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69 lines
1.9 KiB
69 lines
1.9 KiB
---
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线程的消息队列是怎么创建的？
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---
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1. 可以在子线程创建 handler 嘛？
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2. 主线程的 Looper 和子线程的 Looper 有什么区别？
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3. Looper 的 MessageQueue 有什么关系？
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4. MessageQueue 是怎么创建的？
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NativeMessageQueue:
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```c++
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jlong MessageQueue_nativeInit(JNIEnv* env, jclass clazz){
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NativeMessageQueue* nativeMessageQueue = new NativeMessageQueue();
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return reinterpret_cast<jlong>(nativeMessageQueue);
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}
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NativeMessageQueue::NativeMessageQueue(){
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mLooper = Looper::getForThread();
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if(mLooper == NULL){
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mLooper = new Looper(false);
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Looper::setForThread(mLooper);
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}
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}
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sp<Looper> Looper::getForThread(){
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int result = pthread_once(& gTLSOnce, initTLSKey);
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return (Looper*)pthread_getspecific(gTLSKey);
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}
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```
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Native Looper:
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```c++
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Looper::Looper(bool allowNonCallbacks){
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mWakeEventFd = eventfd(0, EFD_NONBLOCK);
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rebuildEpollLocked();
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}
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void Looper::rebuildEpollLocked(){
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mEpollFd = epoll_create(EPOLL_SIZE_HINT);
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struct epoll_event eventItem;
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memset(& eventItem, 0, sizeof(epoll_event));
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eventItem.events = EPOLLIN;
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eventItem.data.fd = mWakeEventFd;
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epoll_ctl(mEpollFd, EPOLL_CTL_ADD, mWakeEventFd, & eventItem);
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}
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void Looper::wake(){
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uint64_t inc = 1;
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ssize_t nWrite = write(mWakeEventFd, &inc, sizeof(uint64_t));
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}
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int Looper::pollOnce(int timeoutMillis, int* outFd, ...){
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for(;;){
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pollInner(timeoutMillis);
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}
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}
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int Looper::pollInner(int timeoutMillis){
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struct epoll_event eventItems[EPOLL_MAX_EVENTS];
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int eventCount = epoll_wait(mEpollFd, eventItems, ...);
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for(int i=0;i<eventCount;i++){
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int fd = eventItems[i].data.fd;
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uint32_t epollEvents = eventItems[i].events;
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if(fd==mWakeEventFd&&(epollEvents&EPOLLIN)){
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awoken();
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}
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}
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}
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void Looper::awoken(){
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uint64_t counter;
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read(mWakeEventFd, &counter, sizeof(uint64_t));
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}
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``` |