[TIMOB-24963] iOS/Android: Added new ScrollView.scrollToTop() method

android/modules/ui/src/java/ti/modules/titanium/ui/ScrollViewProxy.java

@@ -39,6 +39,7 @@ public class ScrollViewProxy extends TiViewProxy
 
 	private static final int MSG_SCROLL_TO = MSG_FIRST_ID + 100;
 	private static final int MSG_SCROLL_TO_BOTTOM = MSG_FIRST_ID + 101;
+	private static final int MSG_SCROLL_TO_TOP = MSG_FIRST_ID + 102;
 	protected static final int MSG_LAST_ID = MSG_FIRST_ID + 999;
 
 	public ScrollViewProxy()
@@ -99,6 +100,15 @@ public void scrollToBottom() {
 		}
 	}
 
+	@Kroll.method
+	public void scrollToTop() {
+		if (!TiApplication.isUIThread()) {
+			TiMessenger.sendBlockingMainMessage(getMainHandler().obtainMessage(MSG_SCROLL_TO_TOP), getActivity());
+		} else {
+			handleScrollToTop();
+		}
+	}
+
 	@Override
 	public boolean handleMessage(Message msg) {
 		if (msg.what == MSG_SCROLL_TO) {
@@ -112,6 +122,11 @@ public boolean handleMessage(Message msg) {
 			AsyncResult result = (AsyncResult) msg.obj;
 			result.setResult(null); // signal scrolled
 			return true;
+		} else if (msg.what == MSG_SCROLL_TO_TOP) {
+			handleScrollToTop();
+			AsyncResult result = (AsyncResult) msg.obj;
+			result.setResult(null); // signal scrolled
+			return true;
 		}
 		return super.handleMessage(msg);
 	}
@@ -124,6 +139,10 @@ public void handleScrollToBottom() {
 		getScrollView().scrollToBottom();
 	}
 
+	public void handleScrollToTop() {
+		getScrollView().scrollToTop();
+	}
+
 	@Override
 	public String getApiName()
 	{

android/modules/ui/src/java/ti/modules/titanium/ui/widget/TiUIScrollView.java

@@ -862,17 +862,34 @@ public boolean getScrollingEnabled()
 
 	public void scrollTo(int x, int y, boolean smoothScroll)
 	{
+		// Fetch the scroll view.
 		final View view = this.scrollView;
+		if (view == null) {
+			return;
+		}
+
+		// Convert the given coordinates to pixels.
+		x = TiConvert.toTiDimension(x, -1).getAsPixels(view);
+		y = TiConvert.toTiDimension(y, -1).getAsPixels(view);
+
+		// Disable smooth scrolling for vertical scroll views if not at top of view.
+		// Note: This works-around a bug in Google's NestedScrollView where attempting to
+		//       smooth scrolls will move to a totally different position or opposite directions.
+		if (smoothScroll && (view instanceof TiVerticalScrollView)) {
+			if (((TiVerticalScrollView)view).getScrollY() > 0) {
+				smoothScroll = false;
+			}
+		}
+
+		// Scroll to the given position.
 		if (smoothScroll) {
 			if (view instanceof TiHorizontalScrollView) {
-				TiHorizontalScrollView scrollView = (TiHorizontalScrollView) view;
-				scrollView.smoothScrollTo(x, y);
+				((TiHorizontalScrollView)view).smoothScrollTo(x, y);
 			} else if (view instanceof TiVerticalScrollView) {
-				TiVerticalScrollView scrollView = (TiVerticalScrollView) view;
-				scrollView.smoothScrollTo(x, y);
+				((TiVerticalScrollView)view).smoothScrollTo(x, y);
 			}
 		} else {
-			view.scrollTo(TiConvert.toTiDimension(x, -1).getAsPixels(view), TiConvert.toTiDimension(y, -1).getAsPixels(view));
+			view.scrollTo(x, y);
 		}
 		view.computeScroll();
 	}
@@ -881,9 +898,30 @@ public void scrollToBottom()
 	{
 		View view = this.scrollView;
 		if (view instanceof TiHorizontalScrollView) {
-			((TiHorizontalScrollView)this.scrollView).fullScroll(View.FOCUS_RIGHT);
+			((TiHorizontalScrollView)view).fullScroll(View.FOCUS_RIGHT);
 		} else if (view instanceof TiVerticalScrollView) {
-			((TiVerticalScrollView)this.scrollView).fullScroll(View.FOCUS_DOWN);
+			((TiVerticalScrollView)view).fullScroll(View.FOCUS_DOWN);
+		}
+	}
+
+	public void scrollToTop()
+	{
+		View view = this.scrollView;
+		if (view instanceof TiHorizontalScrollView) {
+			// Scroll to the left-most side of the horizontal scroll view.
+			((TiHorizontalScrollView)view).fullScroll(View.FOCUS_LEFT);
+		} else if (view instanceof TiVerticalScrollView) {
+			// Scroll to the top of the vertical scroll view.
+			// Note: There is a bug in Google's NestedScrollView where smooth scrolling to top fails
+			//       and can scroll down instead. We must work-around it by temporarily disabling it.
+			TiVerticalScrollView verticalScrollView = (TiVerticalScrollView)view;
+			boolean wasEnabled = verticalScrollView.isSmoothScrollingEnabled();
+			verticalScrollView.setSmoothScrollingEnabled(false);
+			try {
+				((TiVerticalScrollView)view).fullScroll(View.FOCUS_UP);
+			} finally {
+				verticalScrollView.setSmoothScrollingEnabled(wasEnabled);
+			}
 		}
 	}
 

apidoc/Titanium/UI/ScrollView.yml

@@ -90,6 +90,19 @@ methods:
     platforms: [android, iphone, ipad]
     since: {iphone: "2.1.0", ipad: "2.1.0"}
 
+  - name: scrollToTop
+    summary: Moves the top of the scrollable region into the viewable area.
+    description: |
+        On Android the behavior of `scrollToTop` depends on whether this scroll view scrolls
+        horizontally or vertically. For vertical scroll views, `scrollToTop` moves the top
+        of the scrollable region into the viewable area. For horizontal scroll views,
+        `scrollToTop` moves the leftmost edge of of the scrollable region into the viewable area.
+
+        On iOS, `scrollToTop` moves the top-left corner of the scrollable region into the 
+        viewable area.
+    platforms: [iphone, ipad, android]
+    since: "7.0.0"
+
 events:
   - name: scale
     summary: Fired when the zoom scale factor changes.

iphone/Classes/TiUIScrollView.h

@@ -58,6 +58,7 @@
 - (UIView *)wrapperView;
 #endif
 - (void)scrollToBottom;
+- (void)scrollToTop;
 
 @end
 

iphone/Classes/TiUIScrollView.m

@@ -313,6 +313,11 @@ - (void)scrollToBottom
   [currScrollView setContentOffset:newOffset animated:YES];
 }
 
+- (void)scrollToTop
+{
+  [[self scrollView] setContentOffset:CGPointMake(0, -[[self scrollView] contentInset].top) animated:YES];
+}
+
 - (void)setDecelerationRate_:(id)value
 {
   [self.proxy replaceValue:value forKey:@"decelerationRate" notification:NO];

iphone/Classes/TiUIScrollViewProxy.m

@@ -330,14 +330,22 @@ - (void)scrollTo:(id)args
   [offset release];
 }
 
-- (void)scrollToBottom:(id)args
+- (void)scrollToBottom:(id)unused
 {
   TiThreadPerformOnMainThread(^{
     [(TiUIScrollView *)[self view] scrollToBottom];
   },
       YES);
 }
 
+- (void)scrollToTop:(id)unused
+{
+  TiThreadPerformOnMainThread(^{
+    [(TiUIScrollView *)[self view] scrollToTop];
+  },
+      YES);
+}
+
 - (void)setContentOffset:(id)value withObject:(id)animated
 {
   TiThreadPerformOnMainThread(^{

tests/Resources/ti.ui.scrollview.addontest.js

@@ -0,0 +1,18 @@
+/*
+ * Appcelerator Titanium Mobile
+ * Copyright (c) 2011-Present by Appcelerator, Inc. All Rights Reserved.
+ * Licensed under the terms of the Apache Public License
+ * Please see the LICENSE included with this distribution for details.
+ */
+/* eslint-env mocha */
+/* global Ti */
+/* eslint no-unused-expressions: "off" */
+'use strict';
+var should = require('./utilities/assertions');
+
+describe('Titanium.UI.ScrollView', function () {
+	it('#scrollToTop()', function () {
+		var bar = Ti.UI.createScrollView({});
+		should(bar.scrollToTop).be.a.Function;
+	});
+});