jni不通过线程c回调java的函数

Posted 2020-09-25 luzhouxiaoshuai

整个工程的项目如下：

 

1、项目的思路是在activity中启动MyService这个服务，在服务中调用

JniScsManger类中的本地方法startNativeScsService，在

startNativeScsService的c代码实现中回调JniScsManger中的scsConnectStatus方法。
下面我们来看下两种代码的实现：

package com.cetcs.ecmapplication.jni.scs;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;

public class MyService extends Service {
    public MyService() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        // TODO: Return the communication channel to the service.
        throw new UnsupportedOperationException("Not yet implemented");
    }

    @Override
    public void onCreate() {
        super.onCreate();
        JniScsManger.getInstances().startNativeScsService();
    }
}

activity的代码：

package im.weiyuan.com.jni2;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;

import com.cetcs.ecmapplication.jni.scs.JniScsManger;
import com.cetcs.ecmapplication.jni.scs.MyService;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Intent intent = new Intent(MainActivity.this, MyService.class);
        startService(intent);
    }
}

package com.cetcs.ecmapplication.jni.scs;

import android.util.Log;

/**
 * Created by wei.yuan on 2017/6/7.
 */

public class JniScsManger {
    static {
        System.loadLibrary("jniscs");
    }

    private  static JniScsManger jniScsManger = null;
    private JniScsManger(){

    }

    public static JniScsManger getInstances(){
        if(jniScsManger == null){
            jniScsManger = new JniScsManger();
        }
        return  jniScsManger;
    }

    public native int startNativeScsService();


    public  void  scsConnectStatus(int status,String reason){

        Log.d("123456",""+status+","+reason);

    }

    public  void getScsStatus(){
        Log.d("123456",""+",");
    }

    public int onProgressCallBack(long total, long already) {
        //自行执行回调后的操作
        Log.d("123456",""+"onProgressCallBack");
        System.out.println("total123456:"+total);
        System.out.println("already:"+already);
        return 1;
    }

}

我们来看看本地native层实现的代码：

第一种方式：

//
// Created by wei.yuan on 2017/6/7.
//
#include <android/log.h>
#include <string.h>
#include <stdio.h>
#include <pthread.h>
#include <time.h>
#include <dlfcn.h>
#include <jni.h>
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dlfcn.h>
#include <assert.h>
#include <android\\log.h>
#include <errno.h>
#include <pthread.h>

#include "com_cetcs_ecmapplication_jni_scs_JniScsManger.h"
//动态链接库路径
#define LIB_SCS_PATH "libServerCenter.so"
#define LOG_TAG "SCS123456"
#define LOGI_JniSCS(...)  __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)


JNIEXPORT jint JNICALL Java_com_cetcs_ecmapplication_jni_scs_JniScsManger_startNativeScsService(JNIEnv * env, jobject jobj){
    LOGI_JniSCS("start native ServerCenterService");

    //jobj对象就是java层调用startNativeScsService的对象，那个类调用startNativeScsService对应的jobj就是那个对象
    jclass javaClass = (*env)->FindClass(env, "com/cetcs/ecmapplication/jni/scs/JniScsManger");
    if (javaClass == 0) {
              LOGI_JniSCS("Unable to find class");
            return;
        }
        //获取要回调的方法ID
        jmethodID javaCallbackId = (*env)->GetMethodID(env, javaClass,"scsConnectStatus", "(ILjava/lang/String;)V");
        if (javaCallbackId == NULL) {
             LOGI_JniSCS("Unable to find method:onProgressCallBack");
            return;
        }
        //执行回调,注意第二个参数是jobj，不是javaClass
            (*env)->CallVoidMethod(env, jobj, javaCallbackId,1,(*env)->NewStringUTF(env, "Hello from JNI000.0.0.!"));

    return 4000000;

}

第二种方式：

//
// Created by wei.yuan on 2017/6/7.
//
#include <android/log.h>
#include <string.h>
#include <stdio.h>
#include <pthread.h>
#include <time.h>
#include <dlfcn.h>
#include <jni.h>
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dlfcn.h>
#include <assert.h>
#include <android\\log.h>
#include <errno.h>
#include <pthread.h>

#include "com_cetcs_ecmapplication_jni_scs_JniScsManger.h"
//动态链接库路径
#define LIB_SCS_PATH "libServerCenter.so"
#define LOG_TAG "SCS123456"
#define LOGI_JniSCS(...)  __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)


JNIEXPORT jint JNICALL Java_com_cetcs_ecmapplication_jni_scs_JniScsManger_startNativeScsService(JNIEnv * env, jobject jobj){
    LOGI_JniSCS("start native ServerCenterService");

    //jobj对象就是java层调用startNativeScsService的对象，那个类调用startNativeScsService对应的jobj就是那个对象
    jclass javaClass = (*env)->GetObjectClass(env, jobj);
    if (javaClass == 0) {
              LOGI_JniSCS("Unable to find class");
            return;
        }
        //获取要回调的方法ID
        jmethodID javaCallbackId = (*env)->GetMethodID(env, javaClass,"scsConnectStatus", "(ILjava/lang/String;)V");
        if (javaCallbackId == NULL) {
             LOGI_JniSCS("Unable to find method:onProgressCallBack");
            return;
        }
        //执行回调,注意第二个参数是jobj，不是javaClass
            (*env)->CallVoidMethod(env, jobj, javaCallbackId,1,(*env)->NewStringUTF(env, "Hello from JNI000.0.0.!"));

    return 4000000;

}

注意点：

FindClass是通过传java中完整的类名来查找java的class， 而GetObjectClass是通过传入jni中的一个java的引用来获取该引用的类型。 前者要求你必须知道完整的类名，后者要求在Jni有一个类的引用。
上面中传入的

(JNIEnv * env, jobject jobj)中的jobj就是调用startNativeScsService的对象，就是JniScsManger的一个对象实例。

FindClass是通过类名获得该对象的实例，

GetObjectClass是获得该对象的一个引用。

现在增加一个需求：
我们在上传新增加一个类：

我们要在startNativeScsService的c代码实现中回调Sb中的scsConnectStatus方法如何实现了，我们来看c层的代码

package com.cetcs.ecmapplication.jni.scs;

import android.util.Log;

/**
 * Created by wei.yuan on 2017/6/26.
 */

public class Sb {
    public  void  scsConnectStatus(int status,String reason){

        Log.d("123456",""+status+","+reason);

    }
}

 

//
// Created by wei.yuan on 2017/6/7.
//
#include <android/log.h>
#include <string.h>
#include <stdio.h>
#include <pthread.h>
#include <time.h>
#include <dlfcn.h>
#include <jni.h>
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dlfcn.h>
#include <assert.h>
#include <android\\log.h>
#include <errno.h>
#include <pthread.h>

#include "com_cetcs_ecmapplication_jni_scs_JniScsManger.h"
//动态链接库路径
#define LIB_SCS_PATH "libServerCenter.so"
#define LOG_TAG "SCS123456"
#define LOGI_JniSCS(...)  __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)


JNIEXPORT jint JNICALL Java_com_cetcs_ecmapplication_jni_scs_JniScsManger_startNativeScsService(JNIEnv * env, jobject jobj){
    LOGI_JniSCS("start native ServerCenterService");

    //jobj对象就是java层调用startNativeScsService的对象，那个调用startNativeScsService对应的jobj就是那个对象
    jclass javaClass = (*env)->FindClass(env, "com/cetcs/ecmapplication/jni/scs/Sb");
    if (javaClass == 0) {
        LOGI_JniSCS("Unable to find class");
        return;
    }
    //构造Sb这个对象
    jmethodID constructor = (*env)->GetMethodID(env, javaClass, "<init>", "()V");
    //获取要回调的方法ID
    jmethodID javaCallbackId = (*env)->GetMethodID(env, javaClass,"scsConnectStatus", "(ILjava/lang/String;)V");
    if (javaCallbackId == NULL) {
        LOGI_JniSCS("Unable to find method:onProgressCallBack");
        return;
    }
    jobject obj = (*env)->NewObject(env, javaClass, constructor);
    //执行回调,注意第二个参数是obj，不是jobj
    (*env)->CallVoidMethod(env, obj, javaCallbackId,1,(*env)->NewStringUTF(env, "Hello from JNI000.0.0.!0..22"));

    return 4000000;

}

程序代码的下载地址是：

https://pan.baidu.com/s/1gfosrp5