mac上安装软件真的很简单, 一路下一步就可以安装好android studio. 这里有一篇旧文-Mac下安装配置Android Studio 2.x和3.x并配置使用adb可供参考. 而写这篇的目的, 主要是我发现之前的ndk开发方式已经过时了, 需要更新一下新的流程.
CMake的方式是官方默认的ndk构建方式, 先从默认栗子开始看吧.
C++ support
Empty
C++
cpp
#include <jni.h>
#include <string>
extern "C" JNIEXPORT jstring JNICALL
Java_com_so_testcmake_MainActivity_stringFromJNI(
JNIEnv *env,
jobject /* this */) {
std::string hello = "Hello from C++";
return env->NewStringUTF(hello.c_str());
}
CMakeLists.txt
cmake_minimum_required(VERSION 3.4.1)
add_library( # Sets the name of the library.
native-lib
# Sets the library as a shared library.
SHARED
# Provides a relative path to your source file(s).
src/main/cpp/native-lib.cpp)
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)
target_link_libraries( # Specifies the target library.
native-lib
# Links the target library to the log library
# included in the NDK.
${log-lib})
很明显, 关键在于add_library这一段
public class MainActivity extends AppCompatActivity {
// Used to load the 'native-lib' library on application startup.
static {
System.loadLibrary("native-lib");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Example of a call to a native method
TextView tv = (TextView) findViewById(R.id.sample_text);
tv.setText(stringFromJNI());
}
/**
* A native method that is implemented by the 'native-lib' native library,
* which is packaged with this application.
*/
public native String stringFromJNI();
}
build.gradle
Empty
JNI
jni
public class MyJNI {
// Used to load the 'native-lib' library on application startup.
static {
System.loadLibrary("native-lib");
}
/**
* A native method that is implemented by the 'native-lib' native library,
* which is packaged with this application.
*/
public native String stringFromJNI();
}
#include <jni.h>
#include <string>
extern "C" JNIEXPORT jstring JNICALL
Java_com_so_addcmake_MyJNI_stringFromJNI(
JNIEnv *env,
jobject /* this */) {
std::string hello = "Hello from C++";
return env->NewStringUTF(hello.c_str());
}
ndk {
abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
当然, 你可以手动操作进行关联, 右击app目录, 点击Link C++ Project with Gradle, 选择之前的CMakeLists.txt文件.
Link C++ Project with Gradle
手动关联
TextView tvTest = (TextView) findViewById(R.id.tv_test);
tvTest.setText(new MyJNI().stringFromJNI());
效果图
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := HelloNDK
LOCAL_SRC_FILES := helloNDK.cpp
include $(BUILD_SHARED_LIBRARY)
APP_MODULES := HelloNDK
APP_ABI := all
//
// Created by 杨骁 on 2019/2/2.
//
#include <jni.h>
#include <stdio.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* 函数名规则: Java_包名_类名_方法名
* @param env 表示一个指向JNI环境的指针, 可以通过它来方位JNI提供的接口方法
* @param thiz 表示Java对象中的this
* @return
*/
jstring Java_com_so_addndk_HelloNDK_get(JNIEnv *env, jobject thiz) {
printf("invoke get in c++\n");
return env->NewStringUTF("Hello from JNI in helloJni.so !");
}
void Java_com_so_addndk_HelloNDK_set(JNIEnv *env, jobject thiz, jstring string) {
printf("invoke set from C++\n");
char* str = (char*)env->GetStringUTFChars(string,NULL);
printf("%s\n", str);
env->ReleaseStringUTFChars(string, str);
}
#ifdef __cplusplus
}
#endif
ndk-build
拷贝.so
效果图
要说操作上这两种的复杂度感觉差不多, 但是我依旧推荐CMake方案, 至少这种是短时间不会过时的方案.