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();
}
});
}
}