harmony 鸿蒙Native VSync Development (C/C++)
Native VSync Development (C/C++)
When to Use
The NativeVSync module is used to obtain virtual synchronization (VSync) signals from the system. It provides APIs for creating and destroying an OH_NativeVSync instance and setting the VSync callback function, which is triggered when a VSync signal arrives.
Available APIs
| API | Description |
|---|---|
| OH_NativeVSync_Create (const char *name, unsigned int length) | Creates an OH_NativeVSync instance. A new OH_NativeVSync instance is created each time this API is called. This function must be used in pair with OH_NativeVSync_Destroy. Otherwise, memory leak occurs. |
| OH_NativeVSync_Destroy (OH_NativeVSync *nativeVsync) | Destroys an OH_NativeVSync instance. |
| OH_NativeVSync_FrameCallback (long long timestamp, void *data) | Sets a callback function. timestamp indicates the timestamp, and data indicates a pointer to the input parameters of the callback function. |
| OH_NativeVSync_RequestFrame (OH_NativeVSync *nativeVsync, OH_NativeVSync_FrameCallback callback, void *data) | Requests the next VSync signal. When the signal arrives, a callback function is invoked. |
For details about the APIs, see native_vsync.
How to Develop
The following steps describe how to use the native APIs provided by NativeVSync to create and destroy an OH_NativeVSync instance and set the VSync callback function.
Adding Dynamic Link Libraries
Add the following library to CMakeLists.txt:
libnative_vsync.so
Including Header Files
#include <native_vsync/native_vsync.h>
Implement a VSync callback function.
#include <iostream> static bool flag = false; static void OnVSync(long long timestamp, void* data) { flag = true; std::cout << "OnVSync: " << timestamp << std::endl; } OH_NativeVSync_FrameCallback callback = OnVSync; // The callback function must be of the OH_NativeVSync_FrameCallback type.Create an OH_NativeVSync instance.
char name[] = "hello_vsync"; OH_NativeVSync* nativeVSync = OH_NativeVSync_Create(name, strlen(name));Set the VSync callback function through the OH_NativeVSync instance.
#include <unistd.h> #include <iostream> OH_NativeVSync_RequestFrame(nativeVSync, callback, nullptr); while (!flag) { // Check the flag value. The while loop exits only after the VSync callback function is executed, indicating that a VSync signal is received. std::cout << "wait for vsync!\n"; sleep(1); } std::cout << "vsync come, end this thread\n";Destroy the OH_NativeVSync instance.
OH_NativeVSync_Destroy(nativeVSync); // Destroy the OH_NativeVSync instance when the application does not need to receive VSync signals.
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