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。

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