From 3aa60cc11b885fb6ebb19b21ab23325ae6664d3a Mon Sep 17 00:00:00 2001
From: Li Jie <lijie@applean.cn>
Date: Fri, 23 Jun 2017 18:34:07 +0800
Subject: [PATCH] ScrollView scrolls with animation

---
 Libraries/ListView/ScrollResponder.web.js | 10 ++--
 Libraries/ScrollView/ScrollView.web.js    | 20 +++-----
 Libraries/Utilties/animatedScrollTo.js    | 57 +++++++++++++++++++++++
 3 files changed, 70 insertions(+), 17 deletions(-)
 create mode 100644 Libraries/Utilties/animatedScrollTo.js

diff --git a/Libraries/ListView/ScrollResponder.web.js b/Libraries/ListView/ScrollResponder.web.js
index 04eb969..2487fe9 100644
--- a/Libraries/ListView/ScrollResponder.web.js
+++ b/Libraries/ListView/ScrollResponder.web.js
@@ -13,6 +13,7 @@
 import React from 'react';
 import ReactDOM from 'react-dom';
 import warning from 'fbjs/lib/warning';
+import animatedScrollTo from '../Utilties/animatedScrollTo';
 
 /**
  * Mixin that can be integrated in order to handle scrolling that plays well
@@ -93,6 +94,7 @@ import warning from 'fbjs/lib/warning';
  */
 
 const IS_ANIMATING_TOUCH_START_THRESHOLD_MS = 16;
+const ANIMATION_DURATION_MS = 300;
 
 type State = {
     isTouching: boolean;
@@ -351,7 +353,9 @@ let ScrollResponderMixin = {
    */
   scrollResponderScrollTo: function(offsetX: number, offsetY: number) {
     // TODO: Add scroll animation
-    this.scrollResponderScrollWithouthAnimationTo(offsetX, offsetY);
+    let node = ReactDOM.findDOMNode(this);
+
+    animatedScrollTo(node, {y: offsetY, x: offsetX}, ANIMATION_DURATION_MS);
   },
 
   /**
@@ -361,8 +365,8 @@ let ScrollResponderMixin = {
   scrollResponderScrollWithouthAnimationTo: function(offsetX: number, offsetY: number) {
 
     let node = ReactDOM.findDOMNode(this);
-    node.offsetX = offsetX;
-    node.offsetY = offsetY;
+    node.scrollLeft = offsetX;
+    node.scrollTop = offsetY;
   },
 
   /**
diff --git a/Libraries/ScrollView/ScrollView.web.js b/Libraries/ScrollView/ScrollView.web.js
index 53dbfd3..23c1f39 100644
--- a/Libraries/ScrollView/ScrollView.web.js
+++ b/Libraries/ScrollView/ScrollView.web.js
@@ -55,26 +55,18 @@ class ScrollView extends Component {
     return this.refs[INNERVIEW];
   }
 
-  scrollTo(opts) {
+  scrollTo(opts: { x?: number, y?: number, animated?: boolean }) {
     // $FlowFixMe - Don't know how to pass Mixin correctly. Postpone for now
     // this.getScrollResponder().scrollResponderScrollTo(destX || 0, destY || 0);
     if (typeof opts === 'number') {
       opts = { y: opts, x: arguments[1] };
     }
 
-    this.scrollWithoutAnimationTo(opts.y, opts.x);
-  }
-
-  scrollWithoutAnimationTo(destY?: number, destX?: number) {
-    // $FlowFixMe - Don't know how to pass Mixin correctly. Postpone for now
-    // this.getScrollResponder().scrollResponderScrollWithouthAnimationTo(
-    //   destX || 0,
-    //   destY || 0,
-    // );
-
-    this._scrollViewDom = ReactDOM.findDOMNode(this.refs[SCROLLVIEW]);
-    this._scrollViewDom.scrollTop = destY || 0;
-    this._scrollViewDom.scrollLeft = destX || 0;
+    if (opts.animated) {
+      this.getScrollResponder().scrollResponderScrollTo(opts.x || 0, opts.y || 0);
+    } else {
+      this.getScrollResponder().scrollResponderScrollWithouthAnimationTo(opts.x || 0, opts.y || 0);
+    }
   }
 
   handleScroll(e: Event) {
diff --git a/Libraries/Utilties/animatedScrollTo.js b/Libraries/Utilties/animatedScrollTo.js
new file mode 100644
index 0000000..a42f634
--- /dev/null
+++ b/Libraries/Utilties/animatedScrollTo.js
@@ -0,0 +1,57 @@
+// Modified from https://github.com/madebysource/animated-scrollto/blob/master/animatedScrollTo.js
+
+(function (window) {
+    var requestAnimFrame = (function(){return window.requestAnimationFrame||window.webkitRequestAnimationFrame||window.mozRequestAnimationFrame||function(callback){window.setTimeout(callback,1000/60);};})();
+
+    var easeInOutQuad = function (t, b, c, d) {
+        t /= d/2;
+        if (t < 1) return c/2*t*t + b;
+        t--;
+        return -c/2 * (t*(t-2) - 1) + b;
+    };
+
+    var animatedScrollTo = function (element, to, duration, callback) {
+        var startY = element.scrollTop;
+        var startX = element.scrollLeft;
+        var changeY = to.y - startY;
+        var changeX = to.x - startX;
+        var animationStart = +new Date();
+        var animating = true;
+        var lastposX = null;
+        var lastposY = null;
+
+        var animateScroll = function() {
+            if (!animating) {
+                return;
+            }
+            requestAnimFrame(animateScroll);
+            var now = +new Date();
+            var valY = Math.floor(easeInOutQuad(now - animationStart, startY, changeY, duration));
+            var valX = Math.floor(easeInOutQuad(now - animationStart, startX, changeX, duration));
+
+            // If last position is not element's scroll position, maybe user was scrolled.
+            if (lastposY === null ||
+                (lastposY === element.scrollTop && lastposX === element.scrollLeft)) {
+                lastposY = valY;
+                lastposX = valX;
+                element.scrollTop = valY;
+                element.scrollLeft = valX;
+            } else {
+                animating = false;
+            }
+            if (now > animationStart + duration) {
+                element.scrollTop = to.y;
+                element.scrollLeft = to.x;
+                animating = false;
+                if (callback) { callback(); }
+            }
+        };
+        requestAnimFrame(animateScroll);
+    };
+
+    if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
+        module.exports = animatedScrollTo;
+    } else {
+        window.animatedScrollTo = animatedScrollTo;
+    }
+})(window);