MessageQueue.java
//調(diào)用MessageQueue的next方法獲取消息
Message next() {
      、、、
      synchronized (this) {
          //這時候檢查隊列有沒有消息，沒有消息調(diào)用this.wait()等待  
          if (message == null) {
              this.wait();
          }
          if(有消息但消息未到期){
            this.wait(time);
          }
      }
      、、、
  }
//調(diào)用MessageQueue.enqueueMessage()添加消息
enqueueMessage(Message message) {
    、、、
    synchronized (this) {
        //消息加入隊列后會調(diào)用this.notity()喚醒next()方法
        if (message != null) {
            this.notify();
        }
    }
      、、、
  }

  #include <cstdlib>
  #include <inttypes.h>
  #include <iostream>
  #include <stdint.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string>
  #include <sys/eventfd.h>
  #include <unistd.h>
  using namespace std;
  int main(int argc, char* argv[]) {
      int event_fd;
      if (argc < 2) {
          std::cout << "please input llegal argv " << endl;
          exit(EXIT_FAILURE);
      }
      event_fd = eventfd(0, EFD_NONBLOCK);
      if (event_fd == -1) {
          std::cout << "create evebtFd fail" << endl;
          exit(EXIT_FAILURE);
      }
      switch (fork()) {
      case 0:
          for (int j = 1; j < argc; j++) {
              long u = atoi(argv[j]);
              printf("Child writing %lu to efd\n", u);
              write(event_fd, &u, sizeof(long));
          }
          printf("Child completed write loop\n");
          exit(EXIT_SUCCESS);
      default:
          sleep(2);
          long u;
          printf("Parent about to read\n");
          read(event_fd, &u, sizeof(long));
          printf("Parents first read %lu from efd\n", u);
          long u2;
          read(event_fd, &u2, sizeof(long));
          printf("Parents second read %lu from efd\n", u2);
          exit(EXIT_SUCCESS);
      }
  }

    #include <iostream>
    #include <stdio.h>
    #include <string>
    #include <sys/epoll.h>
    #include <sys/eventfd.h>
    #include <unistd.h>
    using namespace std;
    int main(int argc, char* argv[]) {
        if (argc < 2) {
            exit(EXIT_FAILURE);
        }
        int event_fd;
        int epoll_fd;
        event_fd = eventfd(0, EFD_NONBLOCK);
        if (event_fd == -1) {
            std::cout << "create evebtFd fail";
            exit(EXIT_FAILURE);
        }
        epoll_fd = epoll_create(8);
        if (epoll_fd < 0) {
            std::cout << "create epollFd  fail";
        }
        struct epoll_event read_event;
        read_event.events = EPOLLIN;
        epoll_ctl(epoll_fd, EPOLL_CTL_ADD, event_fd, &read_event);
        switch (fork()) {
        case 0:
            for (int j = 1; j < argc; j++) {
                long u = atoi(argv[j]);
                sleep(1);
                printf("Child writing %lu to efd\n", u);
                write(event_fd, &u, sizeof(long));
            }
            printf("Child completed write loop\n");
            exit(EXIT_SUCCESS);
        default:
            printf("Parent about to read\n");
            struct epoll_event events[16];
            int ret;
            while (1) {
                ret = epoll_wait(epoll_fd, events, 1, -1);
                printf("Parent  epoll_wait return ret : %d\n", ret);
                if (ret > 0) {
                    long u;
                    read(event_fd, &u, sizeof(long));
                    printf("Parents  read %lu from efd\n", u);
                }
            }
            exit(EXIT_SUCCESS);
        }
    }

     private native static long nativeInit(); //初始化
     private native void nativePollOnce(long ptr, int timeoutMillis); //阻塞
     private native static void nativeWake(long ptr); //喚醒

      MessageQueue(boolean quitAllowed) {
            mQuitAllowed = quitAllowed;
            mPtr = nativeInit();   //保存NativeMessageQueue
        }

      //android_os_MessageQueue.cpp
      static jlong android_os_MessageQueue_nativeInit(JNIEnv* env, jclass clazz) {
        NativeMessageQueue* nativeMessageQueue = new NativeMessageQueue();
        ...
        return reinterpret_cast<jlong>(nativeMessageQueue);
      }

  NativeMessageQueue::NativeMessageQueue() :
        mPollEnv(NULL), mPollObj(NULL), mExceptionObj(NULL) {
    mLooper = Looper::getForThread();
    if (mLooper == NULL) {
        mLooper = new Looper(false); 
        Looper::setForThread(mLooper);
    }
  }

  Looper::Looper(bool allowNonCallbacks) :
        mAllowNonCallbacks(allowNonCallbacks), ...{
    mWakeEventFd = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
    ...
    rebuildEpollLocked();
  }

  void Looper::rebuildEpollLocked() {
    mEpollFd = epoll_create(EPOLL_SIZE_HINT);
    struct epoll_event eventItem;
    memset(& eventItem, 0, sizeof(epoll_event));
    eventItem.events = EPOLLIN;
    eventItem.data.fd = mWakeEventFd;
    int result = epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mWakeEventFd, & eventItem); 
    ...
  }

    static void android_os_MessageQueue_nativePollOnce(JNIEnv* env, jobject obj,
          jlong ptr, jint timeoutMillis) {
      NativeMessageQueue* nativeMessageQueue = reinterpret_cast<NativeMessageQueue*>(ptr);
      nativeMessageQueue->pollOnce(env, obj, timeoutMillis);
    }
    void NativeMessageQueue::pollOnce(JNIEnv* env, jobject pollObj, int timeoutMillis) {
      mLooper->pollOnce(timeoutMillis);
      ...
    }

     int Looper::pollOnce(int timeoutMillis, int* outFd, int* outEvents, void** outData) {
       for (;;) {
           ...
           result = pollInner(timeoutMillis);
       }
     }
     int Looper::pollInner(int timeoutMillis) {
       ...
       struct epoll_event eventItems[EPOLL_MAX_EVENTS];
       int eventCount = epoll_wait(mEpollFd, eventItems, EPOLL_MAX_EVENTS, timeoutMillis);
       ...

  static void android_os_MessageQueue_nativeWake(JNIEnv* env, jclass clazz, jlong ptr) {
    NativeMessageQueue* nativeMessageQueue = reinterpret_cast<NativeMessageQueue*>(ptr);
    nativeMessageQueue->wake();
  }
  void NativeMessageQueue::wake() {
    mLooper->wake();
  }

void Looper::wake() {
  uint64_t inc = 1;
  ssize_t nWrite = TEMP_FAILURE_RETRY(write(mWakeEventFd, &inc, sizeof(uint64_t)));
  if (nWrite != sizeof(uint64_t)) {
      if (errno != EAGAIN) {
          LOG_ALWAYS_FATAL("Could not write wake signal to fd %d: %s",
                  mWakeEventFd, strerror(errno));
      }
  }
}

MessageQueue.java
//調(diào)用MessageQueue的next方法獲取消息
Message next() {
      、、、
      synchronized (this) {
          //這時候檢查隊列有沒有消息，沒有消息調(diào)用this.wait()等待  
          if (message == null) {
              this.wait();
          }
          if(有消息但消息未到期){
            this.wait(time);
          }
      }
      、、、
  }
//調(diào)用MessageQueue.enqueueMessage()添加消息
enqueueMessage(Message message) {
    、、、
    synchronized (this) {
        //消息加入隊列后會調(diào)用this.notity()喚醒next()方法
        if (message != null) {
            this.notify();
        }
    }
      、、、
  }