編寫native類

編寫native類對應的c檔案

使用命令生成標頭檔案.h
1、main-java中：javah 全類名
2、build-intermediates-classes-debug中：javah -classpath . -jni 全類名

在build.gradle的defaultConfig中加入：

externalNativeBuild {
            cmake {
                cppFlags ""
//              abiFilters "arm64-v8a","armeabi-v7a","x86","x86_64"
            }
        }
 

在build.gradle的android中，加入：

externalNativeBuild {
    cmake {
        path "CMakeLists.txt"
    }
}

新增CMakeLists.txt檔案到build.gradle檔案同級目錄下：

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
             Hello//生成的so庫名稱

             # Sets the library as a shared library.
             SHARED

             # Provides a relative path to your source file(s).
             src/main/jni/Hello.c )//c檔案路徑

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
              log-lib

              # Specifies the name of the NDK library that
              # you want CMake to locate.
              log )

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
                       Hello

                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )
 

點選選單“Build - Make project”生成.so檔案

.so檔案目錄：app-build-intermediates-cmake-debug-obj