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Fixing some edge cases of scrolling in PagedView

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-> See Issue 3242353

Change-Id: I58140172e6f283706c351e66ba643cb018827893
This commit is contained in:
Adam Cohen
2011-02-14 16:39:38 -08:00
parent 917665cd06
commit aefd4e1f51
1 changed files with 32 additions and 9 deletions
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src/com/android/launcher2/PagedView.java
+32 -9
View File
@@ -81,6 +81,7 @@ public abstract class PagedView extends ViewGroup {
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 @@ public abstract class PagedView extends ViewGroup {
mLastMotionX = x;
mLastMotionY = y;
mLastMotionXRemainder = 0;
mTotalMotionX = 0;
mActivePointerId = ev.getPointerId(0);
mAllowLongPress = true;
@@ -952,6 +954,7 @@ public abstract class PagedView extends ViewGroup {
// 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 @@ public abstract class PagedView extends ViewGroup {
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 @@ public abstract class PagedView extends ViewGroup {
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();
}