C語言-簡單創建線程之pthread.h

背景

在Java調用Native函數時,爲了不阻塞主線程,在native代碼中另起線程處理耗時操作.

必要的庫

#include <pthread.h>

關鍵的函數

    int pthread_create(pthread_t* thread,
            pthread_attr_t const* attr,
            void* (*start_routine)(void*),
            void* args);

• 指向thread_t 類型變量的指針,函數用該指針返回新線程的句柄
• 指向pthread_attr_t 結構的指針形式存在的新線程屬性,可以通過該屬性指定新線程的棧基址,棧大小,守護大小,調度策略和調度優先級等,如果使用默認值,取值可能爲NULL.
• 第三個參數是指向線程啓動程序的函數指針,(類似Java中重寫Thread類中的run方法)啓動程序函數前面的格式 void* start_routine(void* args)
• 第四個參數是傳遞給上述start_routine(…)函數的參數指針,如果沒有參數,它可以爲NULL.

直接上Demo代碼

#include <jni.h>
#include <string.h>
#include <android/log.h>
#include <unistd.h>
#include <pthread.h>
#include <time.h>

#define LOG_TAG "pthread_learn"
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)

void* run(void * args)
{
    LOGI("run() i'm running!");
    clock_t * time = (clock_t *)args;
    int i;
    for (i = 0; i < 5; i++)
    {
        LOGI("Sleep leave %d second! callTime is %ld", (5 - i), *time);
        //sleep one second;
        sleep(1);
    }
    free(time);
}

jstring
Java_com_cm_jnitest_MainActivity_doInBackground(JNIEnv* env, jobject thiz)
{
    int result;
    pthread_t thread1;
    clock_t* time = (clock_t *)malloc(sizeof(clock_t));
    *time = clock();
    LOGI("doInBackground() callTime is %ld", *time);
    //Create Thread
    result = pthread_create(&thread1, NULL, run, (void *)time);
    if (result != 0)
        LOGI("doInBackground() Create POSIX thread fail!");
    else
        LOGI("doInBackground() Create POSIX thread successfully!");
    LOGI("doInBackground() finish!");
    return (*env)->NewStringUTF(env, "doInBackground() finish!");
}

JNIEXPORT jint JNI_OnLoad(JavaVM* pVM, void* reserved) 
{
    LOGI("JNI_OnLoad() start!");
    return JNI_VERSION_1_6;
}