JNI学习2：android 调用C语言方法与C语言调用android方法

#include <jni.h>
#include <stdio.h>
#include <stdlib.h>
#include <jni.h>
#include <android/log.h>
#define LOG_TAG "System.out"
//日志乱码时请将项目文件编码设置为UTF-8
/**debug级别日志：ANDROID_LOG_DEBUG:级别,LOG_TAG:标签,__VA_ARGS__:日志内容)**/
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG,LOG_TAG,__VA_ARGS__)
/**info级别日志：ANDROID_LOG_INFO:级别,LOG_TAG:标签,__VA_ARGS__:日志内容)**/
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)

extern "C" {

/***java语言String转C语言char***/
 char* JstringTochar(JNIEnv *env, jstring jstr) {
	char* rtn = NULL;
	jclass classtring = env->FindClass("java/lang/String");
	jstring strencode = env->NewStringUTF("GB2312");
	jmethodID mid = env->GetMethodID(classtring, "getBytes","(Ljava/lang/String;)[B");
	jbyteArray barr = (jbyteArray) env->CallObjectMethod(jstr, mid, strencode);
	jsize alen = env->GetArrayLength(barr);
	jbyte* ba = env->GetByteArrayElements(barr, JNI_FALSE);
	if (alen > 0) {
		rtn = (char*) malloc(alen + 1);
		memcpy(rtn, ba, alen);
		rtn[alen] = 0;
	}
	env->ReleaseByteArrayElements(barr, ba, 0);
	return rtn;
}

JNIEXPORT jstring Java_com_example_ndktest_JNIProvideer_hello(JNIEnv *env,jobject obj) {
	LOGD("%s", "haha");
	return env->NewStringUTF("Hello from JNI !");
}

/***2个整数相加***/
JNIEXPORT jint Java_com_example_ndktest_JNIProvideer_add(JNIEnv *env,jobject obj,jint x,jint y){
	return x+y;
}

/***字符串转换***/
JNIEXPORT jstring Java_com_example_ndktest_JNIProvideer_sayHello(JNIEnv *env,jobject obj,jstring jstr){
	char* p=JstringTochar(env,jstr);
	LOGI("sss%s",p);
	//strcat(p,helloWord)表示helloWordƴ拼接到p后面
	return env->NewStringUTF(strcat(p,"helloWord"));
}

/***整数数组每一个元素加10***/
JNIEXPORT jintArray Java_com_example_ndktest_JNIProvideer_getIntArray(JNIEnv *env,jobject obj,jintArray jintarr){
	//获取数组长度
	int len=env->GetArrayLength(jintarr);
	LOGI("len=%d",len);
	//获取整数数组地址
	jint* arr=env->GetIntArrayElements(jintarr,0);
	for (int i=0;  i < len; i++) {
		*(arr+i)+=10;
	}
	return jintarr;
}
/***主动调用java对象中方法String getString()
 * ()Ljava/lang/String;表示参数为空，返回值为String***/
JNIEXPORT void Java_com_example_ndktest_JNIProvideer_getJavaMethodForGetString(JNIEnv *env,jobject obj) {
	jclass classz=env->FindClass("com/example/ndktest/JNIProvideer");
	if(classz==0){
		LOGI("can't find class");
	}else{
		LOGI("find class");
	}
	jmethodID javaMethod=env->GetMethodID(classz,"getString","()Ljava/lang/String;");
	if(javaMethod==0){
		LOGI("can't find menthod");
	}else{
		LOGI("find menthod");
	}
    jstring result= (jstring)env->CallObjectMethod(obj,javaMethod);
	char* p=JstringTochar(env,result);
	LOGI("result=%s",p);
}

/***主动调用java对象中方法int getAdd(int x,int y)
 * (II)I表示参数为2个整数，返回值为整数***/
JNIEXPORT void Java_com_example_ndktest_JNIProvideer_getJavaMethodForGetAdd(JNIEnv *env,jobject obj) {
	jclass classz=env->FindClass("com/example/ndktest/JNIProvideer");
	if(classz==0){
		LOGI("can't find class");
	}else{
		LOGI("find class");
	}
	jmethodID javaMethod=env->GetMethodID(classz,"getAdd","(II)I");
	if(javaMethod==0){
		LOGI("can't find menthod");
	}else{
		LOGI("find menthod");
	}
	int result= env->CallIntMethod(obj,javaMethod,7,7);
	LOGI("result=%d",result);

}

/***主动调用java对象中方法void getvoidMethod(String x)
 * (Ljava/lang/String;)V表示参数为String,返回值为空***/
JNIEXPORT void Java_com_example_ndktest_JNIProvideer_getJavaMethodForGetvoidMethod(JNIEnv *env,jobject obj) {
	jclass classz=env->FindClass("com/example/ndktest/JNIProvideer");
	if(classz==0){
		LOGI("can't find class");
	}else{
		LOGI("find class");
	}
	jmethodID javaMethod=env->GetMethodID(classz,"getvoidMethod","(Ljava/lang/String;)V");
	if(javaMethod==0){
		LOGI("can't find menthod");
	}else{
		LOGI("找到方法");
	}
	env->CallVoidMethod(obj,javaMethod,env->NewStringUTF("abc"));
}

}

　　

package com.example.ndktest;

import android.util.Log;

public class JNIProvideer {
  static{
	  System.loadLibrary("ndkTest");
  }
  public native int add(int x,int y);
  public native String sayHello(String s);
  public native int[] getIntArray(int[] ints);
  public native String hello();
  public native void getJavaMethodForGetString();
  public native void getJavaMethodForGetAdd();
  public native void getJavaMethodForGetvoidMethod();
  /**
   *让c语言主动调用的方法
 * @return
 */
public String getString(){
	  return "hello";
  }
/**
 *让c语言主动调用的方法
* @return
*/
  public int getAdd(int x,int y){
	  return x+y;
  }
  /**
   * 让c语言主动调用的方法
  * @return
  */
    public void getvoidMethod(String x){
          Log.i("test", "输入值："+x);
    }
}

　　

package com.example.ndktest;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {
    public native String hello();
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.fragment_main);
		Button tx=  (Button) findViewById(R.id.test);
		tx.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				JNIProvideer jNIProvideer=new JNIProvideer();
				String result="";

				//result=jNIProvideer.hello();

				//int add=jNIProvideer.add(4, 5);
				//result=add+"";

				//int[] intarray=jNIProvideer.getIntArray(new int[]{3,5,5,4});
				//for (int i = 0; i < intarray.length; i++) {
				//result+=intarray[i];
				//}

				//result=jNIProvideer.sayHello("say:");
				//jNIProvideer.getJavaMethodForGetString();
				//jNIProvideer.getJavaMethodForGetAdd();
				jNIProvideer.getJavaMethodForGetvoidMethod();
				//Toast.makeText(getApplicationContext(), result, 0).show();
			}
		});
	}
}