Was wondering if someone might know the answer to this question - is there a cost associated with over hiding a layer.
For example, if a layer is already hidden, does calling layer.hidden = YES over and over have any more overhead than simply stepping through the call stack? Is Cocoa smart enough to know that the layer is already hidden?
- (void) drawRect:(CGRect)rect
{
if ( characterLeftFlag ) {
characterLeftView.layer.hidden = NO;
characterRightView.layer.hidden = YES;
}
else {
characterLeftView.layer.hidden = YES;
characterRightView.layer.hidden = NO;
}
}
Or do I need to always check to see if the layers visibility has changed and then call hidden?
- (void) drawRect:(CGRect)rect
{
if ( characterLeftFlag && characterLeftView.layer.hidden ) {
characterLeftView.layer.hidden = NO;
characterRightView.layer.hidden = YES;
}
else if ( characterRightFlag && characterRightView.layer.hidden ) {
characterLeftView.layer.hidden = YES;
characterRightView.layer.hidden = NO;
}
}
The first pattern allows closure on the conditional statement which results in better coding practice but does result in extra stack calls, while the second pattern is more explicit but results in a conditional statement that falls through.
Thanks,
Bryan
Why not do this:
- (void)setCharacterLeftFlag:flag {
if ( flag ) {
characterLeftView.layer.hidden = NO;
characterRightView.layer.hidden = YES;
}
else {
characterLeftView.layer.hidden = YES;
characterRightView.layer.hidden = NO;
}
}
this is your setter. Now, the OS may not even call drawRect, if it sees that the layer is hidden, and doesn't need to be redrawn.
Quartz will probably optimize setting hidden = YES on a hidden layer, but if you really want to find out you should benchmark.
Related
I am trying to toggle a view on and off which works, but what i need to know is if I am abusing tags with this method. If so is there a better way?
- (IBAction) myButton:(UIButton*)sender {
if ([myLabelText.text isEqualToString:#""])
{
// do nothing
} else {
if ( sender.tag )
{
sender.tag = 0;
[[self firstView] setHidden:YES];
} else {
sender.tag = 1;
firstView.alpha = 100;
[[self firstView] setHidden:NO];
}
}
}
You can use the tag property for anything you like, but in this case you can toggle the visibility without using it:
[self firstView].hidden = ![self firstView].hidden;
Also, the valid range for UIView's alpha property is from 0.0 to 1.0. I'm not sure what you're trying to do there.
-(IBAction) change {
self.imageView.animationImages = myImages;
self.imageView.animationDuration = 2;
if(self.imageView.isAnimating == NO){
[self.imageView startAnimating];
NSLog(#"if bool = %d", self.imageView.isAnimating);
}
else {
self.imageView stopAnimating];
NSLog(#"else bool = %d", self.imageView.isAnimating);
}
}
hello, i'm studying iOS programming.
but i have a question.
i have a button and when i click the button, then this method will be called.
first i click the button, then this code will start the if statement. that's what i want.
i click the button again, i think that will execute the else statement.
but it always execute the if statement only.
why is that?
i really don't know why is that. please help me
I think setting the properties like animationImages or animationDuration will stop the animation, so that by clicking, you every time stop and then just after (re)start it in the if part. Try setting these two properties outside the action method you wrote, and just let the if/else sequence.
-(IBAction) change {
// set these two anywhere else
//self.imageView.animationImages = myImages;
//self.imageView.animationDuration = 2;
if(self.imageView.isAnimating == NO){
[self.imageView startAnimating];
NSLog(#"if bool = %d", self.imageView.isAnimating);
}
else {
self.imageView stopAnimating];
NSLog(#"else bool = %d", self.imageView.isAnimating);
}
}
I have an issue in my application that i wrote coding for the back button in my webView setEnabled = NO, but when the application is launched and webViewDidFinishLoad the back button setEnabled = YES. I tried all possibility to set the back button enabled is equal false but it not works.
-(IBAction) backButton : (id) sender{
backTapped = YES;
[webView goBack];
}
-(IBAction) fwdButton : (id) sender{
forwardTapped = YES;
[webView goForward];
}
- (void)webViewDidStartLoad:(UIWebView *)thisWebView{
NSLog(#"webViewDidStartLoad");
[progressWheel startAnimating];
progressWheel.hidden = NO;
if(!backTapped){
back.enabled = NO;
}
if (!forwardTapped) {
forward.enabled = NO;
}
}
- (void)webViewDidFinishLoad:(UIWebView *)thisWebView
{
[progressWheel stopAnimating];
progressWheel.hidden = YES;
if (!backTapped) {
[back setEnabled:thisWebView.canGoBack];
back.showsTouchWhenHighlighted = YES;
}
if (!forwardTapped) {
[forward setEnabled:thisWebView.canGoForward];
forward.showsTouchWhenHighlighted = YES;
}
}
I can't actually quite understand the problem you are having, but I can see two potential issues:
1) You set backTapped and forwardTapped to YES, but never set them to NO anywhere.
2) Perhaps you don't have "back" or "forward" buttons wired in you xib - if they are nil then back.enabled = NO will do nothing.
Edit:
This logic seems backwards:
if (!backTapped)
back.enabled = NO;
In your code you set backTapped to YES, then this code is hit so !backTapped is ! YES which is NO.
Try
if (backTapped)
back.enabled = NO;
EDIT: It was suggested to me that I implement the strategy pattern (http://en.wikipedia.org/wiki/Strategy_pattern), which I think I would do as several objects that implement a delegate protocol in Objective-C. This accomplishes the encapsulation I want while still allowing me to have a generic view controller in memory.
I have a class called DetailViewController that displays information about various types of data - waypoints, trails, maps, photos.
Right now, this class is 1400 lines long and it has some messy switch statements. For example:
- (void) changeMiniView:(id)sender {
if (self.track) {
[self changeTrackMiniView:[sender selectedSegmentIndex]];
} else if (self.waypoint) {
[self changeWaypointMiniView:[sender selectedSegmentIndex]];
} else if (self.photo) {
[self changePhotoMiniView:[sender selectedSegmentIndex]];
} else if (self.map) {
[self changeMapMiniView:[sender selectedSegmentIndex]];
}
}
This would be a lot neater if I made subclasses of DetailViewController, but my conundrum is I would like to keep the viewController in memory and just change certain elements, so I can have crisp transitions, particularly on 3G phones.
I feel like if I want my code to be neat, I have to take a performance hit.
Have the current view in a field in your object (rather than one field for every type of miniview you have), and implement changeMiniView for each of them.
Then your method would look like:
- (void) changeMiniView: (id)sender {
[self.currentMiniView changeMiniView: [sender selectedSegmentIndex]];
}
How about using selector?
- (void)viewDidLoad {
if (self.track) {
sel = #selector(changeTrackMiniView:);
} else if (self.waypoint) {
sel = #selector(changeWaypointMiniView:);
} else if (self.photo) {
sel = #selector(changePhotoMiniView:);
} else if (self.map) {
sel = #selector(changeMapMiniView:);
}
}
- (void)changeTrackMiniView:(id)sender {
....
}
- (void)changeMiniView:(id)sender {
[self performSelector:sel withObject:sender];
}
Why isn't my UILabel being changed? I am using the following code, and nothing is happening:
- (void)awakeFromNib {
percentCorrect.adjustsFontSizeToFitWidth;
percentCorrect.numberOfLines = 3;
percentCorrect.minimumFontSize = 100;
}
Here is my Implemintation code:
- (void) updateScore {
double percentScore = 100.0 * varRight / (varWrong + varRight);
percentCorrect.text = [NSString stringWithFormat:#"%.2f%%", percentScore];
}
- (void)viewDidLoad {
percentCorrect.adjustsFontSizeToFitWidth = YES;
percentCorrect.numberOfLines = 3;
percentCorrect.minimumFontSize = 100;
percentCorrect.text = #"sesd";
}
- (void)correctAns {
numberRight.text = [NSString stringWithFormat:#"%i Correct", varRight];
}
-(void)wrongAns {
numberWrong.text = [NSString stringWithFormat:#"%i Incorrect", varWrong];
}
#pragma mark Reset Methods
- (IBAction)reset:(id)sender; {
NSString *message = #"Are you sure you would like to reset?";
self.wouldYouLikeToReset = [[UIAlertView alloc] initWithTitle:#"Reset?" message:message delegate:self cancelButtonTitle:#"Cancel" otherButtonTitles:nil];
[wouldYouLikeToReset addButtonWithTitle:#"Continue"];
[self.wouldYouLikeToReset show];
// Now goes to (void)alertView and see's what is being pressed!
}
- (void)alertView:(UIAlertView *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {
if (buttonIndex == 0)
{
NSLog(#"Cancel button pressed");
}
else
{
varRight = 0;
varWrong = 0;
[self wrongAns];
[self correctAns];
percentCorrect.text = [NSString stringWithFormat:#"0.0%%"];
}
}
#pragma mark Button Action Methods
- (IBAction)right:(id)sender; {
varRight++;
[self correctAns];
[self updateScore];
}
- (IBAction)wrong:(id)sender; {
varWrong++;
[self wrongAns];
[self updateScore];
}
- (IBAction)subOneRight:(id)sender {
if (varRight > 0 ) {
varRight--;
[self correctAns];
[self updateScore];
}
}
- (IBAction)subOneWrong:(id)sender {
if (varWrong > 0) {
varWrong--;
[self wrongAns];
[self updateScore];
}
}
-(IBAction)addHalfCredit:(id)sender;
{
varWrong++;
varRight++;
[self wrongAns];
[self correctAns];
[self updateScore];
}
#end
Any ideas?
Thanks
In order for the adjustsFontSizeToFitWidth setting to come into effect, the numberOfLines property must be set to 1. It won't work if it's != 1.
Are awakeFromNib, viewDidLoad, viewWillAppear being called at all?
The minimumFontSize property will do nothing if the text fits in the current bounds with the current font. Did you set the font property for the label?
percentCorrect.font = [UIFont systemFontOfSize:20];
Finally, isn't a minimumFontSize = 100 a little too big for a min font size?
Make sure everything is hooked up correctly. Make sure the IBOutlet for the UITextfield is setup and set break points within the method and see that the code is being touched. If it is, it's possible percentCorrect hasn't been hooked up correctly.
You shouldn't have to init your label if it is in the nib. If you are, then you created the label twice. So who knows which one you are messaging to. As soon as you initialized the label, you leaked the first one. So the label you have on screen is NOT the one you are manipulating in code.
Try placing your code in viewDidLoad instead. It should be initialized by then.
If that doesn't work, try viewDidAppear: simply to try to debug this.
It's possible that percentCorrect hasn't yet been initialized. Is percentCorrect equal to nil when that function is called, by any chance? If so, wait until after it's properly initialized to set its properties.
What are you expecting to happen? Does the label show when your code is commented out? How is percentCorrect defined in the nib?
Have you tried:
- (void)awakeFromNib {
percentCorrect.adjustsFontSizeToFitWidth = YES;
percentCorrect.numberOfLines = 3;
percentCorrect.minimumFontSize = 100;
percentcorrent.text = #"What is the text in percentCorrect?";
}
I had the same problem. Seems that setText doesn't automatically force a redraw when the change happens on a non-main thread. UI updates should always be done on the main thread to ensure responsiveness. There's another way to force it, using a selector:
label = [[UILabel alloc] init]; //assumes label is a data member of some class
...
(some later method where you want to update the label)
...
[label performSelectorOnMainThread:#selector(setText) withObject:#"New label value" waitUntilDone:false];
You may also get results from simply saying:
[label setNeedsDisplay];
which will force the update internally, but at the SDK's discretion. I found that didn't work for me, thus why I recommend the selector on the main thread.
What I found is sometimes , don't rely too much on IB , just add a line to set the frame :
labelx.frame=CGRectMake(labelx.frame.origin.x,labelx.frame.origin.y, 300, labelx.frame.size.height);
Then , autoresize works !