I am using the following code with the label instantiated in a getter method:
-(UILabel *)switchUpLabel
{
if (!_switchUpLabel) _switchUpLabel = [[UILabel alloc]init];
return _switchUpLabel;
}
-(void)shouldShowSwitchupLabel:(BOOL)show
{
if (show)
{
self.switchUpLabel.text = #"🔀";
self.switchUpLabel.font = [UIFont systemFontOfSize:30.0];
[self.switchUpLabel sizeToFit];
self.switchUpLabel.frame = CGRectMake(self.imageView.center.x-self.switchUpLabel.frame.size.width/2, 10, self.switchUpLabel.frame.size.width, self.switchUpLabel.frame.size.height);
[self.view addSubview:self.switchUpLabel];
}
else [self.switchUpLabel removeFromSuperview];
}
When I execute [self.switchUpLabel removeFromSuperview]; the label remains on screen. The only way I can get the label "off" is to do something like
self.switchUpLabel.text = #"";
A few notes:
1/ I tried adding the remove statement immediately after the add statement which should have resulted in the label not showing at all. However, the label did show and was never removed.
2/ I verified that the label is not nil and is pointing to the same label in both cases (I output the label object to NSLog)
3/ I put the remove statement inside a main queue block to ensure it was executing on the main thread. No difference.
Related
For the tutorial for my app, I am trying to create a UILabel that drifts across the displayed screen when a view appears and then is destroyed so that if the user comes back to that view during the tutorial, the UILabel will be created anew and again drift across the page. Here's a sample of one of the custom view controllers I am displaying with my UIPageViewController:
//this is just a custom UILabel with some padding
#property (nonatomic) PaddedLabel *directionsLabel;
//I have tried setting UILabel to nil or removing it from view
-(void)viewWillDisappear:(BOOL)animated
{
NSLog(#"view is disappearing");
//this does not remove the label
self.directionsLabel = nil;
//nor does this
[self.directionsLabel removeFromSuperview];
}
- (void)viewDidAppear:(BOOL)animated
{
[self messageTutorial];
}
- (void)messageTutorial
{
CGFloat width = [[UIScreen mainScreen] bounds].size.width;
CGFloat height = [[UIScreen mainScreen] bounds].size.height;
PaddedLabel *directionsLabel = [[PaddedLabel alloc] initWithFrame:CGRectMake(_width/2, _height/2, 100, 100)];
directionsLabel.text = #"test";
CGRect f = directionsLabel.frame;
f.size = size;
directionsLabel.frame = f;
directionsLabel.center = self.view.center;
f = directionsLabel.frame;
f = directionsLabel.frame;
f.origin.y = .1*height;
directionsLabel.frame = f;
[self.view addSubview:directionsLabel];
[UIView animateWithDuration:TUTORIAL_DISAPPEAR_TIME animations:^{
directionsLabel.alpha = .5;
CGRect f = directionsLabel.frame;
f.origin.y = height - f.size.height*1.4;
directionsLabel.frame = f;
NSLog(#"animating");
} completion:^(BOOL finished) {
[directionsLabel removeFromSuperview];
//this also doesn't actually remove the label
}];
}
The problem is that if the user pages back to see this view she now sees a new label and the old one, so that if you page back and forth back and forth you end up with many many labels all saying the same thing, in different stages of progressing across the screen.
How can I remove the UILabel when the view disappears and add/create a new one when the view appears/reappears?
Thank you.
The code in your viewWillDisappear method is backwards. You need:
- (void)viewWillDisappear:(BOOL)animated {
NSLog(#"view is disappearing");
[self.directionsLabel removeFromSuperview];
self.directionsLabel = nil;
}
As you had it, setting self.directionsLabel to nil before trying to remove it results in a no-op.
Also, be sure to set self.directionsLabel when you create the label.
Instead of setting your label to nil and effectively destroying the label object (assuming automatic reference counting is on) rather use the following method to hide and show the label as and when your need it.
[self.directionsLabel setHidden:YES]; // hides it
[self.directionsLabel setHidden:NO]; // shows it
You've got the right idea setting objects you're not using to nil and removing them from the super view but it's over kill. A UILabel object uses a negligible amount of memory and you're better off creating the object once and then changing it's properties as you need to.
You don't seem to be setting self.directionsLabel to anything when you create the directionsLabel inside the messageTutorial method. It is a local instance of the label there. You should set it in the method somewhere.
Afterwards, removing it from the superview in viewWillDisappear will work (tested to verify).
I am getting a strange behavior setting the selectedRange property for a textView within the textViewDidChangeSelection delegate.
My code in viewDidLoad is:
hiddenTextView = [[UITextView alloc] initWithFrame:CGRectMake(0, 0, 500, 500)];
//[hiddenTextView setHidden:YES];
_hiddenTextViewText=#"ulrd";
hiddenTextView.text = _hiddenTextViewText;
hiddenTextView.delegate = self;
_hiddenTextViewDefaultRange = NSMakeRange(2,0);
hiddenTextView.selectedRange = _hiddenTextViewDefaultRange; //horizontal and vertical center of the textview
[self.view addSubview:hiddenTextView];
[hiddenTextView becomeFirstResponder];
if (_keyboardShown)
[hiddenTextView resignFirstResponder];
I define the textViewDidChangeSelection as follows:
- (void)textViewDidChangeSelection:(UITextView *)textView {
NSLog(#"%lu",(unsigned long)textView.selectedRange.location);
if (textView.selectedRange.location != _hiddenTextViewDefaultRange.location)
{
hiddenTextView.selectedRange = _hiddenTextViewDefaultRange;
}
}
I set a 4 character text and put the selection index in position 2 (middle). The result is that if I press up arrow on the keyboard in simulator NSLog outputs 0 (start of text) and then 2 (reseting the position) which is correct. If I press up again it does the same thing so still correct. Problem is that if I hit up x times I have to hit down equal times before I am able to go to the end of the text (position 4).
I tried resetting the position with a UIButton instead of doing it programmatically and there it works fine. Any ideas?
I managed to overcome the problem. Instead of:
hiddenTextView.selectedRange = _hiddenTextViewDefaultRange;
I used:
dispatch_async(dispatch_get_main_queue(), ^{
textView.selectedRange = hiddenTextViewDefaultRange;
});
...to execute the command async. It worked, however I am not sure why it needed to be like that.
I am trying to programatically generate two UILabels in my application for each UIImageView on my storyboard. The code runs and works correctly, however, on first load the two UILabels form in the (0.0) coordinate of the main view, as opposed to the UIImageView frame origin.x,origin.y. I can't understand why this is happening.
If I then click on a different tab and return to the page, the labels generate in the correct location.
Why is this? How can I get it to initially generate the labels in the correct location?
-(void) viewWillAppear:(BOOL)animated
{
//removed unneccessary code above...
int i = 0;
for (UIImageView *plantScreen in self.view.subviews)
{
if ([plantScreen isMemberOfClass:[Plant class]])
{
#try
{
//the label which will hold the name
UILabel *plantName = [[UILabel alloc] initWithFrame:CGRectMake((plantScreen.frame.origin.x), (plantScreen.frame.origin.y+ plantScreen.frame.size.height), 160, 30.0)];
plantName.numberOfLines = 1;
plantName.minimumScaleFactor = .5;
plantName.adjustsFontSizeToFitWidth = YES;
[plantName setTextAlignment:NSTextAlignmentCenter];
[plantName setBackgroundColor:[UIColor clearColor]];
[self.view addSubview:plantName];
plantName.hidden = false;
[self.view bringSubviewToFront:plantName];
//create the label which will hold the quantity
UILabel *quantity = [[UILabel alloc] initWithFrame:CGRectMake((plantScreen.frame.origin.x), (plantScreen.frame.origin.y+ plantScreen.frame.size.height + 20), 160, 30.0)];
[quantity setTextAlignment:NSTextAlignmentCenter];
[quantity setBackgroundColor:[UIColor clearColor]];
quantity.text = [NSString stringWithFormat:#"%d",plant.quantity];
[self.view addSubview:quantity];
quantity.hidden = false;
[self.view bringSubviewToFront:quantity];
i++;
}
#catch (NSException *exception)
{
NSLog(#"An exception occured: %#", [exception reason]);
}
#finally
{
}
}
}
}
Frame of the UIImageView depends on the image being drawn and its contentMode property. You can try setting the contentMode to UIViewContentModeScaleAspectFill to see if it forces to keep its assigned frame.
First things first, you're missing a call to [super viewWillAppear:animated]. You need to give the superclass (including the UIViewController base class) a chance to "do its magic".
Never forget about giving the parent class a chance to do its magic, unless you know really really well what you're doing.
Second, UI creation should be done in -loadView, not in viewWillAppear:.
Try these two things first.
Alright. Now I'm curious about how you moved things to -loadView. Did you add [super loadView];?
In fact, now that I think about it, moving to -loadView is wrong in this case; you obviously instantiate some views through a nib. UIViewController's implementation of -loadView typically just loads the nib file. Once that's done, UIViewController's -loadView calls -viewDidLoad.
So when you're not creating all UI programmatically but are instead allowing UIViewController to load it from nib, you actually probably want to move code into -viewDidLoad. (See template generated by Xcode when you tell it to create a new UIViewController subclass.)
Moving on, let's consider what the frame depends on. It depends on some view class you called Plant.
Please don't call it that way; it's confusing. Call it PlantView, so a casual reader of your code is aware of what the class is supposed to do. Similarly, you might want to call the variables plantView instead of plantScreen, and plantNameLabel instead of plantName. plantScreen implies a variable containing UIScreen, and plantName implies an NSString more than it implies a UILabel. Same applies to quantity; call this variable quantityLabel.
Next, let's consider what the variables are depending on -- their origin's x and y do not change based on the counter, variable i. Perhaps you meant to write:
UILabel *plantName = [[UILabel alloc] initWithFrame:CGRectMake((plantScreen.frame.origin.x), (plantScreen.frame.origin.y+ plantScreen.frame.size.height * i), 160, 30.0)];
and later on:
UILabel *quantity = [[UILabel alloc] initWithFrame:CGRectMake((plantScreen.frame.origin.x), (plantScreen.frame.origin.y+ plantScreen.frame.size.height*i + 20), 160, 30.0)];
Next, avoid exceptions and exception handling. Ensure that the exception does not occur via other forms of checking; Apple highly recommends you fix exceptions while writing the application and not handle them when they run:
Important: You should reserve the use of exceptions for programming or
unexpected runtime errors such as out-of-bounds collection access,
attempts to mutate immutable objects, sending an invalid message, and
losing the connection to the window server. You usually take care of
these sorts of errors with exceptions when an application is being
created rather than at runtime.
Next, a small stylistic remark (not very important): you're mixing calling setters via properties and calling setters directly. Nothing wrong (they end up doing exactly the same), but stylistically not very nice.
Next, unless you're using ARC (automatic reference counting), don't forget to release the views once they're added as subviews.
Next, plantScreen (which I named plantView below) can have type set to Plant (which I named PlantView below) when declared inside the loop.
Last but highly important and extremely easy to miss: you call the function isMemberOfClass: instead of isKindOfClass:.
Reworked version of your code (untested):
-(void)viewDidLoad
{
[super viewDidLoad];
int i = 0;
for (PlantView *plantView in self.view.subviews)
{
if ([plantView isKindOfClass:[PlantView class]])
{
//the label which will hold the name
CGRect plantNameLabelFrame = CGRectMake((plantScreenView.frame.origin.x),
(plantScreenView.frame.origin.y + plantScreen.frame.size.height*i),
160,
30.0);
UILabel *plantNameLabel = [[UILabel alloc] initWithFrame: plantNameLabelFrame];
plantNameLabel.numberOfLines = 1;
plantNameLabel.minimumScaleFactor = .5;
plantNameLabel.adjustsFontSizeToFitWidth = YES;
plantNameLabel.textAlignment = NSTextAlignmentCenter;
plantNameLabel.backgroundColor:[UIColor clearColor];
[self.view addSubview:plantNameLabel];
[plantNameLabel release];
//create the label which will hold the quantity
CGRect quantityLabelFrame = CGRectMake((plantScreenView.frame.origin.x),
(plantScreenView.frame.origin.y + plantScreen.frame.size.height*i + 20),
160,
30.0);
UILabel *quantityLabel = [[UILabel alloc] initWithFrame: quantityLabelFrame];
quantityLabel.textAlignment = NSTextAlignmentCenter;
quantityLabel.backgroundColor = [UIColor clearColor];
quantityLabel.text = [NSString stringWithFormat:#"%d", plant.quantity]; // NB: what's "plant"?
[self.view addSubview:quantityLabel];
i++;
}
}
}
I've also removed .hidden = false (which should actually read .hidden = NO; this is Objective-C, and not C++), and bringSubviewToFront: (it's already in front, having just been added by addSubview:).
Here's my code:
if([pantallas objectForKey:par]){
UIView *vista= [[UIView alloc] initWithFrame:self.Botones.frame];
vista.backgroundColor= [UIColor brownColor];
CGSize la= CGSizeMake(50,60);
int cuantos= [part2 count];
NSArray *arr= [COLGenerales tileN:cuantos RectsOfSize:la intoSpaceOf:vista.frame withMaxPerRow:5 spaceVertical:10 spaceHorizontal:10];
for(int j=0; j<cuantos; j++){
UIButton *bot= [[UIButton alloc] initWithFrame:[[arr objectAtIndex:j] CGRectValue]];
bot.tag=j;
bot.titleLabel.text=par;
bot.titleLabel.hidden=true;
bot.imageView.image = [UIImage imageNamed:[[part2 allKeys] objectAtIndex:j]];
[bot addTarget:self action:#selector(registrar:) forControlEvents:UIControlEventTouchDown];
[vista addSubview:bot];
}
[pantallas setObject:vista forKey:par];
self.Botones= vista;
}else{
self.Botones= [pantallas objectForKey:par];
}
Botones is a simple view embedded into the view this class controls (first initiated by the Nib file), the class method of COLGenerales returns an array of CGRects coded as NSValues, and registrar: is a local method.
Everything gets properly set (I've thoroughly checked this with the debugger). The view gets successfully created, set, and added to the dictionary.
However, I absolutely never get the actual screen to change. I even included the background color change just to check if it isn't some kind of problem with the buttons. Nothing. Any suggested solution to this?
A property that is an IBOutlet does not have an intrinsic connection to the view hierarchy—it only makes it possible to populate that property from a xib. When you set self.Botones, you'll need to do something like the following:
[self.Botones removeFromSuperview];
self.Botones = newValue;
[self.BotonesSuperview addSubview:self.Botones];
If you update self.Botones in many places, and you always want the change reflected on-screen, you could add this into a setter implementation:
-(void)setBotones:(UIView*)newValue {
if (newValue != _Botones) {
[_Botones removeFromSuperview];
_Botones = newValue;
[self.BotonesSuperview addSubview:_Botones];
}
}
I recommend using a UINavigation controller that houses these two views.
You can reference this link Swapping between UIViews in one UIViewController
Basically, you create one view, removeSubview for the first and then add the second one with addSubview!
[view1 removeFromSuperview];
[self.view addSubview: view2];
Other reference sources:
An easy, clean way to switch/swap views?
How to animate View swap on simple View iPhone App?
Hopefully this helps!
I am facing a problem with updating my labels.. it doesn't remove the old values so new values go on top of old ones.. any help with this will be appreciated..
timer = [NSTimer scheduledTimerWithTimeInterval:1
target:self
selector:#selector(updateLabels)
userInfo:nil
repeats:YES];
-(void) updateLabels{
for (GraphView *graph in arr){
// retrieve the graph values
valLabel = [[UILabel alloc] initWithFrame:CGRectMake(i * 200, 0, 90, 100)];
valLabel.textColor = [UIColor whiteColor];
valLabel.backgroundColor = [UIColor clearColor];
valLabel.text = [NSString stringWithFormat:#"Value: %f", x];
i++;
}
}
If you set the text of your label you do not need to call setNeedsDisplay or clearContext etc.
In your code, I do not know what are your variables i and x?
The main problem is that you are creating and adding new labels on your view. When you call updateLabels method, may cause a Memory leak. Simply you have n times labels overlapped.
You need to remove the labels before you create and add new labels or you can reuse which you already have. To reuse your labels you need to save them to an array and update texts.
If you want to create new labels then you can do like this unless you have other labels in your view
-(void) updateLabels{
// remove all labels in your view
for (UIView *labelView in self.view.subviews) {
if ([labelView isKindOfClass:[UILabel class]]) {
[labelView removeFromSuperview];
}
for (GraphView *graph in arr){
// retrieve the graph values
valLabel = [[UILabel alloc] initWithFrame:CGRectMake(i * 200, 0, 90, 100)];
valLabel.textColor = [UIColor whiteColor];
valLabel.backgroundColor = [UIColor clearColor];
valLabel.text = [NSString stringWithFormat:#"Value: %f", x];
i++;
}
}
When you create new labels like this you need to add them to your view as subview
[self.view addSubview: valLabel];
if you have other labels in your view then you can save them in an array and remove just them
Your updateLabels method is actually creating new UILabel controls each time so they will simply appear "on top of" older ones. I'm guessing this is not what you want, although it's not perfectly clear so apologies if I've misunderstood what you're trying to do.
If I'm correct about that, create your UILabel controls just once maybe in your viewDidLoad or similar. Then just set their .text properties when your timer fires.
You need to call setNeedsDisplay so that the app knows it has changed and redraw it.
- (void)setNeedsDisplay
Set clearsContextBeforeDrawing property of your label to YES
you can set this from nib as well as code.
label.clearsContextBeforeDrawing = YES;