Port AutoScroller to launcher3
Change-Id: Ic2b7b5faac4878f3b4645c291e36c5f7734c7f8b
diff --git a/src/com/android/launcher3/AutoScrollHelper.java b/src/com/android/launcher3/AutoScrollHelper.java
new file mode 100644
index 0000000..9a7c3b0
--- /dev/null
+++ b/src/com/android/launcher3/AutoScrollHelper.java
@@ -0,0 +1,867 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.launcher3;
+
+import android.content.res.Resources;
+import android.os.SystemClock;
+import android.support.v4.view.MotionEventCompat;
+import android.support.v4.view.ViewCompat;
+import android.util.DisplayMetrics;
+import android.view.MotionEvent;
+import android.view.View;
+import android.view.ViewConfiguration;
+import android.view.animation.AccelerateInterpolator;
+import android.view.animation.AnimationUtils;
+import android.view.animation.Interpolator;
+
+/**
+ * AutoScrollHelper is a utility class for adding automatic edge-triggered
+ * scrolling to Views.
+ * <p>
+ * <b>Note:</b> Implementing classes are responsible for overriding the
+ * {@link #scrollTargetBy}, {@link #canTargetScrollHorizontally}, and
+ * {@link #canTargetScrollVertically} methods. See
+ * {@link ListViewAutoScrollHelper} for a {@link android.widget.ListView}
+ * -specific implementation.
+ * <p>
+ * <h1>Activation</h1> Automatic scrolling starts when the user touches within
+ * an activation area. By default, activation areas are defined as the top,
+ * left, right, and bottom 20% of the host view's total area. Touching within
+ * the top activation area scrolls up, left scrolls to the left, and so on.
+ * <p>
+ * As the user touches closer to the extreme edge of the activation area,
+ * scrolling accelerates up to a maximum velocity. When using the default edge
+ * type, {@link #EDGE_TYPE_INSIDE_EXTEND}, moving outside of the view bounds
+ * will scroll at the maximum velocity.
+ * <p>
+ * The following activation properties may be configured:
+ * <ul>
+ * <li>Delay after entering activation area before auto-scrolling begins, see
+ * {@link #setActivationDelay}. Default value is
+ * {@link ViewConfiguration#getTapTimeout()} to avoid conflicting with taps.
+ * <li>Location of activation areas, see {@link #setEdgeType}. Default value is
+ * {@link #EDGE_TYPE_INSIDE_EXTEND}.
+ * <li>Size of activation areas relative to view size, see
+ * {@link #setRelativeEdges}. Default value is 20% for both vertical and
+ * horizontal edges.
+ * <li>Maximum size used to constrain relative size, see
+ * {@link #setMaximumEdges}. Default value is {@link #NO_MAX}.
+ * </ul>
+ * <h1>Scrolling</h1> When automatic scrolling is active, the helper will
+ * repeatedly call {@link #scrollTargetBy} to apply new scrolling offsets.
+ * <p>
+ * The following scrolling properties may be configured:
+ * <ul>
+ * <li>Acceleration ramp-up duration, see {@link #setRampUpDuration}. Default
+ * value is 2500 milliseconds.
+ * <li>Acceleration ramp-down duration, see {@link #setRampDownDuration}.
+ * Default value is 500 milliseconds.
+ * <li>Target velocity relative to view size, see {@link #setRelativeVelocity}.
+ * Default value is 100% per second for both vertical and horizontal.
+ * <li>Minimum velocity used to constrain relative velocity, see
+ * {@link #setMinimumVelocity}. When set, scrolling will accelerate to the
+ * larger of either this value or the relative target value. Default value is
+ * approximately 5 centimeters or 315 dips per second.
+ * <li>Maximum velocity used to constrain relative velocity, see
+ * {@link #setMaximumVelocity}. Default value is approximately 25 centimeters or
+ * 1575 dips per second.
+ * </ul>
+ */
+public abstract class AutoScrollHelper implements View.OnTouchListener {
+ /**
+ * Constant passed to {@link #setRelativeEdges} or
+ * {@link #setRelativeVelocity}. Using this value ensures that the computed
+ * relative value is ignored and the absolute maximum value is always used.
+ */
+ public static final float RELATIVE_UNSPECIFIED = 0;
+
+ /**
+ * Constant passed to {@link #setMaximumEdges}, {@link #setMaximumVelocity},
+ * or {@link #setMinimumVelocity}. Using this value ensures that the
+ * computed relative value is always used without constraining to a
+ * particular minimum or maximum value.
+ */
+ public static final float NO_MAX = Float.MAX_VALUE;
+
+ /**
+ * Constant passed to {@link #setMaximumEdges}, or
+ * {@link #setMaximumVelocity}, or {@link #setMinimumVelocity}. Using this
+ * value ensures that the computed relative value is always used without
+ * constraining to a particular minimum or maximum value.
+ */
+ public static final float NO_MIN = 0;
+
+ /**
+ * Edge type that specifies an activation area starting at the view bounds
+ * and extending inward. Moving outside the view bounds will stop scrolling.
+ *
+ * @see #setEdgeType
+ */
+ public static final int EDGE_TYPE_INSIDE = 0;
+
+ /**
+ * Edge type that specifies an activation area starting at the view bounds
+ * and extending inward. After activation begins, moving outside the view
+ * bounds will continue scrolling.
+ *
+ * @see #setEdgeType
+ */
+ public static final int EDGE_TYPE_INSIDE_EXTEND = 1;
+
+ /**
+ * Edge type that specifies an activation area starting at the view bounds
+ * and extending outward. Moving inside the view bounds will stop scrolling.
+ *
+ * @see #setEdgeType
+ */
+ public static final int EDGE_TYPE_OUTSIDE = 2;
+
+ private static final int HORIZONTAL = 0;
+ private static final int VERTICAL = 1;
+
+ /** Scroller used to control acceleration toward maximum velocity. */
+ private final ClampedScroller mScroller = new ClampedScroller();
+
+ /** Interpolator used to scale velocity with touch position. */
+ private final Interpolator mEdgeInterpolator = new AccelerateInterpolator();
+
+ /** The view to auto-scroll. Might not be the source of touch events. */
+ private final View mTarget;
+
+ /** Runnable used to animate scrolling. */
+ private Runnable mRunnable;
+
+ /** Edge insets used to activate auto-scrolling. */
+ private float[] mRelativeEdges = new float[] { RELATIVE_UNSPECIFIED, RELATIVE_UNSPECIFIED };
+
+ /** Clamping values for edge insets used to activate auto-scrolling. */
+ private float[] mMaximumEdges = new float[] { NO_MAX, NO_MAX };
+
+ /** The type of edge being used. */
+ private int mEdgeType;
+
+ /** Delay after entering an activation edge before auto-scrolling begins. */
+ private int mActivationDelay;
+
+ /** Relative scrolling velocity at maximum edge distance. */
+ private float[] mRelativeVelocity = new float[] { RELATIVE_UNSPECIFIED, RELATIVE_UNSPECIFIED };
+
+ /** Clamping values used for scrolling velocity. */
+ private float[] mMinimumVelocity = new float[] { NO_MIN, NO_MIN };
+
+ /** Clamping values used for scrolling velocity. */
+ private float[] mMaximumVelocity = new float[] { NO_MAX, NO_MAX };
+
+ /** Whether to start activation immediately. */
+ private boolean mAlreadyDelayed;
+
+ /** Whether to reset the scroller start time on the next animation. */
+ private boolean mNeedsReset;
+
+ /** Whether to send a cancel motion event to the target view. */
+ private boolean mNeedsCancel;
+
+ /** Whether the auto-scroller is actively scrolling. */
+ private boolean mAnimating;
+
+ /** Whether the auto-scroller is enabled. */
+ private boolean mEnabled;
+
+ /** Whether the auto-scroller consumes events when scrolling. */
+ private boolean mExclusive;
+
+ // Default values.
+ private static final int DEFAULT_EDGE_TYPE = EDGE_TYPE_INSIDE_EXTEND;
+ private static final int DEFAULT_MINIMUM_VELOCITY_DIPS = 315;
+ private static final int DEFAULT_MAXIMUM_VELOCITY_DIPS = 1575;
+ private static final float DEFAULT_MAXIMUM_EDGE = NO_MAX;
+ private static final float DEFAULT_RELATIVE_EDGE = 0.2f;
+ private static final float DEFAULT_RELATIVE_VELOCITY = 1f;
+ private static final int DEFAULT_ACTIVATION_DELAY = ViewConfiguration.getTapTimeout();
+ private static final int DEFAULT_RAMP_UP_DURATION = 2500;
+ private static final int DEFAULT_RAMP_DOWN_DURATION = 500;
+
+ /**
+ * Creates a new helper for scrolling the specified target view.
+ * <p>
+ * The resulting helper may be configured by chaining setter calls and
+ * should be set as a touch listener on the target view.
+ * <p>
+ * By default, the helper is disabled and will not respond to touch events
+ * until it is enabled using {@link #setEnabled}.
+ *
+ * @param target The view to automatically scroll.
+ */
+ public AutoScrollHelper(View target) {
+ mTarget = target;
+
+ final DisplayMetrics metrics = Resources.getSystem().getDisplayMetrics();
+ final int maxVelocity = (int) (DEFAULT_MAXIMUM_VELOCITY_DIPS * metrics.density + 0.5f);
+ final int minVelocity = (int) (DEFAULT_MINIMUM_VELOCITY_DIPS * metrics.density + 0.5f);
+ setMaximumVelocity(maxVelocity, maxVelocity);
+ setMinimumVelocity(minVelocity, minVelocity);
+
+ setEdgeType(DEFAULT_EDGE_TYPE);
+ setMaximumEdges(DEFAULT_MAXIMUM_EDGE, DEFAULT_MAXIMUM_EDGE);
+ setRelativeEdges(DEFAULT_RELATIVE_EDGE, DEFAULT_RELATIVE_EDGE);
+ setRelativeVelocity(DEFAULT_RELATIVE_VELOCITY, DEFAULT_RELATIVE_VELOCITY);
+ setActivationDelay(DEFAULT_ACTIVATION_DELAY);
+ setRampUpDuration(DEFAULT_RAMP_UP_DURATION);
+ setRampDownDuration(DEFAULT_RAMP_DOWN_DURATION);
+ }
+
+ /**
+ * Sets whether the scroll helper is enabled and should respond to touch
+ * events.
+ *
+ * @param enabled Whether the scroll helper is enabled.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setEnabled(boolean enabled) {
+ if (mEnabled && !enabled) {
+ requestStop();
+ }
+
+ mEnabled = enabled;
+ return this;
+ }
+
+ /**
+ * @return True if this helper is enabled and responding to touch events.
+ */
+ public boolean isEnabled() {
+ return mEnabled;
+ }
+
+ /**
+ * Enables or disables exclusive handling of touch events during scrolling.
+ * By default, exclusive handling is disabled and the target view receives
+ * all touch events.
+ * <p>
+ * When enabled, {@link #onTouch} will return true if the helper is
+ * currently scrolling and false otherwise.
+ *
+ * @param exclusive True to exclusively handle touch events during scrolling,
+ * false to allow the target view to receive all touch events.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setExclusive(boolean exclusive) {
+ mExclusive = exclusive;
+ return this;
+ }
+
+ /**
+ * Indicates whether the scroll helper handles touch events exclusively
+ * during scrolling.
+ *
+ * @return True if exclusive handling of touch events during scrolling is
+ * enabled, false otherwise.
+ * @see #setExclusive(boolean)
+ */
+ public boolean isExclusive() {
+ return mExclusive;
+ }
+
+ /**
+ * Sets the absolute maximum scrolling velocity.
+ * <p>
+ * If relative velocity is not specified, scrolling will always reach the
+ * same maximum velocity. If both relative and maximum velocities are
+ * specified, the maximum velocity will be used to clamp the calculated
+ * relative velocity.
+ *
+ * @param horizontalMax The maximum horizontal scrolling velocity, or
+ * {@link #NO_MAX} to leave the relative value unconstrained.
+ * @param verticalMax The maximum vertical scrolling velocity, or
+ * {@link #NO_MAX} to leave the relative value unconstrained.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setMaximumVelocity(float horizontalMax, float verticalMax) {
+ mMaximumVelocity[HORIZONTAL] = horizontalMax / 1000f;
+ mMaximumVelocity[VERTICAL] = verticalMax / 1000f;
+ return this;
+ }
+
+ /**
+ * Sets the absolute minimum scrolling velocity.
+ * <p>
+ * If both relative and minimum velocities are specified, the minimum
+ * velocity will be used to clamp the calculated relative velocity.
+ *
+ * @param horizontalMin The minimum horizontal scrolling velocity, or
+ * {@link #NO_MIN} to leave the relative value unconstrained.
+ * @param verticalMin The minimum vertical scrolling velocity, or
+ * {@link #NO_MIN} to leave the relative value unconstrained.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setMinimumVelocity(float horizontalMin, float verticalMin) {
+ mMinimumVelocity[HORIZONTAL] = horizontalMin / 1000f;
+ mMinimumVelocity[VERTICAL] = verticalMin / 1000f;
+ return this;
+ }
+
+ /**
+ * Sets the target scrolling velocity relative to the host view's
+ * dimensions.
+ * <p>
+ * If both relative and maximum velocities are specified, the maximum
+ * velocity will be used to clamp the calculated relative velocity.
+ *
+ * @param horizontal The target horizontal velocity as a fraction of the
+ * host view width per second, or {@link #RELATIVE_UNSPECIFIED}
+ * to ignore.
+ * @param vertical The target vertical velocity as a fraction of the host
+ * view height per second, or {@link #RELATIVE_UNSPECIFIED} to
+ * ignore.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setRelativeVelocity(float horizontal, float vertical) {
+ mRelativeVelocity[HORIZONTAL] = horizontal / 1000f;
+ mRelativeVelocity[VERTICAL] = vertical / 1000f;
+ return this;
+ }
+
+ /**
+ * Sets the activation edge type, one of:
+ * <ul>
+ * <li>{@link #EDGE_TYPE_INSIDE} for edges that respond to touches inside
+ * the bounds of the host view. If touch moves outside the bounds, scrolling
+ * will stop.
+ * <li>{@link #EDGE_TYPE_INSIDE_EXTEND} for inside edges that continued to
+ * scroll when touch moves outside the bounds of the host view.
+ * <li>{@link #EDGE_TYPE_OUTSIDE} for edges that only respond to touches
+ * that move outside the bounds of the host view.
+ * </ul>
+ *
+ * @param type The type of edge to use.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setEdgeType(int type) {
+ mEdgeType = type;
+ return this;
+ }
+
+ /**
+ * Sets the activation edge size relative to the host view's dimensions.
+ * <p>
+ * If both relative and maximum edges are specified, the maximum edge will
+ * be used to constrain the calculated relative edge size.
+ *
+ * @param horizontal The horizontal edge size as a fraction of the host view
+ * width, or {@link #RELATIVE_UNSPECIFIED} to always use the
+ * maximum value.
+ * @param vertical The vertical edge size as a fraction of the host view
+ * height, or {@link #RELATIVE_UNSPECIFIED} to always use the
+ * maximum value.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setRelativeEdges(float horizontal, float vertical) {
+ mRelativeEdges[HORIZONTAL] = horizontal;
+ mRelativeEdges[VERTICAL] = vertical;
+ return this;
+ }
+
+ /**
+ * Sets the absolute maximum edge size.
+ * <p>
+ * If relative edge size is not specified, activation edges will always be
+ * the maximum edge size. If both relative and maximum edges are specified,
+ * the maximum edge will be used to constrain the calculated relative edge
+ * size.
+ *
+ * @param horizontalMax The maximum horizontal edge size in pixels, or
+ * {@link #NO_MAX} to use the unconstrained calculated relative
+ * value.
+ * @param verticalMax The maximum vertical edge size in pixels, or
+ * {@link #NO_MAX} to use the unconstrained calculated relative
+ * value.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setMaximumEdges(float horizontalMax, float verticalMax) {
+ mMaximumEdges[HORIZONTAL] = horizontalMax;
+ mMaximumEdges[VERTICAL] = verticalMax;
+ return this;
+ }
+
+ /**
+ * Sets the delay after entering an activation edge before activation of
+ * auto-scrolling. By default, the activation delay is set to
+ * {@link ViewConfiguration#getTapTimeout()}.
+ * <p>
+ * Specifying a delay of zero will start auto-scrolling immediately after
+ * the touch position enters an activation edge.
+ *
+ * @param delayMillis The activation delay in milliseconds.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setActivationDelay(int delayMillis) {
+ mActivationDelay = delayMillis;
+ return this;
+ }
+
+ /**
+ * Sets the amount of time after activation of auto-scrolling that is takes
+ * to reach target velocity for the current touch position.
+ * <p>
+ * Specifying a duration greater than zero prevents sudden jumps in
+ * velocity.
+ *
+ * @param durationMillis The ramp-up duration in milliseconds.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setRampUpDuration(int durationMillis) {
+ mScroller.setRampUpDuration(durationMillis);
+ return this;
+ }
+
+ /**
+ * Sets the amount of time after de-activation of auto-scrolling that is
+ * takes to slow to a stop.
+ * <p>
+ * Specifying a duration greater than zero prevents sudden jumps in
+ * velocity.
+ *
+ * @param durationMillis The ramp-down duration in milliseconds.
+ * @return The scroll helper, which may used to chain setter calls.
+ */
+ public AutoScrollHelper setRampDownDuration(int durationMillis) {
+ mScroller.setRampDownDuration(durationMillis);
+ return this;
+ }
+
+ /**
+ * Handles touch events by activating automatic scrolling, adjusting scroll
+ * velocity, or stopping.
+ * <p>
+ * If {@link #isExclusive()} is false, always returns false so that
+ * the host view may handle touch events. Otherwise, returns true when
+ * automatic scrolling is active and false otherwise.
+ */
+ @Override
+ public boolean onTouch(View v, MotionEvent event) {
+ if (!mEnabled) {
+ return false;
+ }
+
+ final int action = MotionEventCompat.getActionMasked(event);
+ switch (action) {
+ case MotionEvent.ACTION_DOWN:
+ mNeedsCancel = true;
+ mAlreadyDelayed = false;
+ // $FALL-THROUGH$
+ case MotionEvent.ACTION_MOVE:
+ final float xTargetVelocity = computeTargetVelocity(
+ HORIZONTAL, event.getX(), v.getWidth(), mTarget.getWidth());
+ final float yTargetVelocity = computeTargetVelocity(
+ VERTICAL, event.getY(), v.getHeight(), mTarget.getHeight());
+ mScroller.setTargetVelocity(xTargetVelocity, yTargetVelocity);
+
+ // If the auto scroller was not previously active, but it should
+ // be, then update the state and start animations.
+ if (!mAnimating && shouldAnimate()) {
+ startAnimating();
+ }
+ break;
+ case MotionEvent.ACTION_UP:
+ case MotionEvent.ACTION_CANCEL:
+ requestStop();
+ break;
+ }
+
+ return mExclusive && mAnimating;
+ }
+
+ /**
+ * @return whether the target is able to scroll in the requested direction
+ */
+ private boolean shouldAnimate() {
+ final ClampedScroller scroller = mScroller;
+ final int verticalDirection = scroller.getVerticalDirection();
+ final int horizontalDirection = scroller.getHorizontalDirection();
+
+ return verticalDirection != 0 && canTargetScrollVertically(verticalDirection)
+ || horizontalDirection != 0 && canTargetScrollHorizontally(horizontalDirection);
+ }
+
+ /**
+ * Starts the scroll animation.
+ */
+ private void startAnimating() {
+ if (mRunnable == null) {
+ mRunnable = new ScrollAnimationRunnable();
+ }
+
+ mAnimating = true;
+ mNeedsReset = true;
+
+ if (!mAlreadyDelayed && mActivationDelay > 0) {
+ ViewCompat.postOnAnimationDelayed(mTarget, mRunnable, mActivationDelay);
+ } else {
+ mRunnable.run();
+ }
+
+ // If we start animating again before the user lifts their finger, we
+ // already know it's not a tap and don't need an activation delay.
+ mAlreadyDelayed = true;
+ }
+
+ /**
+ * Requests that the scroll animation slow to a stop. If there is an
+ * activation delay, this may occur between posting the animation and
+ * actually running it.
+ */
+ private void requestStop() {
+ if (mNeedsReset) {
+ // The animation has been posted, but hasn't run yet. Manually
+ // stopping animation will prevent it from running.
+ mAnimating = false;
+ } else {
+ mScroller.requestStop();
+ }
+ }
+
+ private float computeTargetVelocity(
+ int direction, float coordinate, float srcSize, float dstSize) {
+ final float relativeEdge = mRelativeEdges[direction];
+ final float maximumEdge = mMaximumEdges[direction];
+ final float value = getEdgeValue(relativeEdge, srcSize, maximumEdge, coordinate);
+ if (value == 0) {
+ // The edge in this direction is not activated.
+ return 0;
+ }
+
+ final float relativeVelocity = mRelativeVelocity[direction];
+ final float minimumVelocity = mMinimumVelocity[direction];
+ final float maximumVelocity = mMaximumVelocity[direction];
+ final float targetVelocity = relativeVelocity * dstSize;
+
+ // Target velocity is adjusted for interpolated edge position, then
+ // clamped to the minimum and maximum values. Later, this value will be
+ // adjusted for time-based acceleration.
+ if (value > 0) {
+ return constrain(value * targetVelocity, minimumVelocity, maximumVelocity);
+ } else {
+ return -constrain(-value * targetVelocity, minimumVelocity, maximumVelocity);
+ }
+ }
+
+ /**
+ * Override this method to scroll the target view by the specified number of
+ * pixels.
+ *
+ * @param deltaX The number of pixels to scroll by horizontally.
+ * @param deltaY The number of pixels to scroll by vertically.
+ */
+ public abstract void scrollTargetBy(int deltaX, int deltaY);
+
+ /**
+ * Override this method to return whether the target view can be scrolled
+ * horizontally in a certain direction.
+ *
+ * @param direction Negative to check scrolling left, positive to check
+ * scrolling right.
+ * @return true if the target view is able to horizontally scroll in the
+ * specified direction.
+ */
+ public abstract boolean canTargetScrollHorizontally(int direction);
+
+ /**
+ * Override this method to return whether the target view can be scrolled
+ * vertically in a certain direction.
+ *
+ * @param direction Negative to check scrolling up, positive to check
+ * scrolling down.
+ * @return true if the target view is able to vertically scroll in the
+ * specified direction.
+ */
+ public abstract boolean canTargetScrollVertically(int direction);
+
+ /**
+ * Returns the interpolated position of a touch point relative to an edge
+ * defined by its relative inset, its maximum absolute inset, and the edge
+ * interpolator.
+ *
+ * @param relativeValue The size of the inset relative to the total size.
+ * @param size Total size.
+ * @param maxValue The maximum size of the inset, used to clamp (relative *
+ * total).
+ * @param current Touch position within within the total size.
+ * @return Interpolated value of the touch position within the edge.
+ */
+ private float getEdgeValue(float relativeValue, float size, float maxValue, float current) {
+ // For now, leading and trailing edges are always the same size.
+ final float edgeSize = constrain(relativeValue * size, NO_MIN, maxValue);
+ final float valueLeading = constrainEdgeValue(current, edgeSize);
+ final float valueTrailing = constrainEdgeValue(size - current, edgeSize);
+ final float value = (valueTrailing - valueLeading);
+ final float interpolated;
+ if (value < 0) {
+ interpolated = -mEdgeInterpolator.getInterpolation(-value);
+ } else if (value > 0) {
+ interpolated = mEdgeInterpolator.getInterpolation(value);
+ } else {
+ return 0;
+ }
+
+ return constrain(interpolated, -1, 1);
+ }
+
+ private float constrainEdgeValue(float current, float leading) {
+ if (leading == 0) {
+ return 0;
+ }
+
+ switch (mEdgeType) {
+ case EDGE_TYPE_INSIDE:
+ case EDGE_TYPE_INSIDE_EXTEND:
+ if (current < leading) {
+ if (current > 0) {
+ // Movement up to the edge is scaled.
+ return 1f - current / leading;
+ } else if (mAnimating && (mEdgeType == EDGE_TYPE_INSIDE_EXTEND)) {
+ // Movement beyond the edge is always maximum.
+ return 1f;
+ }
+ }
+ break;
+ case EDGE_TYPE_OUTSIDE:
+ if (current < 0) {
+ // Movement beyond the edge is scaled.
+ return current / -leading;
+ }
+ break;
+ }
+
+ return 0;
+ }
+
+ private static int constrain(int value, int min, int max) {
+ if (value > max) {
+ return max;
+ } else if (value < min) {
+ return min;
+ } else {
+ return value;
+ }
+ }
+
+ private static float constrain(float value, float min, float max) {
+ if (value > max) {
+ return max;
+ } else if (value < min) {
+ return min;
+ } else {
+ return value;
+ }
+ }
+
+ /**
+ * Sends a {@link MotionEvent#ACTION_CANCEL} event to the target view,
+ * canceling any ongoing touch events.
+ */
+ private void cancelTargetTouch() {
+ final long eventTime = SystemClock.uptimeMillis();
+ final MotionEvent cancel = MotionEvent.obtain(
+ eventTime, eventTime, MotionEvent.ACTION_CANCEL, 0, 0, 0);
+ mTarget.onTouchEvent(cancel);
+ cancel.recycle();
+ }
+
+ private class ScrollAnimationRunnable implements Runnable {
+ @Override
+ public void run() {
+ if (!mAnimating) {
+ return;
+ }
+
+ if (mNeedsReset) {
+ mNeedsReset = false;
+ mScroller.start();
+ }
+
+ final ClampedScroller scroller = mScroller;
+ if (scroller.isFinished() || !shouldAnimate()) {
+ mAnimating = false;
+ return;
+ }
+
+ if (mNeedsCancel) {
+ mNeedsCancel = false;
+ cancelTargetTouch();
+ }
+
+ scroller.computeScrollDelta();
+
+ final int deltaX = scroller.getDeltaX();
+ final int deltaY = scroller.getDeltaY();
+ scrollTargetBy(deltaX, deltaY);
+
+ // Keep going until the scroller has permanently stopped.
+ ViewCompat.postOnAnimation(mTarget, this);
+ }
+ }
+
+ /**
+ * Scroller whose velocity follows the curve of an {@link Interpolator} and
+ * is clamped to the interpolated 0f value before starting and the
+ * interpolated 1f value after a specified duration.
+ */
+ private static class ClampedScroller {
+ private int mRampUpDuration;
+ private int mRampDownDuration;
+ private float mTargetVelocityX;
+ private float mTargetVelocityY;
+
+ private long mStartTime;
+
+ private long mDeltaTime;
+ private int mDeltaX;
+ private int mDeltaY;
+
+ private long mStopTime;
+ private float mStopValue;
+ private int mEffectiveRampDown;
+
+ /**
+ * Creates a new ramp-up scroller that reaches full velocity after a
+ * specified duration.
+ */
+ public ClampedScroller() {
+ mStartTime = Long.MIN_VALUE;
+ mStopTime = -1;
+ mDeltaTime = 0;
+ mDeltaX = 0;
+ mDeltaY = 0;
+ }
+
+ public void setRampUpDuration(int durationMillis) {
+ mRampUpDuration = durationMillis;
+ }
+
+ public void setRampDownDuration(int durationMillis) {
+ mRampDownDuration = durationMillis;
+ }
+
+ /**
+ * Starts the scroller at the current animation time.
+ */
+ public void start() {
+ mStartTime = AnimationUtils.currentAnimationTimeMillis();
+ mStopTime = -1;
+ mDeltaTime = mStartTime;
+ mStopValue = 0.5f;
+ mDeltaX = 0;
+ mDeltaY = 0;
+ }
+
+ /**
+ * Stops the scroller at the current animation time.
+ */
+ public void requestStop() {
+ final long currentTime = AnimationUtils.currentAnimationTimeMillis();
+ mEffectiveRampDown = constrain((int) (currentTime - mStartTime), 0, mRampDownDuration);
+ mStopValue = getValueAt(currentTime);
+ mStopTime = currentTime;
+ }
+
+ public boolean isFinished() {
+ return mStopTime > 0
+ && AnimationUtils.currentAnimationTimeMillis() > mStopTime + mEffectiveRampDown;
+ }
+
+ private float getValueAt(long currentTime) {
+ if (currentTime < mStartTime) {
+ return 0f;
+ } else if (mStopTime < 0 || currentTime < mStopTime) {
+ final long elapsedSinceStart = currentTime - mStartTime;
+ return 0.5f * constrain(elapsedSinceStart / (float) mRampUpDuration, 0, 1);
+ } else {
+ final long elapsedSinceEnd = currentTime - mStopTime;
+ return (1 - mStopValue) + mStopValue
+ * constrain(elapsedSinceEnd / (float) mEffectiveRampDown, 0, 1);
+ }
+ }
+
+ /**
+ * Interpolates the value along a parabolic curve corresponding to the equation
+ * <code>y = -4x * (x-1)</code>.
+ *
+ * @param value The value to interpolate, between 0 and 1.
+ * @return the interpolated value, between 0 and 1.
+ */
+ private float interpolateValue(float value) {
+ return -4 * value * value + 4 * value;
+ }
+
+ /**
+ * Computes the current scroll deltas. This usually only be called after
+ * starting the scroller with {@link #start()}.
+ *
+ * @see #getDeltaX()
+ * @see #getDeltaY()
+ */
+ public void computeScrollDelta() {
+ if (mDeltaTime == 0) {
+ throw new RuntimeException("Cannot compute scroll delta before calling start()");
+ }
+
+ final long currentTime = AnimationUtils.currentAnimationTimeMillis();
+ final float value = getValueAt(currentTime);
+ final float scale = interpolateValue(value);
+ final long elapsedSinceDelta = currentTime - mDeltaTime;
+
+ mDeltaTime = currentTime;
+ mDeltaX = (int) (elapsedSinceDelta * scale * mTargetVelocityX);
+ mDeltaY = (int) (elapsedSinceDelta * scale * mTargetVelocityY);
+ }
+
+ /**
+ * Sets the target velocity for this scroller.
+ *
+ * @param x The target X velocity in pixels per millisecond.
+ * @param y The target Y velocity in pixels per millisecond.
+ */
+ public void setTargetVelocity(float x, float y) {
+ mTargetVelocityX = x;
+ mTargetVelocityY = y;
+ }
+
+ public int getHorizontalDirection() {
+ return (int) (mTargetVelocityX / Math.abs(mTargetVelocityX));
+ }
+
+ public int getVerticalDirection() {
+ return (int) (mTargetVelocityY / Math.abs(mTargetVelocityY));
+ }
+
+ /**
+ * The distance traveled in the X-coordinate computed by the last call
+ * to {@link #computeScrollDelta()}.
+ */
+ public int getDeltaX() {
+ return mDeltaX;
+ }
+
+ /**
+ * The distance traveled in the Y-coordinate computed by the last call
+ * to {@link #computeScrollDelta()}.
+ */
+ public int getDeltaY() {
+ return mDeltaY;
+ }
+ }
+}
\ No newline at end of file