HarmonyOS鸿蒙Next：NativeWindow 开发指导

场景介绍

NativeWindow是HarmonyOS本地平台化窗口，表示图形队列的生产者端。开发者可以通过NativeWindow接口进行申请和提交Buffer，配置Buffer属性信息。

针对NativeWindow，常见的开发场景如下：

• 通过NativeWindow提供的Native API接口申请图形Buffer，并将生产图形内容写入图形Buffer，最终提交Buffer到图形队列
• 在适配EGL层的eglswapbuffer接口时，进行申请和提交Buffer

接口说明

接口名

详细的接口说明请参考native_window。

开发步骤

以下步骤描述了在HarmonyOS中如何使用NativeWindow提供的Native API接口，申请图形Buffer，并将生产图形内容写入图形Buffer后，最终提交Buffer到图形队列。

添加动态链接库

CMakeLists.txt中添加以下lib。

libace_ndk.z.so
libnative_window.so

头文件

#include <ace/xcomponent/native_interface_xcomponent.h>
#include <native_window/external_window.h>

获取OHNativeWindow实例

可在OH_NativeXComponent_Callback提供的接口中获取OHNativeWindow，下面提供一份代码示例。XComponent模块的具体使用方法请参考XComponent开发指导。

在xxx.ets中添加一个XComponent组件

XComponent({ id: 'xcomponentId', type: 'surface', libraryname: 'entry'})
    .width(360)
    .height(360)

在 native c++ 层获取 NativeXComponent

napi_value exportInstance = nullptr;
// 用来解析出被wrap了NativeXComponent指针的属性
napi_get_named_property(env, exports, OH_NATIVE_XCOMPONENT_OBJ, &exportInstance);
OH_NativeXComponent *nativeXComponent = nullptr;
// 通过napi_unwrap接口，解析出NativeXComponent的实例指针
napi_unwrap(env, exportInstance, reinterpret_cast<void**>(&nativeXComponent));
// 获取XComponentId
char idStr[OH_XCOMPONENT_ID_LEN_MAX + 1] = {};
uint64_t idSize = OH_XCOMPONENT_ID_LEN_MAX + 1;
OH_NativeXComponent_GetXComponentId(nativeXComponent, idStr, &idSize);

定义 OH_NativeXComponent_Callback

// 定义回调函数
void OnSurfaceCreatedCB(OH_NativeXComponent* component, void* window)
{
    // 可获取 OHNativeWindow 实例
    OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
    // ...
}
void OnSurfaceChangedCB(OH_NativeXComponent* component, void* window)
{
    // 可获取 OHNativeWindow 实例
    OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
    // ...
}
void OnSurfaceDestroyedCB(OH_NativeXComponent* component, void* window)
{
    // 可获取 OHNativeWindow 实例
    OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
    // ...
}
void DispatchTouchEventCB(OH_NativeXComponent* component, void* window)
{
    // 可获取 OHNativeWindow 实例
    OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
    // ...
}

// 初始化 OH_NativeXComponent_Callback
OH_NativeXComponent_Callback callback;
callback.OnSurfaceCreated = OnSurfaceCreatedCB;
callback.OnSurfaceChanged = OnSurfaceChangedCB;
callback.OnSurfaceDestroyed = OnSurfaceDestroyedCB;
callback.DispatchTouchEvent = DispatchTouchEventCB;

将 OH_NativeXComponent_Callback 注册给 NativeXComponent

// 注册回调函数
OH_NativeXComponent_RegisterCallback(nativeXComponent, &callback);

设置OHNativeWindowBuffer的属性

使用OH_NativeWindow_NativeWindowHandleOpt设置OHNativeWindowBuffer的属性。

// 设置 OHNativeWindowBuffer 的宽高
int32_t code = SET_BUFFER_GEOMETRY;
int32_t width = 0x100;
int32_t height = 0x100;
// 这里的nativeWindow是从上一步骤中的回调函数中获得的
int32_t ret = OH_NativeWindow_NativeWindowHandleOpt(nativeWindow, code, width, height);

从图形队列申请OHNativeWindowBuffer

OHNativeWindowBuffer* buffer = nullptr;
int fenceFd;
// 通过 OH_NativeWindow_NativeWindowRequestBuffer 获取 OHNativeWindowBuffer 实例
OH_NativeWindow_NativeWindowRequestBuffer(nativeWindow, &buffer, &fenceFd);
// 通过 OH_NativeWindow_GetBufferHandleFromNative 获取 buffer 的 handle
BufferHandle* bufferHandle = OH_NativeWindow_GetBufferHandleFromNative(buffer);

内存映射mmap

#include <sys/mman.h>

// 使用系统接口mmap将bufferHandle对应的共享内存映射到用户空间，可以通过映射出来的虚拟地址向bufferHandle中写入图像数据
// bufferHandle->virAddr是bufferHandle在共享内存中的起始地址，bufferHandle->size是bufferHandle在共享内存中的内存占用大小
void* mappedAddr = mmap(bufferHandle->virAddr, bufferHandle->size, PROT_READ | PROT_WRITE, MAP_SHARED, bufferHandle->fd, 0);
if (mappedAddr == MAP_FAILED) {
    // mmap failed
}

将生产的内容写入OHNativeWindowBuffer

static uint32_t value = 0x00;
value++;
uint32_t *pixel = static_cast<uint32_t *>(mappedAddr); // 使用mmap获取到的地址来访问内存
for (uint32_t x = 0; x < width; x++) {
    for (uint32_t y = 0;  y < height; y++) {
        *pixel++ = value;
    }
}

提交OHNativeWindowBuffer到图形队列

// 设置刷新区域，如果Region中的Rect为nullptr,或者rectNumber为0，则认为OHNativeWindowBuffer全部有内容更改。
Region region{nullptr, 0};
// 通过OH_NativeWindow_NativeWindowFlushBuffer 提交给消费者使用，例如：显示在屏幕上。
OH_NativeWindow_NativeWindowFlushBuffer(nativeWindow, buffer, fenceFd, region);

取消内存映射munmap

// 内存使用完记得去掉内存映射
int result = munmap(mappedAddr, bufferHandle->size);
if (result == -1) {
    // munmap failed
}