android jni 调用结构体示例

MainActivity

package com.example.hello2;

import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity implements OnClickListener {
   private Button btn;
   static{
	   System.loadLibrary("hello2");
   }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn=(Button) findViewById(R.id.btn);
        btn.setOnClickListener(this);
    }


    public native void add(int a,int b);
    public native DiskInfo getStruct(DiskInfo disk_info);

	@Override
	public void onClick(View arg0) {
		DiskInfo disk_info=new DiskInfo(1,"ZKK");
		getStruct(disk_info);
		Log.i("zhouke", "::"+disk_info.name+"::"+disk_info.serial);
	}
    
}

package com.example.hello2;

public class DiskInfo {
	public String name; // 
	public int serial; //

	public DiskInfo(int num, String myname) {
		serial = num;
		name = myname;
	}
}

.h 文件

/* DO NOT EDIT THIS FILE - it is machine generated */
#include 
/* Header for class com_example_hello2_MainActivity */

#ifndef _Included_com_example_hello2_MainActivity
#define _Included_com_example_hello2_MainActivity
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_example_hello2_MainActivity
 * Method:    add
 * Signature: (II)V
 */
JNIEXPORT void JNICALL Java_com_example_hello2_MainActivity_add
  (JNIEnv *, jobject, jint, jint);

/*
 * Class:     com_example_hello2_MainActivity
 * Method:    getStruct
 * Signature: (Lcom/example/hello2/DiskInfo;)Lcom/example/hello2/DiskInfo;
 */
JNIEXPORT jobject JNICALL Java_com_example_hello2_MainActivity_getStruct
  (JNIEnv *, jobject, jobject);

#ifdef __cplusplus
}
#endif
#endif

c文件

#include "com_example_hello2_MainActivity.h"
#include 
#include 
#include 
#define LOG_TAG "cTag"
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
struct{
   char name[256];
   int serial;
};
JNIEXPORT void JNICALL Java_com_example_hello2_MainActivity_add
  (JNIEnv * env, jobject  obj, jint x, jint y)
{
	int result = x + y;
	LOGD("result=%d", result);
}

JNIEXPORT jobject JNICALL Java_com_example_hello2_MainActivity_getStruct
  (JNIEnv * env, jobject obj, jobject diskobj){
	jclass objectClass = (*env)->FindClass(env, "com/example/hello2/DiskInfo");
	jfieldID name = (*env)->GetFieldID(env, objectClass,"name","Ljava/lang/String;");
	jfieldID serial=(*env)->GetFieldID(env,objectClass,"serial","I");
	(*env)->SetObjectField(env,diskobj,name, (*env)->NewStringUTF(env, "hello world"));
	(*env)->SetIntField(env,diskobj,serial,10);
	//(*env)->setIn
	return diskobj;
}

示例2

MainActiviy

package com.example.hello2;

import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity implements OnClickListener {
	private Button btn;
	static {
		System.loadLibrary("hello2");
	}
	public class Foo {
		public int len;
		public String name;
	}
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		btn = (Button) findViewById(R.id.btn);
		btn.setOnClickListener(this);
	}

	public native void add(int a, int b);

	public native DiskInfo getStruct(DiskInfo disk_info);

	private static native int foo(Foo fooObj);

	@Override
	public void onClick(View arg0) {
		/*
		 * DiskInfo disk_info=new DiskInfo(1,"ZKK"); getStruct(disk_info);
		 * Log.i("zhouke", "::"+disk_info.name+"::"+disk_info.serial);
		 */
		Foo foo = new Foo();
        foo(foo);
        Log.i("zhouke", foo.name);
        Log.i("zhouke", foo.len+"");
	}

}

hello2.c

#include "com_example_hello2_MainActivity.h"
#include 
#include 
#include 
#define LOG_TAG "cTag"
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
struct {
	char name[256];
	int serial;
};
typedef struct Foo {
	int len;
	char name[100];
} Foo_t;
JNIEXPORT void JNICALL Java_com_example_hello2_MainActivity_add(JNIEnv * env,
		jobject obj, jint x, jint y) {
	int result = x + y;
	LOGD("result=%d", result);
}

JNIEXPORT jobject JNICALL Java_com_example_hello2_MainActivity_getStruct(
		JNIEnv * env, jobject obj, jobject diskobj) {
	jclass objectClass = (*env)->FindClass(env, "com/example/hello2/DiskInfo");
	jfieldID name = (*env)->GetFieldID(env, objectClass, "name",
			"Ljava/lang/String;");
	jfieldID serial = (*env)->GetFieldID(env, objectClass, "serial", "I");
	(*env)->SetObjectField(env, diskobj, name,
			(*env)->NewStringUTF(env, "hello world"));
	(*env)->SetIntField(env, diskobj, serial, 10);
	//(*env)->setIn
	return diskobj;
}
JNIEXPORT jint JNICALL Java_com_example_hello2_MainActivity_foo(JNIEnv *env,
		jobject obj, jobject fooObj) {
	Foo_t * bar = malloc(sizeof(Foo_t));
	jclass clazz;
	jfieldID fid;

	//init the bar data of C
	strcpy(bar->name, "Yachun Miao");
	bar->len = strlen(bar->name);

	// mapping bar of C to foo
	clazz = (*env)->GetObjectClass(env, fooObj);
	if (0 == clazz) {
		LOGD("0==clazz");
		return (-1);
	}
	fid = (*env)->GetFieldID(env, clazz, "len", "I");
	//(*env)->SetLongField(env, fooObj, fid, bar->len);
	(*env)->SetIntField(env,fooObj,fid,bar->len);

	fid = (*env)->GetFieldID(env, clazz, "name", "Ljava/lang/String;");
	jstring name = (*env)->NewStringUTF(env, bar->name);
	(*env)->SetObjectField(env, fooObj, fid, name);

	free(bar);
	return 0;
}

h 文件

/* DO NOT EDIT THIS FILE - it is machine generated */
#include 
/* Header for class com_example_hello2_MainActivity */

#ifndef _Included_com_example_hello2_MainActivity
#define _Included_com_example_hello2_MainActivity
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     com_example_hello2_MainActivity
 * Method:    add
 * Signature: (II)V
 */
JNIEXPORT void JNICALL Java_com_example_hello2_MainActivity_add
  (JNIEnv *, jobject, jint, jint);

/*
 * Class:     com_example_hello2_MainActivity
 * Method:    getStruct
 * Signature: (Lcom/example/hello2/DiskInfo;)Lcom/example/hello2/DiskInfo;
 */
JNIEXPORT jobject JNICALL Java_com_example_hello2_MainActivity_getStruct
  (JNIEnv *, jobject, jobject);


JNIEXPORT jint JNICALL Java_com_example_hello2_MainActivity_foo
  (JNIEnv *, jclass, jobject);

#ifdef __cplusplus
}
#endif
#endif

.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := hello2
LOCAL_SRC_FILES := hello2.c
LOCAL_LDLIBS :=-llog 
include $(BUILD_SHARED_LIBRARY)