scrollViewWillBeginDecelerating alternative, too slow for tracking page change - objective-c

I am currently using pagination in a UIScrollView, and for tracking any page change I use;
-(void) scrollViewWillBeginDecelerating:(UIScrollView *)scrollView
{
if (_previousContentOffset > _pageContainer.contentOffset.x)
{
NSLog(#"Less");
_currentPageIdx--;
}
else if (_previousContentOffset < _pageContainer.contentOffset.x)
{
_currentPageIdx++;
NSLog(#"More");
}
}
Now the problem is that, this method isn't tracking the touch fast enough, so when this method is called, the user can be 3 pages along if he/she is paging like a maniac. I tried setting
_pageContainer.decelerationRate = UIScrollViewDecelerationRateFast;
but that didn't make the tracking much faster.
Is there a solution or alternative for this?

Use scrollViewDidScroll: instead. It is being called continuously while the user scrolls.

Related

UIScrollview paging issue

I have a UIScrollView with paging enabled, my goal is to detect if the user reaches third page by swiping, I want to redirect the user to another view. I have tried many ways. tried it in scrollViewWillBeginDragging , tried inbuilt pan gesture in scrollview methods using handleSwipeGesture . But unfortunately nothing worked. Can any body please tell me how to face this issue. Thanks in advance.
I recommend you to use this code
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
int page=scrollview.contentoffset.x/scrollview.frame.size.width
if(page == 3)
{
// redirect to your view.
}
}
This will give you the page no. you are currently on. and the condition will redirect to a specified view.

Can I preload the web content for Safari View Controller?

I can create Safari View Controller without problem:
let svc = SFSafariViewController(URL: NSURL(string: remote_url)!, entersReaderIfAvailable: true)
self.presentViewController(svc, animated: true, completion: nil)
Is there any way I can preload the URL before I present the view controller to the user?
For example, I can preload the URL (web content) in the background first, and after the user clicks on something, I can show the Safari View Controller with the content right away. The user will feel the page loading is faster or instant.
P.S. Workarounds/hacks are also acceptable. For example, using cache or starting the view controller in background, etc.
EDIT: please consider SFSafariViewController only.
Here is a solution.
Obviously, if you click on the button right away you'll see the loading.
But basically, I load the Browser and put the view behind another one and I put a button in this other view.
When you press the button, the browser is bring to the front, already loaded.
The only problem here is that I'm not using any transition but that's one solution at least.
import UIKit
import SafariServices
class ViewController: UIViewController {
var svc = SFSafariViewController(URL: NSURL(string: "https://microsoft.com/")!, entersReaderIfAvailable: true)
var safariView:UIView?
let containerView = UIView()
let btn = UIButton()
override func viewDidLoad() {
super.viewDidLoad()
//let tmpView = svc.view
addChildViewController(svc)
svc.didMoveToParentViewController(self)
svc.view.frame = view.frame
containerView.frame = view.frame
containerView.backgroundColor = UIColor.redColor()
safariView = svc.view
view.addSubview(safariView!)
view.addSubview(containerView)
btn.setTitle("Webizer", forState: UIControlState.Normal)
btn.titleLabel!.textColor = UIColor.blackColor()
btn.addTarget(self, action: "buttonTouched:", forControlEvents: .TouchUpInside)
btn.frame = CGRectMake(20, 50, 100, 100)
containerView.addSubview(btn)
view.sendSubviewToBack(safariView!)
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func buttonTouched(sender: AnyObject) {
view.bringSubviewToFront(safariView!)
//self.presentViewController(svc, animated: true, completion: nil)
}
}
Sadly this behaviour is not supported with the current implementation of SFSafariViewController. I would encourage filing a radar with Apple to add support for this behaviour but like others have suggested your best bet is to use WKWebView and start loading before its added to the hierarchy.
I came across a lovely radar from Twitter that actually mentions exactly what you're asking for. I think you might find the following requests useful:
High Priority:
- Ability to warm the SFSafariViewController before actually presenting it with a URL, URL request, HTML data or file on disk
- Currently, are investing heavily into warming the shared URL cache for high priority Tweets so that if the user hits that Tweet we
will open UIWebView (sadly not WKWebView) with that pre-cached web
page. If we could just warm an SFSafariViewController with the
desired link, this would eliminate an enormous amount of effort on our
end.
You can see in their implementation they simply cache responses using UIWebView since WKWebView seems to obfuscate the caching semantics a bit. The only risk is that UIWebView is a likely candidate for deprecation as you see in their docs "In apps that run in iOS 8 and later, use the WKWebView class instead of using UIWebView."
So unfortunately it seems that their are many hoops you need to jump through to get this all going so your best bet for now is to just pester Apple and dupe Twitters radar.
You could try using a http cache, but I don't think it would work as the Safari View Controller is working as a separate process (probably the same as Safari), so that's why it e.g. circumvents ATS.
The only way I can think of this working is to somehow force the user's Safari to load it? openURL: or adding to Reading List maybe? This doesn't sound like a viable solution.
You can always experiment with custom presentation of the view controller, attach it the view hierarchy, trigger appearance events, but set its frame to CGRectMake(0,0,1,1) or attach it somewhere off-screen, then wait a while and represent it with a correct frame.
you can download the web page using the following code . and represent it with the help of svc
let data:NSData?
do {
let weatherData = try NSData(contentsOfURL: NSURL(string: remote_url)!, options: NSDataReadingOptions())
data = weatherData
print(weatherData)
} catch {
print(error)
}
and load it when you needed in the svc
While it's technically possible to use the solution above to achieve what you're asking, this may not pass App Store review. Per the SFSafariViewController docs:
In accordance with App Store Review Guidelines, this view controller must be used to visibly present information to users; the controller may not be hidden or obscured by other views or layers. Additionally, an app may not use SFSafariViewController to track users without their knowledge and consent.

How can I get a specific button running on tvOS (AppleTV) to take focus? (Objective C)

The project have some views with different buttons. When I hide a view and show the other view, I can't get the focus on my button.
I think is related to setNeedsFocusUpdate. I have read the Apple doc. There is not any example.
Does anyone know how to do it and put an example (Objective C)?
You need to override preferredFocusedView, and when you are hiding one view and showing there call this method setNeedsFocusUpdate, your preferredFocusedView implementation should be something like this
- (UIView *)preferredFocusedView
{
// Add your logic here, it could be more complicated then what is below
if (view1.hidden)
{
return _button;
}
else
{
return _button2
}
}
And if you want to make custom view get focus, override canBecomeFocused method and return true
Edit
You can use add a breakpoint and execute this command po [buttonYouWantToFocus _whyIsThisViewNotFocusable] it will tell you why its not focusable.
If you are adding a sub view programmatically, maybe this is what you want:
- (UIView *)preferredFocusedView {
return [view1 preferredFocusedView];
}
I realize your question is specific to Objective-C but here is a way to solve for this in Swift. You need to override the preferredFocusedView property.
override var preferredFocusedView: UIView? {
guard primaryView.hidden == false else {
return secondaryView
}
return primaryView
}
Then just call setNeedsFocusUpdate() whenever an event happens that causes your views to be hidden. Hope this helps...
Another option (if you don't want to use preferredFocusedView) is, instead of setting your view to be hidden, simply remove it from it's superview, like so:
myView.removeFromSuperview()
This automatically takes the focus away from the button that is removed and gives it to another one that is still on screen.

How to hide the iOS 8 Today Widget when there is nothing to display?

I'm using the today widget for iOS8 to display information relevant to the current day. The problem is I don't want to display the widget/section at all if there are no relevant messages to show.
I know it must be possible as the BA app does it (it only shows the widget when there is a flight, the rest of the time its not visible at all). I just cant figure out a way to achieve this behaviour.
Does anyone know how this can be done?
I found the way to do this is using the NCWidgetController. This allows you to easily specify when the today widget should be displayed based on whatever criteria you see fit.
Simply add the following into your viewDidLoad method (or anywhere that will be called when the widget reloads) in the today widget view controller and it will work:
BOOL hasDataToDisplay = NO;
NCWidgetController *widgetController = [NCWidgetController widgetController];
[widgetController setHasContent:hasDataToDisplay forWidgetWithBundleIdentifier:#"com.my-company.my-app.my-widget"];
Apple Docs: https://developer.apple.com/library/ios/documentation/NotificationCenter/Reference/NCWidgetController_Class/index.html#//apple_ref/occ/cl/NCWidgetController
WARNING: The NCWidgetController cannot be reset from the widget itself once you have set there is no content to display. In other words once you set it to NO then there is no going back unless you trigger it from the parent/containing app.
In the widget's ViewController's viewDidLoad method add the following:
BOOL DisplayWidget = NO;
[[NCWidgetController widgetController] setHasContent:DisplayWidget
forWidgetWithBundleIdentifier:#"<widget's bunder identifier>"];
This will disable the widget from showing.
To enable it again, you must do that from the containing app using the same line passing YES to setHasContent parameter. Make sure to add the necessary imports to the containing app in the ViewController which will re-enable the widget:
#import <NotificationCenter/NotificationCenter.h>
#interface ViewController () <NCWidgetProviding> {...}
[Check out page 41 of the documentations for widgets
https://developer.apple.com/library/ios/documentation/General/Conceptual/ExtensibilityPG/ExtensibilityPG.pdf ]
The approach which I used, though not perfect and has a small remnant in Notification Center, but worked for me:
In viewDidLoad() set preferred content size height to 1:
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view from its nib.
preferredContentSize = CGSizeMake(0, 1)
view.setNeedsLayout()
}
then when widget updates, gets real height and set it:
var data: NSData?
func updateData() {
// fetch data
if let data = data {
let viewHeight: CGFloat
// UI preperation and initialize viewHeight var
preferredContentSize = CGSizeMake(0, viewHeight);
} else {
preferredContentSize = CGSizeMake(0, 1);
}
}
func widgetPerformUpdateWithCompletionHandler(completionHandler: ((NCUpdateResult) -> Void)) {
// Perform any setup necessary in order to update the view.
// If an error is encountered, use NCUpdateResult.Failed
// If there's no update required, use NCUpdateResult.NoData
// If there's an update, use NCUpdateResult.NewData
updateData()
completionHandler(data != nil ? NCUpdateResult.NewData : NCUpdateResult.NoData)
}
It is better use
+ (instancetype)widgetController
then call
- (void)setHasContent:(BOOL)flag forWidgetWithBundleIdentifier:(NSString *)bundleID

Check if user finished sliding on a continuous UISlider?

In my app, I have a couple of UISlider instances to change various values. The values are displayed right next to the slider, as well as rendered in a 3d space in another visible part of the app.
The 3d part includes some rather heavy calculations, and right now it doesn't seem possible to update it live as the slider changes. That would imply that I'd have to set the slider's continuous property to NO, therefore only getting updates when the slider has finished changing.
I'd prefer to have the displayed value update live, however. Is there a way to have a slider that is continuous (so I can update my value-label in real time) and still sends some kind of message once the user has finished interacting with it? My gut feeling right now is to subclass UISlider and override the touchesEnded: method. Is that feasible?
You can do this with simple target/actions.
Set a target and action for the UIControlEventValueChanged event, and then another target and action for the UIControlEventTouchUpInside event. With the continuous property set to YES, the value changed event will fire as the slider changes value, while the touch up inside event will only fire when the user releases the control.
I just had to do this, so I looked up touch properties, and used the full IBAction header.
This should be a viable alternative for people who want some extra control, though Jas's is definitely easier on the code side.
- (IBAction)itemSlider:(UISlider *)itemSlider withEvent:(UIEvent*)e;
{
UITouch * touch = [e.allTouches anyObject];
if( touch.phase != UITouchPhaseMoved && touch.phase != UITouchPhaseBegan)
{
//The user hasn't ended using the slider yet.
}
}
:D
Also note you should connect the UIControlEventTouchUpOutside event as well in case the user drags his finger out of the control before lifting it.
In Swift 3:
#IBAction func sliderValueChanged(_ slider: UISlider, _ event: UIEvent) {
guard let touch = event.allTouches?.first, touch.phase != .ended else {
// ended
return
}
// not ended yet
}