flutter与C++交互

Dart调用C++的库

1. 安装ffi库 flutter pub add ffi
2. 如果是C++必须使用C的方式导出接口

import 'dart:ffi';
import 'dart:io';
import "package:ffi/ffi.dart";

final DynamicLibrary ff = Platform.isWindows
    ? DynamicLibrary.open("live666.dll")
    : throw UnsupportedError("only Windows is supported");

// 定义 C 函数的签名
typedef CLive666Init = Pointer<Void> Function(Pointer<Utf8>, Pointer<Utf8>);

// 定义 Dart 函数的签名
typedef DartLive666Init = Pointer<Void> Function(Pointer<Utf8>, Pointer<Utf8>);

// 查找并绑定函数
final live666Init = ff.lookupFunction<CLive666Init, DartLive666Init>('live666_init');

3. 调用

  void _invokeCpp(){
    try{
      debugPrint("Current working directory: ${Directory.current.path}");

      final handle = live666Init(url, reg);
      if (handle.address == 0) {
        debugPrint("Initialization failed, null pointer returned.");
      } else {
        debugPrint("Initialization succeeded, handle: 0x${handle.address.toRadixString(16)}");
      }
    } on UnsupportedError{
      debugPrint("没有找到动态库");
    }
    malloc.free(url);
    malloc.free(reg);
  }

使用ffigen工具包调用C++库

1. 安装工具包 dart pub add -d ffigen && dart pub add ffi
2. 在 pubspec.yaml 文件中添加以下配置

ffigen:
  output: 'lib/cpp/api/generated_bindings.dart'
  name: 'live666'
  headers:
    entry-points:
      - 'cpp/api/test.h'
  llvm-path:
    - 'C:\Users\Jack-PC\llvm'

3. 生成绑定

dart run ffigen

4. 调用

import 'generated_bindings.dart';
 
void main() {
  final lib = NativeLibrary(DynamicLibrary.open('path_to_your_library.so'));
  final result = lib.sum(1, 2);
  print('Sum: $result');
}

flutter与C++源码交互

1. 在源码目录新建 CMakeLists.txt 文件

cmake_minimum_required(VERSION 3.4)

# 项目名称
if (CMAKE_SYSTEM_NAME MATCHES "Windows")
    set(PROJECT_NAME "libNative")
else()
    set(PROJECT_NAME "Native")
endif()

project(${PROJECT_NAME} LANGUAGES CXX)

# 源文件
add_library(${PROJECT_NAME} SHARED
        "./test1.cpp"
)

# Windows 需要把dll拷贝到bin目录
IF (WIN32)
    # 动态库的输出目录
    set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/$<$<CONFIG:DEBUG>:Debug>$<$<CONFIG:RELEASE>:Release>")
    # 安装动态库的目标目录
    set(INSTALL_BUNDLE_LIB_DIR "${CMAKE_INSTALL_PREFIX}")
    # 安装动态库，到执行目录
    install(FILES "${CMAKE_LIBRARY_OUTPUT_DIRECTORY}/${PROJECT_NAME}.dll" DESTINATION "${INSTALL_BUNDLE_LIB_DIR}" COMPONENT Runtime)
ENDIF()

2. 如果是Android在 .\android\app\build.gradle 文件添加如下代码

    externalNativeBuild {
        // Encapsulates your CMake build configurations.
        cmake {
            // 指定一个CMake 编译脚本的相对目录。
            path "../../cpp/api/CMakeLists.txt"
        }
    }

3. 如果是Windows在./Windows/CMakeLists.txt中添加如下代码

add_subdirectory("../cpp/api/" test1)

4. 编写源代码

#include <stdint.h>

#ifdef WIN32
#define DART_API extern "C" __declspec(dllexport)
#else
#define DART_API extern "C" __attribute__((visibility("default"))) __attribute__((used))
#endif

DART_API int32_t native_add(int32_t x, int32_t y) {
    return x + y;
}

5. 使用 dart run ffigen生成dart代码