android studio hello jni-优快云博客

本文通过一个具体实例详细介绍了如何在Android Studio中使用NDK进行JNI开发，包括创建Java接口、生成并编译C/C++源代码等关键步骤。

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###步骤：

写接口文件MainActivity.java

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView  tv = new TextView(this);
        tv.setText( stringFromJNI() );
        setContentView(tv);
    }

    public native String  stringFromJNI();
    public native String  unimplementedStringFromJNI();
    static {
        System.loadLibrary("hello-jni");
    }
}

编译生成.class文件

执行Build->Make Project就生成文件 #见g:\as\hellojni\app\build\intermediates\classes\all\debug\com\example\decode\hellojni\MainActivity.class

javah生成c头文件

cd g:

cd g:\as\hellojni\app\src\main #生成的 .h 文件要在app\src\main路径下，见g:\as\hellojni\app\src\main\jni\com_example_decode_hellojni_MainActivity.h

javah -d jni -classpath d:\android-studio\sdk\platforms\android-23\android.jar;..\..\build\intermediates\classes\all\debug com.example.decode.hellojni.MainActivity

编辑功能c文件

#include <string.h>
#include <jni.h>

jstring Java_com_example_decode_hellojni_MainActivity_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"
#endif

  return (*env)->NewStringUTF(env, "Hello from JNI !  Compiled with ABI " ABI ".");
}