react-native/Libraries/Components/ScrollView/ScrollView.js

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule ScrollView
 * @flow
 */
'use strict';

var EdgeInsetsPropType = require('EdgeInsetsPropType');
var Platform = require('Platform');
var PointPropType = require('PointPropType');
var RCTScrollView = require('NativeModules').UIManager.RCTScrollView;
var React = require('React');
var ReactNativeViewAttributes = require('ReactNativeViewAttributes');
var RCTUIManager = require('NativeModules').UIManager;
var ScrollResponder = require('ScrollResponder');
var StyleSheet = require('StyleSheet');
var StyleSheetPropType = require('StyleSheetPropType');
var View = require('View');
var ViewStylePropTypes = require('ViewStylePropTypes');

var createReactNativeComponentClass = require('createReactNativeComponentClass');
var deepDiffer = require('deepDiffer');
var dismissKeyboard = require('dismissKeyboard');
var flattenStyle = require('flattenStyle');
var insetsDiffer = require('insetsDiffer');
var invariant = require('invariant');
var pointsDiffer = require('pointsDiffer');
var requireNativeComponent = require('requireNativeComponent');

var PropTypes = React.PropTypes;

var SCROLLVIEW = 'ScrollView';
var INNERVIEW = 'InnerScrollView';

/**
 * Component that wraps platform ScrollView while providing
 * integration with touch locking "responder" system.
 *
 * Keep in mind that ScrollViews must have a bounded height in order to work,
 * since they contain unbounded-height children into a bounded container (via
 * a scroll interaction). In order to bound the height of a ScrollView, either
 * set the height of the view directly (discouraged) or make sure all parent
 * views have bounded height. Forgetting to transfer `{flex: 1}` down the
 * view stack can lead to errors here, which the element inspector makes
 * easy to debug.
 *
 * Doesn't yet support other contained responders from blocking this scroll
 * view from becoming the responder.
 */
var ScrollView = React.createClass({
  propTypes: {
    /**
     * Controls whether iOS should automatically adjust the content inset
     * for scroll views that are placed behind a navigation bar or
     * tab bar/ toolbar. The default value is true.
     * @platform ios
     */
    automaticallyAdjustContentInsets: PropTypes.bool,
    /**
     * The amount by which the scroll view content is inset from the edges
     * of the scroll view. Defaults to `{0, 0, 0, 0}`.
     * @platform ios
     */
    contentInset: EdgeInsetsPropType,
    /**
     * Used to manually set the starting scroll offset.
     * The default value is `{x: 0, y: 0}`.
     * @platform ios
     */
    contentOffset: PointPropType,
    /**
     * When true, the scroll view bounces when it reaches the end of the
     * content if the content is larger then the scroll view along the axis of
     * the scroll direction. When false, it disables all bouncing even if
     * the `alwaysBounce*` props are true. The default value is true.
     * @platform ios
     */
    bounces: PropTypes.bool,
    /**
     * When true, gestures can drive zoom past min/max and the zoom will animate
     * to the min/max value at gesture end, otherwise the zoom will not exceed
     * the limits.
     * @platform ios
     */
    bouncesZoom: PropTypes.bool,
    /**
     * When true, the scroll view bounces horizontally when it reaches the end
     * even if the content is smaller than the scroll view itself. The default
     * value is true when `horizontal={true}` and false otherwise.
     * @platform ios
     */
    alwaysBounceHorizontal: PropTypes.bool,
    /**
     * When true, the scroll view bounces vertically when it reaches the end
     * even if the content is smaller than the scroll view itself. The default
     * value is false when `horizontal={true}` and true otherwise.
     * @platform ios
     */
    alwaysBounceVertical: PropTypes.bool,
    /**
     * When true, the scroll view automatically centers the content when the
     * content is smaller than the scroll view bounds; when the content is
     * larger than the scroll view, this property has no effect. The default
     * value is false.
     * @platform ios
     */
    centerContent: PropTypes.bool,
    /**
     * These styles will be applied to the scroll view content container which
     * wraps all of the child views. Example:
     *
     *   return (
     *     <ScrollView contentContainerStyle={styles.contentContainer}>
     *     </ScrollView>
     *   );
     *   ...
     *   var styles = StyleSheet.create({
     *     contentContainer: {
     *       paddingVertical: 20
     *     }
     *   });
     */
    contentContainerStyle: StyleSheetPropType(ViewStylePropTypes),
    /**
     * A floating-point number that determines how quickly the scroll view
     * decelerates after the user lifts their finger. Reasonable choices include
     *   - Normal: 0.998 (the default)
     *   - Fast: 0.9
     * @platform ios
     */
    decelerationRate: PropTypes.number,
    /**
     * When true, the scroll view's children are arranged horizontally in a row
     * instead of vertically in a column. The default value is false.
     */
    horizontal: PropTypes.bool,
    /**
     * When true, the ScrollView will try to lock to only vertical or horizontal
     * scrolling while dragging.  The default value is false.
     * @platform ios
     */
    directionalLockEnabled: PropTypes.bool,
    /**
     * When false, once tracking starts, won't try to drag if the touch moves.
     * The default value is true.
     * @platform ios
     */
    canCancelContentTouches: PropTypes.bool,
    /**
     * Determines whether the keyboard gets dismissed in response to a drag.
     *   - 'none' (the default), drags do not dismiss the keyboard.
     *   - 'on-drag', the keyboard is dismissed when a drag begins.
     *   - 'interactive', the keyboard is dismissed interactively with the drag and moves in
     *     synchrony with the touch; dragging upwards cancels the dismissal.
     *     On android this is not supported and it will have the same behavior as 'none'.
     */
    keyboardDismissMode: PropTypes.oneOf([
      'none', // default
      'interactive',
      'on-drag',
    ]),
    /**
     * When false, tapping outside of the focused text input when the keyboard
     * is up dismisses the keyboard. When true, the scroll view will not catch
     * taps, and the keyboard will not dismiss automatically. The default value
     * is false.
     */
    keyboardShouldPersistTaps: PropTypes.bool,
    /**
     * The maximum allowed zoom scale. The default value is 1.0.
     * @platform ios
     */
    maximumZoomScale: PropTypes.number,
    /**
     * The minimum allowed zoom scale. The default value is 1.0.
     * @platform ios
     */
    minimumZoomScale: PropTypes.number,
    /**
     * Fires at most once per frame during scrolling. The frequency of the
     * events can be contolled using the `scrollEventThrottle` prop.
     */
    onScroll: PropTypes.func,
    /**
     * Called when a scrolling animation ends.
     * @platform ios
     */
    onScrollAnimationEnd: PropTypes.func,
    /**
     * When true, the scroll view stops on multiples of the scroll view's size
     * when scrolling. This can be used for horizontal pagination. The default
     * value is false.
     * @platform ios
     */
    pagingEnabled: PropTypes.bool,
    /**
     * When false, the content does not scroll.
     * The default value is true.
     * @platform ios
     */
    scrollEnabled: PropTypes.bool,
    /**
     * This controls how often the scroll event will be fired while scrolling
     * (in events per seconds). A higher number yields better accuracy for code
     * that is tracking the scroll position, but can lead to scroll performance
     * problems due to the volume of information being send over the bridge.
     * The default value is zero, which means the scroll event will be sent
     * only once each time the view is scrolled.
     * @platform ios
     */
    scrollEventThrottle: PropTypes.number,
    /**
     * The amount by which the scroll view indicators are inset from the edges
     * of the scroll view. This should normally be set to the same value as
     * the `contentInset`. Defaults to `{0, 0, 0, 0}`.
     * @platform ios
     */
    scrollIndicatorInsets: EdgeInsetsPropType,
    /**
     * When true, the scroll view scrolls to top when the status bar is tapped.
     * The default value is true.
     * @platform ios
     */
    scrollsToTop: PropTypes.bool,
    /**
     * When true, shows a horizontal scroll indicator.
     */
    showsHorizontalScrollIndicator: PropTypes.bool,
    /**
     * When true, shows a vertical scroll indicator.
     */
    showsVerticalScrollIndicator: PropTypes.bool,
    /**
     * An array of child indices determining which children get docked to the
     * top of the screen when scrolling. For example, passing
     * `stickyHeaderIndices={[0]}` will cause the first child to be fixed to the
     * top of the scroll view. This property is not supported in conjunction
     * with `horizontal={true}`.
     * @platform ios
     */
    stickyHeaderIndices: PropTypes.arrayOf(PropTypes.number),
    style: StyleSheetPropType(ViewStylePropTypes),
    /**
     * When set, causes the scroll view to stop at multiples of the value of
     * `snapToInterval`. This can be used for paginating through children
     * that have lengths smaller than the scroll view. Used in combination
     * with `snapToAlignment`.
     * @platform ios
     */
    snapToInterval: PropTypes.number,
    /**
     * When `snapToInterval` is set, `snapToAlignment` will define the relationship
     * of the the snapping to the scroll view.
     *   - `start` (the default) will align the snap at the left (horizontal) or top (vertical)
     *   - `center` will align the snap in the center
     *   - `end` will align the snap at the right (horizontal) or bottom (vertical)
     * @platform ios
     */
    snapToAlignment: PropTypes.oneOf([
      'start', // default
      'center',
      'end',
    ]),
    /**
     * Experimental: When true, offscreen child views (whose `overflow` value is
     * `hidden`) are removed from their native backing superview when offscreen.
     * This can improve scrolling performance on long lists. The default value is
     * false.
     */
    removeClippedSubviews: PropTypes.bool,
    /**
     * The current scale of the scroll view content. The default value is 1.0.
     * @platform ios
     */
    zoomScale: PropTypes.number,
  },

  mixins: [ScrollResponder.Mixin],

  getInitialState: function() {
    return this.scrollResponderMixinGetInitialState();
  },

  setNativeProps: function(props: Object) {
    this.refs[SCROLLVIEW].setNativeProps(props);
  },

  /**
   * Returns a reference to the underlying scroll responder, which supports
   * operations like `scrollTo`. All ScrollView-like components should
   * implement this method so that they can be composed while providing access
   * to the underlying scroll responder's methods.
   */
  getScrollResponder: function(): ReactComponent {
    return this;
  },

  getInnerViewNode: function(): any {
    return React.findNodeHandle(this.refs[INNERVIEW]);
  },

  scrollTo: function(destY?: number, destX?: number) {
    // $FlowFixMe - Don't know how to pass Mixin correctly. Postpone for now
    this.getScrollResponder().scrollResponderScrollTo(destX || 0, destY || 0);
  },

  scrollWithoutAnimationTo: function(destY?: number, destX?: number) {
    // $FlowFixMe - Don't know how to pass Mixin correctly. Postpone for now
    this.getScrollResponder().scrollResponderScrollWithouthAnimationTo(
      destX || 0,
      destY || 0,
    );
  },

  handleScroll: function(e: Event) {
    if (__DEV__) {
      if (this.props.onScroll && !this.props.scrollEventThrottle) {
        console.log(
          'You specified `onScroll` on a <ScrollView> but not ' +
          '`scrollEventThrottle`. You will only receive one event. ' +
          'Using `16` you get all the events but be aware that it may ' +
          'cause frame drops, use a bigger number if you don\'t need as ' +
          'much precision.'
        );
      }
    }
    if (Platform.OS === 'android') {
      if (this.props.keyboardDismissMode === 'on-drag') {
        dismissKeyboard();
      }
    }
    this.scrollResponderHandleScroll(e);
  },

  render: function() {
    var contentContainerStyle = [
      this.props.horizontal && styles.contentContainerHorizontal,
      this.props.contentContainerStyle,
    ];
    if (__DEV__ && this.props.style) {
      var style = flattenStyle(this.props.style);
      var childLayoutProps = ['alignItems', 'justifyContent']
        .filter((prop) => style && style[prop] !== undefined);
      invariant(
        childLayoutProps.length === 0,
        'ScrollView child layout (' + JSON.stringify(childLayoutProps) +
          ') must by applied through the contentContainerStyle prop.'
      );
    }

    var contentContainer =
      <View
        ref={INNERVIEW}
        style={contentContainerStyle}
        removeClippedSubviews={this.props.removeClippedSubviews}
        collapsable={false}>
        {this.props.children}
      </View>;

    var alwaysBounceHorizontal =
      this.props.alwaysBounceHorizontal !== undefined ?
        this.props.alwaysBounceHorizontal :
        this.props.horizontal;

    var alwaysBounceVertical =
      this.props.alwaysBounceVertical !== undefined ?
        this.props.alwaysBounceVertical :
        !this.props.horizontal;

    var props = {
      ...this.props,
      alwaysBounceHorizontal,
      alwaysBounceVertical,
      style: ([styles.base, this.props.style]: ?Array<any>),
      onTouchStart: this.scrollResponderHandleTouchStart,
      onTouchMove: this.scrollResponderHandleTouchMove,
      onTouchEnd: this.scrollResponderHandleTouchEnd,
      onScrollBeginDrag: this.scrollResponderHandleScrollBeginDrag,
      onScrollEndDrag: this.scrollResponderHandleScrollEndDrag,
      onMomentumScrollBegin: this.scrollResponderHandleMomentumScrollBegin,
      onMomentumScrollEnd: this.scrollResponderHandleMomentumScrollEnd,
      onStartShouldSetResponder: this.scrollResponderHandleStartShouldSetResponder,
      onStartShouldSetResponderCapture: this.scrollResponderHandleStartShouldSetResponderCapture,
      onScrollShouldSetResponder: this.scrollResponderHandleScrollShouldSetResponder,
      onScroll: this.handleScroll,
      onResponderGrant: this.scrollResponderHandleResponderGrant,
      onResponderTerminationRequest: this.scrollResponderHandleTerminationRequest,
      onResponderTerminate: this.scrollResponderHandleTerminate,
      onResponderRelease: this.scrollResponderHandleResponderRelease,
      onResponderReject: this.scrollResponderHandleResponderReject,
    };

    var ScrollViewClass;
    if (Platform.OS === 'ios') {
      ScrollViewClass = RCTScrollView;
    } else if (Platform.OS === 'android') {
      if (this.props.horizontal) {
        ScrollViewClass = AndroidHorizontalScrollView;
      } else {
        ScrollViewClass = AndroidScrollView;
      }
    }
    invariant(
      ScrollViewClass !== undefined,
      'ScrollViewClass must not be undefined'
    );

    return (
      <ScrollViewClass {...props} ref={SCROLLVIEW}>
        {contentContainer}
      </ScrollViewClass>
    );
  }
});

var styles = StyleSheet.create({
  base: {
    flex: 1,
  },
  contentContainerHorizontal: {
    alignSelf: 'flex-start',
    flexDirection: 'row',
  },
});

var validAttributes = {
  ...ReactNativeViewAttributes.UIView,
  alwaysBounceHorizontal: true,
  alwaysBounceVertical: true,
  automaticallyAdjustContentInsets: true,
  bounces: true,
  centerContent: true,
  contentInset: {diff: insetsDiffer},
  contentOffset: {diff: pointsDiffer},
  decelerationRate: true,
  horizontal: true,
  keyboardDismissMode: true,
  keyboardShouldPersistTaps: true,
  maximumZoomScale: true,
  minimumZoomScale: true,
  pagingEnabled: true,
  removeClippedSubviews: true,
  scrollEnabled: true,
  scrollIndicatorInsets: {diff: insetsDiffer},
  scrollsToTop: true,
  showsHorizontalScrollIndicator: true,
  showsVerticalScrollIndicator: true,
  snapToInterval: true,
  snapToAlignment: true,
  stickyHeaderIndices: {diff: deepDiffer},
  scrollEventThrottle: true,
  zoomScale: true,
};

if (Platform.OS === 'android') {
  var AndroidScrollView = createReactNativeComponentClass({
    validAttributes: validAttributes,
    uiViewClassName: 'RCTScrollView',
  });
  var AndroidHorizontalScrollView = createReactNativeComponentClass({
    validAttributes: validAttributes,
    uiViewClassName: 'AndroidHorizontalScrollView',
  });
} else if (Platform.OS === 'ios') {
  var RCTScrollView = requireNativeComponent('RCTScrollView', ScrollView);
}

module.exports = ScrollView;