Add tests to SwipeDetector (formerly VerticalPullDetector).

Change-Id: I09ab4f22d7204ad806825ab0d6374c2b9616bf39

1 files changed, 303 insertions, 0 deletions

diff --git a/src/com/android/launcher3/touch/SwipeDetector.java b/src/com/android/launcher3/touch/SwipeDetector.java
new file mode 100644
index 000000000..b47065490
--- /dev/null
+++ b/src/com/android/launcher3/touch/SwipeDetector.java
@@ -0,0 +1,303 @@
+package com.android.launcher3.touch;
+
+import android.content.Context;
+import android.util.Log;
+import android.view.MotionEvent;
+import android.view.ViewConfiguration;
+import android.view.animation.Interpolator;
+
+/**
+ * One dimensional scroll/drag/swipe gesture detector.
+ */
+public class SwipeDetector {
+
+    private static final boolean DBG = false;
+    private static final String TAG = "SwipeDetector";
+
+    private final float mTouchSlop;
+
+    private int mScrollConditions;
+    public static final int DIRECTION_UP = 1 << 0;
+    public static final int DIRECTION_DOWN = 1 << 1;
+    public static final int DIRECTION_BOTH = DIRECTION_DOWN | DIRECTION_UP;
+
+    private static final float ANIMATION_DURATION = 1200;
+    private static final float FAST_FLING_PX_MS = 10;
+
+    /**
+     * 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
+    }
+
+    //------------------- 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 float mDownX;
+    private float mDownY;
+
+    private float mLastY;
+    private long mCurrentMillis;
+
+    private float mVelocity;
+    private float mLastDisplacement;
+    private float mDisplacementY;
+    private float mDisplacementX;
+
+    private float mSubtractDisplacement;
+    private boolean mIgnoreSlopWhenSettling;
+
+    /* Client of this gesture detector can register a callback. */
+    private Listener mListener;
+
+    public void setListener(Listener l) {
+        mListener = l;
+    }
+
+    public interface Listener {
+        void onDragStart(boolean start);
+
+        boolean onDrag(float displacement, float velocity);
+
+        void onDragEnd(float velocity, boolean fling);
+    }
+
+    public SwipeDetector(Context context) {
+        mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
+    }
+
+    public void setDetectableScrollConditions(int scrollDirectionFlags, boolean ignoreSlop) {
+        mScrollConditions = scrollDirectionFlags;
+        mIgnoreSlopWhenSettling = ignoreSlop;
+    }
+
+    private boolean shouldScrollStart() {
+        // reject cases where the slop condition is not met.
+        if (Math.abs(mDisplacementY) < mTouchSlop) {
+            return false;
+        }
+
+        // reject cases where the angle condition is not met.
+        float deltaY = Math.abs(mDisplacementY);
+        float deltaX = Math.max(Math.abs(mDisplacementX), 1);
+        if (deltaX > deltaY) {
+            return false;
+        }
+        // Check if the client is interested in scroll in current direction.
+        if (((mScrollConditions & DIRECTION_DOWN) > 0 && mDisplacementY > 0) ||
+                ((mScrollConditions & DIRECTION_UP) > 0 && mDisplacementY < 0)) {
+            return true;
+        }
+        return false;
+    }
+
+    public boolean onTouchEvent(MotionEvent ev) {
+        switch (ev.getAction()) {
+            case MotionEvent.ACTION_DOWN:
+                mDownX = ev.getX();
+                mDownY = ev.getY();
+                mLastDisplacement = 0;
+                mDisplacementY = 0;
+                mVelocity = 0;
+
+                if (mState == ScrollState.SETTLING && mIgnoreSlopWhenSettling) {
+                    setState(ScrollState.DRAGGING);
+                }
+                break;
+            case MotionEvent.ACTION_MOVE:
+                mDisplacementX = ev.getX() - mDownX;
+                mDisplacementY = ev.getY() - mDownY;
+                computeVelocity(ev);
+
+                // handle state and listener calls.
+                if (mState != ScrollState.DRAGGING && shouldScrollStart()) {
+                    setState(ScrollState.DRAGGING);
+                }
+                if (mState == ScrollState.DRAGGING) {
+                    reportDragging();
+                }
+                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:
+                //TODO: add multi finger tracking by tracking active pointer.
+                break;
+        }
+        // Do house keeping.
+        mLastDisplacement = mDisplacementY;
+        mLastY = ev.getY();
+        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 (mDisplacementY > 0) {
+            mSubtractDisplacement = mTouchSlop;
+        } else {
+            mSubtractDisplacement = -mTouchSlop;
+        }
+    }
+
+    private boolean reportDragging() {
+        float delta = mDisplacementY - mLastDisplacement;
+        if (delta != 0) {
+            if (DBG) {
+                Log.d(TAG, String.format("onDrag disp=%.1f, velocity=%.1f",
+                        mDisplacementY, mVelocity));
+            }
+
+            return mListener.onDrag(mDisplacementY - mSubtractDisplacement, mVelocity);
+        }
+        return true;
+    }
+
+    private void reportDragEnd() {
+        if (DBG) {
+            Log.d(TAG, String.format("onScrollEnd disp=%.1f, velocity=%.1f",
+                    mDisplacementY, mVelocity));
+        }
+        mListener.onDragEnd(mVelocity, Math.abs(mVelocity) > RELEASE_VELOCITY_PX_MS);
+
+    }
+
+    /**
+     * Computes the damped velocity using the two motion events and the previous velocity.
+     */
+    private float computeVelocity(MotionEvent to) {
+        return computeVelocity(to.getY() - mLastY, to.getEventTime());
+    }
+
+    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 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;
+    }
+
+    public static class ScrollInterpolator implements Interpolator {
+
+        boolean mSteeper;
+
+        public void setVelocityAtZero(float velocity) {
+            mSteeper = velocity > FAST_FLING_PX_MS;
+        }
+
+        public float getInterpolation(float t) {
+            t -= 1.0f;
+            float output = t * t * t;
+            if (mSteeper) {
+                output *= t * t; // Make interpolation initial slope steeper
+            }
+            return output + 1;
+        }
+    }
+}