lawnchair/src/com/android/launcher3/touch/AbstractStateChangeTouchController.java

/*
 * Copyright (C) 2019 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.launcher3.touch;

import static com.android.launcher3.anim.Interpolators.scrollInterpolatorForVelocity;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ValueAnimator;
import android.util.Log;
import android.view.MotionEvent;

import com.android.launcher3.Launcher;
import com.android.launcher3.LauncherState;
import com.android.launcher3.Utilities;
import com.android.launcher3.anim.AnimatorPlaybackController;
import com.android.launcher3.userevent.nano.LauncherLogProto.Action.Direction;
import com.android.launcher3.userevent.nano.LauncherLogProto.Action.Touch;
import com.android.launcher3.util.TouchController;

/**
 * TouchController for handling state changes
 */
public abstract class AbstractStateChangeTouchController extends AnimatorListenerAdapter
        implements TouchController, SwipeDetector.Listener {

    private static final String TAG = "ASCTouchController";
    public static final float RECATCH_REJECTION_FRACTION = .0875f;
    public static final int SINGLE_FRAME_MS = 16;

    // Progress after which the transition is assumed to be a success in case user does not fling
    public static final float SUCCESS_TRANSITION_PROGRESS = 0.5f;

    protected final Launcher mLauncher;
    protected final SwipeDetector mDetector;

    private boolean mNoIntercept;
    protected int mStartContainerType;

    protected LauncherState mFromState;
    protected LauncherState mToState;
    protected AnimatorPlaybackController mCurrentAnimation;

    private float mStartProgress;
    // Ratio of transition process [0, 1] to drag displacement (px)
    private float mProgressMultiplier;
    private float mDisplacementShift;

    public AbstractStateChangeTouchController(Launcher l, SwipeDetector.Direction dir) {
        mLauncher = l;
        mDetector = new SwipeDetector(l, this, dir);
    }

    protected abstract boolean canInterceptTouch(MotionEvent ev);

    /**
     * Initializes the {@code mFromState} and {@code mToState} and swipe direction to use for
     * the detector. In case of disabling swipe, return 0.
     */
    protected abstract int getSwipeDirection(MotionEvent ev);

    @Override
    public final boolean onControllerInterceptTouchEvent(MotionEvent ev) {
        if (ev.getAction() == MotionEvent.ACTION_DOWN) {
            mNoIntercept = !canInterceptTouch(ev);
            if (mNoIntercept) {
                return false;
            }

            // Now figure out which direction scroll events the controller will start
            // calling the callbacks.
            final int directionsToDetectScroll;
            boolean ignoreSlopWhenSettling = false;

            if (mCurrentAnimation != null) {
                if (mCurrentAnimation.getProgressFraction() > 1 - RECATCH_REJECTION_FRACTION) {
                    directionsToDetectScroll = SwipeDetector.DIRECTION_POSITIVE;
                } else if (mCurrentAnimation.getProgressFraction() < RECATCH_REJECTION_FRACTION ) {
                    directionsToDetectScroll = SwipeDetector.DIRECTION_NEGATIVE;
                } else {
                    directionsToDetectScroll = SwipeDetector.DIRECTION_BOTH;
                    ignoreSlopWhenSettling = true;
                }
            } else {
                directionsToDetectScroll = getSwipeDirection(ev);
                if (directionsToDetectScroll == 0) {
                    mNoIntercept = true;
                    return false;
                }
            }
            mDetector.setDetectableScrollConditions(
                    directionsToDetectScroll, ignoreSlopWhenSettling);
        }

        if (mNoIntercept) {
            return false;
        }

        onControllerTouchEvent(ev);
        return mDetector.isDraggingOrSettling();
    }

    @Override
    public final boolean onControllerTouchEvent(MotionEvent ev) {
        return mDetector.onTouchEvent(ev);
    }

    protected float getShiftRange() {
        return mLauncher.getAllAppsController().getShiftRange();
    }

    protected abstract LauncherState getTargetState(LauncherState fromState,
            boolean isDragTowardPositive);

    protected abstract float initCurrentAnimation();

    private boolean reinitCurrentAnimation(boolean reachedToState, boolean isDragTowardPositive) {
        LauncherState newFromState = mFromState == null ? mLauncher.getStateManager().getState()
                : reachedToState ? mToState : mFromState;
        LauncherState newToState = getTargetState(newFromState, isDragTowardPositive);

        if (newFromState == mFromState && newToState == mToState || (newFromState == newToState)) {
            return false;
        }

        mFromState = newFromState;
        mToState = newToState;

        mStartProgress = 0;
        mProgressMultiplier = initCurrentAnimation();
        mCurrentAnimation.getTarget().addListener(this);
        mCurrentAnimation.dispatchOnStart();
        return true;
    }

    @Override
    public void onDragStart(boolean start) {
        if (mCurrentAnimation == null) {
            mFromState = mToState = null;
            reinitCurrentAnimation(false, mDetector.wasInitialTouchPositive());
            mDisplacementShift = 0;
        } else {
            mCurrentAnimation.pause();
            mStartProgress = mCurrentAnimation.getProgressFraction();
        }
    }

    @Override
    public boolean onDrag(float displacement, float velocity) {
        float deltaProgress = mProgressMultiplier * (displacement - mDisplacementShift);
        float progress = deltaProgress + mStartProgress;
        updateProgress(progress);
        boolean isDragTowardPositive = (displacement - mDisplacementShift) < 0;
        if (progress <= 0) {
            if (reinitCurrentAnimation(false, isDragTowardPositive)) {
                mDisplacementShift = displacement;
            }
        } else if (progress >= 1) {
            if (reinitCurrentAnimation(true, isDragTowardPositive)) {
                mDisplacementShift = displacement;
            }
        }
        return true;
    }

    protected void updateProgress(float fraction) {
        mCurrentAnimation.setPlayFraction(fraction);
    }

    @Override
    public void onDragEnd(float velocity, boolean fling) {
        final int logAction;
        final LauncherState targetState;
        final float progress = mCurrentAnimation.getProgressFraction();

        if (fling) {
            logAction = Touch.FLING;
            targetState =
                    Float.compare(Math.signum(velocity), Math.signum(mProgressMultiplier)) == 0
                            ? mToState : mFromState;
            // snap to top or bottom using the release velocity
        } else {
            logAction = Touch.SWIPE;
            targetState = (progress > SUCCESS_TRANSITION_PROGRESS) ? mToState : mFromState;
        }


        final float endProgress;
        final float startProgress;
        final long duration;

        if (targetState == mToState) {
            endProgress = 1;
            if (progress >= 1) {
                duration = 0;
                startProgress = 1;
            } else {
                startProgress = Utilities.boundToRange(
                        progress + velocity * SINGLE_FRAME_MS * mProgressMultiplier, 0f, 1f);
                duration = SwipeDetector.calculateDuration(velocity,
                        endProgress - Math.max(progress, 0));
            }
        } else {
            endProgress = 0;
            if (progress <= 0) {
                duration = 0;
                startProgress = 0;
            } else {
                startProgress = Utilities.boundToRange(
                        progress + velocity * SINGLE_FRAME_MS * mProgressMultiplier, 0f, 1f);
                duration = SwipeDetector.calculateDuration(velocity,
                        Math.min(progress, 1) - endProgress);
            }
        }

        mCurrentAnimation.setEndAction(() -> onSwipeInteractionCompleted(targetState, logAction));
        ValueAnimator anim = mCurrentAnimation.getAnimationPlayer();
        anim.setFloatValues(startProgress, endProgress);
        updateSwipeCompleteAnimation(anim, duration, targetState, velocity, fling);
        anim.start();
    }

    protected void updateSwipeCompleteAnimation(ValueAnimator animator, long expectedDuration,
            LauncherState targetState, float velocity, boolean isFling) {
        animator.setDuration(expectedDuration)
                .setInterpolator(scrollInterpolatorForVelocity(velocity));
    }

    protected int getDirectionForLog() {
        return mToState.ordinal > mFromState.ordinal ? Direction.UP : Direction.DOWN;
    }

    protected void onSwipeInteractionCompleted(LauncherState targetState, int logAction) {
        if (targetState != mFromState) {
            // Transition complete. log the action
            mLauncher.getUserEventDispatcher().logStateChangeAction(logAction,
                    getDirectionForLog(),
                    mStartContainerType,
                    mFromState.containerType,
                    mToState.containerType,
                    mLauncher.getWorkspace().getCurrentPage());
        }
        clearState();
        mLauncher.getStateManager().goToState(targetState, false /* animated */);
    }

    protected void clearState() {
        mCurrentAnimation = null;
        mDetector.finishedScrolling();
    }

    @Override
    public void onAnimationCancel(Animator animation) {
        if (mCurrentAnimation != null && animation == mCurrentAnimation.getOriginalTarget()) {
            Log.e(TAG, "Who dare cancel the animation when I am in control", new Exception());
            clearState();
        }
    }
}