Android输入输出系统之TouchEvent流程

一个是InputReader，一个是InputDispatcher。方法是dispatchTouch。

入口点是InputReader 的loopOnce方法.

InputReader里面有个线程叫做InputReaderThread，threadLoop

[code="java"]InputReaderThread::InputReaderThread(const sp& reader) :
        Thread(/*canCallJava*/ true), mReader(reader) {
}

InputReaderThread::~InputReaderThread() {
}

bool InputReaderThread::threadLoop() {
    mReader->loopOnce();
    return true;
}

void InputDispatcher::dispatchOnce() {
    nsecs_t keyRepeatTimeout = mPolicy->getKeyRepeatTimeout();
    nsecs_t keyRepeatDelay = mPolicy->getKeyRepeatDelay();

    nsecs_t nextWakeupTime = LONG_LONG_MAX;
    { // acquire lock
        AutoMutex _l(mLock);
        dispatchOnceInnerLocked(keyRepeatTimeout, keyRepeatDelay, & nextWakeupTime);

        if (runCommandsLockedInterruptible()) {
            nextWakeupTime = LONG_LONG_MIN;  // force next poll to wake up immediately
        }
    } // release lock

    // Wait for callback or timeout or wake.  (make sure we round up, not down)
    nsecs_t currentTime = now();
    int32_t timeoutMillis;
    if (nextWakeupTime > currentTime) {
        uint64_t timeout = uint64_t(nextWakeupTime - currentTime);
        timeout = (timeout + 999999LL) / 1000000LL;
        timeoutMillis = timeout > INT_MAX ? -1 : int32_t(timeout);
    } else {
        timeoutMillis = 0;
    }

    mLooper->pollOnce(timeoutMillis);
}

 

case EventEntry::TYPE_MOTION: {
    MotionEntry* typedEntry = static_cast<MotionEntry*>(mPendingEvent);
    if (dropReason == DROP_REASON_NOT_DROPPED && isAppSwitchDue) {
        dropReason = DROP_REASON_APP_SWITCH;
    }
    done = dispatchMotionLocked(currentTime, typedEntry,
            &dropReason, nextWakeupTime);
    break;

 

bool InputDispatcher::dispatchMotionLocked(
        nsecs_t currentTime, MotionEntry* entry, DropReason* dropReason, nsecs_t* nextWakeupTime) {
    // Preprocessing.
    if (! entry->dispatchInProgress) {
        entry->dispatchInProgress = true;
        resetTargetsLocked();

        logOutboundMotionDetailsLocked("dispatchMotion - ", entry);
    }

    // Clean up if dropping the event.
    if (*dropReason != DROP_REASON_NOT_DROPPED) {
        resetTargetsLocked();
        setInjectionResultLocked(entry, *dropReason == DROP_REASON_POLICY
                ? INPUT_EVENT_INJECTION_SUCCEEDED : INPUT_EVENT_INJECTION_FAILED);
        return true;
    }

    bool isPointerEvent = entry->source & AINPUT_SOURCE_CLASS_POINTER;

    // Identify targets.
    if (! mCurrentInputTargetsValid) {
        int32_t injectionResult;
        if (isPointerEvent) {
            // Pointer event.  (eg. touchscreen)
            injectionResult = findTouchedWindowTargetsLocked(currentTime,
                    entry, nextWakeupTime);
        } else {
            // Non touch event.  (eg. trackball)
            injectionResult = findFocusedWindowTargetsLocked(currentTime,
                    entry, nextWakeupTime);
        }
        if (injectionResult == INPUT_EVENT_INJECTION_PENDING) {
            return false;
        }

        setInjectionResultLocked(entry, injectionResult);
        if (injectionResult != INPUT_EVENT_INJECTION_SUCCEEDED) {
            return true;
        }

        addMonitoringTargetsLocked();
        commitTargetsLocked();
    }

    // Dispatch the motion.
    dispatchEventToCurrentInputTargetsLocked(currentTime, entry, false);
    return true;
}

 

startDispatchCycleLocked 中的方法
 status = connection->inputPublisher.publishMotionEvent(motionEntry->deviceId,
                motionEntry->source, action, flags, motionEntry->edgeFlags, motionEntry->metaState,
                xOffset, yOffset,
                motionEntry->xPrecision, motionEntry->yPrecision,
                motionEntry->downTime, firstMotionSample->eventTime,
                motionEntry->pointerCount, motionEntry->pointerIds,
                firstMotionSample->pointerCoords);

 

ViewRoot有个InputHandler

 

private final InputHandler mInputHandler = new InputHandler() {
    public void handleKey(KeyEvent event, Runnable finishedCallback) {
        startInputEvent(finishedCallback);
        dispatchKey(event, true);
    }

    public void handleMotion(MotionEvent event, Runnable finishedCallback) {
        startInputEvent(finishedCallback);
        dispatchMotion(event, true);
    }
};

 InputHandler注册给了系统

InputQueue.registerInputChannel(mInputChannel, mInputHandler,
                           Looper.myQueue());

 

dispatchMotion(event, true);方法如下
rivate void dispatchMotion(MotionEvent event, boolean sendDone) {
       int source = event.getSource();
       if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) {
           dispatchPointer(event, sendDone);
       } else if ((source & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) {
           dispatchTrackball(event, sendDone);
       } else {
           // TODO
           Log.v(TAG, "Dropping unsupported motion event (unimplemented): " + event);
           if (sendDone) {
               finishInputEvent();
           }
       }
   }

 

调用了dispatchPointer

 ViewRoot本身就是Handler直接sendMessageAtTime

然后就进入了View的焦点系统。

下面就说一下Activity的焦点是怎么回事。

InputDisapatcher.cpp中调用了如下方法

 dispatchEventToCurrentInputTargetsLocked(currentTime, motionEntry,
                            true /*resumeWithAppendedMotionSample*/);

 然后

dispatchEventToCurrentInputTargetsLocked

调用了如下方法

int32_t InputDispatcher::findFocusedWindowTargetsLocked(nsecs_t currentTime,
        const EventEntry* entry, nsecs_t* nextWakeupTime) {
    mCurrentInputTargets.clear();

    int32_t injectionResult;

    // If there is no currently focused window and no focused application
    // then drop the event.
    if (! mFocusedWindow) {
        if (mFocusedApplication) {
#if DEBUG_FOCUS
            LOGD("Waiting because there is no focused window but there is a "
                    "focused application that may eventually add a window: %s.",
                    getApplicationWindowLabelLocked(mFocusedApplication, NULL).string());
#endif
            injectionResult = handleTargetsNotReadyLocked(currentTime, entry,
                    mFocusedApplication, NULL, nextWakeupTime);
            goto Unresponsive;
        }

        LOGI("Dropping event because there is no focused window or focused application.");
        injectionResult = INPUT_EVENT_INJECTION_FAILED;
        goto Failed;
    }

    // Check permissions.
    if (! checkInjectionPermission(mFocusedWindow, entry->injectionState)) {
        injectionResult = INPUT_EVENT_INJECTION_PERMISSION_DENIED;
        goto Failed;
    }

    // If the currently focused window is paused then keep waiting.
    if (mFocusedWindow->paused) {
#if DEBUG_FOCUS
        LOGD("Waiting because focused window is paused.");
#endif
        injectionResult = handleTargetsNotReadyLocked(currentTime, entry,
                mFocusedApplication, mFocusedWindow, nextWakeupTime);
        goto Unresponsive;
    }

    // If the currently focused window is still working on previous events then keep waiting.
    if (! isWindowFinishedWithPreviousInputLocked(mFocusedWindow)) {
#if DEBUG_FOCUS
        LOGD("Waiting because focused window still processing previous input.");
#endif
        injectionResult = handleTargetsNotReadyLocked(currentTime, entry,
                mFocusedApplication, mFocusedWindow, nextWakeupTime);
        goto Unresponsive;
    }

    // Success!  Output targets.
    injectionResult = INPUT_EVENT_INJECTION_SUCCEEDED;
    addWindowTargetLocked(mFocusedWindow, InputTarget::FLAG_FOREGROUND, BitSet32(0));

    // Done.
Failed:
Unresponsive:
    nsecs_t timeSpentWaitingForApplication = getTimeSpentWaitingForApplicationLocked(currentTime);
    updateDispatchStatisticsLocked(currentTime, entry,
            injectionResult, timeSpentWaitingForApplication);
#if DEBUG_FOCUS
    LOGD("findFocusedWindow finished: injectionResult=%d, "
            "timeSpendWaitingForApplication=%0.1fms",
            injectionResult, timeSpentWaitingForApplication / 1000000.0);
#endif
    return injectionResult;
}

 

move事件的处理和Down事件的处理很不相同。

新建立的Window在处理焦点的时候，按下事件没有起来之前，保持了原来的焦点窗口。除非ACTION_UP事件收到以后

/* Updates the cached window information provided to the input dispatcher. */
       public void updateInputWindowsLw() {
           // Populate the input window list with information about all of the windows that
           // could potentially receive input.
           // As an optimization, we could try to prune the list of windows but this turns
           // out to be difficult because only the native code knows for sure which window
           // currently has touch focus.
           final ArrayList<WindowState> windows = mWindows;
           final int N = windows.size();
           for (int i = N - 1; i >= 0; i--) {
               final WindowState child = windows.get(i);
               if (child.mInputChannel == null || child.mRemoved) {
                   // Skip this window because it cannot possibly receive input.
                   continue;
               }

               final int flags = child.mAttrs.flags;
               final int type = child.mAttrs.type;

               final boolean hasFocus = (child == mInputFocus);
               final boolean isVisible = child.isVisibleLw();
               final boolean hasWallpaper = (child == mWallpaperTarget)
                       && (type != WindowManager.LayoutParams.TYPE_KEYGUARD);

               // Add a window to our list of input windows.
               final InputWindow inputWindow = mTempInputWindows.add();
               inputWindow.inputChannel = child.mInputChannel;
               inputWindow.name = child.toString();
               inputWindow.layoutParamsFlags = flags;
               inputWindow.layoutParamsType = type;
               inputWindow.dispatchingTimeoutNanos = child.getInputDispatchingTimeoutNanos();
               inputWindow.visible = isVisible;
               inputWindow.canReceiveKeys = child.canReceiveKeys();
               inputWindow.hasFocus = hasFocus;
               inputWindow.hasWallpaper = hasWallpaper;
               inputWindow.paused = child.mAppToken != null ? child.mAppToken.paused : false;
               inputWindow.layer = child.mLayer;
               inputWindow.ownerPid = child.mSession.mPid;
               inputWindow.ownerUid = child.mSession.mUid;

               final Rect frame = child.mFrame;
               inputWindow.frameLeft = frame.left;
               inputWindow.frameTop = frame.top;
               inputWindow.frameRight = frame.right;
               inputWindow.frameBottom = frame.bottom;

               final Rect visibleFrame = child.mVisibleFrame;
               inputWindow.visibleFrameLeft = visibleFrame.left;
               inputWindow.visibleFrameTop = visibleFrame.top;
               inputWindow.visibleFrameRight = visibleFrame.right;
               inputWindow.visibleFrameBottom = visibleFrame.bottom;

               switch (child.mTouchableInsets) {
                   default:
                   case ViewTreeObserver.InternalInsetsInfo.TOUCHABLE_INSETS_FRAME:
                       inputWindow.touchableAreaLeft = frame.left;
                       inputWindow.touchableAreaTop = frame.top;
                       inputWindow.touchableAreaRight = frame.right;
                       inputWindow.touchableAreaBottom = frame.bottom;
                       break;

                   case ViewTreeObserver.InternalInsetsInfo.TOUCHABLE_INSETS_CONTENT: {
                       Rect inset = child.mGivenContentInsets;
                       inputWindow.touchableAreaLeft = frame.left + inset.left;
                       inputWindow.touchableAreaTop = frame.top + inset.top;
                       inputWindow.touchableAreaRight = frame.right - inset.right;
                       inputWindow.touchableAreaBottom = frame.bottom - inset.bottom;
                       break;
                   }

                   case ViewTreeObserver.InternalInsetsInfo.TOUCHABLE_INSETS_VISIBLE: {
                       Rect inset = child.mGivenVisibleInsets;
                       inputWindow.touchableAreaLeft = frame.left + inset.left;
                       inputWindow.touchableAreaTop = frame.top + inset.top;
                       inputWindow.touchableAreaRight = frame.right - inset.right;
                       inputWindow.touchableAreaBottom = frame.bottom - inset.bottom;
                       break;
                   }
               }
           }

           // Send windows to native code.
           mInputManager.setInputWindows(mTempInputWindows.toNullTerminatedArray());

           // Clear the list in preparation for the next round.
           // Also avoids keeping InputChannel objects referenced unnecessarily.
           mTempInputWindows.clear();
       }

  真正的Input的控制是通过以下方式

      /**
     * Z-ordered (bottom-most first) list of all Window objects.
     */
    final ArrayList<WindowState> mWindows = new ArrayList<WindowState>();

/**
 * Z-ordered (bottom-most first) list of all Window objects.
 */
final ArrayList<WindowState> mWindows = new ArrayList<WindowState>();

 

另外的touch的target并不是通过input focus 获得的。而是通过visible来获得

int32_t InputDispatcher::findTouchedWindowTargetsLocked(nsecs_t currentTime,
        const MotionEntry* entry, nsecs_t* nextWakeupTime) {
    enum InjectionPermission {
        INJECTION_PERMISSION_UNKNOWN,
        INJECTION_PERMISSION_GRANTED,
        INJECTION_PERMISSION_DENIED
    };

    mCurrentInputTargets.clear();

    nsecs_t startTime = now();

    // For security reasons, we defer updating the touch state until we are sure that
    // event injection will be allowed.
    //
    // FIXME In the original code, screenWasOff could never be set to true.
    //       The reason is that the POLICY_FLAG_WOKE_HERE
    //       and POLICY_FLAG_BRIGHT_HERE flags were set only when preprocessing raw
    //       EV_KEY, EV_REL and EV_ABS events.  As it happens, the touch event was
    //       actually enqueued using the policyFlags that appeared in the final EV_SYN
    //       events upon which no preprocessing took place.  So policyFlags was always 0.
    //       In the new native input dispatcher we're a bit more careful about event
    //       preprocessing so the touches we receive can actually have non-zero policyFlags.
    //       Unfortunately we obtain undesirable behavior.
    //
    //       Here's what happens:
    //
    //       When the device dims in anticipation of going to sleep, touches
    //       in windows which have FLAG_TOUCHABLE_WHEN_WAKING cause
    //       the device to brighten and reset the user activity timer.
    //       Touches on other windows (such as the launcher window)
    //       are dropped.  Then after a moment, the device goes to sleep.  Oops.
    //
    //       Also notice how screenWasOff was being initialized using POLICY_FLAG_BRIGHT_HERE
    //       instead of POLICY_FLAG_WOKE_HERE...
    //
    bool screenWasOff = false; // original policy: policyFlags & POLICY_FLAG_BRIGHT_HERE;

    int32_t action = entry->action;
    int32_t maskedAction = action & AMOTION_EVENT_ACTION_MASK;

    // Update the touch state as needed based on the properties of the touch event.
    int32_t injectionResult = INPUT_EVENT_INJECTION_PENDING;
    InjectionPermission injectionPermission = INJECTION_PERMISSION_UNKNOWN;
    if (maskedAction == AMOTION_EVENT_ACTION_DOWN) {
        mTempTouchState.reset();
        mTempTouchState.down = true;
    } else {
        mTempTouchState.copyFrom(mTouchState);
    }

    bool isSplit = mTempTouchState.split && mTempTouchState.down;
    if (maskedAction == AMOTION_EVENT_ACTION_DOWN
            || (isSplit && maskedAction == AMOTION_EVENT_ACTION_POINTER_DOWN)) {
        /* Case 1: New splittable pointer going down. */

        int32_t pointerIndex = getMotionEventActionPointerIndex(action);
        int32_t x = int32_t(entry->firstSample.pointerCoords[pointerIndex].x);
        int32_t y = int32_t(entry->firstSample.pointerCoords[pointerIndex].y);
        const InputWindow* newTouchedWindow = NULL;
        const InputWindow* topErrorWindow = NULL;

        // Traverse windows from front to back to find touched window and outside targets.
        size_t numWindows = mWindows.size();
        for (size_t i = 0; i < numWindows; i++) {
            const InputWindow* window = & mWindows.editItemAt(i);
            int32_t flags = window->layoutParamsFlags;

            if (flags & InputWindow::FLAG_SYSTEM_ERROR) {
                if (! topErrorWindow) {
                    topErrorWindow = window;
                }
            }

            if (window->visible) {
                if (! (flags & InputWindow::FLAG_NOT_TOUCHABLE)) {
                    bool isTouchModal = (flags & (InputWindow::FLAG_NOT_FOCUSABLE
                            | InputWindow::FLAG_NOT_TOUCH_MODAL)) == 0;
                    if (isTouchModal || window->touchableAreaContainsPoint(x, y)) {
                        if (! screenWasOff || flags & InputWindow::FLAG_TOUCHABLE_WHEN_WAKING) {
                            newTouchedWindow = window;
                        }
                        break; // found touched window, exit window loop
                    }
                }

                if (maskedAction == AMOTION_EVENT_ACTION_DOWN
                        && (flags & InputWindow::FLAG_WATCH_OUTSIDE_TOUCH)) {
                    int32_t outsideTargetFlags = InputTarget::FLAG_OUTSIDE;
                    if (isWindowObscuredAtPointLocked(window, x, y)) {
                        outsideTargetFlags |= InputTarget::FLAG_WINDOW_IS_OBSCURED;
                    }

                    mTempTouchState.addOrUpdateWindow(window, outsideTargetFlags, BitSet32(0));
                }
            }
        }

        // If there is an error window but it is not taking focus (typically because
        // it is invisible) then wait for it.  Any other focused window may in
        // fact be in ANR state.
        if (topErrorWindow && newTouchedWindow != topErrorWindow) {
#if DEBUG_FOCUS
            LOGD("Waiting because system error window is pending.");
#endif
            injectionResult = handleTargetsNotReadyLocked(currentTime, entry,
                    NULL, NULL, nextWakeupTime);
            injectionPermission = INJECTION_PERMISSION_UNKNOWN;
            goto Unresponsive;
        }

        // Figure out whether splitting will be allowed for this window.
        if (newTouchedWindow
                && (newTouchedWindow->layoutParamsFlags & InputWindow::FLAG_SPLIT_TOUCH)) {
            // New window supports splitting.
            isSplit = true;
        } else if (isSplit) {
            // New window does not support splitting but we have already split events.
            // Assign the pointer to the first foreground window we find.
            // (May be NULL which is why we put this code block before the next check.)
            newTouchedWindow = mTempTouchState.getFirstForegroundWindow();
        }

        // If we did not find a touched window then fail.
        if (! newTouchedWindow) {
            if (mFocusedApplication) {
#if DEBUG_FOCUS
                LOGD("Waiting because there is no touched window but there is a "
                        "focused application that may eventually add a new window: %s.",
                        getApplicationWindowLabelLocked(mFocusedApplication, NULL).string());
#endif
                injectionResult = handleTargetsNotReadyLocked(currentTime, entry,
                        mFocusedApplication, NULL, nextWakeupTime);
                goto Unresponsive;
            }

            LOGI("Dropping event because there is no touched window or focused application.");
            injectionResult = INPUT_EVENT_INJECTION_FAILED;
            goto Failed;
        }

        // Set target flags.
        int32_t targetFlags = InputTarget::FLAG_FOREGROUND;
        if (isSplit) {
            targetFlags |= InputTarget::FLAG_SPLIT;
        }
        if (isWindowObscuredAtPointLocked(newTouchedWindow, x, y)) {
            targetFlags |= InputTarget::FLAG_WINDOW_IS_OBSCURED;
        }

        // Update the temporary touch state.
        BitSet32 pointerIds;
        if (isSplit) {
            uint32_t pointerId = entry->pointerIds[pointerIndex];
            pointerIds.markBit(pointerId);
        }
        mTempTouchState.addOrUpdateWindow(newTouchedWindow, targetFlags, pointerIds);
    } else {
        /* Case 2: Pointer move, up, cancel or non-splittable pointer down. */

        // If the pointer is not currently down, then ignore the event.
        if (! mTempTouchState.down) {
            LOGI("Dropping event because the pointer is not down.");
            injectionResult = INPUT_EVENT_INJECTION_FAILED;
            goto Failed;
        }
    }

    // Check permission to inject into all touched foreground windows and ensure there
    // is at least one touched foreground window.
    {
        bool haveForegroundWindow = false;
        for (size_t i = 0; i < mTempTouchState.windows.size(); i++) {
            const TouchedWindow& touchedWindow = mTempTouchState.windows[i];
            if (touchedWindow.targetFlags & InputTarget::FLAG_FOREGROUND) {
                haveForegroundWindow = true;
                if (! checkInjectionPermission(touchedWindow.window, entry->injectionState)) {
                    injectionResult = INPUT_EVENT_INJECTION_PERMISSION_DENIED;
                    injectionPermission = INJECTION_PERMISSION_DENIED;
                    goto Failed;
                }
            }
        }
        if (! haveForegroundWindow) {
#if DEBUG_INPUT_DISPATCHER_POLICY
            LOGD("Dropping event because there is no touched foreground window to receive it.");
#endif
            injectionResult = INPUT_EVENT_INJECTION_FAILED;
            goto Failed;
        }

        // Permission granted to injection into all touched foreground windows.
        injectionPermission = INJECTION_PERMISSION_GRANTED;
    }

    // Ensure all touched foreground windows are ready for new input.
    for (size_t i = 0; i < mTempTouchState.windows.size(); i++) {
        const TouchedWindow& touchedWindow = mTempTouchState.windows[i];
        if (touchedWindow.targetFlags & InputTarget::FLAG_FOREGROUND) {
            // If the touched window is paused then keep waiting.
            if (touchedWindow.window->paused) {
#if DEBUG_INPUT_DISPATCHER_POLICY
                LOGD("Waiting because touched window is paused.");
#endif
                injectionResult = handleTargetsNotReadyLocked(currentTime, entry,
                        NULL, touchedWindow.window, nextWakeupTime);
                goto Unresponsive;
            }

            // If the touched window is still working on previous events then keep waiting.
            if (! isWindowFinishedWithPreviousInputLocked(touchedWindow.window)) {
#if DEBUG_FOCUS
                LOGD("Waiting because touched window still processing previous input.");
#endif
                injectionResult = handleTargetsNotReadyLocked(currentTime, entry,
                        NULL, touchedWindow.window, nextWakeupTime);
                goto Unresponsive;
            }
        }
    }

    // If this is the first pointer going down and the touched window has a wallpaper
    // then also add the touched wallpaper windows so they are locked in for the duration
    // of the touch gesture.
    if (maskedAction == AMOTION_EVENT_ACTION_DOWN) {
        const InputWindow* foregroundWindow = mTempTouchState.getFirstForegroundWindow();
        if (foregroundWindow->hasWallpaper) {
            for (size_t i = 0; i < mWindows.size(); i++) {
                const InputWindow* window = & mWindows[i];
                if (window->layoutParamsType == InputWindow::TYPE_WALLPAPER) {
                    mTempTouchState.addOrUpdateWindow(window,
                            InputTarget::FLAG_WINDOW_IS_OBSCURED, BitSet32(0));
                }
            }
        }
    }

    // Success!  Output targets.
    injectionResult = INPUT_EVENT_INJECTION_SUCCEEDED;

    for (size_t i = 0; i < mTempTouchState.windows.size(); i++) {
        const TouchedWindow& touchedWindow = mTempTouchState.windows.itemAt(i);
        addWindowTargetLocked(touchedWindow.window, touchedWindow.targetFlags,
                touchedWindow.pointerIds);
    }

    // Drop the outside touch window since we will not care about them in the next iteration.
    mTempTouchState.removeOutsideTouchWindows();

Failed:
    // Check injection permission once and for all.
    if (injectionPermission == INJECTION_PERMISSION_UNKNOWN) {
        if (checkInjectionPermission(NULL, entry->injectionState)) {
            injectionPermission = INJECTION_PERMISSION_GRANTED;
        } else {
            injectionPermission = INJECTION_PERMISSION_DENIED;
        }
    }

    // Update final pieces of touch state if the injector had permission.
    if (injectionPermission == INJECTION_PERMISSION_GRANTED) {
        if (maskedAction == AMOTION_EVENT_ACTION_UP
                || maskedAction == AMOTION_EVENT_ACTION_CANCEL) {
            // All pointers up or canceled.
            mTempTouchState.reset();
        } else if (maskedAction == AMOTION_EVENT_ACTION_DOWN) {
            // First pointer went down.
            if (mTouchState.down) {
#if DEBUG_FOCUS
                LOGD("Pointer down received while already down.");
#endif
            }
        } else if (maskedAction == AMOTION_EVENT_ACTION_POINTER_UP) {
            // One pointer went up.
            if (isSplit) {
                int32_t pointerIndex = getMotionEventActionPointerIndex(action);
                uint32_t pointerId = entry->pointerIds[pointerIndex];

                for (size_t i = 0; i < mTempTouchState.windows.size(); ) {
                    TouchedWindow& touchedWindow = mTempTouchState.windows.editItemAt(i);
                    if (touchedWindow.targetFlags & InputTarget::FLAG_SPLIT) {
                        touchedWindow.pointerIds.clearBit(pointerId);
                        if (touchedWindow.pointerIds.isEmpty()) {
                            mTempTouchState.windows.removeAt(i);
                            continue;
                        }
                    }
                    i += 1;
                }
            }
        }

        // Save changes to touch state.
        mTouchState.copyFrom(mTempTouchState);
    } else {
#if DEBUG_FOCUS
        LOGD("Not updating touch focus because injection was denied.");
#endif
    }

Unresponsive:
    // Reset temporary touch state to ensure we release unnecessary references to input channels.
    mTempTouchState.reset();

    nsecs_t timeSpentWaitingForApplication = getTimeSpentWaitingForApplicationLocked(currentTime);
    updateDispatchStatisticsLocked(currentTime, entry,
            injectionResult, timeSpentWaitingForApplication);
#if DEBUG_FOCUS
    LOGD("findTouchedWindow finished: injectionResult=%d, injectionPermission=%d, "
            "timeSpentWaitingForApplication=%0.1fms",
            injectionResult, injectionPermission, timeSpentWaitingForApplication / 1000000.0);
#endif
    return injectionResult;
}

  最关键的几行代码，说明了Windows是如何找到触屏的输入焦点的：

if (window->visible) {
              if (! (flags & InputWindow::FLAG_NOT_TOUCHABLE)) {
                  bool isTouchModal = (flags & (InputWindow::FLAG_NOT_FOCUSABLE
                          | InputWindow::FLAG_NOT_TOUCH_MODAL)) == 0;
                  if (isTouchModal || window->touchableAreaContainsPoint(x, y)) {
                      if (! screenWasOff || flags & InputWindow::FLAG_TOUCHABLE_WHEN_WAKING) {
                          newTouchedWindow = window;
                      }
                      break; // found touched window, exit window loop
                  }
              }

              if (maskedAction == AMOTION_EVENT_ACTION_DOWN
                      && (flags & InputWindow::FLAG_WATCH_OUTSIDE_TOUCH)) {
                  int32_t outsideTargetFlags = InputTarget::FLAG_OUTSIDE;
                  if (isWindowObscuredAtPointLocked(window, x, y)) {
                      outsideTargetFlags |= InputTarget::FLAG_WINDOW_IS_OBSCURED;
                  }

                  mTempTouchState.addOrUpdateWindow(window, outsideTargetFlags, BitSet32(0));
              }
          }

 

 // Focus tracking for touch.
    struct TouchedWindow {
        const InputWindow* window;
        int32_t targetFlags;
        BitSet32 pointerIds;
        sp<InputChannel> channel;
    };
    struct TouchState {
        bool down;
        bool split;
        Vector<TouchedWindow> windows;

        TouchState();
        ~TouchState();
        void reset();
        void copyFrom(const TouchState& other);
        void addOrUpdateWindow(const InputWindow* window, int32_t targetFlags, BitSet32 pointerIds);
        void removeOutsideTouchWindows();
        const InputWindow* getFirstForegroundWindow();
    };



另外如何定义按键和其他触屏焦点的：


        /* Updates the cached window information provided to the input dispatcher. */
        public void updateInputWindowsLw() {
            // Populate the input window list with information about all of the windows that
            // could potentially receive input.
            // As an optimization, we could try to prune the list of windows but this turns
            // out to be difficult because only the native code knows for sure which window
            // currently has touch focus.
            final ArrayList<WindowState> windows = mWindows;
            final int N = windows.size();
            for (int i = N - 1; i >= 0; i--) {
                final WindowState child = windows.get(i);
                if (child.mInputChannel == null || child.mRemoved) {
                    // Skip this window because it cannot possibly receive input.
                    continue;
                }

                final int flags = child.mAttrs.flags;
                final int type = child.mAttrs.type;

               <span style="color: #ff6600;"> final boolean hasFocus = (child == mInputFocus);</span>
//本行代码确定，一次性的focusWindow只有一个。
                final boolean isVisible = child.isVisibleLw();
                final boolean hasWallpaper = (child == mWallpaperTarget)
                        && (type != WindowManager.LayoutParams.TYPE_KEYGUARD);