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/*
* 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 android.content.Context;
import android.graphics.PointF;
import android.view.MotionEvent;
import android.view.ViewConfiguration;
import androidx.annotation.NonNull;
import androidx.annotation.VisibleForTesting;
import com.android.launcher3.Utilities;
/**
* One dimensional scroll/drag/swipe gesture detector (either HORIZONTAL or VERTICAL).
*/
public class SingleAxisSwipeDetector extends BaseSwipeDetector {
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;
public static final Direction VERTICAL = new Direction() {
@Override
boolean isPositive(float displacement) {
// Up
return displacement < 0;
}
@Override
boolean isNegative(float displacement) {
// Down
return displacement > 0;
}
@Override
float extractDirection(PointF direction) {
return direction.y;
}
@Override
boolean canScrollStart(PointF displacement, float touchSlop) {
return Math.abs(displacement.y) >= Math.max(Math.abs(displacement.x), touchSlop);
}
};
public static final Direction HORIZONTAL = new Direction() {
@Override
boolean isPositive(float displacement) {
// Right
return displacement > 0;
}
@Override
boolean isNegative(float displacement) {
// Left
return displacement < 0;
}
@Override
float extractDirection(PointF direction) {
return direction.x;
}
@Override
boolean canScrollStart(PointF displacement, float touchSlop) {
return Math.abs(displacement.x) >= Math.max(Math.abs(displacement.y), touchSlop);
}
};
private final Direction mDir;
/* Client of this gesture detector can register a callback. */
private final Listener mListener;
private int mScrollDirections;
public SingleAxisSwipeDetector(@NonNull Context context, @NonNull Listener l,
@NonNull Direction dir) {
this(ViewConfiguration.get(context), l, dir, Utilities.isRtl(context.getResources()));
}
@VisibleForTesting
protected SingleAxisSwipeDetector(@NonNull ViewConfiguration config, @NonNull Listener l,
@NonNull Direction dir, boolean isRtl) {
super(config, isRtl);
mListener = l;
mDir = dir;
}
public void setDetectableScrollConditions(int scrollDirectionFlags, boolean ignoreSlop) {
mScrollDirections = scrollDirectionFlags;
mIgnoreSlopWhenSettling = ignoreSlop;
}
public int getScrollDirections() {
return mScrollDirections;
}
/**
* Returns if the start drag was towards the positive direction or negative.
*
* @see #setDetectableScrollConditions(int, boolean)
* @see #DIRECTION_BOTH
*/
public boolean wasInitialTouchPositive() {
return mDir.isPositive(mDir.extractDirection(mSubtractDisplacement));
}
@Override
protected boolean shouldScrollStart(PointF displacement) {
// Reject cases where the angle or slop condition is not met.
if (!mDir.canScrollStart(displacement, mTouchSlop)) {
return false;
}
// Check if the client is interested in scroll in current direction.
float displacementComponent = mDir.extractDirection(displacement);
return canScrollNegative(displacementComponent) || canScrollPositive(displacementComponent);
}
private boolean canScrollNegative(float displacement) {
return (mScrollDirections & DIRECTION_NEGATIVE) > 0 && mDir.isNegative(displacement);
}
private boolean canScrollPositive(float displacement) {
return (mScrollDirections & DIRECTION_POSITIVE) > 0 && mDir.isPositive(displacement);
}
@Override
protected void reportDragStartInternal(boolean recatch) {
mListener.onDragStart(!recatch);
}
@Override
protected void reportDraggingInternal(PointF displacement, MotionEvent event) {
mListener.onDrag(mDir.extractDirection(displacement), event);
}
@Override
protected void reportDragEndInternal(PointF velocity) {
float velocityComponent = mDir.extractDirection(velocity);
mListener.onDragEnd(velocityComponent);
}
/** Listener to receive updates on the swipe. */
public interface Listener {
void onDragStart(boolean start);
// TODO remove
boolean onDrag(float displacement);
default boolean onDrag(float displacement, MotionEvent event) {
return onDrag(displacement);
}
void onDragEnd(float velocity);
}
public abstract static class Direction {
abstract boolean isPositive(float displacement);
abstract boolean isNegative(float displacement);
/** Returns the part of the given {@link PointF} that is relevant to this direction. */
abstract float extractDirection(PointF point);
/** Reject cases where the angle or slop condition is not met. */
abstract boolean canScrollStart(PointF displacement, float touchSlop);
}
}
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