Tweak ViewPager behavior for more DWIM goodness
* Enforce a more deliberate motion in the direction of paging to begin
paging
* Use a pumped-up minimum velocity threshold for flinging to next page
* Bias dropped paging (below velocity threshold) toward staying on the
current page
Bug 7726180
Change-Id: Ie38f77d1a52a7152e86a6b9c40b0941e24138532
diff --git a/v4/java/android/support/v4/view/ViewPager.java b/v4/java/android/support/v4/view/ViewPager.java
index cbeefb0..e6d1b20 100644
--- a/v4/java/android/support/v4/view/ViewPager.java
+++ b/v4/java/android/support/v4/view/ViewPager.java
@@ -93,6 +93,8 @@
private static final int DEFAULT_GUTTER_SIZE = 16; // dips
+ private static final int MIN_FLING_VELOCITY = 400; // dips
+
private static final int[] LAYOUT_ATTRS = new int[] {
android.R.attr.layout_gravity
};
@@ -158,12 +160,13 @@
private int mDefaultGutterSize;
private int mGutterSize;
private int mTouchSlop;
- private float mInitialMotionX;
/**
* Position of the last motion event.
*/
private float mLastMotionX;
private float mLastMotionY;
+ private float mInitialMotionX;
+ private float mInitialMotionY;
/**
* ID of the active pointer. This is used to retain consistency during
* drags/flings if multiple pointers are used.
@@ -350,13 +353,14 @@
final Context context = getContext();
mScroller = new Scroller(context, sInterpolator);
final ViewConfiguration configuration = ViewConfiguration.get(context);
+ final float density = context.getResources().getDisplayMetrics().density;
+
mTouchSlop = ViewConfigurationCompat.getScaledPagingTouchSlop(configuration);
- mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
+ mMinimumVelocity = (int) (MIN_FLING_VELOCITY * density);
mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
mLeftEdge = new EdgeEffectCompat(context);
mRightEdge = new EdgeEffectCompat(context);
- final float density = context.getResources().getDisplayMetrics().density;
mFlingDistance = (int) (MIN_DISTANCE_FOR_FLING * density);
mCloseEnough = (int) (CLOSE_ENOUGH * density);
mDefaultGutterSize = (int) (DEFAULT_GUTTER_SIZE * density);
@@ -1778,33 +1782,32 @@
final float dx = x - mLastMotionX;
final float xDiff = Math.abs(dx);
final float y = MotionEventCompat.getY(ev, pointerIndex);
- final float yDiff = Math.abs(y - mLastMotionY);
+ final float yDiff = Math.abs(y - mInitialMotionY);
if (DEBUG) Log.v(TAG, "Moved x to " + x + "," + y + " diff=" + xDiff + "," + yDiff);
if (dx != 0 && !isGutterDrag(mLastMotionX, dx) &&
canScroll(this, false, (int) dx, (int) x, (int) y)) {
// Nested view has scrollable area under this point. Let it be handled there.
- mInitialMotionX = mLastMotionX = x;
+ mLastMotionX = x;
mLastMotionY = y;
mIsUnableToDrag = true;
return false;
}
- if (xDiff > mTouchSlop && xDiff > yDiff) {
+ if (xDiff > mTouchSlop && xDiff * 0.5f > yDiff) {
if (DEBUG) Log.v(TAG, "Starting drag!");
mIsBeingDragged = true;
setScrollState(SCROLL_STATE_DRAGGING);
mLastMotionX = dx > 0 ? mInitialMotionX + mTouchSlop :
mInitialMotionX - mTouchSlop;
+ mLastMotionY = y;
setScrollingCacheEnabled(true);
- } else {
- if (yDiff > mTouchSlop) {
- // The finger has moved enough in the vertical
- // direction to be counted as a drag... abort
- // any attempt to drag horizontally, to work correctly
- // with children that have scrolling containers.
- if (DEBUG) Log.v(TAG, "Starting unable to drag!");
- mIsUnableToDrag = true;
- }
+ } else if (yDiff > mTouchSlop) {
+ // The finger has moved enough in the vertical
+ // direction to be counted as a drag... abort
+ // any attempt to drag horizontally, to work correctly
+ // with children that have scrolling containers.
+ if (DEBUG) Log.v(TAG, "Starting unable to drag!");
+ mIsUnableToDrag = true;
}
if (mIsBeingDragged) {
// Scroll to follow the motion event
@@ -1821,7 +1824,7 @@
* ACTION_DOWN always refers to pointer index 0.
*/
mLastMotionX = mInitialMotionX = ev.getX();
- mLastMotionY = ev.getY();
+ mLastMotionY = mInitialMotionY = ev.getY();
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
mIsUnableToDrag = false;
@@ -1900,6 +1903,7 @@
// Remember where the motion event started
mLastMotionX = mInitialMotionX = ev.getX();
+ mLastMotionY = mInitialMotionY = ev.getY();
mActivePointerId = MotionEventCompat.getPointerId(ev, 0);
break;
}
@@ -1916,6 +1920,7 @@
mIsBeingDragged = true;
mLastMotionX = x - mInitialMotionX > 0 ? mInitialMotionX + mTouchSlop :
mInitialMotionX - mTouchSlop;
+ mLastMotionY = y;
setScrollState(SCROLL_STATE_DRAGGING);
setScrollingCacheEnabled(true);
}
@@ -2084,7 +2089,8 @@
pageOffset >= 0.5f) {
targetPage = currentPage - 1;
} else {
- targetPage = (int) (currentPage + pageOffset + 0.5f);
+ final float truncator = currentPage >= mCurItem ? 0.4f : 0.6f;
+ targetPage = (int) (currentPage + pageOffset + truncator);
}
if (mItems.size() > 0) {
