Implements Scroll Into View (#236)

* Implements Scroll Into View

* fix linting issues and incorrect implementation

Author: sebasgarcep

README.md

@@ -142,6 +142,7 @@ Use `innerRef` to get the component reference and use `this.scrollRef.props` to
 | `getScrollResponder` | `void` | Get `ScrollResponder` |
 | `scrollToPosition` | `x: number, y: number, animated: bool = true` | Scroll to specific position with or without animation. |
 | `scrollToEnd` | `animated?: bool = true` | Scroll to end with or without animation. |
+| `scrollIntoView` | `element: React.Element<*>, options: { getScrollPosition: ?(parentLayout, childLayout, contentOffset) => { x: number, y: number, animated: boolean } }` | Scrolls an element inside a KeyboardAwareScrollView into view. |
 
 ### Using high order component
 Enabling any component to be keyboard-aware is very easy. Take a look at the code of `KeyboardAwareListView`:

lib/KeyboardAwareHOC.js

@@ -6,7 +6,8 @@ import ReactNative, {
   Keyboard,
   Platform,
   UIManager,
-  TextInput
+  TextInput,
+  findNodeHandle
 } from 'react-native'
 import { isIphoneX } from 'react-native-iphone-x-helper'
 
@@ -36,6 +37,32 @@ export type KeyboardAwareHOCState = {
   keyboardSpace: number
 }
 
+export type ElementLayout = {
+  x: number,
+  y: number,
+  width: number,
+  height: number
+}
+
+export type ContentOffset = {
+  x: number,
+  y: number
+}
+
+export type ScrollPosition = {
+  x: number,
+  y: number,
+  animated: boolean
+}
+
+export type ScrollIntoViewOptions = ?{
+  getScrollPosition?: (
+    parentLayout: ElementLayout,
+    childLayout: ElementLayout,
+    contentOffset: ContentOffset
+  ) => ScrollPosition
+}
+
 function listenToKeyboardEvents(ScrollableComponent: React$Component) {
   return class extends React.Component<
     KeyboardAwareHOCProps,
@@ -44,7 +71,7 @@ function listenToKeyboardEvents(ScrollableComponent: React$Component) {
     _rnkasv_keyboardView: any
     keyboardWillShowEvent: ?Function
     keyboardWillHideEvent: ?Function
-    position: { x: number, y: number }
+    position: ContentOffset
     defaultResetScrollToCoords: ?{ x: number, y: number }
     resetCoords: ?{ x: number, y: number }
     mountedComponent: boolean
@@ -180,6 +207,48 @@ function listenToKeyboardEvents(ScrollableComponent: React$Component) {
       }, keyboardOpeningTime)
     }
 
+    scrollIntoView = async (
+      element: React.Element<*>,
+      options: ScrollIntoViewOptions = {}
+    ) => {
+      if (!this._rnkasv_keyboardView || !element) {
+        return
+      }
+
+      const [
+        parentLayout,
+        childLayout
+      ] = await Promise.all([
+        this._measureElement(this._rnkasv_keyboardView),
+        this._measureElement(element)
+      ])
+
+      const getScrollPosition = options.getScrollPosition || this._defaultGetScrollPosition
+      const { x, y, animated } = getScrollPosition(parentLayout, childLayout, this.position)
+      this.scrollToPosition(x, y, animated)
+    }
+
+    _defaultGetScrollPosition = (
+      parentLayout: ElementLayout,
+      childLayout: ElementLayout,
+      contentOffset: ContentOffset
+    ): ScrollPosition => {
+      return {
+        x: 0,
+        y: Math.max(0, childLayout.y - parentLayout.y + contentOffset.y),
+        animated: true,
+      }
+    }
+
+    _measureElement = (element: React.Element<*>): Promise<ElementLayout> => {
+      const node = findNodeHandle(element)
+      return new Promise((resolve: (ElementLayout) => void) => {
+        UIManager.measureInWindow(node, (x: number, y: number, width: number, height: number) => {
+          resolve({ x, y, width, height })
+        })
+      })
+    }
+
     // Keyboard actions
     _updateKeyboardSpace = (frames: Object) => {
       // Automatically scroll to focused TextInput