFACE_H
#include "EglSurfaceBase.h"
class OffscreenSurface : public EglSurfaceBase {
public:
OffscreenSurface(EglCore *eglCore, int width, int height);
void release();
};
#endif //CAINCAMERA_OFFSCREENSURFACE_H
OffscreenSurface.cpp:
#include "OffscreenSurface.h"
OffscreenSurface::OffscreenSurface(EglCore *eglCore, int width, int height)
: EglSurfaceBase(eglCore) {
createOffscreenSurface(width, height);
}
void OffscreenSurface::release() {
releaseEglSurface();
}
到这里，我们就在Native实现了跟Grafika 的Java层一样的EGL封装。在封装好EGL 之后，我们需要一个GLRender，跟Java 层 GLSurfaceView 差不多。废话不多说，直接上源码：
GLRender.h:
#ifndef EGLNATIVESAMPLE_GLRENDER_H
#define EGLNATIVESAMPLE_GLRENDER_H
#include <android/native_window.h>
#include "../caingles/EglCore.h"
#include "../caingles/WindowSurface.h"
#include "Triangle.h"
class GLRender {
public:
GLRender();
virtual ~GLRender();
void surfaceCreated(ANativeWindow *window);
void surfaceChanged(int width, int height);
void surfaceDestroyed(void);
private:
EglCore *mEglCore;
WindowSurface *mWindowSurface;
Triangle *mTriangle;
};
#endif //EGLNATIVESAMPLE_GLRENDER_H
GLRender.cpp:
#include "GLRender.h"
#include "../caingles/GlUtils.h"
#include <GLES2/gl2.h>
#include <GLES2/gl2ext.h>
#include <GLES2/gl2platform.h>
#include <assert.h>
GLRender::GLRender() {
mEglCore = NULL;
mWindowSurface = NULL;
}
GLRender::~GLRender() {
if (mEglCore) {
mEglCore->release();
delete mEglCore;
mEglCore = NULL;
}
}
void GLRender::surfaceCreated(ANativeWindow *window) {
if (mEglCore == NULL) {
mEglCore = new EglCore(NULL, FLAG_RECORDABLE);
}
mWindowSurface = new WindowSurface(mEglCore, window, false);
assert(mWindowSurface != NULL && mEglCore != NULL);
mWindowSurface->makeCurrent();
mTriangle = new Triangle();
mTriangle->init();
}
void GLRender::surfaceChanged(int width, int height) {
mWindowSurface->makeCurrent();
mTriangle->onDraw(width, height);
mWindowSurface->swapBuffers();
}
void GLRender::surfaceDestroyed() {
if (mTriangle) {
mTriangle->destroy();
delete mTriangle;
mTriangle = NULL;
}
if (mWindowSurface) {
mWindowSurface->release();
delete mWindowSurface;
mWindowSurface = NULL;
}
if (mEglCore) {
mEglCore->release();
delete mEglCore;
mEglCore = NULL;
}
}
其中Triangle是使用OpenGLES绘制三角形的类，实现如下：
Triangle.h:
#ifndef EGLNATIVERENDER_TRIANGLE_H
#define EGLNATIVERENDER_TRIANGLE_H
#include "../caingles/GlUtils.h"
#include "../caingles/GlShaders.h"
#include "../common/native_log.h"
class Triangle {
public:
Triangle();
virtual ~Triangle();
int init(void);
void onDraw(int width, int height);
void destroy();
private:
int programHandle;
};
#endif //EGLNATIVERENDER_TRIANGLE_H
Triangle.cpp:
#include "Triangle.h"
const GLint COORDS_PER_VERTEX = 3;
const GLint vertexStride = COORDS_PER_VERTEX * 4;
Triangle::Triangle() {}
Triangle::~Triangle() {
}
int Triangle::init() {
char vertexShader[] =
"#version 300 es\n"
"layout(location = 0) in vec4 a_position;\n"
"layout(location = 1) in vec4 a_color;\n"
"out vec4 v_color;"
"void main()\n"
"{\n"
" gl_Position = a_position;\n"
" v_color = a_color;\n"
"}\n";
char fragmentShader[] =
"#version 300 es\n"
"precision mediump float;\n"
"in vec4 v_color;\n"
"out vec4 fragColor;\n"
"void main()\n"
"{\n"
// " fragColor = vec4 ( 1.0, 0.0, 0.0, 1.0 );\n"
" fragColor = v_color;\n"
"}\n";
programHandle = createProgram(vertexShader, fragmentShader);
if (programHandle <= 0) {
return -1;
}
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
return 0;
}
void Triangle::onDraw(int width, int height) {
GLfloat vertices[] = {
0.0f, 0.5f, 0.0f,
-0.5f, -0.5f, 0.0f,
0.5f, -0.5f, 0.0f
};
GLfloat color[] = {
1.0f, 0.0f, 0.0f, 1.0f
};
GLint vertexCount = sizeof(vertices) / (sizeof(vertices[0]) * COORDS_PER_VERTEX);
glViewport(0, 0, width, height);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(programHandle);
GLint positionHandle = glGetAttribLocation(programHandle, "a_position");
glVertexAttribPointer(positionHandle, COORDS_PER_VERTEX, GL_FLOAT, GL_FALSE, vertexStride, vertices);
glEnableVertexAttribArray(positionHandle);
glVertexAttrib4fv(1, color);
glDrawArrays(GL_TRIANGLES, 0, vertexCount);
glDisableVertexAttribArray(positionHandle);
}
void Triangle::destroy() {
if (programHandle > 0) {
glDeleteProgram(programHandle);
}
programHandle = -1;
}
Looper线程的实现
由于在使用OpenGLES时需要单独一个线程空间，可参考GLSurfaceview的源码，GLSurfaceView就是通过开辟一个Looper 线程GLThread来调用EGL的API实现的。因此，我们也要创建一个Looper 线程，但Native层并没有提供跟Java层那么好用的Looper，只提供了ALooper，但个人觉得ALooper 使用并不是很友好。Looper的底层是基于epoll来实现的。我们这里不用epoll，而是采用信号量来搭建Looper，可以参考Google官方的android-ndk项目中的native-codec，native-codec项目就是用了信号量来创建Looper，并调用AMediaCodec渲染的。我们也有样学样，直接封装一个比较实用的Looper线程。废话不多数，直接上代码：
Looper.h:
#ifndef CAINPLAYER_LOOPER_H
#define CAINPLAYER_LOOPER_H
#include <pthread.h>
#include <sys/types.h>
#include <semaphore.h>
struct LooperMessage {
int what;
int arg1;
int arg2;
void *obj;
LooperMessage *next;
bool quit;
};
class Looper {
public:
Looper();
Looper&operator=(const Looper& ) = delete;
Looper(Looper&) = delete;
virtual ~Looper();
// 发送消息
void postMessage(int what, bool flush = false);
void postMessage(int what, void *obj, bool flush = false);
void postMessage(int what, int arg1, int arg2, bool flush = false);
void postMessage(int what, int arg1, int arg2, void *obj, bool flush = false);
// 退出Looper循环
void quit();
// 处理消息
virtual void handleMessage(LooperMessage *msg);
private:
// 添加消息
void addMessage(LooperMessage *msg, bool flush);
// 消息线程句柄
static void *trampoline(void *p);
// 循环体
void loop(void);
LooperMessage *head;
pthread_t worker;
sem_t headwriteprotect;
sem_t headdataavailable;
bool running;
};
#endif //CAINPLAYER_LOOPER_H
Looper.cpp:
#include "Looper.h"
#include <jni.h>
#include <pthread.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <semaphore.h>
#include "native_log.h"
struct LooperMessage;
typedef struct LooperMessage LooperMessage;
/**
* 线程执行句柄
* @param p
* @return
*/
void* Looper::trampoline(void* p) {
((Looper*)p)->loop();
return NULL;
}
Looper::Looper() {
head = NULL;
sem_init(&headdataavailable, 0, 0);
sem_init(&headwriteprotect, 0, 1);
pthread_attr_t attr;
pthread_attr_init(&attr);
pthread_create(&worker, &attr, trampoline, this);
running = true;
}
Looper::~Looper() {
if (running) {
ALOGD("Looper deleted while still running. Some messages will not be processed");
quit();
}
}
/**
* 入队消息
* @param what
* @param flush
*/
void Looper::postMessage(int what, bool flush) {
postMessage(what, 0, 0, NULL, flush);
}
/**
* 入队消息
* @param what
* @param obj
* @param flush
*/
void Looper::postMessage(int what, void *obj, bool flush) {
postMessage(what, 0, 0, obj, flush);
}
/**
* 入队消息
* @param what
* @param arg1
* @param arg2
* @param flush
*/
void Looper::postMessage(int what, int arg1, int arg2, bool flush) {
postMessage(what, arg1, arg2, NULL, flush);
}
/**
*
* @param what
* @param arg1
* @param arg2
* @param obj
* @param flush
*/
void Looper::postMessage(int what, int arg1, int arg2, void *obj, bool flush) {
LooperMessage *msg = new LooperMessage();
msg->what = what;
msg->obj = obj;
msg->arg1 = arg1;
msg->arg2 = arg2;
msg->next = NULL;
msg->quit = false;
addMessage(msg, flush);
}
/**
* 添加消息
* @param msg
* @param flush
*/
void Looper::addMessage(LooperMessage *msg, bool flush) {
sem_wait(&headwriteprotect);
LooperMessage *h = head;
if (flush) {
while(h) {
LooperMessage *next = h->next;
delete h;
h = next;
}
h = NULL;
}
if (h) {
while (h->next) {
h = h->next;
}
h->next = msg;
} else {
head = msg;
}
ALOGD("post msg %d", msg->what);
sem_post(&headwriteprotect);
sem_post(&headdataavailable);
}
/**
* 循环体
*/
void Looper::loop() {
while(true) {
// wait for available message
sem_wait(&headdataavailable);
// get next available message
sem_wait(&headwriteprotect);
LooperMessage *msg = head;
if (msg == NULL) {
ALOGD("no msg");
sem_post(&headwriteprotect);
continue;
}
head = msg->next;
sem_post(&headwriteprotect);
if (msg->quit) {
ALOGD("quitting");
delete msg;
return;
}
ALOGD("processing msg %d", msg->what);
handleMessage(msg);
delete msg;
}
}
/**
* 退出Looper循环
*/
void Looper::quit() {
ALOGD("quit");
LooperMessage *msg = new LooperMessage();
msg->what = 0;
msg->obj = NULL;
msg->next = NULL;
msg->quit = true;
addMessage(msg, false);
void *retval;
pthread_join(worker, &retval);
sem_destroy(&headdataavailable);
sem_destroy(&headwriteprotect);
running = false;
}
/**
* 处理消息
* @param what
* @param data
*/
void Looper::handleMessage(LooperMessage *msg) {
ALOGD("dropping msg %d %p", msg->what, msg->obj);
}
此时，我们封装了一个Looper 基类，里面集成了跟Handler一样的消息队列，这里就不再需要创建MessageQueue了。
接下来，我们在使用的时候，可以继承的Looper，实现MyLooper对象：
MyLooper.h
#ifndef EGLNATIVESAMPLE_MYLOOPER_H
#define EGLNATIVESAMPLE_MYLOOPER_H
#include "Looper.h"
#include "../cainrender/GLRender.h"
enum {
kMsgSurfaceCreated,
kMsgSurfaceChanged,
kMsgSurfaceDestroyed
};
class MyLooper : public Looper {
public:
MyLooper();
virtual ~MyLooper();
virtual void handleMessage(LooperMessage *msg);
private:
GLRender *mRender;
};
#endif //EGLNATIVESAMPLE_MYLOOPER_H
MyLooper.cpp:
#include "MyLooper.h"
MyLooper::MyLooper() {
mRender = new GLRender();
}
void MyLooper::handleMessage(LooperMessage *msg) {
switch (msg && msg->what) {
case kMsgSurfaceCreated:
if (mRender) {
mRender->surfaceCreated((ANativeWindow *) msg->obj);
}
break;
case kMsgSurfaceChanged:
if (mRender) {
mRender->surfaceChanged(msg->arg1, msg->arg2);
}
break;
case kMsgSurfaceDestroyed:
if (mRender) {
mRender->surfaceDestroyed();
}
break;
}
}
MyLooper::~MyLooper() {
delete mRender;
}
至此，我们在Native层实现了自己的EGL以及GLRender的封装。那么接下来我们应该怎么使用呢？请看下面的步骤：
1、在MainActivity中添加一个SurfaceView，并实现SurfaceHolder.Callback 方法。加载nativeEgl库，并创建几个native方法，如下所示：
public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback {
// Used to load the 'native-lib' library on application startup.
static {
System.loadLibrary("nativeEgl");
}
private native void nativeInit();
private native void nativeRelease();
private native void onSurfaceCreated(Surface surface);
private native void onSurfaceChanged(int width, int height);
private native void onSurfaceDestroyed();
private SurfaceView mSurfaceView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
nativeInit();
mSurfaceView = (SurfaceView) findViewById(R.id.surface_view);
mSurfaceView.getHolder().addCallback(this);
}
@Override
protected void onDestroy() {
nativeRelease();
super.onDestroy();
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
onSurfaceCreated(holder.getSurface());
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
onSurfaceChanged(width, height);
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
onSurfaceDestroyed();
}
}
native层实现上面的方法如下：
NativeEglController.cpp:
#include <jni.h>
#include "common/Looper.h"
#include "common/MyLooper.h"
#include <android/native_window.h>
#include <android/native_window_jni.h>
MyLooper *mLooper = NULL;
ANativeWindow *mWindow = NULL;
extern "C"
JNIEXPORT void JNICALL
Java_com_cgfay_eglnativerender_MainActivity_nativeInit(JNIEnv *env, jobject instance) {
// TODO
mLooper = new MyLooper();
}
extern "C"
JNIEXPORT void JNICALL
Java_com_cgfay_eglnativerender_MainActivity_nativeRelease(JNIEnv *env, jobject instance) {
if (mLooper != NULL) {
mLooper->quit();
delete mLooper;
mLooper = NULL;
}
if (mWindow) {
ANativeWindow_release(mWindow);
mWindow = NULL;
}
}
extern "C"
JNIEXPORT void JNICALL
Java_com_cgfay_eglnativerender_MainActivity_onSurfaceCreated(JNIEnv *env, jobject instance,
jobject surface) {
if (mWindow) {
ANativeWindow_release(mWindow);
mWindow = NULL;
}
mWindow = ANativeWindow_fromSurface(env, surface);
if (mLooper) {
mLooper->postMessage(kMsgSurfaceCreated, mWindow);
}
}
extern "C"
JNIEXPORT void JNICALL
Java_com_cgfay_eglnativerender_MainActivity_onSurfaceChanged(JNIEnv *env, jobject instance,
jint width, jint height) {
if (mLooper) {
mLooper->postMessage(kMsgSurfaceChanged, width, height);
}
}
extern "C"
JNIEXPORT void JNICALL
Java_com_cgfay_eglnativerender_MainActivity_onSurfaceDestroyed(JNIEnv *env, jobject instance) {
if (mLooper) {
mLooper->postMessage(kMsgSurfaceDestroyed);
}
}
编译运行程序，就可以看到Demo成功绘制了一个红色的三角形，如下图所示：
运行结果
使用方式跟我们Java层使用GLSurfaceView没什么两样，至此，我们就封装好EGL + C/C++ 编写OpenGLES的基本框架。Github地址：EGLNativeRender
