Fixes #1444844. Set a maximum fling velocity in scrollable views.

3 files changed, 46 insertions, 5 deletions

diff --git a/core/java/android/view/GestureDetector.java b/core/java/android/view/GestureDetector.java
index 23f3e3c..1e558be 100644
--- a/core/java/android/view/GestureDetector.java
+++ b/core/java/android/view/GestureDetector.java
@@ -198,6 +198,7 @@ public class GestureDetector {
     private int mTouchSlopSquare;
     private int mDoubleTapSlopSquare;
     private int mMinimumFlingVelocity;
+    private int mMaximumFlingVelocity;
 
     private static final int LONGPRESS_TIMEOUT = ViewConfiguration.getLongPressTimeout();
     private static final int TAP_TIMEOUT = ViewConfiguration.getTapTimeout();
@@ -361,11 +362,13 @@ public class GestureDetector {
             doubleTapSlop = ViewConfiguration.getDoubleTapSlop();
             //noinspection deprecation
             mMinimumFlingVelocity = ViewConfiguration.getMinimumFlingVelocity();
+            mMaximumFlingVelocity = ViewConfiguration.getMaximumFlingVelocity();
         } else {
             final ViewConfiguration configuration = ViewConfiguration.get(context);
             touchSlop = configuration.getScaledTouchSlop();
             doubleTapSlop = configuration.getScaledDoubleTapSlop();
             mMinimumFlingVelocity = configuration.getScaledMinimumFlingVelocity();
+            mMaximumFlingVelocity = configuration.getScaledMaximumFlingVelocity();
         }
         mTouchSlopSquare = touchSlop * touchSlop;
         mDoubleTapSlopSquare = doubleTapSlop * doubleTapSlop;
@@ -505,7 +508,7 @@ public class GestureDetector {
 
                 // A fling must travel the minimum tap distance
                 final VelocityTracker velocityTracker = mVelocityTracker;
-                velocityTracker.computeCurrentVelocity(1000);
+                velocityTracker.computeCurrentVelocity(1000, mMaximumFlingVelocity);
                 final float velocityY = velocityTracker.getYVelocity();
                 final float velocityX = velocityTracker.getXVelocity();
 
diff --git a/core/java/android/view/VelocityTracker.java b/core/java/android/view/VelocityTracker.java
index c708f54..5d89c46 100644
--- a/core/java/android/view/VelocityTracker.java
+++ b/core/java/android/view/VelocityTracker.java
@@ -165,7 +165,17 @@ public final class VelocityTracker implements Poolable<VelocityTracker> {
             pastTime[i] = 0;
         }
     }
-    
+
+    /**
+     * Equivalent to invoking {@link #computeCurrentVelocity(int, float)} with a maximum
+     * velocity of Float.MAX_VALUE.
+     * 
+     * @see #computeCurrentVelocity(int, float) 
+     */
+    public void computeCurrentVelocity(int units) {
+        computeCurrentVelocity(units, Float.MAX_VALUE);
+    }
+
     /**
      * Compute the current velocity based on the points that have been
      * collected.  Only call this when you actually want to retrieve velocity
@@ -175,8 +185,11 @@ public final class VelocityTracker implements Poolable<VelocityTracker> {
      * 
      * @param units The units you would like the velocity in.  A value of 1
      * provides pixels per millisecond, 1000 provides pixels per second, etc.
+     * @param maxVelocity The maximum velocity that can be computed by this method.
+     * This value must be declared in the same unit as the units parameter. This value
+     * must be positive.
      */
-    public void computeCurrentVelocity(int units) {
+    public void computeCurrentVelocity(int units, float maxVelocity) {
         final float[] pastX = mPastX;
         final float[] pastY = mPastY;
         final long[] pastTime = mPastTime;
@@ -210,8 +223,8 @@ public final class VelocityTracker implements Poolable<VelocityTracker> {
             if (accumY == 0) accumY = vel;
             else accumY = (accumY + vel) * .5f;
         }
-        mXVelocity = accumX;
-        mYVelocity = accumY;
+        mXVelocity = accumX < 0.0f ? Math.max(accumX, -maxVelocity) : Math.min(accumX, maxVelocity);
+        mYVelocity = accumY < 0.0f ? Math.max(accumY, -maxVelocity) : Math.min(accumY, maxVelocity);
         
         if (localLOGV) Log.v(TAG, "Y velocity=" + mYVelocity +" X velocity="
                 + mXVelocity + " N=" + N);
diff --git a/core/java/android/view/ViewConfiguration.java b/core/java/android/view/ViewConfiguration.java
index 8e1524b..0e36ec2 100644
--- a/core/java/android/view/ViewConfiguration.java
+++ b/core/java/android/view/ViewConfiguration.java
@@ -106,6 +106,11 @@ public class ViewConfiguration {
      * Minimum velocity to initiate a fling, as measured in pixels per second
      */
     private static final int MINIMUM_FLING_VELOCITY = 50;
+    
+    /**
+     * Maximum velocity to initiate a fling, as measured in pixels per second
+     */
+    private static final int MAXIMUM_FLING_VELOCITY = 4000;
 
     /**
      * The maximum size of View's drawing cache, expressed in bytes. This size
@@ -122,6 +127,7 @@ public class ViewConfiguration {
     private final int mEdgeSlop;
     private final int mFadingEdgeLength;
     private final int mMinimumFlingVelocity;
+    private final int mMaximumFlingVelocity;
     private final int mScrollbarSize;
     private final int mTouchSlop;
     private final int mDoubleTapSlop;
@@ -139,6 +145,7 @@ public class ViewConfiguration {
         mEdgeSlop = EDGE_SLOP;
         mFadingEdgeLength = FADING_EDGE_LENGTH;
         mMinimumFlingVelocity = MINIMUM_FLING_VELOCITY;
+        mMaximumFlingVelocity = MAXIMUM_FLING_VELOCITY;
         mScrollbarSize = SCROLL_BAR_SIZE;
         mTouchSlop = TOUCH_SLOP;
         mDoubleTapSlop = DOUBLE_TAP_SLOP;
@@ -164,6 +171,7 @@ public class ViewConfiguration {
         mEdgeSlop = (int) (density * EDGE_SLOP + 0.5f);
         mFadingEdgeLength = (int) (density * FADING_EDGE_LENGTH + 0.5f);
         mMinimumFlingVelocity = (int) (density * MINIMUM_FLING_VELOCITY + 0.5f);
+        mMaximumFlingVelocity = (int) (density * MAXIMUM_FLING_VELOCITY + 0.5f);
         mScrollbarSize = (int) (density * SCROLL_BAR_SIZE + 0.5f);
         mTouchSlop = (int) (density * TOUCH_SLOP + 0.5f);
         mDoubleTapSlop = (int) (density * DOUBLE_TAP_SLOP + 0.5f);
@@ -367,6 +375,23 @@ public class ViewConfiguration {
     }
 
     /**
+     * @return Maximum velocity to initiate a fling, as measured in pixels per second.
+     *
+     * @deprecated Use {@link #getScaledMaximumFlingVelocity()} instead.
+     */
+    @Deprecated
+    public static int getMaximumFlingVelocity() {
+        return MAXIMUM_FLING_VELOCITY;
+    }
+
+    /**
+     * @return Maximum velocity to initiate a fling, as measured in pixels per second.
+     */
+    public int getScaledMaximumFlingVelocity() {
+        return mMaximumFlingVelocity;
+    }
+    
+    /**
      * The maximum drawing cache size expressed in bytes.
      *
      * @return the maximum size of View's drawing cache expressed in bytes