# HelloAndroidModuleInCpp

**Repository Path**: weekend/hello_andorid_module_in_cpp

## Basic Information

- **Project Name**: HelloAndroidModuleInCpp
- **Description**: using c++ in android
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2025-04-14
- **Last Updated**: 2025-04-16

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README




## Using c++ in Android
1. Create a project with Native c++ template
2. Create a new Module with type of Android Native Library

## Using aar
1. Export the Android Native Library to aar
```bash
# 1. new Android Native Library Module
# 2. generate aar
gradle nativelib:assemble
```

2. Import the aar to your project
```java
// 1. copy the aar to the libs folder(create it if not exists)
app/libs/nativelib-release.aar

// 2. import the aar in app/build.gradle
dependencies {
    implementation fileTree(include: ['*.aar'], dir: 'libs')
}

// 3. invoke functions in aar
// app/src/main/java/com/example/hellondk/MainActivity.java
import com.example.nativelib.NativeLib;
binding.sampleText.append(String.format("\n%s", NativeLib.stringFromJNI()));
```

## Pack third-party libs info arr
1. Copy the libs and headers into your project
```
 nativelib/src/main/jniLibs/arm64-v8a/libmylib.so     | Bin 0 -> 9192 bytes
 nativelib/src/main/jniLibs/x86_64/libmylib.so        | Bin 0 -> 8296 bytes
 nativelib/src/main/third_party/mylib/include/mylib.h |  14 ++++++++++++++
```

2. Set the abi and load libs in build.gradle
```gradle
android {
    defaultConfig {
        ndk {
            abiFilters 'arm64-v8a', 'x86_64'
        }
    }
    sourceSets.main {
        jniLibs.srcDirs = ['src/main/jniLibs']
    }
}
```

3. Link mylib to your android native lib in it's CMakeLists.txt
```cmake
# thirdparty headers and libs
include_directories(src/main/third_party/mylib/include)
add_library(mylib SHARED IMPORTED)
set_target_properties(mylib PROPERTIES IMPORTED_LOCATION
        "${CMAKE_CURRENT_SOURCE_DIR}/../jniLibs/${CMAKE_ANDROID_ARCH_ABI}/libmylib.so")

# link mylib
target_link_libraries(${CMAKE_PROJECT_NAME}
        # List libraries link to the target library
        android
        log
        mylib)
```

4. Export mylib through NativeLib
```cpp
// NativeLib.cpp
#include "../third_party/mylib/include/mylib.h"

extern "C" JNIEXPORT jint JNICALL
Java_com_example_nativelib_NativeLib_addNumbers(
        JNIEnv* env,
        jobject /* this */,
        jint a,
        jint b) {
    return add(a, b);
}
```

```java
// NativeLib.java
public class NativeLib {
    // ...
    public native static int addNumbers(int a, int b);
}
```

5. Gen the aar of NativeLib and copy to your project and Test
```java
binding.sampleText.append("\nSum from nativelib: " + NativeLib.addNumbers(2, 3));
```

![](./hello_aar.png)


## To build the mylib, please refer to this: 
[CMake cross-compile a lib with NDK](https://gitee.com/weekend/hello_cmake_ndklib)

## ref
Create an Android library
https://developer.android.com/studio/projects/android-library

Add C and C++ code to your project
https://developer.android.com/studio/projects/add-native-code

Prepare your library for release
https://developer.android.com/build/publish-library/prep-lib-release