Jni API:https://docs.oracle.com/javase/8/docs/technotes/guides/jni/spec/jniTOC.html
JNIEnv、jobject和jclass这三种基本类型

操作API都在JNIEnv中，JNIEnv为Java与C/C++通信桥梁
jobject：Java层传递的对象（普通native方法传递）
jclass:Java层对应的Class类（静态native方法传递）

native普通方法与静态方法区别：Jni传递参数是jobject和jclass区别

android studio ndk api自动补齐
安装插件：
Android NDK Support
NDK WorkspaceManager Support

属性，方法，数组例子：
Java层
public class MainActivity extends AppCompatActivity {

private static final String TAG = "MainActivity";
//测试属性
public String strName ="test";//排序数组
private int[] array = {89,2,4,34,88,100,1};
// 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 methodTextView tv = (TextView) findViewById(R.id.sample_text);//测试属性操作tv.setText(updateStringFromC());//测试方法调用tv.setText(getJavaMethod());//测试数组操作this.operateArraySort(array);for (int i = 0; i < array.length; i++){Log.e(TAG, "onCreate: " + array[i]);}//异常处理 C++的异常 JAVA是无法try catch的，如果jni层出现了异常，那么Java的代码调用中止try {exception();}catch (Exception e){Log.e(TAG, "onCreate: " + e.getMessage());}Log.e(TAG, "onCreate: " + "end");}
//测试方法
public String getMethod(int a){return "method" + a;
}/*** A native method that is implemented by the 'native-lib' native library,* which is packaged with this application.*/
public native String stringFromJNI();
//从C返回字符串
public native String updateStringFromC();
//调用Java方法
public native String getJavaMethod();
//对array数组进行排序操作
public native void operateArraySort(int[] array);
//异常处理
public native void exception();

}

Jni层：

#include <jni.h>
#include <string>
#include "stdlib.h"//C C++混编int compare(const void* lhs, const void* rhs){return (*(int*)lhs - *(int*)rhs);
}//异常处理
extern "C"
JNIEXPORT void JNICALL
Java_com_home_adproj_androidndktest_MainActivity_exception(JNIEnv *env, jobject instance) {jclass  _jclass = env->GetObjectClass(instance);jfieldID _jfieldID = env->GetFieldID(_jclass,"strName2","Ljava/lang/String;");//strName2不存在有异常if(env->ExceptionCheck()){//检测异常env->ExceptionClear();//清除异常 不会使Java层崩溃//抛异常给Java层jclass exceptionClass = env->FindClass("java/lang/IllegalArgumentException");env->ThrowNew(exceptionClass,"strName2 不存在");//抛异常到Java层，Java层进行捕获}
}//对Java数组进行操作
extern "C"
JNIEXPORT void JNICALL
Java_com_home_adproj_androidndktest_MainActivity_operateArraySort(JNIEnv *env, jobject instance,jintArray array_) {jint *arrays = env->GetIntArrayElements(array_, NULL);int _len = env->GetArrayLength(array_);//获取数组长度//qsort(void* __base, size_t __nmemb, size_t __size, int (*__comparator)(const void* __lhs, const void* __rhs));qsort(arrays,_len, sizeof(int),compare);//数组排序env->ReleaseIntArrayElements(array_, arrays, 0);//释放
}//调用Java层方法
extern "C"
JNIEXPORT jstring JNICALL
Java_com_home_adproj_androidndktest_MainActivity_getJavaMethod(JNIEnv *env, jobject instance) {jclass _jclass =env->GetObjectClass(instance);//(jclass clazz, const char* name, const char* sig)jmethodID _jmethodID = env->GetMethodID(_jclass,"getMethod","(I)Ljava/lang/String;");//(参数类型)Ljava/lang/String返回值类型jstring result = (jstring) env->CallObjectMethod(instance, _jmethodID,100);char* str = (char *) env->GetStringUTFChars(result, NULL);//string 转charreturn env->NewStringUTF(str);
}//测试Java属性操作
extern "C"
JNIEXPORT jstring JNICALL
Java_com_home_adproj_androidndktest_MainActivity_updateStringFromC(JNIEnv *env, jobject instance) {// TODOjclass _jclass = env->GetObjectClass(instance);//(jclass clazz, const char* name, const char* sig)//name:属性名  sig:属性类型jfieldID _jfieldID = env->GetFieldID(_jclass,"strName","Ljava/lang/String;");jstring _result = (jstring) env->GetObjectField(instance, _jfieldID);//如何转化成java stringchar* str = (char *) env->GetStringUTFChars(_result, NULL);char text[20] = "success";return env->NewStringUTF(strcat(str,text));
}extern "C"
JNIEXPORT jstring JNICALL
Java_com_home_adproj_androidndktest_MainActivity_stringFromJNI(JNIEnv* env,jobject /* this */) {std::string hello = "Hello from C++";return env->NewStringUTF(hello.c_str());
}

lldb：jni调试工具
官网：http://lldb.llvm.org/tutorial.html