459 lines
18 KiB
JavaScript
459 lines
18 KiB
JavaScript
/**
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* Copyright 2004-present Facebook. All Rights Reserved.
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*
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* @providesModule ScrollResponder
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*/
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'use strict';
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var NativeModules = require('NativeModules');
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var NativeModules = require('NativeModules');
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var RCTDeviceEventEmitter = require('RCTDeviceEventEmitter');
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var Subscribable = require('Subscribable');
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var TextInputState = require('TextInputState');
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var RCTUIManager = NativeModules.UIManager;
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var RCTUIManagerDeprecated = NativeModules.UIManager;
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var RCTScrollViewConsts = RCTUIManager.RCTScrollView.Constants;
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var warning = require('warning');
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/**
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* Mixin that can be integrated in order to handle scrolling that plays well
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* with `ResponderEventPlugin`. Integrate with your platform specific scroll
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* views, or even your custom built (every-frame animating) scroll views so that
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* all of these systems play well with the `ResponderEventPlugin`.
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*
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* iOS scroll event timing nuances:
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* ===============================
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*
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*
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* Scrolling without bouncing, if you touch down:
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* -------------------------------
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*
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* 1. `onMomentumScrollBegin` (when animation begins after letting up)
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* ... physical touch starts ...
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* 2. `onTouchStartCapture` (when you press down to stop the scroll)
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* 3. `onTouchStart` (same, but bubble phase)
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* 4. `onResponderRelease` (when lifting up - you could pause forever before * lifting)
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* 5. `onMomentumScrollEnd`
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*
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*
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* Scrolling with bouncing, if you touch down:
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* -------------------------------
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*
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* 1. `onMomentumScrollBegin` (when animation begins after letting up)
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* ... bounce begins ...
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* ... some time elapses ...
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* ... physical touch during bounce ...
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* 2. `onMomentumScrollEnd` (Makes no sense why this occurs first during bounce)
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* 3. `onTouchStartCapture` (immediately after `onMomentumScrollEnd`)
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* 4. `onTouchStart` (same, but bubble phase)
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* 5. `onTouchEnd` (You could hold the touch start for a long time)
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* 6. `onMomentumScrollBegin` (When releasing the view starts bouncing back)
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*
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* So when we receive an `onTouchStart`, how can we tell if we are touching
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* *during* an animation (which then causes the animation to stop)? The only way
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* to tell is if the `touchStart` occurred immediately after the
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* `onMomentumScrollEnd`.
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*
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* This is abstracted out for you, so you can just call this.scrollResponderIsAnimating() if
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* necessary
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*
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* `ScrollResponder` also includes logic for blurring a currently focused input
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* if one is focused while scrolling. The `ScrollResponder` is a natural place
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* to put this logic since it can support not dismissing the keyboard while
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* scrolling, unless a recognized "tap"-like gesture has occurred.
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*
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* The public lifecycle API includes events for keyboard interaction, responder
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* interaction, and scrolling (among others). The keyboard callbacks
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* `onKeyboardWill/Did/*` are *global* events, but are invoked on scroll
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* responder's props so that you can guarantee that the scroll responder's
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* internal state has been updated accordingly (and deterministically) by
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* the time the props callbacks are invoke. Otherwise, you would always wonder
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* if the scroll responder is currently in a state where it recognizes new
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* keyboard positions etc. If coordinating scrolling with keyboard movement,
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* *always* use these hooks instead of listening to your own global keyboard
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* events.
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*
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* Public keyboard lifecycle API: (props callbacks)
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*
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* Standard Keyboard Appearance Sequence:
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*
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* this.props.onKeyboardWillShow
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* this.props.onKeyboardDidShow
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*
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* `onScrollResponderKeyboardDismissed` will be invoked if an appropriate
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* tap inside the scroll responder's scrollable region was responsible
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* for the dismissal of the keyboard. There are other reasons why the
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* keyboard could be dismissed.
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*
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* this.props.onScrollResponderKeyboardDismissed
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*
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* Standard Keyboard Hide Sequence:
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*
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* this.props.onKeyboardWillHide
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* this.props.onKeyboardDidHide
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*/
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var IS_ANIMATING_TOUCH_START_THRESHOLD_MS = 16;
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var ScrollResponderMixin = {
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mixins: [Subscribable.Mixin],
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statics: RCTScrollViewConsts,
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scrollResponderMixinGetInitialState: function() {
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return {
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isTouching: false,
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lastMomentumScrollBeginTime: 0,
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lastMomentumScrollEndTime: 0,
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// Reset to false every time becomes responder. This is used to:
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// - Determine if the scroll view has been scrolled and therefore should
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// refuse to give up its responder lock.
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// - Determine if releasing should dismiss the keyboard when we are in
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// tap-to-dismiss mode (!this.props.keyboardShouldPersistTaps).
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observedScrollSinceBecomingResponder: false,
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becameResponderWhileAnimating: false,
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};
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},
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/**
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* Invoke this from an `onScroll` event.
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*/
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scrollResponderHandleScrollShouldSetResponder: function() {
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return this.state.isTouching;
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},
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/**
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* Merely touch starting is not sufficient for a scroll view to become the
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* responder. Being the "responder" means that the very next touch move/end
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* event will result in an action/movement.
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*
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* Invoke this from an `onStartShouldSetResponder` event.
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*
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* `onStartShouldSetResponder` is used when the next move/end will trigger
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* some UI movement/action, but when you want to yield priority to views
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* nested inside of the view.
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*
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* There may be some cases where scroll views actually should return `true`
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* from `onStartShouldSetResponder`: Any time we are detecting a standard tap
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* that gives priority to nested views.
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*
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* - If a single tap on the scroll view triggers an action such as
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* recentering a map style view yet wants to give priority to interaction
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* views inside (such as dropped pins or labels), then we would return true
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* from this method when there is a single touch.
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*
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* - Similar to the previous case, if a two finger "tap" should trigger a
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* zoom, we would check the `touches` count, and if `>= 2`, we would return
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* true.
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*
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*/
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scrollResponderHandleStartShouldSetResponder: function() {
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return false;
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},
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/**
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* There are times when the scroll view wants to become the responder
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* (meaning respond to the next immediate `touchStart/touchEnd`), in a way
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* that *doesn't* give priority to nested views (hence the capture phase):
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*
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* - Currently animating.
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* - Tapping anywhere that is not the focused input, while the keyboard is
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* up (which should dismiss the keyboard).
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*
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* Invoke this from an `onStartShouldSetResponderCapture` event.
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*/
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scrollResponderHandleStartShouldSetResponderCapture: function(e) {
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// First see if we want to eat taps while the keyboard is up
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var currentlyFocusedTextInput = TextInputState.currentlyFocusedField();
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if (!this.props.keyboardShouldPersistTaps &&
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currentlyFocusedTextInput != null &&
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e.target != currentlyFocusedTextInput) {
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return true;
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}
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return this.scrollResponderIsAnimating();
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},
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/**
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* Invoke this from an `onResponderReject` event.
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*
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* Some other element is not yielding its role as responder. Normally, we'd
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* just disable the `UIScrollView`, but a touch has already began on it, the
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* `UIScrollView` will not accept being disabled after that. The easiest
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* solution for now is to accept the limitation of disallowing this
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* altogether. To improve this, find a way to disable the `UIScrollView` after
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* a touch has already started.
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*/
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scrollResponderHandleResponderReject: function() {
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warning(false, "ScrollView doesn't take rejection well - scrolls anyway");
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},
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/**
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* We will allow the scroll view to give up its lock iff it acquired the lock
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* during an animation. This is a very useful default that happens to satisfy
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* many common user experiences.
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*
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* - Stop a scroll on the left edge, then turn that into an outer view's
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* backswipe.
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* - Stop a scroll mid-bounce at the top, continue pulling to have the outer
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* view dismiss.
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* - However, without catching the scroll view mid-bounce (while it is
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* motionless), if you drag far enough for the scroll view to become
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* responder (and therefore drag the scroll view a bit), any backswipe
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* navigation of a swipe gesture higher in the view hierarchy, should be
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* rejected.
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*/
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scrollResponderHandleTerminationRequest: function() {
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return !this.state.observedScrollSinceBecomingResponder;
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},
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/**
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* Invoke this from an `onTouchEnd` event.
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*
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* @param {SyntheticEvent} e Event.
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*/
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scrollResponderHandleTouchEnd: function(e) {
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var nativeEvent = e.nativeEvent;
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this.state.isTouching = nativeEvent.touches.length !== 0;
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this.props.onTouchEnd && this.props.onTouchEnd(e);
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},
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/**
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* Invoke this from an `onResponderRelease` event.
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*/
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scrollResponderHandleResponderRelease: function(e) {
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this.props.onResponderRelease && this.props.onResponderRelease(e);
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// By default scroll views will unfocus a textField
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// if another touch occurs outside of it
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var currentlyFocusedTextInput = TextInputState.currentlyFocusedField();
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if (!this.props.keyboardShouldPersistTaps &&
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currentlyFocusedTextInput != null &&
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e.target != currentlyFocusedTextInput &&
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!this.state.observedScrollSinceBecomingResponder &&
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!this.state.becameResponderWhileAnimating) {
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this.props.onScrollResponderKeyboardDismissed &&
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this.props.onScrollResponderKeyboardDismissed(e);
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TextInputState.blurTextInput(currentlyFocusedTextInput);
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}
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},
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scrollResponderHandleScroll: function(e) {
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this.state.observedScrollSinceBecomingResponder = true;
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this.props.onScroll && this.props.onScroll(e);
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},
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/**
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* Invoke this from an `onResponderGrant` event.
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*/
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scrollResponderHandleResponderGrant: function(e) {
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this.state.observedScrollSinceBecomingResponder = false;
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this.props.onResponderGrant && this.props.onResponderGrant(e);
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this.state.becameResponderWhileAnimating = this.scrollResponderIsAnimating();
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},
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/**
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* Unfortunately, `onScrollBeginDrag` also fires when *stopping* the scroll
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* animation, and there's not an easy way to distinguish a drag vs. stopping
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* momentum.
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*
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* Invoke this from an `onScrollBeginDrag` event.
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*/
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scrollResponderHandleScrollBeginDrag: function(e) {
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this.props.onScrollBeginDrag && this.props.onScrollBeginDrag(e);
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},
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/**
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* Invoke this from an `onScrollEndDrag` event.
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*/
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scrollResponderHandleScrollEndDrag: function(e) {
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this.props.onScrollEndDrag && this.props.onScrollEndDrag(e);
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},
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/**
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* Invoke this from an `onMomentumScrollBegin` event.
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*/
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scrollResponderHandleMomentumScrollBegin: function(e) {
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this.state.lastMomentumScrollBeginTime = Date.now();
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this.props.onMomentumScrollBegin && this.props.onMomentumScrollBegin(e);
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},
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/**
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* Invoke this from an `onMomentumScrollEnd` event.
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*/
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scrollResponderHandleMomentumScrollEnd: function(e) {
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this.state.lastMomentumScrollEndTime = Date.now();
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this.props.onMomentumScrollEnd && this.props.onMomentumScrollEnd(e);
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},
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/**
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* Invoke this from an `onTouchStart` event.
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*
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* Since we know that the `SimpleEventPlugin` occurs later in the plugin
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* order, after `ResponderEventPlugin`, we can detect that we were *not*
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* permitted to be the responder (presumably because a contained view became
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* responder). The `onResponderReject` won't fire in that case - it only
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* fires when a *current* responder rejects our request.
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*
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* @param {SyntheticEvent} e Touch Start event.
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*/
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scrollResponderHandleTouchStart: function(e) {
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this.state.isTouching = true;
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this.props.onTouchStart && this.props.onTouchStart(e);
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},
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/**
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* Invoke this from an `onTouchMove` event.
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*
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* Since we know that the `SimpleEventPlugin` occurs later in the plugin
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* order, after `ResponderEventPlugin`, we can detect that we were *not*
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* permitted to be the responder (presumably because a contained view became
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* responder). The `onResponderReject` won't fire in that case - it only
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* fires when a *current* responder rejects our request.
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*
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* @param {SyntheticEvent} e Touch Start event.
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*/
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scrollResponderHandleTouchMove: function(e) {
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this.props.onTouchMove && this.props.onTouchMove(e);
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},
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/**
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* A helper function for this class that lets us quickly determine if the
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* view is currently animating. This is particularly useful to know when
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* a touch has just started or ended.
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*/
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scrollResponderIsAnimating: function() {
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var now = Date.now();
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var timeSinceLastMomentumScrollEnd = now - this.state.lastMomentumScrollEndTime;
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var isAnimating = timeSinceLastMomentumScrollEnd < IS_ANIMATING_TOUCH_START_THRESHOLD_MS ||
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this.state.lastMomentumScrollEndTime < this.state.lastMomentumScrollBeginTime;
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return isAnimating;
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},
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/**
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* A helper function to scroll to a specific point in the scrollview.
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* This is currently used to help focus on child textview's, but this
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* can also be used to quickly scroll to any element we want to focus
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*/
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scrollResponderScrollTo: function(offsetX, offsetY) {
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RCTUIManagerDeprecated.scrollTo(this.getNodeHandle(), offsetX, offsetY);
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},
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/**
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* A helper function to zoom to a specific rect in the scrollview.
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* @param {object} rect Should have shape {x, y, w, h}
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*/
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scrollResponderZoomTo: function(rect) {
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RCTUIManagerDeprecated.zoomToRect(this.getNodeHandle(), rect);
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},
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/**
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* This method should be used as the callback to onFocus in a TextInputs'
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* parent view. Note that any module using this mixin needs to return
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* the parent view's ref in getScrollViewRef() in order to use this method
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*/
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scrollResponderScrollNativeHandleToKeyboard: function(nodeHandle, additionalOffset) {
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this.additionalScrollOffset = additionalOffset || 0;
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RCTUIManager.measureLayout(
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nodeHandle,
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this.getNodeHandle(),
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this.scrollResponderTextInputFocusError,
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this.scrollResponderInputMeasureAndScrollToKeyboard
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);
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},
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/**
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* The calculations performed here assume the scroll view takes up the entire
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* screen - even if has some content inset. We then measure the offsets of the
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* keyboard, and compensate both for the scroll view's "contentInset".
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*
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* @param {number} left Position of input w.r.t. table view.
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* @param {number} top Position of input w.r.t. table view.
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* @param {number} width Width of the text input.
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* @param {number} height Height of the text input.
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*/
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scrollResponderInputMeasureAndScrollToKeyboard: function(left, top, width, height) {
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if (this.keyboardWillOpenTo) {
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var scrollOffsetY =
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top - this.keyboardWillOpenTo.endCoordinates.screenY + height +
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this.additionalScrollOffset;
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this.scrollResponderScrollTo(0, scrollOffsetY);
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}
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this.additionalOffset = 0;
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},
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scrollResponderTextInputFocusError: function(e) {
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console.error('Error measuring text field: ', e);
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},
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/**
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* `componentWillMount` is the closest thing to a standard "constructor" for
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* React components.
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*
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* The `keyboardWillShow` is called before input focus.
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*/
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componentWillMount: function() {
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this.keyboardWillOpenTo = null;
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this.additionalScrollOffset = 0;
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this.addListenerOn(RCTDeviceEventEmitter, 'keyboardWillShow', this.scrollResponderKeyboardWillShow);
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this.addListenerOn(RCTDeviceEventEmitter, 'keyboardWillHide', this.scrollResponderKeyboardWillHide);
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this.addListenerOn(RCTDeviceEventEmitter, 'keyboardDidShow', this.scrollResponderKeyboardDidShow);
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this.addListenerOn(RCTDeviceEventEmitter, 'keyboardDidHide', this.scrollResponderKeyboardDidHide);
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},
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/**
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* Warning, this may be called several times for a single keyboard opening.
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* It's best to store the information in this method and then take any action
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* at a later point (either in `keyboardDidShow` or other).
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*
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* Here's the order that events occur in:
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* - focus
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* - willShow {startCoordinates, endCoordinates} several times
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* - didShow several times
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* - blur
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* - willHide {startCoordinates, endCoordinates} several times
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* - didHide several times
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*
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* The `ScrollResponder` providesModule callbacks for each of these events.
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* Even though any user could have easily listened to keyboard events
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* themselves, using these `props` callbacks ensures that ordering of events
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* is consistent - and not dependent on the order that the keyboard events are
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* subscribed to. This matters when telling the scroll view to scroll to where
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* the keyboard is headed - the scroll responder better have been notified of
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* the keyboard destination before being instructed to scroll to where the
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* keyboard will be. Stick to the `ScrollResponder` callbacks, and everything
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* will work.
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*
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* WARNING: These callbacks will fire even if a keyboard is displayed in a
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* different navigation pane. Filter out the events to determine if they are
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* relevant to you. (For example, only if you receive these callbacks after
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* you had explicitly focused a node etc).
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*/
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scrollResponderKeyboardWillShow: function(e) {
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this.keyboardWillOpenTo = e;
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this.props.onKeyboardWillShow && this.props.onKeyboardWillShow(e);
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},
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scrollResponderKeyboardWillHide: function(e) {
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this.keyboardWillOpenTo = null;
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this.props.onKeyboardWillHide && this.props.onKeyboardWillHide(e);
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},
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scrollResponderKeyboardDidShow: function() {
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this.keyboardWillOpenTo = null;
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this.props.onKeyboardDidShow && this.props.onKeyboardDidShow();
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},
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scrollResponderKeyboardDidHide: function() {
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this.keyboardWillOpenTo = null;
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this.props.onKeyboardDidHide && this.props.onKeyboardDidHide();
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}
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};
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var ScrollResponder = {
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Mixin: ScrollResponderMixin,
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};
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module.exports = ScrollResponder;
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