ResponderEventPlugin.extractEvents() — react Function Reference

Source Code

packages/react-native-renderer/src/legacy-events/ResponderEventPlugin.js lines 697–788

  extractEvents: function (
    topLevelType,
    targetInst,
    nativeEvent,
    nativeEventTarget,
    eventSystemFlags,
  ) {
    if (isStartish(topLevelType)) {
      trackedTouchCount += 1;
    } else if (isEndish(topLevelType)) {
      if (trackedTouchCount >= 0) {
        trackedTouchCount -= 1;
      } else {
        if (__DEV__) {
          console.warn(
            'Ended a touch event which was not counted in `trackedTouchCount`.',
          );
        }
        return null;
      }
    }

    ResponderTouchHistoryStore.recordTouchTrack(topLevelType, nativeEvent);

    let extracted = canTriggerTransfer(topLevelType, targetInst, nativeEvent)
      ? setResponderAndExtractTransfer(
          topLevelType,
          targetInst,
          nativeEvent,
          nativeEventTarget,
        )
      : null;
    // Responder may or may not have transferred on a new touch start/move.
    // Regardless, whoever is the responder after any potential transfer, we
    // direct all touch start/move/ends to them in the form of
    // `onResponderMove/Start/End`. These will be called for *every* additional
    // finger that move/start/end, dispatched directly to whoever is the
    // current responder at that moment, until the responder is "released".
    //
    // These multiple individual change touch events are are always bookended
    // by `onResponderGrant`, and one of
    // (`onResponderRelease/onResponderTerminate`).
    const isResponderTouchStart = responderInst && isStartish(topLevelType);
    const isResponderTouchMove = responderInst && isMoveish(topLevelType);
    const isResponderTouchEnd = responderInst && isEndish(topLevelType);
    const incrementalTouch = isResponderTouchStart
      ? eventTypes.responderStart
      : isResponderTouchMove
        ? eventTypes.responderMove
        : isResponderTouchEnd
          ? eventTypes.responderEnd
          : null;

    if (incrementalTouch) {
      const gesture = ResponderSyntheticEvent.getPooled(
        incrementalTouch,
        responderInst,
        nativeEvent,
        nativeEventTarget,
      );
      gesture.touchHistory = ResponderTouchHistoryStore.touchHistory;
      accumulateDirectDispatches(gesture);
      extracted = accumulate(extracted, gesture);
    }

    const isResponderTerminate =
      responderInst && topLevelType === TOP_TOUCH_CANCEL;
    const isResponderRelease =
      responderInst &&
      !isResponderTerminate &&
      isEndish(topLevelType) &&
      noResponderTouches(nativeEvent);
    const finalTouch = isResponderTerminate
      ? eventTypes.responderTerminate
      : isResponderRelease
        ? eventTypes.responderRelease
        : null;
    if (finalTouch) {
      const finalEvent = ResponderSyntheticEvent.getPooled(
        finalTouch,
        responderInst,