Android 输入事件流程

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;