Add overscroll support for QS.

Add SwipeDetector and OverScroll from Launcher3 to QS to acheive the
same overscroll behavior.

Bug: 70799330
Test: visual
Change-Id: I3b83ba4e45bd090bfe5866b3320a1cbd83fce6e0

packages/SystemUI/src/com/android/systemui/qs/QSScrollLayout.java

@@ -14,8 +14,11 @@
 
 package com.android.systemui.qs;
 
+import android.animation.ObjectAnimator;
 import android.content.Context;
+import android.graphics.Canvas;
 import android.support.v4.widget.NestedScrollView;
+import android.util.Property;
 import android.view.MotionEvent;
 import android.view.View;
 import android.view.ViewConfiguration;
@@ -23,6 +26,8 @@ import android.view.ViewParent;
 import android.widget.LinearLayout;
 
 import com.android.systemui.R;
+import com.android.systemui.qs.touch.OverScroll;
+import com.android.systemui.qs.touch.SwipeDetector;
 
 /**
  * Quick setting scroll view containing the brightness slider and the QS tiles.
@@ -35,6 +40,9 @@ public class QSScrollLayout extends NestedScrollView {
     private final int mTouchSlop;
     private final int mFooterHeight;
     private int mLastMotionY;
+    private final SwipeDetector mSwipeDetector;
+    private final OverScrollHelper mOverScrollHelper;
+    private float mContentTranslationY;
 
     public QSScrollLayout(Context context, View... children) {
         super(context);
@@ -49,15 +57,19 @@ public class QSScrollLayout extends NestedScrollView {
             linearLayout.addView(view);
         }
         addView(linearLayout);
+        setOverScrollMode(OVER_SCROLL_NEVER);
+        mOverScrollHelper = new OverScrollHelper();
+        mSwipeDetector = new SwipeDetector(context, mOverScrollHelper, SwipeDetector.VERTICAL);
+        mSwipeDetector.setDetectableScrollConditions(SwipeDetector.DIRECTION_BOTH, true);
     }
 
-
     @Override
     public boolean onInterceptTouchEvent(MotionEvent ev) {
         if (canScrollVertically(1) || canScrollVertically(-1)) {
             return super.onInterceptTouchEvent(ev);
         }
-        return false;
+        mSwipeDetector.onTouchEvent(ev);
+        return super.onInterceptTouchEvent(ev) || mOverScrollHelper.isInOverScroll();
     }
 
     @Override
@@ -65,7 +77,15 @@ public class QSScrollLayout extends NestedScrollView {
         if (canScrollVertically(1) || canScrollVertically(-1)) {
             return super.onTouchEvent(ev);
         }
-        return false;
+        mSwipeDetector.onTouchEvent(ev);
+        return super.onTouchEvent(ev);
+    }
+
+    @Override
+    protected void dispatchDraw(Canvas canvas) {
+        canvas.translate(0, mContentTranslationY);
+        super.dispatchDraw(canvas);
+        canvas.translate(0, -mContentTranslationY);
     }
 
     public boolean shouldIntercept(MotionEvent ev) {
@@ -98,4 +118,81 @@ public class QSScrollLayout extends NestedScrollView {
             parent.requestDisallowInterceptTouchEvent(disallowIntercept);
         }
     }
+
+    private void setContentTranslationY(float contentTranslationY) {
+        mContentTranslationY = contentTranslationY;
+        invalidate();
+    }
+
+    private static final Property<QSScrollLayout, Float> CONTENT_TRANS_Y =
+            new Property<QSScrollLayout, Float>(Float.class, "qsScrollLayoutContentTransY") {
+                @Override
+                public Float get(QSScrollLayout qsScrollLayout) {
+                    return qsScrollLayout.mContentTranslationY;
+                }
+
+                @Override
+                public void set(QSScrollLayout qsScrollLayout, Float y) {
+                    qsScrollLayout.setContentTranslationY(y);
+                }
+            };
+
+    private class OverScrollHelper implements SwipeDetector.Listener {
+        private boolean mIsInOverScroll;
+
+        // We use this value to calculate the actual amount the user has overscrolled.
+        private float mFirstDisplacement = 0;
+
+        @Override
+        public void onDragStart(boolean start) {}
+
+        @Override
+        public boolean onDrag(float displacement, float velocity) {
+            // Only overscroll if the user is scrolling down when they're already at the bottom
+            // or scrolling up when they're already at the top.
+            boolean wasInOverScroll = mIsInOverScroll;
+            mIsInOverScroll = (!canScrollVertically(1) && displacement < 0) ||
+                    (!canScrollVertically(-1) && displacement > 0);
+
+            if (wasInOverScroll && !mIsInOverScroll) {
+                // Exit overscroll. This can happen when the user is in overscroll and then
+                // scrolls the opposite way. Note that this causes the reset translation animation
+                // to run while the user is dragging, which feels a bit unnatural.
+                reset();
+            } else if (mIsInOverScroll) {
+                if (Float.compare(mFirstDisplacement, 0) == 0) {
+                    // Because users can scroll before entering overscroll, we need to
+                    // subtract the amount where the user was not in overscroll.
+                    mFirstDisplacement = displacement;
+                }
+                float overscrollY = displacement - mFirstDisplacement;
+                setContentTranslationY(getDampedOverScroll(overscrollY));
+            }
+
+            return mIsInOverScroll;
+        }
+
+        @Override
+        public void onDragEnd(float velocity, boolean fling) {
+            reset();
+        }
+
+        private void reset() {
+            if (Float.compare(mContentTranslationY, 0) != 0) {
+                ObjectAnimator.ofFloat(QSScrollLayout.this, CONTENT_TRANS_Y, 0)
+                        .setDuration(100)
+                        .start();
+            }
+            mIsInOverScroll = false;
+            mFirstDisplacement = 0;
+        }
+
+        public boolean isInOverScroll() {
+            return mIsInOverScroll;
+        }
+
+        private float getDampedOverScroll(float y) {
+            return OverScroll.dampedScroll(y, getHeight());
+        }
+    }
 }

packages/SystemUI/src/com/android/systemui/qs/touch/OverScroll.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2018 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.systemui.qs.touch;
+
+/**
+ * Utility methods for overscroll damping and related effect.
+ *
+ * Copied from packages/apps/Launcher3/src/com/android/launcher3/touch/OverScroll.java
+ */
+public class OverScroll {
+
+    private static final float OVERSCROLL_DAMP_FACTOR = 0.07f;
+
+    /**
+     * This curve determines how the effect of scrolling over the limits of the page diminishes
+     * as the user pulls further and further from the bounds
+     *
+     * @param f The percentage of how much the user has overscrolled.
+     * @return A transformed percentage based on the influence curve.
+     */
+    private static float overScrollInfluenceCurve(float f) {
+        f -= 1.0f;
+        return f * f * f + 1.0f;
+    }
+
+    /**
+     * @param amount The original amount overscrolled.
+     * @param max The maximum amount that the View can overscroll.
+     * @return The dampened overscroll amount.
+     */
+    public static int dampedScroll(float amount, int max) {
+        if (Float.compare(amount, 0) == 0) return 0;
+
+        float f = amount / max;
+        f = f / (Math.abs(f)) * (overScrollInfluenceCurve(Math.abs(f)));
+
+        // Clamp this factor, f, to -1 < f < 1
+        if (Math.abs(f) >= 1) {
+            f /= Math.abs(f);
+        }
+
+        return Math.round(OVERSCROLL_DAMP_FACTOR * f * max);
+    }
+}

packages/SystemUI/src/com/android/systemui/qs/touch/SwipeDetector.java

@@ -0,0 +1,356 @@
+/*
+ * Copyright (C) 2018 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.systemui.qs.touch;
+
+import static android.view.MotionEvent.INVALID_POINTER_ID;
+
+import android.content.Context;
+import android.graphics.PointF;
+import android.support.annotation.NonNull;
+import android.support.annotation.VisibleForTesting;
+import android.util.Log;
+import android.view.MotionEvent;
+import android.view.ViewConfiguration;
+
+/**
+ * One dimensional scroll/drag/swipe gesture detector.
+ *
+ * Definition of swipe is different from android system in that this detector handles
+ * 'swipe to dismiss', 'swiping up/down a container' but also keeps scrolling state before
+ * swipe action happens
+ *
+ * Copied from packages/apps/Launcher3/src/com/android/launcher3/touch/SwipeDetector.java
+ */
+public class SwipeDetector {
+
+    private static final boolean DBG = false;
+    private static final String TAG = "SwipeDetector";
+
+    private int mScrollConditions;
+    public static final int DIRECTION_POSITIVE = 1 << 0;
+    public static final int DIRECTION_NEGATIVE = 1 << 1;
+    public static final int DIRECTION_BOTH = DIRECTION_NEGATIVE | DIRECTION_POSITIVE;
+
+    private static final float ANIMATION_DURATION = 1200;
+
+    protected int mActivePointerId = INVALID_POINTER_ID;
+
+    /**
+     * The minimum release velocity in pixels per millisecond that triggers fling..
+     */
+    public static final float RELEASE_VELOCITY_PX_MS = 1.0f;
+
+    /**
+     * The time constant used to calculate dampening in the low-pass filter of scroll velocity.
+     * Cutoff frequency is set at 10 Hz.
+     */
+    public static final float SCROLL_VELOCITY_DAMPENING_RC = 1000f / (2f * (float) Math.PI * 10);
+
+    /* Scroll state, this is set to true during dragging and animation. */
+    private ScrollState mState = ScrollState.IDLE;
+
+    enum ScrollState {
+        IDLE,
+        DRAGGING,      // onDragStart, onDrag
+        SETTLING       // onDragEnd
+    }
+
+    public static abstract class Direction {
+
+        abstract float getDisplacement(MotionEvent ev, int pointerIndex, PointF refPoint);
+
+        /**
+         * Distance in pixels a touch can wander before we think the user is scrolling.
+         */
+        abstract float getActiveTouchSlop(MotionEvent ev, int pointerIndex, PointF downPos);
+    }
+
+    public static final Direction VERTICAL = new Direction() {
+
+        @Override
+        float getDisplacement(MotionEvent ev, int pointerIndex, PointF refPoint) {
+            return ev.getY(pointerIndex) - refPoint.y;
+        }
+
+        @Override
+        float getActiveTouchSlop(MotionEvent ev, int pointerIndex, PointF downPos) {
+            return Math.abs(ev.getX(pointerIndex) - downPos.x);
+        }
+    };
+
+    public static final Direction HORIZONTAL = new Direction() {
+
+        @Override
+        float getDisplacement(MotionEvent ev, int pointerIndex, PointF refPoint) {
+            return ev.getX(pointerIndex) - refPoint.x;
+        }
+
+        @Override
+        float getActiveTouchSlop(MotionEvent ev, int pointerIndex, PointF downPos) {
+            return Math.abs(ev.getY(pointerIndex) - downPos.y);
+        }
+    };
+
+    //------------------- ScrollState transition diagram -----------------------------------
+    //
+    // IDLE ->      (mDisplacement > mTouchSlop) -> DRAGGING
+    // DRAGGING -> (MotionEvent#ACTION_UP, MotionEvent#ACTION_CANCEL) -> SETTLING
+    // SETTLING -> (MotionEvent#ACTION_DOWN) -> DRAGGING
+    // SETTLING -> (View settled) -> IDLE
+
+    private void setState(ScrollState newState) {
+        if (DBG) {
+            Log.d(TAG, "setState:" + mState + "->" + newState);
+        }
+        // onDragStart and onDragEnd is reported ONLY on state transition
+        if (newState == ScrollState.DRAGGING) {
+            initializeDragging();
+            if (mState == ScrollState.IDLE) {
+                reportDragStart(false /* recatch */);
+            } else if (mState == ScrollState.SETTLING) {
+                reportDragStart(true /* recatch */);
+            }
+        }
+        if (newState == ScrollState.SETTLING) {
+            reportDragEnd();
+        }
+
+        mState = newState;
+    }
+
+    public boolean isDraggingOrSettling() {
+        return mState == ScrollState.DRAGGING || mState == ScrollState.SETTLING;
+    }
+
+    /**
+     * There's no touch and there's no animation.
+     */
+    public boolean isIdleState() {
+        return mState == ScrollState.IDLE;
+    }
+
+    public boolean isSettlingState() {
+        return mState == ScrollState.SETTLING;
+    }
+
+    public boolean isDraggingState() {
+        return mState == ScrollState.DRAGGING;
+    }
+
+    private final PointF mDownPos = new PointF();
+    private final PointF mLastPos = new PointF();
+    private final Direction mDir;
+
+    private final float mTouchSlop;
+
+    /* Client of this gesture detector can register a callback. */
+    private final Listener mListener;
+
+    private long mCurrentMillis;
+
+    private float mVelocity;
+    private float mLastDisplacement;
+    private float mDisplacement;
+
+    private float mSubtractDisplacement;
+    private boolean mIgnoreSlopWhenSettling;
+
+    public interface Listener {
+        void onDragStart(boolean start);
+
+        boolean onDrag(float displacement, float velocity);
+
+        void onDragEnd(float velocity, boolean fling);
+    }
+
+    public SwipeDetector(@NonNull Context context, @NonNull Listener l, @NonNull Direction dir) {
+        this(ViewConfiguration.get(context).getScaledTouchSlop(), l, dir);
+    }
+
+    @VisibleForTesting
+    protected SwipeDetector(float touchSlope, @NonNull Listener l, @NonNull Direction dir) {
+        mTouchSlop = touchSlope;
+        mListener = l;
+        mDir = dir;
+    }
+
+    public void setDetectableScrollConditions(int scrollDirectionFlags, boolean ignoreSlop) {
+        mScrollConditions = scrollDirectionFlags;
+        mIgnoreSlopWhenSettling = ignoreSlop;
+    }
+
+    private boolean shouldScrollStart(MotionEvent ev, int pointerIndex) {
+        // reject cases where the angle or slop condition is not met.
+        if (Math.max(mDir.getActiveTouchSlop(ev, pointerIndex, mDownPos), mTouchSlop)
+                > Math.abs(mDisplacement)) {
+            return false;
+        }
+
+        // Check if the client is interested in scroll in current direction.
+        if (((mScrollConditions & DIRECTION_NEGATIVE) > 0 && mDisplacement > 0) ||
+                ((mScrollConditions & DIRECTION_POSITIVE) > 0 && mDisplacement < 0)) {
+            return true;
+        }
+        return false;
+    }
+
+    public boolean onTouchEvent(MotionEvent ev) {
+        switch (ev.getActionMasked()) {
+            case MotionEvent.ACTION_DOWN:
+                mActivePointerId = ev.getPointerId(0);
+                mDownPos.set(ev.getX(), ev.getY());
+                mLastPos.set(mDownPos);
+                mLastDisplacement = 0;
+                mDisplacement = 0;
+                mVelocity = 0;
+
+                if (mState == ScrollState.SETTLING && mIgnoreSlopWhenSettling) {
+                    setState(ScrollState.DRAGGING);
+                }
+                break;
+            //case MotionEvent.ACTION_POINTER_DOWN:
+            case MotionEvent.ACTION_POINTER_UP:
+                int ptrIdx = ev.getActionIndex();
+                int ptrId = ev.getPointerId(ptrIdx);
+                if (ptrId == mActivePointerId) {
+                    final int newPointerIdx = ptrIdx == 0 ? 1 : 0;
+                    mDownPos.set(
+                            ev.getX(newPointerIdx) - (mLastPos.x - mDownPos.x),
+                            ev.getY(newPointerIdx) - (mLastPos.y - mDownPos.y));
+                    mLastPos.set(ev.getX(newPointerIdx), ev.getY(newPointerIdx));
+                    mActivePointerId = ev.getPointerId(newPointerIdx);
+                }
+                break;
+            case MotionEvent.ACTION_MOVE:
+                int pointerIndex = ev.findPointerIndex(mActivePointerId);
+                if (pointerIndex == INVALID_POINTER_ID) {
+                    break;
+                }
+                mDisplacement = mDir.getDisplacement(ev, pointerIndex, mDownPos);
+                computeVelocity(mDir.getDisplacement(ev, pointerIndex, mLastPos),
+                        ev.getEventTime());
+
+                // handle state and listener calls.
+                if (mState != ScrollState.DRAGGING && shouldScrollStart(ev, pointerIndex)) {
+                    setState(ScrollState.DRAGGING);
+                }
+                if (mState == ScrollState.DRAGGING) {
+                    reportDragging();
+                }
+                mLastPos.set(ev.getX(pointerIndex), ev.getY(pointerIndex));
+                break;
+            case MotionEvent.ACTION_CANCEL:
+            case MotionEvent.ACTION_UP:
+                // These are synthetic events and there is no need to update internal values.
+                if (mState == ScrollState.DRAGGING) {
+                    setState(ScrollState.SETTLING);
+                }
+                break;
+            default:
+                break;
+        }
+        return true;
+    }
+
+    public void finishedScrolling() {
+        setState(ScrollState.IDLE);
+    }
+
+    private boolean reportDragStart(boolean recatch) {
+        mListener.onDragStart(!recatch);
+        if (DBG) {
+            Log.d(TAG, "onDragStart recatch:" + recatch);
+        }
+        return true;
+    }
+
+    private void initializeDragging() {
+        if (mState == ScrollState.SETTLING && mIgnoreSlopWhenSettling) {
+            mSubtractDisplacement = 0;
+        }
+        if (mDisplacement > 0) {
+            mSubtractDisplacement = mTouchSlop;
+        } else {
+            mSubtractDisplacement = -mTouchSlop;
+        }
+    }
+
+    private boolean reportDragging() {
+        if (mDisplacement != mLastDisplacement) {
+            if (DBG) {
+                Log.d(TAG, String.format("onDrag disp=%.1f, velocity=%.1f",
+                        mDisplacement, mVelocity));
+            }
+
+            mLastDisplacement = mDisplacement;
+            return mListener.onDrag(mDisplacement - mSubtractDisplacement, mVelocity);
+        }
+        return true;
+    }
+
+    private void reportDragEnd() {
+        if (DBG) {
+            Log.d(TAG, String.format("onScrollEnd disp=%.1f, velocity=%.1f",
+                    mDisplacement, mVelocity));
+        }
+        mListener.onDragEnd(mVelocity, Math.abs(mVelocity) > RELEASE_VELOCITY_PX_MS);
+
+    }
+
+    /**
+     * Computes the damped velocity.
+     */
+    public float computeVelocity(float delta, long currentMillis) {
+        long previousMillis = mCurrentMillis;
+        mCurrentMillis = currentMillis;
+
+        float deltaTimeMillis = mCurrentMillis - previousMillis;
+        float velocity = (deltaTimeMillis > 0) ? (delta / deltaTimeMillis) : 0;
+        if (Math.abs(mVelocity) < 0.001f) {
+            mVelocity = velocity;
+        } else {
+            float alpha = computeDampeningFactor(deltaTimeMillis);
+            mVelocity = interpolate(mVelocity, velocity, alpha);
+        }
+        return mVelocity;
+    }
+
+    /**
+     * Returns a time-dependent dampening factor using delta time.
+     */
+    private static float computeDampeningFactor(float deltaTime) {
+        return deltaTime / (SCROLL_VELOCITY_DAMPENING_RC + deltaTime);
+    }
+
+    /**
+     * Returns the linear interpolation between two values
+     */
+    private static float interpolate(float from, float to, float alpha) {
+        return (1.0f - alpha) * from + alpha * to;
+    }
+
+    public static long calculateDuration(float velocity, float progressNeeded) {
+        // TODO: make these values constants after tuning.
+        float velocityDivisor = Math.max(2f, Math.abs(0.5f * velocity));
+        float travelDistance = Math.max(0.2f, progressNeeded);
+        long duration = (long) Math.max(100, ANIMATION_DURATION / velocityDivisor * travelDistance);
+        if (DBG) {
+            Log.d(TAG, String.format("calculateDuration=%d, v=%f, d=%f", duration, velocity, progressNeeded));
+        }
+        return duration;
+    }
+}
+