chrome/android/java/src/org/chromium/chrome/browser/widget/bottomsheet/BottomSheetSwipeDetector.java - chromium/src - Git at Google

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 package org.chromium.chrome.browser.widget.bottomsheet;

 import android.content.Context;
 import android.view.GestureDetector;
 import android.view.MotionEvent;
 import android.view.VelocityTracker;

 import org.chromium.base.ThreadUtils;
 import org.chromium.chrome.browser.util.MathUtils;

 /**
  * A class that determines whether a sequence of motion events is a valid swipe in the context of a
  * bottom sheet. The {@link SwipeableBottomSheet} that this class is built with provides information
  * useful to determining if a swipe is valid. This class does not move the sheet itself, it only
  * provides information on if/where it should move and whether it should animate. The
  * {@link SwipeableBottomSheet} is responsible for applying the changes to the relevant views. Each
  * swipe or fling is converted into a sequence of calls to
  * {@link SwipeableBottomSheet#setSheetOffset(float, boolean)}.
  */
 public class BottomSheetSwipeDetector extends GestureDetector.SimpleOnGestureListener {
     /** The minimum y/x ratio that a scroll must have to be considered vertical. */
     private static final float MIN_VERTICAL_SCROLL_SLOPE = 2.0f;

     /**
      * The base duration of the settling animation of the sheet. 218 ms is a spec for material
      * design (this is the minimum time a user is guaranteed to pay attention to something).
      */
     public static final long BASE_ANIMATION_DURATION_MS = 218;

     /** For detecting scroll and fling events on the bottom sheet. */
     private final GestureDetector mGestureDetector;

     /** An interface for retrieving information from a bottom sheet. */
     private final SwipeableBottomSheet mSheetDelegate;

     /** Track the velocity of the user's scrolls to determine up or down direction. */
     private VelocityTracker mVelocityTracker;

     /** Whether or not the user is scrolling the bottom sheet. */
     private boolean mIsScrolling;

     /**
      * An interface for views that are swipable from the bottom of the screen. This interface
      * assumes that any part of the bottom sheet visible at the peeking state is the toolbar.
      */
     public interface SwipeableBottomSheet {
         /**
          * @return Whether the content being shown in the sheet is scrolled to the top.
          */
         boolean isContentScrolledToTop();

         /**
          * Gets the sheet's offset from the bottom of the screen.
          * @return The sheet's distance from the bottom of the screen.
          */
         float getCurrentOffsetPx();

         /**
          * Gets the minimum offset of the bottom sheet.
          * @return The min offset.
          */
         float getMinOffsetPx();

         /**
          * Gets the maximum offset of the bottom sheet.
          * @return The max offset.
          */
         float getMaxOffsetPx();

         /**
          * @param event The motion event to test.
          * @return Whether the provided motion event is inside the toolbar.
          */
         boolean isTouchEventInToolbar(MotionEvent event);

         /**
          * Check if a particular gesture or touch event should move the bottom sheet when in peeking
          * mode. If the "chrome-home-swipe-logic" flag is not set this function returns true.
          * @param initialDownEvent The event that started the scroll.
          * @param currentEvent The current motion event.
          * @return True if the bottom sheet should move.
          */
         boolean shouldGestureMoveSheet(MotionEvent initialDownEvent, MotionEvent currentEvent);

         /**
          * Set the sheet's offset.
          * @param offset The target offset.
          * @param shouldAnimate Whether the sheet should animate to that position.
          */
         void setSheetOffset(float offset, boolean shouldAnimate);
     }

     /**
      * This class is responsible for detecting swipe and scroll events on the bottom sheet or
      * ignoring them when appropriate.
      */
     private class SwipeGestureListener extends GestureDetector.SimpleOnGestureListener {
         @Override
         public boolean onDown(MotionEvent e) {
             if (e == null) return false;
             return mSheetDelegate.shouldGestureMoveSheet(e, e);
         }

         @Override
         public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
             if (e1 == null || !mSheetDelegate.shouldGestureMoveSheet(e1, e2)) return false;

             // Only start scrolling if the scroll is up or down. If the user is already scrolling,
             // continue moving the sheet.
             float slope = Math.abs(distanceX) > 0f ? Math.abs(distanceY) / Math.abs(distanceX)
                                                    : MIN_VERTICAL_SCROLL_SLOPE;
             if (!mIsScrolling && slope < MIN_VERTICAL_SCROLL_SLOPE) {
                 mVelocityTracker.clear();
                 return false;
             }

             mVelocityTracker.addMovement(e2);

             boolean isSheetInMaxPosition = MathUtils.areFloatsEqual(
                     mSheetDelegate.getCurrentOffsetPx(), mSheetDelegate.getMaxOffsetPx());

             // Allow the bottom sheet's content to be scrolled up without dragging the sheet down.
             if (!mSheetDelegate.isTouchEventInToolbar(e2) && isSheetInMaxPosition
                     && !mSheetDelegate.isContentScrolledToTop()) {
                 return false;
             }

             // If the sheet is in the max position, don't move the sheet if the scroll is upward.
             // Instead, allow the sheet's content to handle it if it needs to.
             if (isSheetInMaxPosition && distanceY > 0) return false;

             boolean isSheetInMinPosition = MathUtils.areFloatsEqual(
                     mSheetDelegate.getCurrentOffsetPx(), mSheetDelegate.getMinOffsetPx());

             // Similarly, if the sheet is in the min position, don't move if the scroll is downward.
             if (isSheetInMinPosition && distanceY < 0) return false;

             float newOffset = mSheetDelegate.getCurrentOffsetPx() + distanceY;

             mIsScrolling = true;

             mSheetDelegate.setSheetOffset(
                     MathUtils.clamp(newOffset, mSheetDelegate.getMinOffsetPx(),
                             mSheetDelegate.getMaxOffsetPx()),
                     false);

             return true;
         }

         @Override
         public void onLongPress(MotionEvent e) {
             mIsScrolling = false;
         }

         @Override
         public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
             if (e1 == null || !mSheetDelegate.shouldGestureMoveSheet(e1, e2) || !mIsScrolling) {
                 return false;
             }

             mIsScrolling = false;

             float newOffset = mSheetDelegate.getCurrentOffsetPx() + getFlingDistance(-velocityY);

             mSheetDelegate.setSheetOffset(
                     MathUtils.clamp(newOffset, mSheetDelegate.getMinOffsetPx(),
                             mSheetDelegate.getMaxOffsetPx()),
                     true);

             return true;
         }
     }

     /**
      * Default constructor.
      * @param context A context for the GestureDetector this class uses.
      * @param delegate A SwipeableBottomSheet that processes swipes.
      */
     public BottomSheetSwipeDetector(Context context, SwipeableBottomSheet delegate) {
         mGestureDetector = new GestureDetector(
                 context, new SwipeGestureListener(), ThreadUtils.getUiThreadHandler());
         mGestureDetector.setIsLongpressEnabled(true);

         mSheetDelegate = delegate;
         mVelocityTracker = VelocityTracker.obtain();
     }

     /**
      * Test whether or not a motion event should be intercepted by this class.
      * @param e The motion event to test.
      * @return Whether or not the event was intercepted.
      */
     public boolean onInterceptTouchEvent(MotionEvent e) {
         // The incoming motion event may have been adjusted by the view sending it down. Create a
         // motion event with the raw (x, y) coordinates of the original so the gesture detector
         // functions properly.
         mGestureDetector.onTouchEvent(createRawMotionEvent(e));

         return mIsScrolling;
     }

     /**
      * Process a motion event.
      * @param e The motion event to process.
      * @return Whether or not the motion event was used.
      */
     public boolean onTouchEvent(MotionEvent e) {
         // The down event is interpreted above in onInterceptTouchEvent, it does not need to be
         // interpreted a second time.
         if (e.getActionMasked() != MotionEvent.ACTION_DOWN) {
             mGestureDetector.onTouchEvent(createRawMotionEvent(e));
         }

         // If the user is scrolling and the event is a cancel or up action, update scroll state and
         // return. Fling should have already cleared the mIsScrolling flag, the following is for the
         // non-fling release.
         if (mIsScrolling
                 && (e.getActionMasked() == MotionEvent.ACTION_UP
                            || e.getActionMasked() == MotionEvent.ACTION_CANCEL)) {
             mIsScrolling = false;

             mVelocityTracker.computeCurrentVelocity(1000);

             float newOffset = mSheetDelegate.getCurrentOffsetPx()
                     + getFlingDistance(-mVelocityTracker.getYVelocity());

             mSheetDelegate.setSheetOffset(
                     MathUtils.clamp(newOffset, mSheetDelegate.getMinOffsetPx(),
                             mSheetDelegate.getMaxOffsetPx()),
                     true);
         }

         return true;
     }

     /**
      * @return Whether or not a gesture is currently being detected as a scroll.
      */
     public boolean isScrolling() {
         return mIsScrolling;
     }

     /**
      * Creates an unadjusted version of a MotionEvent.
      * @param e The original event.
      * @return The unadjusted version of the event.
      */
     private MotionEvent createRawMotionEvent(MotionEvent e) {
         MotionEvent rawEvent = MotionEvent.obtain(e);
         rawEvent.setLocation(e.getRawX(), e.getRawY());
         return rawEvent;
     }

     /**
      * Gets the distance of a fling based on the velocity and the base animation time. This formula
      * assumes the deceleration curve is quadratic (t^2), hence the displacement formula should be:
      * displacement = initialVelocity * duration / 2.
      * @param velocity The velocity of the fling.
      * @return The distance the fling would cover.
      */
     private float getFlingDistance(float velocity) {
         // This includes conversion from seconds to ms.
         return velocity * BASE_ANIMATION_DURATION_MS / 2000f;
     }
 }
	// Copyright 2017 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	package org.chromium.chrome.browser.widget.bottomsheet;

	import android.content.Context;
	import android.view.GestureDetector;
	import android.view.MotionEvent;
	import android.view.VelocityTracker;

	import org.chromium.base.ThreadUtils;
	import org.chromium.chrome.browser.util.MathUtils;

	/**
	* A class that determines whether a sequence of motion events is a valid swipe in the context of a
	* bottom sheet. The {@link SwipeableBottomSheet} that this class is built with provides information
	* useful to determining if a swipe is valid. This class does not move the sheet itself, it only
	* provides information on if/where it should move and whether it should animate. The
	* {@link SwipeableBottomSheet} is responsible for applying the changes to the relevant views. Each
	* swipe or fling is converted into a sequence of calls to
	* {@link SwipeableBottomSheet#setSheetOffset(float, boolean)}.
	*/
	public class BottomSheetSwipeDetector extends GestureDetector.SimpleOnGestureListener {
	/** The minimum y/x ratio that a scroll must have to be considered vertical. */
	private static final float MIN_VERTICAL_SCROLL_SLOPE = 2.0f;

	/**
	* The base duration of the settling animation of the sheet. 218 ms is a spec for material
	* design (this is the minimum time a user is guaranteed to pay attention to something).
	*/
	public static final long BASE_ANIMATION_DURATION_MS = 218;

	/** For detecting scroll and fling events on the bottom sheet. */
	private final GestureDetector mGestureDetector;

	/** An interface for retrieving information from a bottom sheet. */
	private final SwipeableBottomSheet mSheetDelegate;

	/** Track the velocity of the user's scrolls to determine up or down direction. */
	private VelocityTracker mVelocityTracker;

	/** Whether or not the user is scrolling the bottom sheet. */
	private boolean mIsScrolling;

	/**
	* An interface for views that are swipable from the bottom of the screen. This interface
	* assumes that any part of the bottom sheet visible at the peeking state is the toolbar.
	*/
	public interface SwipeableBottomSheet {
	/**
	* @return Whether the content being shown in the sheet is scrolled to the top.
	*/
	boolean isContentScrolledToTop();

	/**
	* Gets the sheet's offset from the bottom of the screen.
	* @return The sheet's distance from the bottom of the screen.
	*/
	float getCurrentOffsetPx();

	/**
	* Gets the minimum offset of the bottom sheet.
	* @return The min offset.
	*/
	float getMinOffsetPx();

	/**
	* Gets the maximum offset of the bottom sheet.
	* @return The max offset.
	*/
	float getMaxOffsetPx();

	/**
	* @param event The motion event to test.
	* @return Whether the provided motion event is inside the toolbar.
	*/
	boolean isTouchEventInToolbar(MotionEvent event);

	/**
	* Check if a particular gesture or touch event should move the bottom sheet when in peeking
	* mode. If the "chrome-home-swipe-logic" flag is not set this function returns true.
	* @param initialDownEvent The event that started the scroll.
	* @param currentEvent The current motion event.
	* @return True if the bottom sheet should move.
	*/
	boolean shouldGestureMoveSheet(MotionEvent initialDownEvent, MotionEvent currentEvent);

	/**
	* Set the sheet's offset.
	* @param offset The target offset.
	* @param shouldAnimate Whether the sheet should animate to that position.
	*/
	void setSheetOffset(float offset, boolean shouldAnimate);
	}

	/**
	* This class is responsible for detecting swipe and scroll events on the bottom sheet or
	* ignoring them when appropriate.
	*/
	private class SwipeGestureListener extends GestureDetector.SimpleOnGestureListener {
	@Override
	public boolean onDown(MotionEvent e) {
	if (e == null) return false;
	return mSheetDelegate.shouldGestureMoveSheet(e, e);
	}

	@Override
	public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
	if (e1 == null \|\| !mSheetDelegate.shouldGestureMoveSheet(e1, e2)) return false;

	// Only start scrolling if the scroll is up or down. If the user is already scrolling,
	// continue moving the sheet.
	float slope = Math.abs(distanceX) > 0f ? Math.abs(distanceY) / Math.abs(distanceX)
	: MIN_VERTICAL_SCROLL_SLOPE;
	if (!mIsScrolling && slope < MIN_VERTICAL_SCROLL_SLOPE) {
	mVelocityTracker.clear();
	return false;
	}

	mVelocityTracker.addMovement(e2);

	boolean isSheetInMaxPosition = MathUtils.areFloatsEqual(
	mSheetDelegate.getCurrentOffsetPx(), mSheetDelegate.getMaxOffsetPx());

	// Allow the bottom sheet's content to be scrolled up without dragging the sheet down.
	if (!mSheetDelegate.isTouchEventInToolbar(e2) && isSheetInMaxPosition
	&& !mSheetDelegate.isContentScrolledToTop()) {
	return false;
	}

	// If the sheet is in the max position, don't move the sheet if the scroll is upward.
	// Instead, allow the sheet's content to handle it if it needs to.
	if (isSheetInMaxPosition && distanceY > 0) return false;

	boolean isSheetInMinPosition = MathUtils.areFloatsEqual(
	mSheetDelegate.getCurrentOffsetPx(), mSheetDelegate.getMinOffsetPx());

	// Similarly, if the sheet is in the min position, don't move if the scroll is downward.
	if (isSheetInMinPosition && distanceY < 0) return false;

	float newOffset = mSheetDelegate.getCurrentOffsetPx() + distanceY;

	mIsScrolling = true;

	mSheetDelegate.setSheetOffset(
	MathUtils.clamp(newOffset, mSheetDelegate.getMinOffsetPx(),
	mSheetDelegate.getMaxOffsetPx()),
	false);

	return true;
	}

	@Override
	public void onLongPress(MotionEvent e) {
	mIsScrolling = false;
	}

	@Override
	public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
	if (e1 == null \|\| !mSheetDelegate.shouldGestureMoveSheet(e1, e2) \|\| !mIsScrolling) {
	return false;
	}

	mIsScrolling = false;

	float newOffset = mSheetDelegate.getCurrentOffsetPx() + getFlingDistance(-velocityY);

	mSheetDelegate.setSheetOffset(
	MathUtils.clamp(newOffset, mSheetDelegate.getMinOffsetPx(),
	mSheetDelegate.getMaxOffsetPx()),
	true);

	return true;
	}
	}

	/**
	* Default constructor.
	* @param context A context for the GestureDetector this class uses.
	* @param delegate A SwipeableBottomSheet that processes swipes.
	*/
	public BottomSheetSwipeDetector(Context context, SwipeableBottomSheet delegate) {
	mGestureDetector = new GestureDetector(
	context, new SwipeGestureListener(), ThreadUtils.getUiThreadHandler());
	mGestureDetector.setIsLongpressEnabled(true);

	mSheetDelegate = delegate;
	mVelocityTracker = VelocityTracker.obtain();
	}

	/**
	* Test whether or not a motion event should be intercepted by this class.
	* @param e The motion event to test.
	* @return Whether or not the event was intercepted.
	*/
	public boolean onInterceptTouchEvent(MotionEvent e) {
	// The incoming motion event may have been adjusted by the view sending it down. Create a
	// motion event with the raw (x, y) coordinates of the original so the gesture detector
	// functions properly.
	mGestureDetector.onTouchEvent(createRawMotionEvent(e));

	return mIsScrolling;
	}

	/**
	* Process a motion event.
	* @param e The motion event to process.
	* @return Whether or not the motion event was used.
	*/
	public boolean onTouchEvent(MotionEvent e) {
	// The down event is interpreted above in onInterceptTouchEvent, it does not need to be
	// interpreted a second time.
	if (e.getActionMasked() != MotionEvent.ACTION_DOWN) {
	mGestureDetector.onTouchEvent(createRawMotionEvent(e));
	}

	// If the user is scrolling and the event is a cancel or up action, update scroll state and
	// return. Fling should have already cleared the mIsScrolling flag, the following is for the
	// non-fling release.
	if (mIsScrolling
	&& (e.getActionMasked() == MotionEvent.ACTION_UP
	\|\| e.getActionMasked() == MotionEvent.ACTION_CANCEL)) {
	mIsScrolling = false;

	mVelocityTracker.computeCurrentVelocity(1000);

	float newOffset = mSheetDelegate.getCurrentOffsetPx()
	+ getFlingDistance(-mVelocityTracker.getYVelocity());

	mSheetDelegate.setSheetOffset(
	MathUtils.clamp(newOffset, mSheetDelegate.getMinOffsetPx(),
	mSheetDelegate.getMaxOffsetPx()),
	true);
	}

	return true;
	}

	/**
	* @return Whether or not a gesture is currently being detected as a scroll.
	*/
	public boolean isScrolling() {
	return mIsScrolling;
	}

	/**
	* Creates an unadjusted version of a MotionEvent.
	* @param e The original event.
	* @return The unadjusted version of the event.
	*/
	private MotionEvent createRawMotionEvent(MotionEvent e) {
	MotionEvent rawEvent = MotionEvent.obtain(e);
	rawEvent.setLocation(e.getRawX(), e.getRawY());
	return rawEvent;
	}

	/**
	* Gets the distance of a fling based on the velocity and the base animation time. This formula
	* assumes the deceleration curve is quadratic (t^2), hence the displacement formula should be:
	* displacement = initialVelocity * duration / 2.
	* @param velocity The velocity of the fling.
	* @return The distance the fling would cover.
	*/
	private float getFlingDistance(float velocity) {
	// This includes conversion from seconds to ms.
	return velocity * BASE_ANIMATION_DURATION_MS / 2000f;
	}
	}