I ran into a weird bug :
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc]initWithTarget:self action:#selector(tap)];
TestView *testView = [[TestView alloc] initWithFrame:self.view.bounds];
[testView addGestureRecognizer:tap];
testView.backgroundColor = [UIColor orangeColor];
[self.view addSubview:testView];
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, 2.5 * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
NSLog(#"testView removeFromSuperview");
[testView removeFromSuperview];
});
}
-(void)tap{
NSLog(#"test");
}
TestView is a subclass of UIView that prints log when -(void)dealloc is called.
If I do nothing and wait till the testView removes from its superview,the console logs :
2016-08-25 15:08:30.176 TapTest[12786:238984] testView removeFromSuperview
2016-08-25 15:08:30.176 TapTest[12786:238984] test view dealloc
However , if i tap on the view that actually triggers the tap action,the console only logs :
2016-08-25 15:09:43.605 TapTest[12802:240217] test
2016-08-25 15:09:45.306 TapTest[12802:240217] testView removeFromSuperview
I've done quite some research , but still have no idea of what's going on.
I am using Xcode 7.3(7D175) and iOS9.
EDIT: A friend of mine says this has something to do with runloop and autorealease pool , and after testView is removed from superview , i tap on the view again to trigger the next runloop , and the text view is deallocated.
This is probably due to an implementation detail of the touch management system.
As you've mentioned in your edit, if you touch the view once more after your TestView has been removed, you will notice that it gets deallocated at this point.
If you set a breakpoint in dealloc, you will see that it gets deallocated when a UITouch gets deallocated.
At this point you can only guess what is happening, but most probable thing is that iOS keeps around the last touch that happened with a UITouch object. An a UITouch keeps a reference to the view in which the touch happened (see the view property of UITouch). In this case this is your TestView and this is why it doesn't get deallocated immediately.
I have figured something.
I added some tricks for catching retain count on arc.
NSLog(#"testView removeFromSuperview -> %d", (int)[testView performSelector:NSSelectorFromString(#"retainCount")]);
none tap:
testView removeFromSuperview -> 3
with tap:
testView removeFromSuperview -> 4
something has grabbed testview in tap gesture with click tap event once or more. I guess this happening by relative with some logic on main run loop event.
so funny question. thank you. I will digging more.
Related
my didAddSubview is not being called.
This is what I am doing.
In my viewController
- (void)viewDidLoad {
[super viewDidLoad];
SomeView *view = [[SomeView alloc] initWithFrame:CGRectMake(0.0, 0.0, CGRectGetWidth(self.view.frame), CGRectGetHeight(self.view.frame))];
[self.view addSubview:view];
}
Where my SomeView is a UI view (.h file)
#import <UIKit/UIKit.h>
#interface DyteMeetingView : UIView
#end
in which I have didAddSubview like this
- (void)didAddSubview:(UIView *)subview{
[super didAddSubview:subview];
[self someFunc];
}
I placed debugger in didAddSubview but the debugger never reaches here and hence [self someFunc]; is also not called.
Since didAddSubview is a lifecycle method for UI view, I am also not calling it from anywhere.
Can someone help me in figure out the concept I missed out on/what I could be doing wrong?
PS: I don't have any xib file for UIView.
PS: Intentionally added swift tag as well since there isn't large chunk of code and I am confident that swift developers would be able to understand the question/code and might be able to help me out.
didAddSubview in SomeView will be called when a sub view is added to an instance of SomeView, but that isn't what you are doing here. You are adding a SomeView as a subview of another view.
You want didMoveToSuperview; in this method you can use the superview property of self to identify the view that it moved to.
The didAddSubview will be called in viewController.view, instead of your SomeView, because you using viewController.view.addSubview(subview)
I want a pretty simple thing - in my top controller (which is navigation controller) to set up a tap gesture recognizer which will catch all the taps everywhere on the view. Currently when I tap on a button the system is not even thinking to bother my recognizer (except the gestureRecognizer:shouldReceiveTouch: delegate method, where I return YES). Instead, it just executes a button click. So I want to install "the strongest" recognizer on a view hierarchy no matter what.
You might try putting an empty UIView on top of all other views and add the UITapGestureRecognizer to it. We do something similar with help overlays. The biggest issue is figuring out how and when to ignore the touches so the underlying buttons get them when needed.
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
UIButton *b = [UIButton buttonWithType:UIButtonTypeInfoDark];
b.frame = CGRectMake(50,50, b.bounds.size.width, b.bounds.size.height );
[self.view addSubview:b];
UIView *invisibleView = [[UIView alloc] initWithFrame:self.view.bounds];
invisibleView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
[invisibleView addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(tapHit:)]];
[self.view addSubview:invisibleView];
}
-(void)tapHit:(UITapGestureRecognizer*)tap {
NSLog( #"tapHit" );
}
#end
I have a few custom UIView objects that all handle drawing like this:
- (void)drawRect:(CGRect)rect {
// ^ I init the layers 1 and 2
[self.layer insertSublayer:layer1 atIndex:0]; // 1 or more
[self.layer insertSublayer:layer2 atIndex:1];
}
They also have a - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event; with nothing else inside but a NSLog.
I add them all inside my main ViewController like so:
- (void)viewDidLoad
{
[super viewDidLoad];
CustomView *myViewWith1Layer = [[CustomView alloc] initWithFrame:CGRectMake(20, 20, 440, 260)];
[self.view addSubview:myViewWith1Layer];
CustomViewLayered *myViewWith2Layer = [[CustomViewLayered alloc] initWithFrame:CGRectMake(40, 260, 200, -120)];
[self.view addSubview:myViewWith2Layers];
}
When I run my app, if I tap on a view that has only a single layer - I get my NSLog to show, and everything's fine. If, on the other hand, I tap on views with 1+ layers, the app crashes (objc_msgSend log shows up with "EXC_BAD_ACCES (code=1, address=..."). I guess this is somehow related with ARC, which I have enabled.
How do I add multiple layers to a view, without it being messed up by ARC?
I don't think that this is an ARC problem, but creating and inserting the layers in drawRect
is wrong. This should be done (only once) in the init method of the view, e.g. in initWithFrame.
In my case, the solution was definitely related to ARC.
When initialising my delegates, I immediately assigned them to the layer.delegate property, and ARC would remove the object from existence immediately after that.
So for each layer, I add a strong #property (strong, nonatomic) delegatesClass *delegatesName and initialise straight to the property. After that, I assign the layer.delegate = self.delegatesName.
This did solve the issue, although I'm not sure if it is the right way to do things.
I created three files: MyViewController.h, 'MyViewController.m, MyViewController.xib. In thexib` file I created one UIScrollView as the root level element and made all necessary connections to its file owner.
In my .m file, I overwrite the loadView method to set some additional properties of the ScrollView.
-(void)loadView{
[super loadView];
UIScrollView *tmp = (UIScrollView *)[self view];
[tmp setMaximumZoomScale:3.0]; // crashed here
}
However, the code crashed at the last line of the function, the log said:
-[UIView setMaximumZoomScale:]: unrecognized selector sent to instance 0x1cda5d60
It seems that tmp was recognized as a UIView, not a UIScrollView despite the explicit cast. It's my understanding that [super loadView]; will load the view from the xib file and set the view of the ViewController. It didn't help even when I moved the crashed line of code to the viewDidLoad function.
Edit:
I found similar pattern in Apple's documentation site:
- (void)viewDidLoad {
[super viewDidLoad];
UIScrollView *tempScrollView=(UIScrollView *)self.view;
tempScrollView.contentSize=CGSizeMake(1280,960);
}
Edit 2:
I somewhat narrowed the problem. Now I've moved the code that casts [self view] to viewDidLoad, and the error occurs only when I override loadView. If I add
-(void)loadView{
[super loadView];
}
The error will occur. If I delete these three lines, no error. But isn't the call to super totally the same as not overriding at all? Why the difference?
Check whether the connections inspector for the connections to files owner is like this or not for scroll view...
See the below picture...
Then place your code like this in viewDidLoad...
- (void)viewDidLoad
{
[super viewDidLoad];
UIScrollView *tempScrollView=(UIScrollView *)self.view;
[tempScrollView setMaximumZoomScale:3.0];
}
This is working fine for me.
Edit 2:
-(void)loadView{
[super loadView];
UIScrollView *tempScrollView=(UIScrollView *)self.view;
tempScrollView.contentSize=CGSizeMake(320,960);
[tempScrollView setBackgroundColor:[UIColor grayColor]];
[tempScrollView setMaximumZoomScale:3.0];
}
This is also working fine for me.
I know this is really basic stuff but i need to understand whether my understanding of this is correct.
So what i want to do is this. I want an view with a label on which when double tapped flips and loads another view. On the second view i want a UIPickerView and above i have a button saying back. Both views will be of same size as an UIPickerView which is 320px x 216px.
What i am thinking of to do is create two UIViewclasses named labelView and pickerView. I would then create a viewController which on loadView loads labelView then when user double taps the labelView i get an event in labelView class which is sent to my viewController that then can unload loadView and load the pickerView.
Does this sound as the best way to do this ? Is there a simpler way ? I am also unsure how i route the event from the labelView class to the viewControllerclass.
I dont exactly know the most efficient way to do it(as i am also now to this language),but it is for sure that i have solved ur problem. I made a simple program for that.Three classes involved here in my eg are BaseViewController (which will show two views),LabelView and PickerView (according to ur requirement).
In LabelView.h
#protocol LabelViewDelegate
-(void)didTapTwiceLabelView;
#end
#interface LabelView : UIView {
id <LabelViewDelegate> delegate;
}
#property(nonatomic,retain)id <LabelViewDelegate> delegate;
-(void)didTouch;
#end
In LabelView.m
#synthesize delegate;
-(id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self)
{
UILabel* labl = [[UILabel alloc] initWithFrame:CGRectMake(10, 5, frame.size.width-20,20)];
labl.text = #"Some Text";
[self addSubview:labl];
[labl release]; labl = nil;
self.backgroundColor = [UIColor grayColor];
UITapGestureRecognizer* ges = [[[UITapGestureRecognizer alloc] initWithTarget:self action:#selector(didTouch)] autorelease];
ges.numberOfTapsRequired = 2;
[self addGestureRecognizer:ges];
}
return self;
}
-(void)didTouch
{
[delegate didTapTwiceLabelView];
}
//=============================================================
In Pickerview.h
#protocol PickerViewDelegate
-(void)didTapBackButton;
#end
#interface PickerView : UIView <UIPickerViewDelegate,UIPickerViewDataSource>{
id <PickerViewDelegate> delegate;
}
#property(nonatomic,retain)id <PickerViewDelegate> delegate;
#end
In Pickerview.m
#implementation PickerView
#synthesize delegate;
-(id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self)
{
UIPickerView* picker = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 30, 320, 216)];
picker.delegate = self;
picker.dataSource = self;
[self addSubview:picker];
[picker release]; picker = nil;
self.frame = CGRectMake(frame.origin.x, frame.origin.y, 320, 250);
UIButton* btn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
[btn setFrame:CGRectMake(10, 1, 50, 27)];
[btn setTitle:#"Back" forState:UIControlStateNormal];
[btn addTarget:self action:#selector(backButton) forControlEvents:UIControlEventTouchUpInside];
[self addSubview:btn];
}
return self;
}
-(void)backButton
{
[delegate didTapBackButton];
}
//====================================================================
in BaseViewController.h
#import "LabelView.h"
#import "PickerView.h"
#interface VarticalLabel : UIViewController<UITextFieldDelegate,PickerViewDelegate,LabelViewDelegate> {
PickerView* myPickerView;
LabelView* myLabelView;
}
#end
In BaseViewController.m
-(void)viewDidLoad
{
[super viewDidLoad];
myPickerView= [[PickerView alloc] initWithFrame:CGRectMake(0, 50, 320, 250)];
[self.view addSubview:myPickerView];
myPickerView.delegate = self;
myLabelView= [[LabelView alloc] initWithFrame:CGRectMake(0, 50, 320, 250)];
[self.view addSubview:myLabelView];
myLabelView.delegate = self;
myPickerView.hidden = YES;
}
#pragma mark PickerViewDelgate
-(void)didTapBackButton
{
myPickerView.hidden = YES;
myLabelView.hidden = NO;
}
#pragma mark LabelViewDelegate
-(void)didTapTwiceLabelView
{
myPickerView.hidden = NO;
myLabelView.hidden = YES;
}
To get events from a button to the view controller, just hook up the button's event, e.g. touch up inside, to a method in the view controller, using interface builder. (Double tapping is probably more complicated though.)
When you say 'flips', do you mean it actually shows an animation of flipping over a view to show a 'reverse' side? Like in the weather app when you hit the 'i' button? I'm assuming this is what you mean.
Perhaps check TheElements sample example on the iPhone Reference Library, it has an example of flip animation.
Btw, it's not strictly necessary to unload the loadView that is being 'hidden' when you flip -- it saves you having to construct it again when you flip back -- but it may be pertinent if you have memory use concerns, and/or the system warns you about memory being low.
Also, what do you mean by "create a UIView"? Do you mean subclass UIView, or just instantiate a UIVIew and add children view objects to it? The latter is the usual strategy. Don't subclass UIView just because you want to add some things to a UIView.
If you've got one screen of information that gives way to another screen of information, you'd normally make them separate view controllers. So in your case you'd have one view controller with the label and upon receiving the input you want, you'd switch to the view controller composed of the UIPickerView and the button.
Supposing you use Interface Builder, you would probably have a top level XIB (which the normal project templates will have provided) that defines the app delegate and contains a reference to the initial view controller in a separate XIB (also supplied). In the separate XIB you'd probably want to add another view controller by reference (so, put it in, give it the class name but indicate that its description is contained in another file) and in that view controller put in the picker view and the button.
The point of loadView, as separate from the normal class init, is to facilitate naming and linking to an instance in one XIB while having the layout defined in another. View controllers are alloced and inited when something that has a reference to them is alloced and inited. But the view is only loaded when it is going to be presented, and may be unloaded and reloaded while the app is running (though not while it is showing). Generally speaking, views will be loaded when needed and unnecessary views will be unloaded upon a low memory warning. That's all automatic, even if you don't put anything in the XIBs and just create a view programmatically within loadView or as a result of viewDidLoad.
I've made that all sound more complicated than your solution, but it's actually simpler because of the amount you can do in Interface Builder, once you're past the curve of learning it. It may actually be worth jumping straight to the Xcode 4 beta, as it shakes things up quite a lot in this area and sites have reported that a gold master was seeded at one point, so is likely to become the official thing very soon.
With respect to catching the double tap, the easiest thing is a UITapGestureRecognizer (see here). You'd do something like:
// create a tap gesture recogniser, tell it to send events to this instance
// of this class, and to send them via the 'handleGesture:' message, which
// we'll implement below...
UITapGestureRecognizer *tapGestureRecognizer = [[UITapGestureRecognizer alloc]
initWithTarget:self action:#selector(handleGesture:)];
// we want double taps
tapGestureRecognizer.numberOfTapsRequired = 2;
// attach the gesture recogniser to the view we want to catch taps on
[labelView addGestureRecognizer:tapGestureRecognizer];
// we have an owning reference to the recogniser but have now given it to
// the label. We don't intend to talk to it again without being prompted,
// so should relinquish ownership
[tapGestureRecognizer release];
/* ... elsewhere ... */
// the method we've nominated to receive gesture events
- (void)handleGesture:(UIGestureRecognizer *)gestureRecognizer
{
// could check 'gestureRecognizer' against tapGestureRecognizer above if
// we set the same message for multiple recognisers
// just make sure we're getting this because the gesture occurred
if(gestureRecognizer.state == UIGestureRecognizerStateRecognized)
{
// do something to present the other view
}
}
Gesture recognisers are available as of iOS 3.2 (which was for iPad only; so iOS 4.0 on iPhone and iPod Touch).