ndk开发-6 子线程操作

创建线程

 public static native void demoThread();

//
// Created by Administrator on 2020/3/3 0003.
//

#include "log.h"
#include <jni.h>
#include <string>
#include <pthread.h>


void *doInThread(void *) {
    /*子线程中*/
    LOGD("hello world");
    return nullptr;
}

extern "C"
JNIEXPORT void JNICALL
Java_com_hrg_gys_clfr_myapplication_JniData_demoThread(JNIEnv *env, jclass clazz) {
    pthread_t handless;
    int result = pthread_create(&handless, NULL, doInThread, NULL); /*返回0则表示创建成功*/
    if (result == 0) {
        LOGD("thread create success");
    } else {
        LOGD("thread create fail");
    }
}

向子线程传递参数

struct ThreadArgs {
    int id;
    int num;

    ThreadArgs(int id, int num) : id(id), num(num) {}
};

void *doInThread(void *args) {
    /*子线程中*/
    ThreadArgs *threadArgs = static_cast<ThreadArgs *>(args);
    LOGD("ThreadArgs %d %d", threadArgs->id, threadArgs->num);
    return nullptr;
}

extern "C"
JNIEXPORT void JNICALL
Java_com_hrg_gys_clfr_myapplication_JniData_demoThread(JNIEnv *env, jclass clazz) {
    pthread_t handless;
    ThreadArgs *threadArgs = new ThreadArgs(1, 2);
    int result = pthread_create(&handless, NULL, doInThread, threadArgs); /*返回0则表示创建成功*/
    LOGD("thread create %s", result == 0 ? "success" : "fail");
}

获取线程的返回值

//
// Created by Administrator on 2020/3/3 0003.
//

#include "log.h"
#include <jni.h>
#include <string>
#include <pthread.h>
#include <unistd.h>

void *doInThread(void *args) {
    /*子线程中*/
    struct timeval begin;
    gettimeofday(&begin, nullptr);
    sleep(3); /*线程停止3s*/
    struct timeval end;
    gettimeofday(&end, nullptr);
    LOGD("thread inner time %d ", end.tv_sec - begin.tv_sec);
    return reinterpret_cast<void *>(1);
}

extern "C"
JNIEXPORT void JNICALL
Java_com_hrg_gys_clfr_myapplication_JniData_demoThread(JNIEnv *env, jclass clazz) {
    pthread_t handless;
    int result = pthread_create(&handless, NULL, doInThread, nullptr); /*返回0则表示创建成功*/
    LOGD("thread create %s", result == 0 ? "success" : "fail");
    void *ret = nullptr;
    pthread_join(handless, &ret); /*等handless结束 ret线程的返回*/
    LOGD("thread result %d", ret);
}

输出结果

2020-03-04 16:32:58.772 23566-23566/0 D/native-jni: thread create success
2020-03-04 16:33:01.774 23566-23782/0 D/native-jni: thread inner time 3 
2020-03-04 16:33:01.775 23566-23566/0 D/native-jni: thread result 1

线程同步的问题

#include "log.h"
#include <jni.h>
#include <string>
#include <pthread.h>
#include <unistd.h>


pthread_mutex_t mutex;  /*互斥变量*/
pthread_cond_t cond; /*条件变量*/
pthread_t waitHandle;
pthread_t notifyHandle;


int flag = 0;

void *waitThread(void *args) {
    LOGD("waitThread 1 ...");
    pthread_mutex_lock(&mutex);
    while (flag == 0) {
        LOGD("waitThread wait ...");
        pthread_cond_wait(&cond, &mutex); /*会释放mutex锁放入阻塞序列 state:1*/
    }
    pthread_mutex_unlock(&mutex);
    LOGD("waitThread 2 ...");
    return NULL;
}

void *notifyThread(void *args) {
    LOGI("notifyThread 1 ...");
    pthread_mutex_lock(&mutex);  /*可保证顺序 避免waitThread中的 while在flag为1后调用*/
    flag = 1;
    pthread_mutex_unlock(&mutex);
    LOGI("notifyThread 2 ...");
    pthread_cond_signal(&cond);  /*通知cond  state:1执行*/
    LOGI("notifyThread 3 ...");
    return NULL;
}

extern "C"
JNIEXPORT void JNICALL
Java_com_hrg_gys_clfr_myapplication_JniData_syncThread1(JNIEnv *env, jclass clazz) {
    // TODO: implement syncThread1()
    pthread_mutex_init(&mutex, nullptr);
    pthread_cond_init(&cond, nullptr);
    pthread_create(&waitHandle, NULL, waitThread, NULL);
}

extern "C"
JNIEXPORT void JNICALL
Java_com_hrg_gys_clfr_myapplication_JniData_syncThread2(JNIEnv *env, jclass clazz) {
    // TODO: implement syncThread2()
    pthread_create(&notifyHandle, NULL, notifyThread, NULL);
}