Android Framework层如何截获按键消息

代码位置：

frameworks/base/services/input/InputDispatcher.cpp

所在函数：

void InputDispatcher::notifyKey(const NotifyKeyArgs* args) {#if DEBUG_INBOUND_EVENT_DETAILS    ALOGD("notifyKey - eventTime=%lld, deviceId=%d, source=0x%x, policyFlags=0x%x, action=0x%x, "            "flags=0x%x, keyCode=0x%x, scanCode=0x%x, metaState=0x%x, downTime=%lld",            args->eventTime, args->deviceId, args->source, args->policyFlags,            args->action, args->flags, args->keyCode, args->scanCode,            args->metaState, args->downTime);#endif    if (!validateKeyEvent(args->action)) {        return;    }    uint32_t policyFlags = args->policyFlags;    int32_t flags = args->flags;    int32_t metaState = args->metaState;    if ((policyFlags & POLICY_FLAG_VIRTUAL) || (flags & AKEY_EVENT_FLAG_VIRTUAL_HARD_KEY)) {        policyFlags |= POLICY_FLAG_VIRTUAL;        flags |= AKEY_EVENT_FLAG_VIRTUAL_HARD_KEY;    }    if (policyFlags & POLICY_FLAG_ALT) {        metaState |= AMETA_ALT_ON | AMETA_ALT_LEFT_ON;    }    if (policyFlags & POLICY_FLAG_ALT_GR) {        metaState |= AMETA_ALT_ON | AMETA_ALT_RIGHT_ON;    }    if (policyFlags & POLICY_FLAG_SHIFT) {        metaState |= AMETA_SHIFT_ON | AMETA_SHIFT_LEFT_ON;    }    if (policyFlags & POLICY_FLAG_CAPS_LOCK) {        metaState |= AMETA_CAPS_LOCK_ON;    }    if (policyFlags & POLICY_FLAG_FUNCTION) {        metaState |= AMETA_FUNCTION_ON;    }    policyFlags |= POLICY_FLAG_TRUSTED;    KeyEvent event;    event.initialize(args->deviceId, args->source, args->action,            flags, args->keyCode, args->scanCode, metaState, 0,            args->downTime, args->eventTime);    mPolicy->interceptKeyBeforeQueueing(&event, /*byref*/ policyFlags);    if (policyFlags & POLICY_FLAG_WOKE_HERE) {        flags |= AKEY_EVENT_FLAG_WOKE_HERE;    }    bool needWake;    { // acquire lock        mLock.lock();        if (shouldSendKeyToInputFilterLocked(args)) {            mLock.unlock();            policyFlags |= POLICY_FLAG_FILTERED;            if (!mPolicy->filterInputEvent(&event, policyFlags)) {                return; // event was consumed by the filter            }            mLock.lock();        }        int32_t repeatCount = 0;        KeyEntry* newEntry = new KeyEntry(args->eventTime,                args->deviceId, args->source, policyFlags,                args->action, flags, args->keyCode, args->scanCode,                metaState, repeatCount, args->downTime);        needWake = enqueueInboundEventLocked(newEntry);        mLock.unlock();    } // release lock    if (needWake) {        mLooper->wake();    }}

notifyKey这个函数是按键消息，包括鼠标，键盘，遥控器，游戏手柄，虚拟键值等等消息的中转站
所以，在这个函数里你可以截获任何的按键消息，如HOME键等等，可以说这个函数就是一个水龙头，具体要做什么，就看有什么需求了。

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