Bug 2639807 - Add smarter smoothing to home screen touch scrolling.
Change-Id: I242e11f5aec218ae2b8f80ef3babcb2836c173db
diff --git a/src/com/android/launcher2/Workspace.java b/src/com/android/launcher2/Workspace.java
index f1e8d96..0a658a4 100644
--- a/src/com/android/launcher2/Workspace.java
+++ b/src/com/android/launcher2/Workspace.java
@@ -109,7 +109,6 @@
private boolean mAllowLongPress = true;
private int mTouchSlop;
- private int mPagingTouchSlop;
private int mMaximumVelocity;
private static final int INVALID_POINTER = -1;
@@ -119,9 +118,11 @@
private Drawable mPreviousIndicator;
private Drawable mNextIndicator;
- // Touch scrolling history for smoothing
- private float[] mLastX = new float[6];
- private int mLastCount = 0;
+ private static final float NANOTIME_DIV = 1000000000.0f;
+ private static final float SMOOTHING_SPEED = 0.75f;
+ private static final float SMOOTHING_CONSTANT = (float) (0.016 / Math.log(SMOOTHING_SPEED));
+ private float mSmoothingTime;
+ private float mTouchX;
private WorkspaceOvershootInterpolator mScrollInterpolator;
@@ -196,7 +197,6 @@
final ViewConfiguration configuration = ViewConfiguration.get(getContext());
mTouchSlop = configuration.getScaledTouchSlop();
- mPagingTouchSlop = configuration.getScaledPagingTouchSlop();
mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
}
@@ -431,9 +431,17 @@
}
@Override
+ public void scrollTo(int x, int y) {
+ super.scrollTo(x, y);
+ mTouchX = x;
+ mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
+ }
+
+ @Override
public void computeScroll() {
if (mScroller.computeScrollOffset()) {
- mScrollX = mScroller.getCurrX();
+ mTouchX = mScrollX = mScroller.getCurrX();
+ mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
mScrollY = mScroller.getCurrY();
updateWallpaperOffset();
postInvalidate();
@@ -444,6 +452,18 @@
Launcher.setScreen(mCurrentScreen);
mNextScreen = INVALID_SCREEN;
clearChildrenCache();
+ } else if (mTouchState == TOUCH_STATE_SCROLLING) {
+ final float now = System.nanoTime() / NANOTIME_DIV;
+ final float e = (float) Math.exp((now - mSmoothingTime) / SMOOTHING_CONSTANT);
+ final float dx = mTouchX - mScrollX;
+ mScrollX += dx * e;
+ mSmoothingTime = now;
+
+ // Keep generating points as long as we're more than 1px away from the target
+ if (dx > 1.f || dx < -1.f) {
+ updateWallpaperOffset();
+ postInvalidate();
+ }
}
}
@@ -656,16 +676,17 @@
final int yDiff = (int) Math.abs(y - mLastMotionY);
final int touchSlop = mTouchSlop;
- boolean xPaged = xDiff > mPagingTouchSlop;
boolean xMoved = xDiff > touchSlop;
boolean yMoved = yDiff > touchSlop;
if (xMoved || yMoved) {
- if (xPaged) {
+ if (xMoved) {
// Scroll if the user moved far enough along the X axis
mTouchState = TOUCH_STATE_SCROLLING;
mLastMotionX = x;
+ mTouchX = mScrollX;
+ mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
enableChildrenCache(mCurrentScreen - 1, mCurrentScreen + 1);
}
// Either way, cancel any pending longpress
@@ -755,7 +776,6 @@
if (mVelocityTracker != null) {
mVelocityTracker.clear();
}
- resetFilter();
}
}
@@ -813,25 +833,6 @@
layout.setChildrenDrawnWithCacheEnabled(false);
}
}
-
- private float filterX(float x) {
- final float[] lastX = mLastX;
- final int len = lastX.length;
- final int lastCount = Math.min(len, mLastCount + 1);
-
- float sum = x;
- for (int i = 1; i < lastCount; i++) {
- sum += lastX[i] = lastX[i - 1];
- }
- lastX[0] = x;
-
- mLastCount = lastCount;
- return sum / lastCount;
- }
-
- private void resetFilter() {
- mLastCount = 0;
- }
@Override
public boolean onTouchEvent(MotionEvent ev) {
@@ -876,21 +877,23 @@
if (mTouchState == TOUCH_STATE_SCROLLING) {
// Scroll to follow the motion event
final int pointerIndex = ev.findPointerIndex(mActivePointerId);
- final float x = filterX(ev.getX(pointerIndex));
+ final float x = ev.getX(pointerIndex);
final float deltaX = mLastMotionX - x;
mLastMotionX = x;
if (deltaX < 0) {
- if (mScrollX > 0) {
- scrollBy(Math.round(Math.max(-mScrollX, deltaX)), 0);
- updateWallpaperOffset();
+ if (mTouchX > 0) {
+ mTouchX += Math.max(-mTouchX, deltaX);
+ mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
+ invalidate();
}
} else if (deltaX > 0) {
- final int availableToScroll = getChildAt(getChildCount() - 1).getRight() -
- mScrollX - getWidth();
+ final float availableToScroll = getChildAt(getChildCount() - 1).getRight() -
+ mTouchX - getWidth();
if (availableToScroll > 0) {
- scrollBy(Math.round(Math.min(availableToScroll, deltaX)), 0);
- updateWallpaperOffset();
+ mTouchX += Math.min(availableToScroll, deltaX);
+ mSmoothingTime = System.nanoTime() / NANOTIME_DIV;
+ invalidate();
}
} else {
awakenScrollBars();
@@ -927,7 +930,6 @@
mVelocityTracker.recycle();
mVelocityTracker = null;
}
- resetFilter();
}
mTouchState = TOUCH_STATE_REST;
mActivePointerId = INVALID_POINTER;
@@ -935,7 +937,6 @@
case MotionEvent.ACTION_CANCEL:
mTouchState = TOUCH_STATE_REST;
mActivePointerId = INVALID_POINTER;
- resetFilter();
break;
case MotionEvent.ACTION_POINTER_UP:
onSecondaryPointerUp(ev);