Android编程输入事件流程详解
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。
boolEventHub::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); ... returntrue; }
EventHub对外提供了一个函数用于从输入设备文件中读取数据。
boolEventHub::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,reportanydevicesthathadlastbeenadded/removed. if(mClosingDevices!=NULL){ device_t*device=mClosingDevices; LOGV("Reportingdeviceclosed: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; deletedevice; returntrue; } if(mOpeningDevices!=NULL){ device_t*device=mOpeningDevices; LOGV("Reportingdeviceopened:id=0x%x,name=%s\n", device->id,device->path.string()); mOpeningDevices=device->next; *outDeviceId=device->id; if(*outDeviceId==mFirstKeyboardId)*outDeviceId=0; *outType=DEVICE_ADDED; returntrue; } 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("selectfailed(errno=%d)\n",errno); usleep(100000); } continue; } for(i=1;i<mFDCount;i++){ if(mFDs[i].revents){ LOGV("reventsfor%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("%sgot: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=%doutKeycode=%doutFlags=0x%08xerr=%d\n", iev.code,*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); returntrue; }else{ if(res<0){ LOGW("couldnotgetevent(errno=%d)",errno); }else{ LOGE("couldnotgetevent(wrongsize:%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。
staticjboolean android_server_KeyInputQueue_readEvent(JNIEnv*env,jobjectclazz,jobjectevent) { gLock.lock(); sphub=gHub; if(hub==NULL){ hub=newEventHub; gHub=hub; } gLock.unlock(); int32_tdeviceId; int32_ttype; int32_tscancode,keycode; uint32_tflags; int32_tvalue; nsecs_twhen; boolres=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))); returnres; }
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。
ThreadmThread=newThread("InputDeviceReader"){ publicvoidrun(){ android.os.Process.setThreadPriority( android.os.Process.THREAD_PRIORITY_URGENT_DISPLAY); try{ RawInputEventev=newRawInputEvent(); while(true){ InputDevicedi; 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.getEvent dispatchKey/dispatchPointer/dispatchTrackball
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希望本文所述对大家Android程序设计有所帮助。