I cannot find a way to replace the default UIPanGestureRecognizer of theUIScrollView. However I need to adjust the gesture that causes the UIScrollView to scroll.
I only want to recognize pans with higher velocity. In addition, the velocity of a finger is to be measured after it has moved certain distance (to be sure it is not the initial slow motion). To my knowledge this cannot be achieved with UScrollView's default UIPanGestureRecognizer.
How can I replace it with my own recognizer?
Changing the underlying gesture recognizer is the wrong way to go. What you want to do can probably be accomplished by implementing the gestureRecognizer(_:shouldReceiveTouch:) method of UIGestureRecognizerDelegate.
So long as the scroll view you want to customize isn't a part of a UICollectionView, UITableView, or a similar class then you'll be able to set the delegate of the gesture recognizer. Within the delegate you can then use the velocityInView(_:) method of UIPanGestureRecognizer to decide if you want to allow the gesture recognizer to trigger scrolling.
You could implement the touchesMoved method in here as well. You could do a comparison between touches to check velocity. something like this but it is pseudo code
global firstpoint;
global secondpoint
override func touchesBegan(touches: NSSet, withEvent event: UIEvent){
for touch: AnyObject in touches {
let firstpoint = (touch as UITouch).locationInNode(self);
}
override func touchesMoved(touches: NSSet, withEvent event: UIEvent) {
for touch: AnyObject in touches {
let secondpoint = (touch as UITouch).locationInNode(self);
}
let diffx = secondpoint - firstpoint;
if diffx > "some value you choose for velocity"{
"do some action that you want";
}
else {
firstpoint = secondpoint;
}
}
This will give you some velocity for the movement that you could use to supply a further action.
You could try placing a clear UIView over the scrollView, and could then add a UIPanGestureRecognizer to it. You would then be able to set a selector for that GestureRecognizer that could then tell the scrollView to scroll. But then you will be responsible for determining the distance to scroll for each high velocity pan.
Related
Am I on the right path trying to drag an item from a UIScrollView and drop it over a second UIScrollView? Neither of the UIScrollViews will be altered in the end, but I'd like to have an image follow the touchMoved position until it's released over second UIScrollView.
I have extended the UIScrollView so I can see where a touch begins inside the UIScrollView.
extension UIScrollView {
override open func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
self.next?.touchesBegan(touches, with: event)
print("touchesBegan")
}
}
to get the touched object
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
if let touch = touches.first {
beginningLocation = touch.location(in: self.view)
let position = touch.location(in: itemScrollview)
print("itemScrollview: \(position)")
let whoHit = Int(position.x / 120)
print("whoHit: \(whoHit) \(GameData.items[whoHit].name)")
}
}
I'm trying to use touchesEnded to see if the user dragged up, but touchesEnded doesn't always get called. Works if the touches begin and end over the same UIScrollView, but when dragged off, touchesEnd doesn't get called.
Yo cannot "directly" drag an object (view, image view, label, button, etc) from one view to another (whether it's a UIView or UIScrollView or any other container).
Instead, you need to "move" the object you want to drag from the containing view to the super view (the "main" view), drag it around as a subview of the main view, and then check where it is released.
So, essentially, if you want to drag a UIImageView:
on first touch, move the image view from its containing view to the "main" view
translate the coordinates, so they are now relative to the "main" view
track the touch / drag in main view coordinates, re-positioning the image view as you go
on release, see if the end touch is inside the "target" container view
if so, add the image view as a subview of the target view (translating the position coordinates)
if it's not inside the target frame, either add it back to its original container, or drop it into the main view, or vaporize it, or whatever you desire.
I am working on a tiny project where I want to use the 3D touch screen pressure capabilities (e.g. touch.force).
Right now I can measure force in my ViewController and it is behaving like I want it:
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
if let touch = touches.first {
if traitCollection.forceTouchCapability == UIForceTouchCapability.available {
// 3D Touch capable
let force = touch.force
print("Force: " + force.description)
}
}
}
I have one UIImageView that presents a picture. I also use an custom UICollectionView as overlay, which contains transparent cells and colored cells. What I am trying to achieve is to measure both force, and be able to remove the color from the cells when they are pressed, but I am failing to do both. I can either measure force, or change the color of a cell in the UICollectionView, but not both.
The solution as I see it is to forward touches from the UICollectionView to the next view in the hierarchy. But another solution could be to measure both force and register taps on cells from within the custom UICollectionView.
My question is, is either of my proposed solutions any good? And if so, how do I achieve them?
Apparently the override func touches... methods are part of UIView, not neccesarily UIViewControllers. This means that implementing the touchesMoved and other methods into my custom UICollectionView is perfectly possible and it solved my problem of handling touches and taps at the same time.
I usually use this function to hide the keyboard once any point in screen is touched
override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
self.view.endEditing(true)
}
But when I use it with scroll view it doesn't work.
How I can hide the keyboard once any point of scroll view is touched ?
Try set keyboardDismissMode of UIScrollView to OnDrag or Interactive, it's default to UIScrollViewKeyboardDismissModeNone
The manner in which the keyboard is dismissed when a drag begins in the scroll view.
Add tap gesture recognizer to scrollView object.
let touch = UITapGestureRecognizer(target: self, action: "singleTapGestureCaptured:")
scrollView.addGestureRecognizer(touch)
and receive the touch event and hide keyboard.
func singleTapGestureCaptured(gesture: UITapGestureRecognizer){
self.view.endEditing(true)
}
There is delegate function for scrollview - "scrollview did scroll" you can dismiss the keyboard there.
The problem in short, related to working with pan gesture inside a scrollView.
I have a canvas(which is an UIView itself but bigger in size) where i am drawing some UIView objects with pan gesture enabled over each of them(Each little UIView Objects I am talking about, are making using another UIView class).
Now the canvas can be bigger in height and width...which can be changed as per the user input.
So to achieve that I have placed the canvas inside a UIScrollView. Now the canvas is increasing or decreasing smoothly.
Those tiny UIView objects on the canvas can be rotated also.
Now the problem.
If I am not changing the canvas size(static) i.e. if its not inside the scrollview then each UIView objects inside the canvas are moving superbly and everything is working just fine with the following code.
If the canvas is inside the UIScrollView then the canvas can be scrollable right? Now inside the scrollview if I am panning the UIView objects on the canvas then those little UIView objects are not following the touch of the finger rather than its moving on another point when touch is moving on the canvas.
N.B. - Somehow I figured out that I need to disable the scrolling of the scrollview when any of the subviews are getting touch. For that thing I have implemented NSNotificationCenter to pass the signal to the parent viewController.
Here is the code.
This functions are defined inside the parent viewController class
func canvusScrollDisable(){
print("Scrolling Off")
self.scrollViewForCanvus.scrollEnabled = false
}
func canvusScrollEnable(){
print("Scrolling On")
self.scrollViewForCanvus.scrollEnabled = true
}
override func viewDidLoad() {
super.viewDidLoad()
notificationUpdate.addObserver(self, selector: "canvusScrollEnable", name: "EnableScroll", object: nil)
notificationUpdate.addObserver(self, selector: "canvusScrollDisable", name: "DisableScroll", object: nil)
}
This is the Subview class of the canvas
import UIKit
class ViewClassForUIView: UIView {
let notification: NSNotificationCenter = NSNotificationCenter.defaultCenter()
var lastLocation: CGPoint = CGPointMake(0, 0)
var lastOrigin = CGPoint()
var myFrame = CGRect()
var location = CGPoint(x: 0, y: 0)
var degreeOfThisView = CGFloat()
override init(frame: CGRect){
super.init(frame: frame)
let panRecognizer = UIPanGestureRecognizer(target: self, action: "detectPan:")
self.backgroundColor = addTableUpperViewBtnColor
self.multipleTouchEnabled = false
self.exclusiveTouch = true
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
func detectPan(recognizer: UIPanGestureRecognizer){
let translation = recognizer.translationInView(self.superview!)
self.center = CGPointMake(lastLocation.x + translation.x, lastLocation.y + translation.y)
switch(recognizer.state){
case .Began:
break
case .Changed:
break
case .Ended:
notification.postNotificationName("EnableScroll", object: nil)
default: break
}
}
override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
notification.postNotificationName("DisableScroll", object: nil)
self.superview?.bringSubviewToFront(self)
lastLocation = self.center
lastOrigin = self.frame.origin
let radians:Double = atan2( Double(self.transform.b), Double(self.transform.a))
self.degreeOfThisView = CGFloat(radians) * (CGFloat(180) / CGFloat(M_PI) )
if self.degreeOfThisView != 0.0{
self.transform = CGAffineTransformIdentity
self.lastOrigin = self.frame.origin
self.transform = CGAffineTransformMakeRotation(CGFloat(M_PI_4))
}
myFrame = self.frame
}
override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
notification.postNotificationName("EnableScroll", object: nil)
}
}
Now the scrollView is disabling its scroll perfectly whenever one of the UIView object is receiving touch over the canvas which is inside the scrollview but sometimes those UIView objects are not properly following the touch location over the canvas/screen.
I am using Swift 2.1 with Xcode 7 but anyone can tell me the missing things of mine or the solution using Objective-c/Swift?
Where do you set the lastLocation? I think it would be better for you to use locationInView and compute the translation by yourself. Then save the lastLocation on every event that triggers the method.
Also you might want to handle the Cancel state as well to turn the scrolling back on.
All of this does seem a bit messy though. The notifications are maybe not the best idea in your case nor is putting the gesture recognizers on the subviews. I think you should have a view which handles all those small views; it should also have a gesture recognizer that can simultaneously interact with other recognizers. When the gesture is recognized it should check if any of the subviews are hit and decide if any of them should be moved. If it should be moved then use the delegate to report that the scrolling must be disabled. If not then cancel the recognizer (disable+enable does that). Also in most cases where you put something movable on the scrollview you usually want a long press gesture recognizer and not a pan gesture recognizer. Simply use that one and set some very small minimum press duration. Note that this gesture works exactly the same as the pan gesture but can have a small delay to be detected. It is very useful in these kind of situations.
Update (The architecture):
The hierarchy should be:
View controller -> Scrollview -> Canvas view -> Small views
The canvas view should contain the gesture recognizer that controls the small views. When the gesture begins you should check if any of the views are hit by its location by simply iterating through the subviews and check if their frame contains a point. If so it should start moving the hit small view and it should notify its delegate that it has began moving it. If not it should cancel the gesture recognizer.
As the canvas view has a custom delegate it is the view controller that should implement its protocol and assign itself to the canvas view as a delegate. When the canvas view reports that the view dragging has begin it should disable the scrollview scrolling. When the canvas view reports it has stopped moving the views it should reenable the scrolling of the scroll view.
Create this type of view hierarchy
Create a custom protocol of the canvas view which includes "did begin dragging" and "did end dragging"
When the view controller becomes active assign self as a delegate to the canvas view. Implement the 2 methods to enable or disable the scrolling of the scroll view.
The canvas view should add a gesture recognizer to itself and should contain an array of all the small movable subviews. The recognizer should be able to interact with other recognizers simultaneously which is done through its delegate.
The Canvas gesture recognizer target should on begin check if any of the small views are hit and save it as a property, it should also save the current position of the gesture. When the gesture changes it should move the grabbed view depending on the last and current gesture location and re-save the current location to the property. When the gesture ends it should clear the currently dragged view. On begin and end it should call the delegate to notify the change of the state.
Disable or enable the scrolling in the view controller depending on the canvas view reporting to delegate.
I think this should be all.
I'm creating a subclass of UIView to use in a project, and will handle touches on the main view. I'd like so that when the touch (on the main view) is dragged and contacts the special UIViews, they change their background color. Using UIView's default "touchesMoved" function only detects touches that originate on the specific view. I could set up the main view to check each instance of the custom UIView, but that would be contrary to encapsulation and lead to messy code.
Any ideas?
I'm not sure this is what your after, but if I put the following code in my view controller, whose view has several RDView views in it, the color of those views will change color when I drag from the main view into the RDView.
override func touchesMoved(touches: NSSet, withEvent event: UIEvent) {
var touched = self.view.hitTest((touches.anyObject() as UITouch).locationInView(self.view), withEvent: event)
if touched is RDView {
touched?.backgroundColor = UIColor.redColor()
}
}