引言：

通过一个最简单的测试程序直观Android系统的native层Surface的渲染显示过程。

主程序代码：

#include <cutils/memory.h>
#include <utils/Log.h>
#include <binder/IPCThreadState.h>
#include <binder/ProcessState.h>
#include <binder/IServiceManager.h>
#include <gui/Surface.h>
#include <gui/SurfaceComposerClient.h>
#include <android/native_window.h>

using namespace android;

//int main(int argc, char** argv)
int main()
{
    // 设置线程池
    sp<ProcessState> proc(ProcessState::self());
    ProcessState::self()->startThreadPool();

    // 创建与Surfaceflinger通信的客户端
    sp<SurfaceComposerClient> client = new SurfaceComposerClient();
    // 创建SurfaceControl并设置名称“resize”、宽高、像素格式，红色分量使用 5 位，绿色分量使用 6 位，蓝色分量使用 5 位。
    sp<SurfaceControl> surfaceControl = client->createSurface(String8("resize"),
            400, 600, PIXEL_FORMAT_RGB_565, 0);
    //通过SurfaceControl获取一个Surface
    sp<Surface> surface = surfaceControl->getSurface();

    SurfaceComposerClient::Transaction t;
    //设置Layer层级，数值越大层级越高
    t.setLayer(surfaceControl, 100000)
        .apply();

    ANativeWindow_Buffer outBuffer;
    //从BufferQueue中获取获取一个Buffer
    surface->lock(&outBuffer, NULL);
    //计算每个像素点的字节大小
    ssize_t bpr = outBuffer.stride * bytesPerPixel(outBuffer.format);
    //使用memset16对buffer赋值（颜色值）
    android_memset16((uint16_t*)outBuffer.bits, 0xF800, bpr*outBuffer.height);
    //提交填充后的buffer
    surface->unlockAndPost();
    sleep(1);

    surface->lock(&outBuffer, NULL);
    android_memset16((uint16_t*)outBuffer.bits, 0x07E0, bpr*outBuffer.height);
    surface->unlockAndPost();
    sleep(1);

    surface->lock(&outBuffer, NULL);
    android_memset16((uint16_t*)outBuffer.bits, 0x001F, bpr*outBuffer.height);
    surface->unlockAndPost();
    sleep(1);

    //对outbuffer进行100次连续的获取与释放
    for (int i = 0; i < 100; i++) {
        surface->lock(&outBuffer, NULL);
        printf("%03d buff addr = 0x%x\n", i, (unsigned int)(uintptr_t)outBuffer.bits);
        surface->unlockAndPost();
    }
    
    IPCThreadState::self()->joinThreadPool();

    return 0;
}