android使用GLSurfaceView搭建OpenGL环境
流程
- 新建Android工程,需要配置支持jni。
- 新建一个类继承自GLSurfaceView实现Render
- 通过jni控制渲染
渲染的步骤
初始化
- 编写vertex shader、fragment shader程序.
- 使用glCreateShader创建shader.
- 给创建好的shader加载shader程序
- 编译shader，并查看是否报错
- 创建program
- attach之前shader到program
- link program并查看是否报错
以上初始化步骤非常类似c语言的编译链接过程。
绘制
- 获取vertex shader中定义的attribute
- 将数据传给该attribute
- 使用glDrawArray绘制
实战:在Android屏幕上画一个三角形
自定义View继承GLSurfaceView
public class GL2JNIView extends GLSurfaceView {
private static final String TAG = "GL2JNIView";
public GL2JNIView(Context context) {
this(context, null);
}
public GL2JNIView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public void init() {
Log.d(TAG, "init: ");
setEGLContextFactory(new ContextFactory());
setRenderer(new Render());
}
private static class ContextFactory implements GLSurfaceView.EGLContextFactory {
private static int EGL_CONTEXT_CLIENT_VERSION = 0x3098;
public EGLContext createContext(EGL10 egl, EGLDisplay display, EGLConfig eglConfig) {
Log.w(TAG, "creating OpenGL ES 2.0 context");
int[] attrib_list = {EGL_CONTEXT_CLIENT_VERSION, 2, EGL10.EGL_NONE };
EGLContext context = egl.eglCreateContext(display, eglConfig, EGL10.EGL_NO_CONTEXT, attrib_list);
return context;
}
public void destroyContext(EGL10 egl, EGLDisplay display, EGLContext context) {
egl.eglDestroyContext(display, context);
}
}
public static class Render implements GLSurfaceView.Renderer {
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
Log.d(TAG, "onSurfaceCreated: ");
}
@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
Log.d(TAG, "onSurfaceChanged: width=" + width + ",height=" + height);
String version = gl.glGetString(GL10.GL_VERSION);
Log.d(TAG, "version: "+ version);
GL2JNILib.init(width, height);
}
@Override
public void onDrawFrame(GL10 gl) {
Log.i(TAG, "onDrawFrame: ");
GL2JNILib.step();
}
}
}
jni层
public class GL2JNILib {
public static native void init(int width,int height);
public static native void step();
}
c++
#include "gl2jni.h"
#include
#include
#define TAG "EGL"
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG,TAG,__VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,TAG,__VA_ARGS__)
extern "C" {
auto gVertexShader =
"attribute vec4 vPosition;n"
"void main() {n"
" gl_Position = vPosition;n"
"}n";
auto gFragmentShader =
"precision mediump float;n"
"void main() {n"
" gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);n"
"}n";
const GLfloat gTriangleVertices[] = { 0.0f, 0.5f,
-0.5f, -0.5f,
0.5f, -0.5f };
static void checkGlError(const char * op){
GLenum error = GL_NO_ERROR;
for(error =glGetError();error;error = glGetError()){
LOGE("after %s glGetError:0x%d",op,error);
}
}
GLuint loadShader(GLenum shaderType, const char *pSource) {
GLuint shader = glCreateShader(shaderType);
if (shader) {
// 1. load source
glShaderSource(shader, 1, &pSource, nullptr);
// 2. compile source.
glCompileShader(shader);
GLint compiled = 0;
// 3. Get compiled result.
glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
if (!compiled) {
// if compile failed We should get error msg length then print it .
GLint errorLength = 0;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &errorLength);
if (errorLength) {
char *msg = new char[errorLength];
glGetShaderInfoLog(shader, errorLength, nullptr, msg);
LOGE("We couldn't compile this shader,%s", msg);
delete[] msg;
}
glDeleteShader(shader);
shader = 0;
}
}
return shader;
}
GLuint createGlProgram(const char *pVertexShaderSource, const char *pFragmentShaderSource) {
GLuint vertexShader = loadShader(GL_VERTEX_SHADER, pVertexShaderSource);
if (!vertexShader) {
return 0;
}
GLuint fragmentShader = loadShader(GL_FRAGMENT_SHADER, pFragmentShaderSource);
if (!fragmentShader) {
return 0;
}
GLuint glProgram =glCreateProgram();
if(glProgram){
glAttachShader(glProgram,vertexShader);
checkGlError("attach vertexShader");
glAttachShader(glProgram,fragmentShader);
checkGlError("attach fragmentShader");
glLinkProgram(glProgram);
GLint linkStatus = GL_FALSE;
glGetProgramiv(glProgram,GL_LINK_STATUS,&linkStatus);
if(linkStatus != GL_TRUE){
GLint errorLength = 0;
glGetProgramiv(glProgram,GL_INFO_LOG_LENGTH,&errorLength);
if(errorLength){
char * errorMsg = new char [errorLength];
glGetProgramInfoLog(glProgram,errorLength, nullptr,errorMsg);
LOGE("Link program is error %s",errorMsg);
delete[] errorMsg;
}
glDeleteProgram(glProgram);
glProgram = 0;
}
}
return glProgram;
}
GLuint gProgram;
GLuint gPosition;
JNIEXPORT void JNICALL
Java_com_blueberry_glexampe_GL2JNILib_init(JNIEnv *env, jclass clazz, jint width, jint height) {
auto version = glGetString(GL_VERSION);
auto vendor = glGetString(GL_VENDOR);
auto renderer = glGetString(GL_RENDERER);
auto extension = glGetString(GL_EXTENSIONS);
LOGD("glversion is : %s", version);
LOGD("glvender is : %s", vendor);
LOGD("glrender is : %s", renderer);
LOGD("glextension is : %s", extension);
// We have created glContext in java layer before.
gProgram = createGlProgram(gVertexShader, gFragmentShader);
if (!gProgram) {
LOGE("could not create program.");
return;
}
gPosition =glGetAttribLocation(gProgram,"vPosition");
checkGlError("get attribLocation");
glViewport(0,0,width,height);
}
JNIEXPORT void JNICALL
Java_com_blueberry_glexampe_GL2JNILib_step(JNIEnv *env, jclass clazz) {
static float grey = 0;
grey += 0.01f;
if(grey > 1.0){
grey = 0.0;
}
glClearColor(grey,grey,grey,1.0f);
checkGlError("glClearColor");
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
checkGlError("glClear bufferBit | color buffer.");
glUseProgram(gProgram);
checkGlError("use program.");
// https://www.khronos.org/registry/OpenGL-Refpages/gl4/html/glVertexAttribPointer.xhtml
glVertexAttribPointer(gPosition,
2, // 一个顶点所拥有的数据个数
GL_FLOAT, // 数据类型
GL_FALSE, // 是否需要把数据归一化到 -1，1之间
0,gTriangleVertices);
checkGlError("atrrib pointer.");
glEnableVertexAttribArray(gPosition);
checkGlError("glEnabled Vertext attrib array.");
glDrawArrays(GL_TRIANGLES,0,3);
checkGlError("glDrawArrays error.");
}
}
CMakeLists需要依赖EGL,GLESv2
cmake_minimum_required(VERSION 3.4.1)
# now build app's shared lib
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall")
add_library(gl2jni SHARED
gl_code.cpp)
# add lib dependencies
target_link_libraries(gl2jni
android
log
EGL
GLESv2)
