Android NDK-helloJNI

项目目录结构

CMakeLists.txt

cmake_minimum_required(VERSION 3.4.1)add_library(hello-jni SHAREDhello-jni.c)# Include libraries needed for hello-jni lib
target_link_libraries(hello-jniandroidlog)

编译一个shared library，hello-jin.so.

target_link_libraries中链接需要库

hello-jni.c

#include <string.h>
#include <jni.h>/* This is a trivial JNI example where we use a native method* to return a new VM String. See the corresponding Java source* file located at:**   hello-jni/app/src/main/java/com/example/hellojni/HelloJni.java*/
JNIEXPORT jstring JNICALL
Java_com_example_hellojni_HelloJni_stringFromJNI( JNIEnv* env,jobject thiz )
{
#if defined(__arm__)#if defined(__ARM_ARCH_7A__)#if defined(__ARM_NEON__)#if defined(__ARM_PCS_VFP)#define ABI "armeabi-v7a/NEON (hard-float)"#else#define ABI "armeabi-v7a/NEON"#endif#else#if defined(__ARM_PCS_VFP)#define ABI "armeabi-v7a (hard-float)"#else#define ABI "armeabi-v7a"#endif#endif#else#define ABI "armeabi"#endif
#elif defined(__i386__)
#define ABI "x86"
#elif defined(__x86_64__)
#define ABI "x86_64"
#elif defined(__mips64)  /* mips64el-* toolchain defines __mips__ too */
#define ABI "mips64"
#elif defined(__mips__)
#define ABI "mips"
#elif defined(__aarch64__)
#define ABI "arm64-v8a"
#else
#define ABI "unknown"
#endifreturn (*env)->NewStringUTF(env, "Hello from JNI !  Compiled with ABI " ABI ".");//把C的字符串，转换为Java的字符串
}

hello-jni.java

  TextView tv = (TextView)findViewById(R.id.hello_textview);tv.setText( stringFromJNI() );
}
/* A native method that is implemented by the* 'hello-jni' native library, which is packaged* with this application.*/
public native String  stringFromJNI();/* This is another native method declaration that is *not** implemented by 'hello-jni'. This is simply to show that* you can declare as many native methods in your Java code* as you want, their implementation is searched in the* currently loaded native libraries only the first time* you call them.** Trying to call this function will result in a* java.lang.UnsatisfiedLinkError exception !*/
public native String  unimplementedStringFromJNI();/* this is used to load the 'hello-jni' library on application* startup. The library has already been unpacked into* /data/data/com.example.hellojni/lib/libhello-jni.so at* installation time by the package manager.*/
static {System.loadLibrary("hello-jni");
}

1)定义native的方法

2）loadLibray

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Android NDK-helloJNI

项目目录结构

CMakeLists.txt

hello-jni.c

hello-jni.java

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