Android编程输入事件流程详解

概述本文实例讲述了Android编程输入事件流程。分享给大家供大家参考，具体如下：

本文实例讲述了AndroID编程输入事件流程。分享给大家供大家参考，具体如下：

EventHub对输入设备进行了封装。输入设备驱动程序对用户空间应用程序提供一些设备文件，这些设备文件放在/dev/input里面。

EventHub扫描/dev/input下所有设备文件，并打开它们。

bool EventHub::openPlatforminput(voID){...  mFDCount = 1;  mFDs = (pollfd *)calloc(1,sizeof(mFDs[0]));  mDevices = (device_t **)calloc(1,sizeof(mDevices[0]));  mFDs[0].events = PolliN;  mDevices[0] = NulL;  res = scan_dir(device_path);...  return true;}

EventHub对外提供了一个函数用于从输入设备文件中读取数据。

bool EventHub::getEvent(int32_t* outdeviceid,int32_t* outType,int32_t* outScancode,int32_t* outKeycode,uint32_t *outFlags,int32_t* outValue,nsecs_t* outWhen)    {     ...      while(1) {    // First,report any devices that had last been added/removed.    if (mClosingDevices != NulL) {      device_t* device = mClosingDevices;      LOGV("Reporting device closed: ID=0x%x,name=%s\n",device->ID,device->path.string());      mClosingDevices = device->next;      *outdeviceid = device->ID;      if (*outdeviceid == mFirstKeyboardID) *outdeviceid = 0;      *outType = DEVICE_REMOVED;      delete device;      return true;    }    if (mopeningDevices != NulL) {      device_t* device = mopeningDevices;      LOGV("Reporting device opened: ID=0x%x,device->path.string());      mopeningDevices = device->next;      *outdeviceid = device->ID;      if (*outdeviceid == mFirstKeyboardID) *outdeviceid = 0;      *outType = DEVICE_ADDED;      return true;    }    release_wake_lock(WAKE_LOCK_ID);    pollres = poll(mFDs,mFDCount,-1);    acquire_wake_lock(PARTIAL_WAKE_LOCK,WAKE_LOCK_ID);    if (pollres <= 0) {      if (errno != EINTR) {        LOGW("select Failed (errno=%d)\n",errno);        usleep(100000);      }      continue;    }    for(i = 1; i < mFDCount; i++) {      if(mFDs[i].revents) {        LOGV("revents for %d = 0x%08x",i,mFDs[i].revents);        if(mFDs[i].revents & PolliN) {          res = read(mFDs[i].fd,&IEv,sizeof(IEv));          if (res == sizeof(IEv)) {            LOGV("%s got: t0=%d,t1=%d,type=%d,code=%d,v=%d",mDevices[i]->path.string(),(int) IEv.time.tv_sec,(int) IEv.time.tv_usec,IEv.type,IEv.code,IEv.value);            *outdeviceid = mDevices[i]->ID;            if (*outdeviceid == mFirstKeyboardID) *outdeviceid = 0;            *outType = IEv.type;            *outScancode = IEv.code;            if (IEv.type == EV_KEY) {              err = mDevices[i]->layoutMap->map(IEv.code,outKeycode,outFlags);              LOGV("IEv.code=%d outKeycode=%d outFlags=0x%08x err=%d\n",*outKeycode,*outFlags,err);              if (err != 0) {                *outKeycode = 0;                *outFlags = 0;              }            } else {              *outKeycode = IEv.code;            }            *outValue = IEv.value;            *outWhen = s2ns(IEv.time.tv_sec) + us2ns(IEv.time.tv_usec);            return true;          } else {            if (res<0) {              LOGW("Could not get event (errno=%d)",errno);            } else {              LOGE("Could not get event (wrong size: %d)",res);            }            continue;          }        }      }    } ...}

对于按键事件，调用mDevices[i]->layoutMap->map进行映射。映射实际是由 KeyLayoutMap::map完成的，KeyLayoutMap类里读取配置文件qwerty.kl，由配置文件qwerty.kl决定键值的映射关系。你可以通过修改./development/emulator/keymaps/qwerty.kl来改变键值的映射关系。

JNI函数

在frameworks/base/services/jni/com_androID_server_KeyinputQueue.cpp文件中，向JAVA提供了函数androID_server_KeyinputQueue_readEvent，用于读取输入设备事件。

static jbooleanandroID_server_KeyinputQueue_readEvent(jnienv* env,jobject clazz,jobject event){  gLock.lock();  sp hub = gHub;  if (hub == NulL) {    hub = new EventHub;    gHub = hub;  }  gLock.unlock();  int32_t deviceid;  int32_t type;  int32_t scancode,keycode;  uint32_t flags;  int32_t value;  nsecs_t when;  bool res = hub->getEvent(&deviceid,&type,&scancode,&keycode,&flags,&value,&when);  env->SetIntFIEld(event,ginputOffsets.mdeviceid,(jint)deviceid);  env->SetIntFIEld(event,ginputOffsets.mType,(jint)type);  env->SetIntFIEld(event,ginputOffsets.mScancode,(jint)scancode);  env->SetIntFIEld(event,ginputOffsets.mKeycode,(jint)keycode);  env->SetIntFIEld(event,ginputOffsets.mFlags,(jint)flags);  env->SetIntFIEld(event,ginputOffsets.mValue,value);  env->SetLongFIEld(event,ginputOffsets.mWhen,(jlong)(nanoseconds_to_milliseconds(when)));  return res;}

readEvent调用hub->getEvent读了取事件，然后转换成JAVA的结构。

事件中转线程

在frameworks/base/services/java/com/androID/server/KeyinputQueue.java里创建了一个线程，它循环的读取事件，然后把事件放入事件队列里。

Thread mThread = new Thread("inputDeviceReader") {  public voID run() {      androID.os.Process.setThreadPriority(          androID.os.Process.THREAD_PRIORITY_URGENT_disPLAY);        try {        RawinputEvent ev = new RawinputEvent();        while (true) {          inputDevice di;        readEvent(ev);        send = preprocessEvent(di,ev);          addLocked(di,curTime,ev.flags,...,me);        }    }  };}

输入事件分发线程

在frameworks/base/services/java/com/androID/server/WindowManagerService.java里创建了一个输入事件分发线程，它负责把事件分发到相应的窗口上去。

mQueue.getEventdispatchKey/dispatchPointer/dispatchtrackball

更多关于AndroID相关内容感兴趣的读者可查看本站专题：《Android开发入门与进阶教程》、《Android调试技巧与常见问题解决方法汇总》、《Android多媒体 *** 作技巧汇总(音频,视频,录音等)》、《Android基本组件用法总结》、《Android视图View技巧总结》、《Android布局layout技巧总结》及《Android控件用法总结》

希望本文所述对大家AndroID程序设计有所帮助。

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