File	Doc	Category	Size	Date	Package
AutoScrollHelper.java	API Doc	Android 5.1 API	33325	Thu Mar 12 22:22:56 GMT 2015	android.support.v4.widget

AutoScrollHelper

• java.lang.Object

Fields Summary
public static final float	RELATIVE_UNSPECIFIED 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	NO_MAX 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_MIN 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 int	EDGE_TYPE_INSIDE Edge type that specifies an activation area starting at the view bounds and extending inward. Moving outside the view bounds will stop scrolling.
public static final int	EDGE_TYPE_INSIDE_EXTEND 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.
public static final int	EDGE_TYPE_OUTSIDE Edge type that specifies an activation area starting at the view bounds and extending outward. Moving inside the view bounds will stop scrolling.
private static final int	HORIZONTAL
private static final int	VERTICAL
private final ClampedScroller	mScroller Scroller used to control acceleration toward maximum velocity.
private final android.view.animation.Interpolator	mEdgeInterpolator Interpolator used to scale velocity with touch position.
private final android.view.View	mTarget The view to auto-scroll. Might not be the source of touch events.
private Runnable	mRunnable Runnable used to animate scrolling.
private float[]	mRelativeEdges Edge insets used to activate auto-scrolling.
private float[]	mMaximumEdges Clamping values for edge insets used to activate auto-scrolling.
private int	mEdgeType The type of edge being used.
private int	mActivationDelay Delay after entering an activation edge before auto-scrolling begins.
private float[]	mRelativeVelocity Relative scrolling velocity at maximum edge distance.
private float[]	mMinimumVelocity Clamping values used for scrolling velocity.
private float[]	mMaximumVelocity Clamping values used for scrolling velocity.
private boolean	mAlreadyDelayed Whether to start activation immediately.
private boolean	mNeedsReset Whether to reset the scroller start time on the next animation.
private boolean	mNeedsCancel Whether to send a cancel motion event to the target view.
private boolean	mAnimating Whether the auto-scroller is actively scrolling.
private boolean	mEnabled Whether the auto-scroller is enabled.
private boolean	mExclusive Whether the auto-scroller consumes events when scrolling.
private static final int	DEFAULT_EDGE_TYPE
private static final int	DEFAULT_MINIMUM_VELOCITY_DIPS
private static final int	DEFAULT_MAXIMUM_VELOCITY_DIPS
private static final float	DEFAULT_MAXIMUM_EDGE
private static final float	DEFAULT_RELATIVE_EDGE
private static final float	DEFAULT_RELATIVE_VELOCITY
private static final int	DEFAULT_ACTIVATION_DELAY
private static final int	DEFAULT_RAMP_UP_DURATION
private static final int	DEFAULT_RAMP_DOWN_DURATION

Constructors Summary

public AutoScrollHelper(android.view.View target) Creates a new helper for scrolling the specified target view. The resulting helper may be configured by chaining setter calls and should be set as a touch listener on the target view. 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. 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);

Methods Summary
public abstract boolean	canTargetScrollHorizontally(int direction) 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	canTargetScrollVertically(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.
private void	cancelTargetTouch() Sends a {@link MotionEvent#ACTION_CANCEL} event to the target view, canceling any ongoing touch events. final long eventTime = SystemClock.uptimeMillis(); final MotionEvent cancel = MotionEvent.obtain( eventTime, eventTime, MotionEvent.ACTION_CANCEL, 0, 0, 0); mTarget.onTouchEvent(cancel); cancel.recycle();
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); }
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; }
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 float	getEdgeValue(float relativeValue, float size, float maxValue, float current) 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. // 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);
public boolean	isEnabled() return True if this helper is enabled and responding to touch events. return mEnabled;
public boolean	isExclusive() 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) return mExclusive;
public boolean	onTouch(android.view.View v, android.view.MotionEvent event) Handles touch events by activating automatic scrolling, adjusting scroll velocity, or stopping. 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. 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;
private void	requestStop() 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. 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(); }
public abstract void	scrollTargetBy(int deltaX, int deltaY) 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 android.support.v4.widget.AutoScrollHelper	setActivationDelay(int delayMillis) Sets the delay after entering an activation edge before activation of auto-scrolling. By default, the activation delay is set to {@link ViewConfiguration#getTapTimeout()}. 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. mActivationDelay = delayMillis; return this;
public android.support.v4.widget.AutoScrollHelper	setEdgeType(int type) Sets the activation edge type, one of: {@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. {@link #EDGE_TYPE_INSIDE_EXTEND} for inside edges that continued to scroll when touch moves outside the bounds of the host view. {@link #EDGE_TYPE_OUTSIDE} for edges that only respond to touches that move outside the bounds of the host view. param type The type of edge to use. return The scroll helper, which may used to chain setter calls. mEdgeType = type; return this;
public android.support.v4.widget.AutoScrollHelper	setEnabled(boolean enabled) 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. if (mEnabled && !enabled) { requestStop(); } mEnabled = enabled; return this;
public android.support.v4.widget.AutoScrollHelper	setExclusive(boolean exclusive) Enables or disables exclusive handling of touch events during scrolling. By default, exclusive handling is disabled and the target view receives all touch events. 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. mExclusive = exclusive; return this;
public android.support.v4.widget.AutoScrollHelper	setMaximumEdges(float horizontalMax, float verticalMax) Sets the absolute maximum edge size. 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. mMaximumEdges[HORIZONTAL] = horizontalMax; mMaximumEdges[VERTICAL] = verticalMax; return this;
public android.support.v4.widget.AutoScrollHelper	setMaximumVelocity(float horizontalMax, float verticalMax) Sets the absolute maximum scrolling velocity. 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. mMaximumVelocity[HORIZONTAL] = horizontalMax / 1000f; mMaximumVelocity[VERTICAL] = verticalMax / 1000f; return this;
public android.support.v4.widget.AutoScrollHelper	setMinimumVelocity(float horizontalMin, float verticalMin) Sets the absolute minimum scrolling velocity. 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. mMinimumVelocity[HORIZONTAL] = horizontalMin / 1000f; mMinimumVelocity[VERTICAL] = verticalMin / 1000f; return this;
public android.support.v4.widget.AutoScrollHelper	setRampDownDuration(int durationMillis) Sets the amount of time after de-activation of auto-scrolling that is takes to slow to a stop. 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. mScroller.setRampDownDuration(durationMillis); return this;
public android.support.v4.widget.AutoScrollHelper	setRampUpDuration(int durationMillis) Sets the amount of time after activation of auto-scrolling that is takes to reach target velocity for the current touch position. 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. mScroller.setRampUpDuration(durationMillis); return this;
public android.support.v4.widget.AutoScrollHelper	setRelativeEdges(float horizontal, float vertical) Sets the activation edge size relative to the host view's dimensions. 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. mRelativeEdges[HORIZONTAL] = horizontal; mRelativeEdges[VERTICAL] = vertical; return this;
public android.support.v4.widget.AutoScrollHelper	setRelativeVelocity(float horizontal, float vertical) Sets the target scrolling velocity relative to the host view's dimensions. 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. mRelativeVelocity[HORIZONTAL] = horizontal / 1000f; mRelativeVelocity[VERTICAL] = vertical / 1000f; return this;
private boolean	shouldAnimate() return whether the target is able to scroll in the requested direction final ClampedScroller scroller = mScroller; final int verticalDirection = scroller.getVerticalDirection(); final int horizontalDirection = scroller.getHorizontalDirection(); return verticalDirection != 0 && canTargetScrollVertically(verticalDirection) || horizontalDirection != 0 && canTargetScrollHorizontally(horizontalDirection);
private void	startAnimating() Starts the scroll animation. 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;