276 lines
9.6 KiB
Java
276 lines
9.6 KiB
Java
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/*
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* Copyright (C) 2022 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.window;
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import android.annotation.FloatRange;
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import android.os.SystemProperties;
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import android.util.MathUtils;
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import android.view.MotionEvent;
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import android.view.RemoteAnimationTarget;
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import java.io.PrintWriter;
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/**
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* Helper class to record the touch location for gesture and generate back events.
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* @hide
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*/
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public class BackTouchTracker {
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private static final String PREDICTIVE_BACK_LINEAR_DISTANCE_PROP =
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"persist.wm.debug.predictive_back_linear_distance";
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private static final int LINEAR_DISTANCE = SystemProperties
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.getInt(PREDICTIVE_BACK_LINEAR_DISTANCE_PROP, -1);
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private float mLinearDistance = LINEAR_DISTANCE;
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private float mMaxDistance;
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private float mNonLinearFactor;
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/**
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* Location of the latest touch event
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*/
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private float mLatestTouchX;
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private float mLatestTouchY;
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private boolean mTriggerBack;
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/**
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* Location of the initial touch event of the back gesture.
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*/
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private float mInitTouchX;
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private float mInitTouchY;
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private float mLatestVelocityX;
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private float mLatestVelocityY;
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private float mStartThresholdX;
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private int mSwipeEdge;
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private boolean mShouldUpdateStartLocation = false;
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private TouchTrackerState mState = TouchTrackerState.INITIAL;
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/**
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* Updates the tracker with a new motion event.
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*/
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public void update(float touchX, float touchY, float velocityX, float velocityY) {
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/**
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* If back was previously cancelled but the user has started swiping in the forward
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* direction again, restart back.
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*/
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if ((touchX < mStartThresholdX && mSwipeEdge == BackEvent.EDGE_LEFT)
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|| (touchX > mStartThresholdX && mSwipeEdge == BackEvent.EDGE_RIGHT)) {
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mStartThresholdX = touchX;
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if ((mSwipeEdge == BackEvent.EDGE_LEFT && mStartThresholdX < mInitTouchX)
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|| (mSwipeEdge == BackEvent.EDGE_RIGHT && mStartThresholdX > mInitTouchX)) {
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mInitTouchX = mStartThresholdX;
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}
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}
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mLatestTouchX = touchX;
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mLatestTouchY = touchY;
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mLatestVelocityX = velocityX;
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mLatestVelocityY = velocityY;
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}
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/** Sets whether the back gesture is past the trigger threshold. */
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public void setTriggerBack(boolean triggerBack) {
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if (mTriggerBack != triggerBack && !triggerBack) {
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mStartThresholdX = mLatestTouchX;
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}
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mTriggerBack = triggerBack;
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}
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/** Gets whether the back gesture is past the trigger threshold. */
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public boolean getTriggerBack() {
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return mTriggerBack;
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}
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/** Returns if the start location should be updated. */
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public boolean shouldUpdateStartLocation() {
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return mShouldUpdateStartLocation;
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}
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/** Sets if the start location should be updated. */
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public void setShouldUpdateStartLocation(boolean shouldUpdate) {
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mShouldUpdateStartLocation = shouldUpdate;
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}
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/** Sets the state of the touch tracker. */
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public void setState(TouchTrackerState state) {
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mState = state;
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}
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/** Returns if the tracker is in initial state. */
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public boolean isInInitialState() {
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return mState == TouchTrackerState.INITIAL;
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}
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/** Returns if a back gesture is active. */
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public boolean isActive() {
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return mState == TouchTrackerState.ACTIVE;
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}
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/** Returns if a back gesture has been finished. */
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public boolean isFinished() {
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return mState == TouchTrackerState.FINISHED;
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}
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/** Sets the start location of the back gesture. */
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public void setGestureStartLocation(float touchX, float touchY, int swipeEdge) {
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mInitTouchX = touchX;
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mInitTouchY = touchY;
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mLatestTouchX = touchX;
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mLatestTouchY = touchY;
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mSwipeEdge = swipeEdge;
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mStartThresholdX = mInitTouchX;
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}
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/** Update the start location used to compute the progress to the latest touch location. */
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public void updateStartLocation() {
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mInitTouchX = mLatestTouchX;
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mInitTouchY = mLatestTouchY;
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mStartThresholdX = mInitTouchX;
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mShouldUpdateStartLocation = false;
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}
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/** Resets the tracker. */
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public void reset() {
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mInitTouchX = 0;
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mInitTouchY = 0;
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mStartThresholdX = 0;
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mTriggerBack = false;
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mState = TouchTrackerState.INITIAL;
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mSwipeEdge = BackEvent.EDGE_LEFT;
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mShouldUpdateStartLocation = false;
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}
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/** Creates a start {@link BackMotionEvent}. */
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public BackMotionEvent createStartEvent(RemoteAnimationTarget target) {
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return new BackMotionEvent(
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/* touchX = */ mInitTouchX,
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/* touchY = */ mInitTouchY,
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/* progress = */ 0,
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/* velocityX = */ 0,
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/* velocityY = */ 0,
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/* triggerBack = */ mTriggerBack,
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/* swipeEdge = */ mSwipeEdge,
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/* departingAnimationTarget = */ target);
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}
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/** Creates a progress {@link BackMotionEvent}. */
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public BackMotionEvent createProgressEvent() {
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float progress = getProgress(mLatestTouchX);
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return createProgressEvent(progress);
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}
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/**
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* Progress value computed from the touch position.
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*
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* @param touchX the X touch position of the {@link MotionEvent}.
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* @return progress value
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*/
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@FloatRange(from = 0.0, to = 1.0)
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public float getProgress(float touchX) {
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// If back is committed, progress is the distance between the last and first touch
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// point, divided by the max drag distance. Otherwise, it's the distance between
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// the last touch point and the starting threshold, divided by max drag distance.
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// The starting threshold is initially the first touch location, and updated to
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// the location everytime back is restarted after being cancelled.
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float startX = mTriggerBack ? mInitTouchX : mStartThresholdX;
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float distance;
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if (mSwipeEdge == BackEvent.EDGE_LEFT) {
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distance = touchX - startX;
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} else {
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distance = startX - touchX;
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}
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float deltaX = Math.max(0f, distance);
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float linearDistance = mLinearDistance;
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float maxDistance = getMaxDistance();
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maxDistance = maxDistance == 0 ? 1 : maxDistance;
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float progress;
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if (linearDistance < maxDistance) {
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// Up to linearDistance it behaves linearly, then slowly reaches 1f.
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// maxDistance is composed of linearDistance + nonLinearDistance
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float nonLinearDistance = maxDistance - linearDistance;
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float initialTarget = linearDistance + nonLinearDistance * mNonLinearFactor;
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boolean isLinear = deltaX <= linearDistance;
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if (isLinear) {
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progress = deltaX / initialTarget;
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} else {
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float nonLinearDeltaX = deltaX - linearDistance;
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float nonLinearProgress = nonLinearDeltaX / nonLinearDistance;
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float currentTarget = MathUtils.lerp(
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/* start = */ initialTarget,
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/* stop = */ maxDistance,
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/* amount = */ nonLinearProgress);
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progress = deltaX / currentTarget;
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}
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} else {
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// Always linear behavior.
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progress = deltaX / maxDistance;
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}
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return MathUtils.constrain(progress, 0, 1);
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}
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/**
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* Maximum distance in pixels.
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* Progress is considered to be completed (1f) when this limit is exceeded.
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*/
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public float getMaxDistance() {
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return mMaxDistance;
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}
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public float getLinearDistance() {
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return mLinearDistance;
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}
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public float getNonLinearFactor() {
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return mNonLinearFactor;
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}
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/** Creates a progress {@link BackMotionEvent} for the given progress. */
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public BackMotionEvent createProgressEvent(float progress) {
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return new BackMotionEvent(
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/* touchX = */ mLatestTouchX,
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/* touchY = */ mLatestTouchY,
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/* progress = */ progress,
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/* velocityX = */ mLatestVelocityX,
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/* velocityY = */ mLatestVelocityY,
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/* triggerBack = */ mTriggerBack,
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/* swipeEdge = */ mSwipeEdge,
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/* departingAnimationTarget = */ null);
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}
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/** Sets the thresholds for computing progress. */
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public void setProgressThresholds(float linearDistance, float maxDistance,
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float nonLinearFactor) {
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if (LINEAR_DISTANCE >= 0) {
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mLinearDistance = LINEAR_DISTANCE;
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} else {
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mLinearDistance = linearDistance;
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}
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mMaxDistance = maxDistance;
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mNonLinearFactor = nonLinearFactor;
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}
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/** Dumps debugging info. */
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public void dump(PrintWriter pw, String prefix) {
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pw.println(prefix + "BackTouchTracker state:");
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pw.println(prefix + " mState=" + mState);
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pw.println(prefix + " mTriggerBack=" + mTriggerBack);
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}
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public enum TouchTrackerState {
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INITIAL, ACTIVE, FINISHED
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}
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}
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