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- /*
- * Copyright @ 2017-present Atlassian Pty Ltd
- *
- * 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.
- */
-
- final class DragGestureController {
-
- var insets: UIEdgeInsets = UIEdgeInsets.zero
-
- private var frameBeforeDragging: CGRect = CGRect.zero
- private weak var view: UIView?
- private lazy var panGesture: UIPanGestureRecognizer = {
- return UIPanGestureRecognizer(target: self,
- action: #selector(handlePan(gesture:)))
- }()
-
- func startDragListener(inView view: UIView) {
- self.view = view
- view.addGestureRecognizer(panGesture)
- panGesture.isEnabled = true
- }
-
- func stopDragListener() {
- panGesture.isEnabled = false
- view?.removeGestureRecognizer(panGesture)
- view = nil
- }
-
- @objc private func handlePan(gesture: UIPanGestureRecognizer) {
- guard let view = self.view else { return }
-
- let translation = gesture.translation(in: view.superview)
- let velocity = gesture.velocity(in: view.superview)
- var frame = frameBeforeDragging
-
- switch gesture.state {
- case .began:
- frameBeforeDragging = view.frame
-
- case .changed:
- frame.origin.x = floor(frame.origin.x + translation.x)
- frame.origin.y = floor(frame.origin.y + translation.y)
- view.frame = frame
-
- case .ended:
- let currentPos = view.frame.origin
- let finalPos = calculateFinalPosition()
-
- let distance = CGPoint(x: currentPos.x - finalPos.x,
- y: currentPos.y - finalPos.y)
- let distanceMagnitude = magnitude(vector: distance)
- let velocityMagnitude = magnitude(vector: velocity)
- let animationDuration = 0.5
- let initialSpringVelocity =
- velocityMagnitude / distanceMagnitude / CGFloat(animationDuration)
-
- frame.origin = CGPoint(x: finalPos.x, y: finalPos.y)
-
- UIView.animate(withDuration: animationDuration,
- delay: 0,
- usingSpringWithDamping: 0.9,
- initialSpringVelocity: initialSpringVelocity,
- options: .curveLinear,
- animations: {
- view.frame = frame
- }, completion: nil)
-
- default:
- break
- }
- }
-
- private func calculateFinalPosition() -> CGPoint {
- guard
- let view = self.view,
- let bounds = view.superview?.frame
- else { return CGPoint.zero }
-
- let currentSize = view.frame.size
- let adjustedBounds = UIEdgeInsetsInsetRect(bounds, insets)
- let threshold: CGFloat = 20.0
- let velocity = panGesture.velocity(in: view.superview)
- let location = panGesture.location(in: view.superview)
-
- let goLeft: Bool
- if fabs(velocity.x) > threshold {
- goLeft = velocity.x < -threshold
- } else {
- goLeft = location.x < bounds.midX
- }
-
- let goUp: Bool
- if fabs(velocity.y) > threshold {
- goUp = velocity.y < -threshold
- } else {
- goUp = location.y < bounds.midY
- }
-
- let finalPosX: CGFloat =
- goLeft
- ? adjustedBounds.origin.x
- : bounds.size.width - insets.right - currentSize.width
- let finalPosY: CGFloat =
- goUp
- ? adjustedBounds.origin.y
- : bounds.size.height - insets.bottom - currentSize.height
-
- return CGPoint(x: finalPosX, y: finalPosY)
- }
-
- private func magnitude(vector: CGPoint) -> CGFloat {
- return sqrt(pow(vector.x, 2) + pow(vector.y, 2))
- }
- }
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