Android应用程序键盘（Keyboard）消息处理机制分析（7）
函数首先根据文件名来打开这个设备文件： fd=open(deviceName,O_RDWR); 系统中所有输入设备文件信息都保存在成员变量mDevicesById中，因此，先在mDevicesById找到一个空位置来保存当前打开的设备文件信息： mDevicesById[devid].seq=(mDevicesById[devid].seq+(1<<SEQ_SHIFT))&SEQ_MASK; if(mDevicesById[devid].seq==0){ mDevicesById[devid].seq=1<<SEQ_SHIFT; } 找到了空闲位置后，就为这个输入设备文件创建相应的device_t信息： mDevicesById[devid].seq=(mDevicesById[devid].seq+(1<<SEQ_SHIFT))&SEQ_MASK; if(mDevicesById[devid].seq==0){ mDevicesById[devid].seq=1<<SEQ_SHIFT; } new_mFDs=(pollfd*)realloc(mFDs,sizeof(mFDs[0])*(mFDCount+1)); new_devices=(device_t**)realloc(mDevices,sizeof(mDevices[0])*(mFDCount+1)); if(new_mFDs==NULL||new_devices==NULL){ LOGE("outofmemory"); return-1; } mFDs=new_mFDs; mDevices=new_devices; ...... device_t*device=newdevice_t(devid|mDevicesById[devid].seq,deviceName,name); if(device==NULL){ LOGE("outofmemory"); return-1; } device->fd=fd; 同时，这个设备文件还会保存在数组mFDs中： mFDs[mFDCount].fd=fd; mFDs[mFDCount].events=POLLIN; mFDs[mFDCount].revents=0; 接下来查看这个设备是不是键盘： //Figureoutthekindsofeventsthedevicereports. uint8_tkey_bitmask[sizeof_bit_array(KEY_MAX+1)]; memset(key_bitmask,0,sizeof(key_bitmask)); LOGV("Gettingkeys..."); if(ioctl(fd,EVIOCGBIT(EV_KEY,sizeof(key_bitmask)),key_bitmask)>=0){ //Seeifthisisakeyboard.Ignoreeverythinginthebuttonrangeexceptfor //gamepadswhicharealsoconsideredkeyboards. if(containsNonZeroByte(key_bitmask,0,sizeof_bit_array(BTN_MISC)) ||containsNonZeroByte(key_bitmask,sizeof_bit_array(BTN_GAMEPAD), sizeof_bit_array(BTN_DIGI)) ||containsNonZeroByte(key_bitmask,sizeof_bit_array(KEY_OK), sizeof_bit_array(KEY_MAX+1))){ device->classes|=INPUT_DEVICE_CLASS_KEYBOARD; device->keyBitmask=newuint8_t[sizeof(key_bitmask)]; if(device->keyBitmask!=NULL){ memcpy(device->keyBitmask,key_bitmask,sizeof(key_bitmask)); }else{ deletedevice; LOGE("outofmemoryallocatingkeybitmask"); return-1; } } } 如果是的话，还要继续进一步初始化前面为这个设备文件所创建的device_t结构体，主要就是把结构体device的classes成员变量的INPUT_DEVICE_CLASS_KEYBOARD位置为1了，以表明这是一个键盘。 如果是键盘设备，初始化工作还未完成，还要继续设置键盘的布局等信息： if((device->classes&INPUT_DEVICE_CLASS_KEYBOARD)!=0){ chartmpfn[sizeof(name)]; charkeylayoutFilename[300]; //amoredescriptivename device->name=name; //replaceallthespaceswithunderscores strcpy(tmpfn,name); for(char*p=strchr(tmpfn,'');p&&*p;p=strchr(tmpfn,'')) *p='_'; //findthe.klfileweneedforthisdevice constchar*root=getenv("ANDROID_ROOT"); snprintf(keylayoutFilename,sizeof(keylayoutFilename), "%s/usr/keylayout/%s.kl",root,tmpfn); booldefaultKeymap=false; if(access(keylayoutFilename,R_OK)){ snprintf(keylayoutFilename,sizeof(keylayoutFilename), "%s/usr/keylayout/%s",root,"qwerty.kl"); defaultKeymap=true; } status_tstatus=device->layoutMap->load(keylayoutFilename); if(status){ LOGE("Error%dloadingkeylayout.",status); } //telltheworldaboutthedevname(thedescriptivename) if(!mHaveFirstKeyboard&&!defaultKeymap&&strstr(name,"-keypad")){ //thebuilt-inkeyboardhasawell-knowndeviceIDof0, //thisdevicebetternotgoaway. mHaveFirstKeyboard=true; mFirstKeyboardId=device->id; property_set("hw.keyboards.0.devname",name); }else{ //ensuremFirstKeyboardIdissetto-something-. if(mFirstKeyboardId==0){ mFirstKeyboardId=device->id; } } charpropName[100]; sprintf(propName,"hw.keyboards.%u.devname",device->id); property_set(propName,name); //'Q'keysupport=cheaptestofwhetherthisisanalpha-capablekbd if(hasKeycodeLocked(device,AKEYCODE_Q)){ device->classes|=INPUT_DEVICE_CLASS_ALPHAKEY; } //SeeifthisdevicehasaDPAD. if(hasKeycodeLocked(device,AKEYCODE_DPAD_UP)&& hasKeycodeLocked(device,AKEYCODE_DPAD_DOWN)&& hasKeycodeLocked(device,AKEYCODE_DPAD_LEFT)&& hasKeycodeLocked(device,AKEYCODE_DPAD_RIGHT)&& hasKeycodeLocked(device,AKEYCODE_DPAD_CENTER)){ device->classes|=INPUT_DEVICE_CLASS_DPAD; } //Seeifthisdevicehasagamepad. for(size_ti=0;i<sizeof(GAMEPAD_KEYCODES)/sizeof(GAMEPAD_KEYCODES[0]);i++){ if(hasKeycodeLocked(device,GAMEPAD_KEYCODES[i])){ device->classes|=INPUT_DEVICE_CLASS_GAMEPAD; break; } } LOGI("Newkeyboard:device->id=0x%xdevname='%s'propName='%s'keylayout='%s'\n", device->id,name,propName,keylayoutFilename); } 到这里，系统中的输入设备文件就打开了。 本文转自 Luoshengyang 51CTO博客，原文链接：http://blog.51cto.com/shyluo/966619，如需转载请自行联系原作者
