AndroidQ 图形系统（6）使用纯native API画一个窗口qq34211365的博客-

本篇文章根据前面的分析来实际操作画一个窗口，使用纯native API来实现，这里的native API并非ndk，而是native层函数，需要在AOSP编译环境下进行。

首先在/frameworks/native/libs/gui/目录下创建drawWindowTest测试目录，drawWindowTest目录中创建Android.bp和DrawWindowTest.cpp：

Android.bp：

cc_binary {     name: "drawWindow",     srcs: ["DrawWindowTest.cpp"],     shared_libs: [ "liblog",         "libbinder",         "libgui",         "libui",         "libutils",     ], } 

接着来看看DrawWindowTest.cpp怎么写，前面几篇文章的分析我们大致了解了画一个窗口的流程：

1. 首先需要和SurfaceFlinger进程建立连接
2. 创建图形数据的载体Surface对应SurfaceFlinger进程Layer
3. 有了Surface，还需要将Surface连接到BufferQueue
4. 设置Surface的各种数据，如宽高，格式，Z-order，位置，缩放等
5. 调用dequeueBuffer获取buffer
6. 向buffer中填充图形数据
7. 调用queueBuffer将buffer送到SurfaceFlinger合成

我们的代码就按上面步骤来写，DrawWindowTest.cpp源码如下：

#include <binder/ProcessState.h> #include <binder/IPCThreadState.h> #include <system/window.h> #include <ui/GraphicBuffer.h> #include <ui/Fence.h> #include <utils/Log.h> #include <utils/RefBase.h> #include <gui/SurfaceControl.h> #include <gui/SurfaceComposerClient.h> #include <binder/IBinder.h> #include <ui/DisplayInfo.h> #include <gui/Surface.h> using namespace android; //状态值 status_t err;  sp<SurfaceComposerClient> mSurfaceComposerClient;  sp<SurfaceControl> mSurfaceControl; //屏幕宽高 int mWidth,mHeight; //GraphicBuffer的父类ANativeWindowBuffer ANativeWindowBuffer *mNativeBuffer = nullptr; //连接SurfaceFlinger void connectSurfaceFlinger(); //获取Surface sp<ANativeWindow> getSurface(); //连接BufferQueue void connectBufferQueue(ANativeWindow *surface); //设置Transaction void setBufferTransaction(); //设置其他信息 void setBuffer(ANativeWindow *surface); int main() {     sp<ProcessState> proc(ProcessState::self());     ProcessState::self()->startThreadPool(); //连接SurfaceFlinger connectSurfaceFlinger(); //获取surface     ANativeWindow *surface = getSurface().get(); //surface连接bufferqueue connectBufferQueue(surface); //设置Transaction setBufferTransaction(); //设置其他信息 setBuffer(surface); int fenceFD= -1; //申请buffer     err = surface->dequeueBuffer(surface, &mNativeBuffer, &fenceFD); if (err != NO_ERROR) { ALOGE("dequeueBuffer err...."); } //通过Fence确认申请的buffer是否完全被上一个使用者使用完         sp<Fence> fence(new Fence(fenceFD)); //等待收到releaseFence int waitResult = fence->waitForever("dequeueBuffer_EmptyNative"); if (waitResult != OK) { ALOGE("Fence wait err...."); } //ANativeWindowBuffer转GraphicBuffer         sp<GraphicBuffer> buff(GraphicBuffer::from(mNativeBuffer)); //buffer数据 uint8_t *data = NULL; //通过lock先锁住buffer         err = buff->lock(GRALLOC_USAGE_SW_WRITE_OFTEN, (void**)(&data)); if (err != NO_ERROR) { ALOGE("lock buffer err...."); } //填充数据，这里直接赋值为0，会画一个黑色窗口 *data = 0;         err = buff->unlock(); if (err != NO_ERROR) { ALOGE("unlock buffer err...."); } //将填充好的buffer送到SurfaceFlinger进行合成显示         err = surface->queueBuffer(surface, buff->getNativeBuffer(), -1); if (err != NO_ERROR) { ALOGE("queueBuffer buffer err...."); return err; }     mNativeBuffer = NULL;     IPCThreadState::self()->joinThreadPool(); return EXIT_SUCCESS; } //1.创建SurfaceComposerClient，这是SurfaceFlinger的Client端 void connectSurfaceFlinger(){          mSurfaceComposerClient = new SurfaceComposerClient;     err = mSurfaceComposerClient->initCheck(); if (err != NO_ERROR) { ALOGE("SurfaceComposerClient initCheck err...."); return; } } //2.创建Surface，ANativeWindow是创建Surface父类 sp<ANativeWindow> getSurface(){     sp<IBinder> display = SurfaceComposerClient::getInternalDisplayToken();     android::DisplayInfo mainDisplayInfo; //获取手机的屏幕信息     err = SurfaceComposerClient::getDisplayInfo(display, &mainDisplayInfo); if (err != NO_ERROR) { ALOGE("getDisplayInfo err...."); } //屏幕宽     mWidth = mainDisplayInfo.w; //屏幕高     mHeight = mainDisplayInfo.h; //创建surface对应surfaceflinger进程layer     mSurfaceControl = mSurfaceComposerClient->createSurface( String8("drawWindow"), mWidth/2, mHeight/2,             PIXEL_FORMAT_RGBX_8888, ISurfaceComposerClient::eOpaque); if (mSurfaceControl == NULL || !mSurfaceControl->isValid()) { ALOGE("mSurfaceControl err...."); } //获取surface     sp<ANativeWindow> anw = mSurfaceControl->getSurface(); return anw; } //3.Surface连接BufferQueue void connectBufferQueue(ANativeWindow *surface){     err = native_window_api_connect(surface, NATIVE_WINDOW_API_CPU); if (err != NO_ERROR) { ALOGE("connect bufferqueue err...."); } } //4.设置buffer数据 void setBufferTransaction(){ /*     setLayer()：设置窗口的Z-order     setPosition()：设置窗口显示的位置     show()：设置窗口显示出来     apply()：将设置的窗口信息应用到SurfaceFlinger，真正生效     */     SurfaceComposerClient::Transaction{} .setLayer(mSurfaceControl, 0x7FFFFFFF) .setPosition(mSurfaceControl,mWidth/4,mHeight/4) .show(mSurfaceControl) .apply(); } //5.设置buffer void setBuffer(ANativeWindow *surface){ //设置usage     err = native_window_set_usage(surface, GRALLOC_USAGE_SW_WRITE_OFTEN); if (err != NO_ERROR) { ALOGE("native_window_set_usage err...."); } //设置transform     err = native_window_set_buffers_transform(surface, NATIVE_WINDOW_TRANSFORM_ROT_90); if (err != NO_ERROR) { ALOGE("native_window_set_buffers_transform err...."); } //设置scaling_mode     err = native_window_set_scaling_mode(             surface, NATIVE_WINDOW_SCALING_MODE_SCALE_TO_WINDOW); if (err != NO_ERROR) { ALOGE("native_window_set_scaling_mode err...."); } } 

上面的代码基本上是按照画窗口的流程来实现的，看下上面setBuffer函数，里面调用了一系列native_window_set_XXX函数来个Surface设置各种信息，其实最终都是调用到Surface中setXXX函数，native_window_set_XXX是给外部调用提供操作Surface的接口，这些函数定义在frameworks/native/libs/nativewindow/include/system/window.h中，举个例子看看native_window_set_usage函数

static inline int native_window_set_usage(struct ANativeWindow* window, uint64_t usage) { return window->perform(window, NATIVE_WINDOW_SET_USAGE64, usage); } 

会调用ANativeWindow的perform函数：

int (*perform)(struct ANativeWindow* window, int operation, ... ); 

这个函数指针是在Surface构造函数中赋值的：

 ANativeWindow::perform          = hook_perform; int Surface::hook_perform(ANativeWindow* window, int operation, ...) {     va_list args; va_start(args, operation);     Surface* c = getSelf(window); int result = c->perform(operation, args); va_end(args); return result; } 

hook_perform函数又调用Surface的perform函数：

int Surface::perform(int operation, va_list args) { int res = NO_ERROR; switch (operation) { case NATIVE_WINDOW_CONNECT: // deprecated. must return NO_ERROR. break; case NATIVE_WINDOW_DISCONNECT: // deprecated. must return NO_ERROR. break; case NATIVE_WINDOW_SET_USAGE:         res = dispatchSetUsage(args); break; case NATIVE_WINDOW_SET_CROP:         res = dispatchSetCrop(args); break; case NATIVE_WINDOW_SET_BUFFER_COUNT:         res = dispatchSetBufferCount(args); ....... } 

这里面有很多函数，根据传递过来的参数调用不同的dispatchXXX，比如native_window_set_usage传递的就是NATIVE_WINDOW_SET_USAGE64，从而调用dispatchSetUsage64：

case NATIVE_WINDOW_SET_USAGE64:         res = dispatchSetUsage64(args); break; 

dispatchSetUsage64又调用setUsage最终将数据设置给了Surface

int Surface::dispatchSetUsage64(va_list args) { uint64_t usage = va_arg(args, uint64_t); return setUsage(usage); } 

画一个窗口有很多信息必须设置，在之前分析的dequeueBuffer和queueBuffer中都有相关判断，比如宽高不能小于0，必须连接BufferQueue等。

编译测试程序：mmm frameworks/native/libs/gui/drawWindowTest/

push进手机：
adb push out/target/product/SEOUL_ATT/system/bin/drawWindow /system/bin

运行这个测试程序：adb shell /system/bin/drawWindow
效果如下：

通过这一个测试程序结合前几篇理论的文章可以更好的熟悉Android图形架构。