Fixing some edge cases of scrolling in PagedView
-> See Issue 3242353
Change-Id: I58140172e6f283706c351e66ba643cb018827893
diff --git a/src/com/android/launcher2/PagedView.java b/src/com/android/launcher2/PagedView.java
index e4cdd59..05e4086 100644
--- a/src/com/android/launcher2/PagedView.java
+++ b/src/com/android/launcher2/PagedView.java
@@ -81,6 +81,7 @@
protected float mLastMotionX;
protected float mLastMotionXRemainder;
protected float mLastMotionY;
+ protected float mTotalMotionX;
private int mLastScreenCenter = -1;
protected final static int TOUCH_STATE_REST = 0;
@@ -777,6 +778,7 @@
mLastMotionX = x;
mLastMotionY = y;
mLastMotionXRemainder = 0;
+ mTotalMotionX = 0;
mActivePointerId = ev.getPointerId(0);
mAllowLongPress = true;
@@ -952,6 +954,7 @@
// Remember where the motion event started
mDownMotionX = mLastMotionX = ev.getX();
mLastMotionXRemainder = 0;
+ mTotalMotionX = 0;
mActivePointerId = ev.getPointerId(0);
if (mTouchState == TOUCH_STATE_SCROLLING) {
pageBeginMoving();
@@ -965,6 +968,8 @@
final float x = ev.getX(pointerIndex);
final float deltaX = mLastMotionX + mLastMotionXRemainder - x;
+ mTotalMotionX += Math.abs(deltaX);
+
// Only scroll and update mLastMotionX if we have moved some discrete amount. We
// keep the remainder because we are actually testing if we've moved from the last
// scrolled position (which is discrete).
@@ -995,17 +1000,35 @@
velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
int velocityX = (int) velocityTracker.getXVelocity(activePointerId);
final int deltaX = (int) (x - mDownMotionX);
- boolean isfling = Math.abs(deltaX) > MIN_LENGTH_FOR_FLING;
- boolean isSignificantMove = Math.abs(deltaX) > MIN_LENGTH_FOR_MOVE;
-
+ boolean isSignificantMove = mTotalMotionX > MIN_LENGTH_FOR_MOVE;
final int snapVelocity = mSnapVelocity;
- if ((isSignificantMove && deltaX > 0 ||
- (isfling && velocityX > snapVelocity)) && mCurrentPage > 0) {
- snapToPageWithVelocity(mCurrentPage - 1, velocityX);
- } else if ((isSignificantMove && deltaX < 0 ||
- (isfling && velocityX < -snapVelocity)) &&
+
+ // In the case that the page is moved far to one direction and then is flung
+ // in the opposite direction, we use a threshold to determine whether we should
+ // just return to the starting page, or if we should skip one further.
+ boolean returnToOriginalPage = false;
+ final int pageWidth = getScaledMeasuredWidth(getChildAt(mCurrentPage));
+ if (Math.abs(deltaX) > pageWidth / 3 &&
+ Math.signum(velocityX) != Math.signum(deltaX)) {
+ returnToOriginalPage = true;
+ }
+
+ boolean isFling = Math.abs(deltaX) > MIN_LENGTH_FOR_FLING &&
+ Math.abs(velocityX) > snapVelocity;
+
+ int finalPage;
+ // We give flings precedence over large moves, which is why we short-circuit our
+ // test for a large move if a fling has been registered. That is, a large
+ // move to the left and fling to the right will register as a fling to the right.
+ if (((isSignificantMove && deltaX > 0 && !isFling) ||
+ (isFling && velocityX > 0)) && mCurrentPage > 0) {
+ finalPage = returnToOriginalPage ? mCurrentPage : mCurrentPage - 1;
+ snapToPageWithVelocity(finalPage, velocityX);
+ } else if (((isSignificantMove && deltaX < 0 && !isFling) ||
+ (isFling && velocityX < 0)) &&
mCurrentPage < getChildCount() - 1) {
- snapToPageWithVelocity(mCurrentPage + 1, velocityX);
+ finalPage = returnToOriginalPage ? mCurrentPage : mCurrentPage + 1;
+ snapToPageWithVelocity(finalPage, velocityX);
} else {
snapToDestination();
}