Flutter + C++ FFI 示例教程 (Android 平台)

1
#include <stdint.h>
2

3
extern "C" {
4
    int32_t add(int32_t a, int32_t b) {
5
        return a + b;
6
    }
7
}

1
#ifndef ADD_H
2
#define ADD_H
3

4
#ifdef __cplusplus
5
extern "C" {
6
#endif
7

8
int32_t add(int32_t a, int32_t b);
9

10
#ifdef __cplusplus
11
}
12
#endif
13

14
#endif

1
name: 'NativeAddBindings'
2
description: 'Bindings to native add function'
3
output: 'lib/generated_bindings.dart'
4
headers:
5
  entry-points:
6
    - 'native/include/add.h'
7
  include-directives:
8
    - 'native/include/add.h'
9
preamble: |
10
  // ignore_for_file: always_specify_types
11
  // ignore_for_file: camel_case_types
12
  // ignore_for_file: non_constant_identifier_names

1
cmake_minimum_required(VERSION 3.4.1)
2

3
# 添加你的源文件
4
add_library(native_add SHARED
5
    ../../../../../native/src/add.cpp
6
)
7

8
# 包含头文件目录
9
target_include_directories(native_add PRIVATE
10
    ../../../../../native/include
11
)
12

13
find_library(log-lib log)
14

15
target_link_libraries(native_add
16
    ${log-lib}
17
)

1
android {
2
    // ...
3
    defaultConfig {
4
        // ...
5
        externalNativeBuild {
6
            cmake {
7
                cppFlags.add("-std=c++17")
8
                arguments.add("-DANDROID_STL=c++_shared")
9
            }
10
        }
11
    }
12
    // ...
13
    externalNativeBuild {
14
        cmake {
15
            path = file("src/main/cpp/CMakeLists.txt")
16
            version = "3.22.1"
17
        }
18
    }
19
    // ...
20
}

1
import 'dart:ffi';
2
import 'dart:io';
3

4
import 'generated_bindings.dart';
5

6
class NativeAdd {
7
  static final DynamicLibrary _library = () {
8
    if (Platform.isAndroid) {
9
      return DynamicLibrary.open('libnative_add.so');
10
    } else if (Platform.isIOS) {
11
      return DynamicLibrary.process();
12
    }
13
    throw UnsupportedError('Platform not supported');
14
  }();
15

16
  static final NativeAddBindings _bindings = NativeAddBindings(_library);
17

18
  static int add(int a, int b) => _bindings.add(a, b);
19
}

1
import 'package:flutter/material.dart';
2
import 'native_add.dart';
3

4
void main() {
5
  runApp(const MyApp());
6
}
7

8
class MyApp extends StatelessWidget {
9
  const MyApp({super.key});
10

11
  @override
12
  Widget build(BuildContext context) {
13
    return MaterialApp(
14
      home: Scaffold(
15
        appBar: AppBar(title: const Text('Flutter + C++ Example')),
16
        body: Center(
17
          child: Text(
18
            '3 + 5 = ${NativeAdd.add(3, 5)}',
19
            style: const TextStyle(fontSize: 24),
20
          ),
21
        ),
22
      ),
23
    );
24
  }
25
}

1
flutter_cpp_example/
2
├── android/
3
│   └── app/
4
│       └── src/
5
│           └── main/
6
│               ├── cpp/
7
│               │   └── CMakeLists.txt
8
│               └── java/
9
├── lib/
10
│   ├── generated_bindings.dart
11
│   ├── native_add.dart
12
│   └── main.dart
13
├── native/
14
│   ├── include/
15
│   │   └── add.h
16
│   └── src/
17
│       └── add.cpp
18
├── pubspec.yaml
19
└── ffigen.yaml