From 0061e16e538f800ff995ad05bc21cc7728f160e2 Mon Sep 17 00:00:00 2001
From: Chet Haase <chet@google.com>
Date: Fri, 8 Jun 2012 15:01:56 -0700
Subject: Don't allow apps to request scrolls to out-of-bounds positions

An app was requesting smooth scrolling to a view position beyond the
number of items in the list. This caused our setup logic to execute on
every frame, waiting for the target view to be added.

This fix clamps the requested target position to the number of items
actually in the list.

Issue #6572175 Messaging: Sometimes conversation doesn't scroll when focus is brought to the compose field

Change-Id: I23707aeb213e67af4297713a03c2f5b446c8e2b6
---
 core/java/android/widget/AbsListView.java | 38 ++++++++++++++++---------------
 1 file changed, 20 insertions(+), 18 deletions(-)

(limited to 'core/java')

diff --git a/core/java/android/widget/AbsListView.java b/core/java/android/widget/AbsListView.java
index 5f60735..2fa477c 100644
--- a/core/java/android/widget/AbsListView.java
+++ b/core/java/android/widget/AbsListView.java
@@ -4289,14 +4289,15 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
             final int lastPos = firstPos + childCount - 1;
 
             int viewTravelCount;
-            if (position < firstPos) {
-                viewTravelCount = firstPos - position + 1;
+            int clampedPosition = Math.max(0, Math.min(getCount() - 1, position));
+            if (clampedPosition < firstPos) {
+                viewTravelCount = firstPos - clampedPosition + 1;
                 mMode = MOVE_UP_POS;
-            } else if (position > lastPos) {
-                viewTravelCount = position - lastPos + 1;
+            } else if (clampedPosition > lastPos) {
+                viewTravelCount = clampedPosition - lastPos + 1;
                 mMode = MOVE_DOWN_POS;
             } else {
-                scrollToVisible(position, INVALID_POSITION, SCROLL_DURATION);
+                scrollToVisible(clampedPosition, INVALID_POSITION, SCROLL_DURATION);
                 return;
             }
 
@@ -4305,7 +4306,7 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
             } else {
                 mScrollDuration = SCROLL_DURATION;
             }
-            mTargetPos = position;
+            mTargetPos = clampedPosition;
             mBoundPos = INVALID_POSITION;
             mLastSeenPos = INVALID_POSITION;
 
@@ -4340,14 +4341,15 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
             final int lastPos = firstPos + childCount - 1;
 
             int viewTravelCount;
-            if (position < firstPos) {
+            int clampedPosition = Math.max(0, Math.min(getCount() - 1, position));
+            if (clampedPosition < firstPos) {
                 final int boundPosFromLast = lastPos - boundPosition;
                 if (boundPosFromLast < 1) {
                     // Moving would shift our bound position off the screen. Abort.
                     return;
                 }
 
-                final int posTravel = firstPos - position + 1;
+                final int posTravel = firstPos - clampedPosition + 1;
                 final int boundTravel = boundPosFromLast - 1;
                 if (boundTravel < posTravel) {
                     viewTravelCount = boundTravel;
@@ -4356,14 +4358,14 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
                     viewTravelCount = posTravel;
                     mMode = MOVE_UP_POS;
                 }
-            } else if (position > lastPos) {
+            } else if (clampedPosition > lastPos) {
                 final int boundPosFromFirst = boundPosition - firstPos;
                 if (boundPosFromFirst < 1) {
                     // Moving would shift our bound position off the screen. Abort.
                     return;
                 }
 
-                final int posTravel = position - lastPos + 1;
+                final int posTravel = clampedPosition - lastPos + 1;
                 final int boundTravel = boundPosFromFirst - 1;
                 if (boundTravel < posTravel) {
                     viewTravelCount = boundTravel;
@@ -4373,7 +4375,7 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
                     mMode = MOVE_DOWN_POS;
                 }
             } else {
-                scrollToVisible(position, boundPosition, SCROLL_DURATION);
+                scrollToVisible(clampedPosition, boundPosition, SCROLL_DURATION);
                 return;
             }
 
@@ -4382,7 +4384,7 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
             } else {
                 mScrollDuration = SCROLL_DURATION;
             }
-            mTargetPos = position;
+            mTargetPos = clampedPosition;
             mBoundPos = boundPosition;
             mLastSeenPos = INVALID_POSITION;
 
@@ -4415,7 +4417,7 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
 
             offset += getPaddingTop();
 
-            mTargetPos = position;
+            mTargetPos = Math.max(0, Math.min(getCount() - 1, position));
             mOffsetFromTop = offset;
             mBoundPos = INVALID_POSITION;
             mLastSeenPos = INVALID_POSITION;
@@ -4425,13 +4427,13 @@ public abstract class AbsListView extends AdapterView<ListAdapter> implements Te
             final int lastPos = firstPos + childCount - 1;
 
             int viewTravelCount;
-            if (position < firstPos) {
-                viewTravelCount = firstPos - position;
-            } else if (position > lastPos) {
-                viewTravelCount = position - lastPos;
+            if (mTargetPos < firstPos) {
+                viewTravelCount = firstPos - mTargetPos;
+            } else if (mTargetPos > lastPos) {
+                viewTravelCount = mTargetPos - lastPos;
             } else {
                 // On-screen, just scroll.
-                final int targetTop = getChildAt(position - firstPos).getTop();
+                final int targetTop = getChildAt(mTargetPos - firstPos).getTop();
                 smoothScrollBy(targetTop - offset, duration, true);
                 return;
             }
-- 
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