1, 基本概念

PhoneWindowManager也是運行於systemserver執行緒中,在Event事件分發之前處理,比如電源鍵。Event事件分發後,僅有包含Activity的apk執行緒才可以處理,如果apk中沒有activity但是想處理Event事件怎麼辦呢?可以在PhoneWindowManager做做文章了。

在SystemServer中,

inputManager = new InputManagerService(context);
  wm = WindowManagerService.main(context, inputManager,
        mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL,
        !mFirstBoot, mOnlyCore);
 ServiceManager.addService(Context.WINDOW_SERVICE, wm);
 ServiceManager.addService(Context.INPUT_SERVICE, inputManager);

 mActivityManagerService.setWindowManager(wm);
inputManager.setWindowManagerCallbacks(wm.getInputMonitor()); // 訊息分發之前的回撥
inputManager.start();
 

InputManagerService的建立以及啟動已經論述了,在此就不多說了。在

WindowManagerService中新建了PhoneWindowManager和InputMonitor,並且將設定為InputManagerService物件的回撥物件。其實這2個類都和Event的處理有關,在Event分發之前進行處理,相當於擷取,具體的細節就一層一層抽絲剝繭了。

PhoneWindowManager是沒有對應的C/C++層程式碼了。

看下InputManagerService的setWindowManagerCallbacks方法,

public void setWindowManagerCallbacks(WindowManagerCallbacks callbacks) {
        mWindowManagerCallbacks = callbacks;
    }
 

因此, InputManagerService的變數mWindowManagerCallbacks指向InputMonitor物件。

2處理流程

InputDispatcher的notifyKey方法中,Event進佇列之前,會呼叫interceptKeyBeforeQueueing方法,

mPolicy->interceptKeyBeforeQueueing(&event, /*byref*/ policyFlags);

mPolicy變數是什麼呢?通過查詢,是NativeInputManager物件,

void NativeInputManager::interceptKeyBeforeQueueing(const KeyEvent* keyEvent,
        uint32_t& policyFlags) {
    bool interactive = mInteractive.load();
    if (interactive) {
        policyFlags |= POLICY_FLAG_INTERACTIVE;
    }
    if ((policyFlags & POLICY_FLAG_TRUSTED)) {
        nsecs_t when = keyEvent->getEventTime();
        JNIEnv* env = jniEnv();
        jobject keyEventObj = android_view_KeyEvent_fromNative(env, keyEvent);
        jint wmActions;
        if (keyEventObj) {
            wmActions = env->CallIntMethod(mServiceObj,
                    gServiceClassInfo.interceptKeyBeforeQueueing,
                    keyEventObj, policyFlags);
            if (checkAndClearExceptionFromCallback(env, "interceptKeyBeforeQueueing")) {
                wmActions = 0;
            }
            android_view_KeyEvent_recycle(env, keyEventObj);
            env->DeleteLocalRef(keyEventObj);
        }
•••
}
 

在register_android_server_InputManager方法中,

int res = jniRegisterNativeMethods(env, "com/android/server/input/InputManagerService",
            gInputManagerMethods, NELEM(gInputManagerMethods));
•••
GET_METHOD_ID(gServiceClassInfo.interceptKeyBeforeQueueing, clazz,
            "interceptKeyBeforeQueueing", "(Landroid/view/KeyEvent;I)I");

很明顯了,呼叫Java層InputManagerService的interceptKeyBeforeQueueing方法,後面就沒有什麼困難了,最後呼叫PhoneWindowManager的interceptKeyBeforeQueueing方法。

看下InputMonitor的方法,有一些也是同樣的方法呼叫,關鍵是C/C++層的程式碼什麼時候呼叫,覺得InputMonitor的主要目的還是解耦,防止PhoneWindowManager和InputManagerService太緊,

public void notifyLidSwitchChanged(long whenNanos, boolean lidOpen) {
        mService.mPolicy.notifyLidSwitchChanged(whenNanos, lidOpen);
    }
public void notifyCameraLensCoverSwitchChanged(long whenNanos, boolean lensCovered) {
        mService.mPolicy.notifyCameraLensCoverSwitchChanged(whenNanos, lensCovered);
    }
 public int interceptKeyBeforeQueueing(KeyEvent event, int policyFlags) {
        return mService.mPolicy.interceptKeyBeforeQueueing(event, policyFlags);
    }
    public int interceptMotionBeforeQueueingNonInteractive(long whenNanos, int policyFlags) {
        return mService.mPolicy.interceptMotionBeforeQueueingNonInteractive(
                whenNanos, policyFlags);
    }
    public long interceptKeyBeforeDispatching(
            InputWindowHandle focus, KeyEvent event, int policyFlags) {
        WindowState windowState = focus != null ? (WindowState) focus.windowState : null;
        return mService.mPolicy.interceptKeyBeforeDispatching(windowState, event, policyFlags);
    }
    public KeyEvent dispatchUnhandledKey(
            InputWindowHandle focus, KeyEvent event, int policyFlags) {
        WindowState windowState = focus != null ? (WindowState) focus.windowState : null;
        return mService.mPolicy.dispatchUnhandledKey(windowState, event, policyFlags);
    }
    public int getPointerLayer() {
        return mService.mPolicy.windowTypeToLayerLw(WindowManager.LayoutParams.TYPE_POINTER)
                * WindowManagerService.TYPE_LAYER_MULTIPLIER
                + WindowManagerService.TYPE_LAYER_OFFSET;
    }

在InputDispatcher.cpp的中的Event入佇列之後,dispatchKeyLocked方法中會呼叫doInterceptKeyBeforeDispatchingLockedInterruptible方法,然後呼叫NativeInputManager的interceptKeyBeforeDispatching方法,

nsecs_t delay = mPolicy->interceptKeyBeforeDispatching(commandEntry->inputWindowHandle,
            &event, entry->policyFlags);

最後會呼叫PhoneWindowManager的interceptKeyBeforeDispatching方法。

所以,如果apk中沒有acitivity但是想監聽Event事件怎麼辦呢?

在PhoneWindowManager的interceptKeyBeforeQueueing或者interceptKeyBeforeDispatching方法中稍加處理就可以了。