Android 输入事件流程

核心提示：EventHubEventHub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，Android 输入事件流程，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

EventHubEventHub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 ",

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, name=%s ",

device->id, 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);