Pinch to zoom out into overview mode.

There are 3 classes coordinating the gesture: PinchToOverviewListener,
PinchThresholdManager, and PinchAnimationManager.
- PTOL listens for the pinch gesture on DragLayer.
- When a pinch is detected, the PTOL keeps track of the interpolated
  progress and passes it along to both the PTM and PAM.
- The PTM uses the progress to determine whether a new threshold has
  been passed, and tells the PAM to animate it if so.
- The PAM uses the progress to animate things like workspace scale
  throughout the pinch.
- If the pinch ends early, the PTOL uses the last passed threshold to
  determine whether to animate to workspace or overview, and tells
  PAM to perform the animation at the same velocity as the pinch.

Bug: 24414635
Change-Id: I9e53706c705f8b2982409bf7c223d8d0e9618bf0

1 files changed, 179 insertions, 0 deletions

diff --git a/src/com/android/launcher3/PinchToOverviewListener.java b/src/com/android/launcher3/PinchToOverviewListener.java
new file mode 100644
index 000000000..ef4748528
--- /dev/null
+++ b/src/com/android/launcher3/PinchToOverviewListener.java
@@ -0,0 +1,179 @@
+package com.android.launcher3;
+
+import android.animation.TimeInterpolator;
+import android.content.Context;
+import android.view.MotionEvent;
+import android.view.ScaleGestureDetector;
+
+/**
+ * Detects pinches and animates the Workspace to/from overview mode.
+ *
+ * Usage: Pass MotionEvents to onInterceptTouchEvent() and onTouchEvent(). This class will handle
+ * the pinch detection, and use {@link PinchAnimationManager} to handle the animations.
+ *
+ * @see PinchThresholdManager
+ * @see PinchAnimationManager
+ */
+public class PinchToOverviewListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
+    private static final float OVERVIEW_PROGRESS = 0f;
+    private static final float WORKSPACE_PROGRESS = 1f;
+
+    private ScaleGestureDetector mPinchDetector;
+    private Launcher mLauncher;
+    private Workspace mWorkspace = null;
+    private boolean mPinchStarted = false;
+    private float mPreviousProgress;
+    private float mProgressDelta;
+    private long mPreviousTimeMillis;
+    private long mTimeDelta;
+    private boolean mPinchCanceled = false;
+    private TimeInterpolator mInterpolator;
+
+    private PinchThresholdManager mThresholdManager;
+    private PinchAnimationManager mAnimationManager;
+
+    public PinchToOverviewListener(Launcher launcher) {
+        mLauncher = launcher;
+        mPinchDetector = new ScaleGestureDetector((Context) mLauncher, this);
+    }
+
+    public boolean onInterceptTouchEvent(MotionEvent ev) {
+        mPinchDetector.onTouchEvent(ev);
+        return mPinchStarted;
+    }
+
+    public void onTouchEvent(MotionEvent ev) {
+        if (mPinchStarted) {
+            if (ev.getPointerCount() > 2) {
+                // Using more than two fingers causes weird behavior, so just cancel the pinch.
+                cancelPinch(mPreviousProgress, -1);
+            } else {
+                mPinchDetector.onTouchEvent(ev);
+            }
+        }
+    }
+
+    @Override
+    public boolean onScaleBegin(ScaleGestureDetector detector) {
+        if (mLauncher.mState != Launcher.State.WORKSPACE || mLauncher.isOnCustomContent()) {
+            // Don't listen for the pinch gesture if on all apps, widget picker, -1, etc.
+            return false;
+        }
+        if (mAnimationManager != null && mAnimationManager.isAnimating()) {
+            // Don't listen for the pinch gesture if we are already animating from a previous one.
+            return false;
+        }
+        if (mWorkspace == null) {
+            mWorkspace = mLauncher.mWorkspace;
+            mThresholdManager = new PinchThresholdManager(mWorkspace);
+            mAnimationManager = new PinchAnimationManager(mLauncher);
+        }
+        if (mWorkspace.isSwitchingState() || mWorkspace.mScrollInteractionBegan) {
+            // Don't listen to pinches occurring while switching state, as it will cause a jump
+            // once the state switching animation is complete.
+            return false;
+        }
+
+        mPreviousProgress = mWorkspace.isInOverviewMode() ? OVERVIEW_PROGRESS : WORKSPACE_PROGRESS;
+        mPreviousTimeMillis = System.currentTimeMillis();
+        mInterpolator = mWorkspace.isInOverviewMode() ? new LogDecelerateInterpolator(100, 0)
+                : new LogAccelerateInterpolator(100, 0);
+        mPinchStarted = true;
+        return true;
+    }
+
+    @Override
+    public void onScaleEnd(ScaleGestureDetector detector) {
+        super.onScaleEnd(detector);
+
+        float passedThreshold = mThresholdManager.getPassedThreshold();
+        // If we are going towards overview, mPreviousProgress is how much further we need to
+        // go, since it is going from 1 to 0. If we are going to workspace, we want
+        // 1 - mPreviousProgress.
+        float remainingProgress = mPreviousProgress;
+        if (mWorkspace.isInOverviewMode() || passedThreshold < PinchThresholdManager.THRESHOLD_ONE) {
+            remainingProgress = 1f - mPreviousProgress;
+        }
+        int duration = computeDuration(remainingProgress, mProgressDelta, mTimeDelta);
+
+        if (passedThreshold < PinchThresholdManager.THRESHOLD_ONE) {
+            cancelPinch(mPreviousProgress, duration);
+        } else if (passedThreshold < PinchThresholdManager.THRESHOLD_THREE) {
+            float toProgress = mWorkspace.isInOverviewMode() ?
+                    WORKSPACE_PROGRESS : OVERVIEW_PROGRESS;
+            mAnimationManager.animateToProgress(mPreviousProgress, toProgress, duration,
+                    mThresholdManager);
+        } else {
+            mThresholdManager.reset();
+        }
+        mPinchStarted = false;
+        mPinchCanceled = false;
+    }
+
+    /**
+     * Compute the amount of time required to complete the transition based on the current pinch
+     * speed. If this time is too long, instead return the normal duration, ignoring the speed.
+     */
+    private int computeDuration(float remainingProgress, float progressDelta, long timeDelta) {
+        float progressSpeed = Math.abs(progressDelta) / timeDelta;
+        int remainingMillis = (int) (remainingProgress / progressSpeed);
+        return Math.min(remainingMillis, mAnimationManager.getNormalOverviewTransitionDuration());
+    }
+
+    /**
+     * Cancels the current pinch, returning back to where the pinch started (either workspace or
+     * overview). If duration is -1, the default overview transition duration is used.
+     */
+    private void cancelPinch(float currentProgress, int duration) {
+        if (mPinchCanceled) return;
+        mPinchCanceled = true;
+        float toProgress = mWorkspace.isInOverviewMode() ? OVERVIEW_PROGRESS : WORKSPACE_PROGRESS;
+        mAnimationManager.animateToProgress(currentProgress, toProgress, duration,
+                mThresholdManager);
+        mPinchStarted = false;
+    }
+
+    @Override
+    public boolean onScale(ScaleGestureDetector detector) {
+        if (mThresholdManager.getPassedThreshold() == PinchThresholdManager.THRESHOLD_THREE) {
+            // We completed the pinch, so stop listening to further movement until user lets go.
+            return true;
+        }
+        if (mLauncher.getDragController().isDragging()) {
+            mLauncher.getDragController().cancelDrag();
+        }
+
+        float pinchDist = detector.getCurrentSpan() - detector.getPreviousSpan();
+        if (pinchDist < 0 && mWorkspace.isInOverviewMode() ||
+                pinchDist > 0 && !mWorkspace.isInOverviewMode()) {
+            // Pinching the wrong way, so ignore.
+            return false;
+        }
+        // Pinch distance must equal the workspace width before switching states.
+        int pinchDistanceToCompleteTransition = mWorkspace.getWidth();
+        float overviewScale = mWorkspace.getOverviewModeShrinkFactor();
+        float initialWorkspaceScale = mWorkspace.isInOverviewMode() ? overviewScale : 1f;
+        float pinchScale = initialWorkspaceScale + pinchDist / pinchDistanceToCompleteTransition;
+        // Bound the scale between the overview scale and the normal workspace scale (1f).
+        pinchScale = Math.max(overviewScale, Math.min(pinchScale, 1f));
+        // Progress ranges from 0 to 1, where 0 corresponds to the overview scale and 1
+        // corresponds to the normal workspace scale (1f).
+        float progress = (pinchScale - overviewScale) / (1f - overviewScale);
+        float interpolatedProgress = mInterpolator.getInterpolation(progress);
+
+        mAnimationManager.setAnimationProgress(interpolatedProgress);
+        float passedThreshold = mThresholdManager.updateAndAnimatePassedThreshold(
+                interpolatedProgress, mAnimationManager);
+        if (passedThreshold == PinchThresholdManager.THRESHOLD_THREE) {
+            return true;
+        }
+
+        mProgressDelta = interpolatedProgress - mPreviousProgress;
+        mPreviousProgress = interpolatedProgress;
+        mTimeDelta = System.currentTimeMillis() - mPreviousTimeMillis;
+        mPreviousTimeMillis = System.currentTimeMillis();
+        return false;
+    }
+
+
+}
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