didEnterRegion and didExitRegion animation conflicting - ios

Question

I'm building an app that uses GeoFencing. My didEnterRegion and didExitRegion methods are called as they're supposed to, seemingly in the correct order, but fails to update the UI accordingly.
What works:
User enters region
didEnterRegion gets called
UI is updated correctly within that method
What doesn't work:
User enter region
User goes straight from one region to another
didExitRegion is called
UI updates
didEnterRegion is called
NSLogs indicate that everything executes in the correct order
UI isn't updated. The UI updates that were done in didExitRegion remains.
My methods:
Custom function to update label (called from didEnterRegion and didExitRegion):
-(void)updateCurrentLocationLabelAndImage:(NSString *)locationText subLocationText:(NSString *)subLocationText;
{
// Clear existing animations before we begin
[self.locationLabel.layer removeAllAnimations];
[self.subLocationLabel.layer removeAllAnimations];
[self.ovalImageView.layer removeAllAnimations];
if (![locationText isEqual:#""])
{
// Only animate if the text changes
if (![self.locationLabel.text isEqualToString:locationText])
{
// Update the ovalImageView
CGSize maxLabelSize = CGSizeMake(([UIScreen mainScreen].bounds.size.width - (([UIScreen mainScreen].bounds.size.width * 0.0267) * 2)), 64); // maximum label size
float expectedLabelWidth = [locationText boundingRectWithSize:maxLabelSize options:NSStringDrawingUsesLineFragmentOrigin attributes:#{ NSFontAttributeName:self.locationLabel.font } context:nil].size.width; // get expected width
CGFloat xValueForImage = ((([UIScreen mainScreen].bounds.size.width - expectedLabelWidth) / 2) - 25); // Calcuate the x-coordinate for the ovalImageView
if (xValueForImage < 15)
{
xValueForImage = 15; // we don't want it to display off-screen
}
self.ovalImageViewLeadingConstraint.constant = xValueForImage;
[self.view setNeedsUpdateConstraints];
[self changeLabelText:self.subLocationLabel string:subLocationText];
// Update the subLocationLabel
[UIView animateWithDuration:.15 animations:^{
// Animate
self.locationLabel.alpha = 0;
self.ovalImageView.alpha = 1;
[self.view layoutIfNeeded]; // update the UI
}completion:^(BOOL finished) {
// Set the text
self.locationLabel.text = locationText;
self.locationLabel.adjustsFontSizeToFitWidth = YES;
[UIView animateWithDuration:.15 animations:^{
// Animate
self.locationLabel.alpha = 1;
}completion:^(BOOL finished) {
// Complete
}];
}];
}
} else if ([locationText isEqual:#""])
{
// Move it to the center
self.ovalImageViewLeadingConstraint.constant = (([UIScreen mainScreen].bounds.size.width / 2) - 9); // Default center calculation for this image
[self.view setNeedsUpdateConstraints];
[self changeLabelText:self.subLocationLabel string:subLocationText]; // Update the subLocationLabel
[UIView animateWithDuration:.15 animations:^{
self.locationLabel.alpha = 0;
self.ovalImageView.alpha = 1;
[self.view layoutIfNeeded];
}completion:^(BOOL finished) {
// Complete
self.locationLabel.text = #"";
}];
}
}
But the label stays the same, even though it logs the correct order of execution and everything looks fine. Any ideas? I'm really stuck..
Thanks!

Answer 1

To explain in detail,
lets consider a scenario of user exiting region1 and straight entering region2.
Step 1:
So, the event exit is fired, the following lines are executed,
NSLog(#"changing text from: %#, to: %#", label.text, string);
// Only animate if the text changes
if (![label.text isEqualToString:string])
At this If check, the label text is "inside region" (which is for region 1). Since the method is called from the exit method, the parameter string will have the value "Outside region". Both the values are not same and hence the control enters this region.
Step 2:
At this point you started an animation of duration 0.15, however the value of the label is not changed until the animation is completed as the code is in the completion block.
// Complete
label.text = string;
Step 3:
The did enter region 2 event is fired. The label text is not yet up to date, so it excites the below line
NSLog(#"changing text from: %#, to: %#", label.text, string);
However since the label text is "inside region" and string value is also "inside region", the control moves out of the if condition.
if (![label.text isEqualToString:string])
To verify:
Pass in a customized string value while calling change label text making the text specific viz., "inside region 1", "exiting region 1", "inside region 2" etc., This way the value will be different and would get updated.
Set the value of the label immediately before animation.
Assign the value to the atomic string property and check for the property Value.
for eg:
#property (atomic, strong) NSString * currentLabelText;
-(void)changeLabelText:(UILabel *)label string:(NSString *)string
{
NSLog(#"changing text from: %#, to: %#", label.text, string);
// Only animate if the text changes
if (![self. currentLabelText isEqualToString:string])
{
self. currentLabelText = string; //Ultimately this would be our value
[UIView animateWithDuration:.15 animations:^{
// Animate
label.alpha = 0;
}completion:^(BOOL finished) {
// Complete
label.text = self. currentLabelText;
[UIView animateWithDuration:.15 animations:^{
// Animate
label.alpha = 1;
}completion:^(BOOL finished) {
// Complete
}];
}];
}
}
Or another way as it suites your requirement.

Answer 2

You can try this…
static NSString *currentText;
currentText = locationText;
[UIView animateWithDuration:.15 animations: ^{
// Animate
self.locationLabel.alpha = 0;
self.ovalImageView.alpha = 1;
[self.view layoutIfNeeded]; // update the UI
} completion: ^(BOOL finished) {
// Set the text
if (![currentText isEqualToString:locationText]) {
return;
}
self.locationLabel.text = locationText;
self.locationLabel.adjustsFontSizeToFitWidth = YES;
[UIView animateWithDuration:.15 animations: ^{
// Animate
self.locationLabel.alpha = 1;
} completion: ^(BOOL finished) {
// Complete
}];
}];

Answer 3

I'd recommend you to put your UI update code in a dispatch block to make sure the UI-Update will performed on the main thread.
dispatch_async(dispatch_get_main_queue(), ^{
//... UI Update Code
});
I guess the main thread thing is your biggest problem. To me the code looks a bit strange at this points:
you are mixing different data types (float, CGFloat, int)
refer to CocoaTouch64BitGuide this could be a problem but I think it doesn't solve your layout issue. More critical are the magic numbers in general.
your autolayout code could be a problem
I believe it isn't necessary to move ovalImageView by manipulating the LeadingConstraint. Just set the contentMode to center/left/right and autolayout will do the reset. If you realy need to change the constraint then do it in [yourView updateConstraints] method. If you want the labels width ask for it: [label intrinsicContentsize] and use setPreferredMaxLayoutWidth if you need it. If your autolayout code is correct no view will appear "off-screen".
your animations could be a little bit jumpy
You use removeAllAnimations at first. Basically right but if you expect high frequented updates I'd recommend just to change the labels/images content while a previous animation runs. Otherwise your image jumps back and a new animation will start.