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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。
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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, name=%s\n",
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);
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",
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);
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 jboolean
android_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.getevent dispatchkey/dispatchpointer/dispatchtrackball
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