I was informed recently by meronix that use of beginAnimations is discouraged. Reading through the UIView class reference I see that this is indeed true - according to the Apple class ref:
Use of this method is discouraged in iOS 4.0 and later. You should use
the block-based animation methods to specify your animations instead.
I see that a large number of other methods - which I use frequently - are also "discouraged" which means they'll be around for iOS 6 (hopefully) but probably will be deprecated/removed eventually.
Why are these methods being discouraged?
As a side note, right now I'm using beginAnimations in all sorts of apps, most commonly to move the view up when a keyboard is shown.
//Pushes the view up if one of the table forms is selected for editing
- (void) keyboardDidShow:(NSNotification *)aNotification
{
if ([isRaised boolValue] == NO)
{
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:0.25];
self.view.center = CGPointMake(self.view.center.x, self.view.center.y-moveAmount);
[UIView commitAnimations];
isRaised = [NSNumber numberWithBool:YES];
}
}
Not sure how to duplicate this functionality with block-based methods; a tutorial link would be nice.
They are discouraged because there is a better, cleaner alternative
In this case all a block animation does is automatically wrap your animation changes (setCenter: for example) in begin and commit calls so you dont forget. It also provides a completion block, which means you don't have to deal with delegate methods.
Apple's documentation on this is very good but as an example, to do the same animation in block form it would be
[UIView animateWithDuration:0.25 animations:^{
self.view.center = CGPointMake(self.view.center.x, self.view.center.y-moveAmount);
} completion:^(BOOL finished){
}];
Also ray wenderlich has a good post on block animations: link
Another way is to think about a possible implementation of block animations
+ (void)animateWithDuration:(NSTimeInterval)duration animations:(void (^)(void))animations
{
[UIView beginAnimations];
[UIView setAnimationDuration:duration];
animations();
[UIView commitAnimations];
}
Check out this method on UIView, which makes it quite simple. The trickiest part nowadays is not allowing a block to have a strong pointer to self:
//Pushes the view up if one of the table forms is selected for editing
- (void) keyboardDidShow:(NSNotification *)aNotification
{
if ([isRaised boolValue] == NO)
{
__block UIView *myView = self.view;
[UIView animateWithDuration:0.25 animations:^(){
myView.center = CGPointMake(self.view.center.x, self.view.center.y-moveAmount);
}];
isRaised = [NSNumber numberWithBool:YES];
}
}
Related
I have a UIScrollView which contains various subviews (UIImageViews, UILabels and standard UIViews). Some of the UIImageViews are partially covered by other UIViews.
However, when I fade out the UIScrollView, the partially covered parts of the UIImageViews are being exposed for the brief moment of the animation.
I want to be able to fade the scrollview and all it's contents at the same time in the same animation - i.e. not revealing any of the partially covered images.
If it's not possible, I can always add a UIView on top of all the other controls and fade it from alpha 0 upto 1 to hide everything, but I'm sure there's a way to perform a complete fade on a view and all it's subviews.
I tried this:
[UIView beginAnimations:nil context:NULL];
[scrollViewResults setAlpha:0.0f];
[UIView commitAnimations];
And I've tried this:
- (IBAction)questionGroupChanged:(UIButton*)sender {
[UIView beginAnimations:nil context:NULL];
[self fadeViewHierarchy:scrollViewResults toAlpha:0.0f];
[UIView commitAnimations];
}
- (void)fadeViewHierarchy:(UIView*)parentView toAlpha:(float)alpha {
[parentView setAlpha:alpha];
for (UIView *subView in parentView.subviews) {
[self fadeViewHierarchy:subView toAlpha:alpha];
}
}
But I've still not cracked it. Any ideas?
This happens because of the way the compositor works. You need to enable rasterization on the view's layer when fading it in/out:
view.layer.shouldRasterize = YES;
You should probably only enable this for the duration of the animation because it will take up some extra memory and graphics processing time.
Mike's answer is the correct one and he deserves all credit for this. Just to illustrate, it might look like:
- (void)fadeView:(UIView*)view toAlpha:(CGFloat)alpha
{
view.layer.shouldRasterize = YES;
[UIView animateWithDuration:0.75
animations:^{
view.alpha = alpha;
}
completion:^(BOOL finished){
view.layer.shouldRasterize = NO;
}];
}
Thus, using your scrollViewResults, it would be invoked as:
[self fadeView:scrollViewResults toAlpha:0.0f];
Did you try with UIView class methods +animateWithDuration:* (available on iOS 4 and +)
Like :
- (void)fadeAllViews
{
[UIView animateWithDuration:2
animations:^{
for (UIView *view in allViewsToFade)
view.alpha = 0.0;
}
completion:^(BOOL finished){}
];
}
I am trying to perform multiple UIView animations one after the other. However, I've heard that it's bad practice to perform multiple UIView animations one after the other, and that I should instead use Core Animation. I tried this code:
//First Animation
[UIView beginAnimations:#"animation1" context:nil];
[UIView setAnimationDuration:2];
nwView.backgroundColor = [UIColor redColor];
nwView.frame = CGRectMake(CGRectGetMidX(screenSize),
CGRectGetMinY(screenSize),
width,
height);
nwView.transform = CGAffineTransformMakeRotation(45.0f);
[UIView commitAnimations];
//Second Animation
[UIView beginAnimations:#"second animation" context:nil];
[UIView setAnimationDuration:2];
nwView.transform = CGAffineTransformMakeScale(0.5, 0.33);
nwView.backgroundColor = [UIColor purpleColor];
[UIView commitAnimations];
But it only does the second animation. I know this question is similar to UIView two animations coexisting, but it has a slightly different context.
I don't think there is anything wrong with doing 2 animations in a row using UIView blocks. Just make sure you start your second animation in the completino block of the first animation.
Without blocks (your example) it is not working as you will have to set a delegate to the animation or set a selector for setAnimationDidStopSelector. There you should start the second animation.
But again, nothing wrong in doing animations with blocks (it is the preferred way).
If you are looking to do multiple animations right after another this is not the way to do it. The code you posted with execute at almost the same time, meaning the animations would be performed at about the same time.
Instead what you should do is set the delegate for the first animation, and then do the first animation. Then when the animationDidStop method is called for the first animation, you should do the second animation. This makes sure they are one after another.
This is how you would do it, assuming you call doMyAnimations to start the animation.
-(void)doMyAnimations{
//First Animation
[UIView beginAnimations:#"animation1" context:nil];
[UIView setAnimationDuration:2];
[UIView setAnimationDelegate:self];
nwView.backgroundColor = [UIColor redColor];
nwView.frame = CGRectMake(CGRectGetMidX(screenSize),
CGRectGetMinY(screenSize),
width,
height);
nwView.transform = CGAffineTransformMakeRotation(45.0f);
[UIView commitAnimations];
}
- (void)animationWillStart:(NSString *)animationID context:(void *)context{
}
- (void)animationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context{
if([animationID isEqualToString:#"animation1"]){
//Second Animation
[UIView beginAnimations:#"second animation" context:nil];
[UIView setAnimationDuration:2];
nwView.transform = CGAffineTransformMakeScale(0.5, 0.33);
nwView.backgroundColor = [UIColor purpleColor];
[UIView commitAnimations];
}
}
Keep in mind that the nwView would have to be accessible throughout the entire class. If it isn't you can either make it an instance variable, or find another way to get access to it in the animationDidStop method.
You can use blocks for this purpose and get a very clean result.
NSMutableArray* animationBlocks = [NSMutableArray new];
typedef void(^animationBlock)(BOOL);
// getNextAnimation
// removes the first block in the queue and returns it
animationBlock (^getNextAnimation)() = ^{
animationBlock block = (animationBlock)[animationBlocks firstObject];
if (block){
[animationBlocks removeObjectAtIndex:0];
return block;
}else{
return ^(BOOL finished){};
}
};
//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
[UIView animateWithDuration:1.0 animations:^{
//...animation code...
} completion: getNextAnimation()];
}];
//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
[UIView animateWithDuration:1.0 animations:^{
//...animation code...
} completion: getNextAnimation()];
}];
//add a block to our queue
[animationBlocks addObject:^(BOOL finished){;
NSLog(#"Multi-step Animation Complete!");
}];
// execute the first block in the queue
getNextAnimation()(YES);
Taken from: http://xibxor.com/objective-c/uiview-animation-without-nested-hell/
I'm looking for an equivalent core animation for the following UIView animation?
[UIView animateWithDuration:0.25 animations:^(void) {
cell.frame = newCellFrame;
} completion:^(BOOL finished) {
[UIView animateWithDuration:0.25 animation:^(void) {
cell.frame = finalCellFrame;
}];
}];
What I would like to know in particular is how you mimic the "completion" part of this animation with core animation. Is the only option to use core animation delegation or is there a solution as elegant as the above code snippet?
In CoreAnimation it's done with delegates. You can set a delegate on your CAAnimation/CABasicAnimation instance, and the animation will make animationDidStart: and animationDidStop:finished: callbacks to you.
I have a small UIView and want to let it move to center of screen first, and then, zoom to full screen.
But when I begin start an animation like
[UIView beginAnimations:#"animation1" context:nil];
[UIView setAnimationDuration:0.5];
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:#selector(showDetailToFullscreen)];
self.currentDetailVC.frame = centerFrame;
[UIView commitAnimations];
And in the same controller, I have a method:showDetailToFullscreen
- (void)showDetailToFullscreen {
CGRect screenFrame = CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height);
[UIView beginAnimations:#"animation2" context:nil];
[UIView setAnimationDuration:0.5];
self.currentDetailVC.view.frame = screenFrame;
[UIView commitAnimations];
}
but when start, it still executed together.
I think the problem they are still in the same transaction. But how can I let these two animation executed one by one? Appreciate for any answer!
Try this instead of the setAnimationDidStopSelector:
[self performSelector:#selector(showDetailToFullscreen) withObject:nil afterDelay:0.5];
It's now considered much better to annimate views using the 'blocks' methods that can be found in the "Animating Views with Blocks" section in the UIView Class Reference.
In most of these methods you can specify a "completion" block of code that can be used to start off a second animation when the first animation completes. You could also call showDetailToFullscreen within this completion block.
I'd reccommend trying this method instead.
Are you targetting iOS 4 or later? If so, I recommend using the block-based animation methods instead. What you want to do is very easy:
Example from UIView docs:
[UIView animateWithDuration:0.2
animations:^{view.alpha = 0.0;}
completion:^(BOOL finished){ [view removeFromSuperview]; }];
I'm having a fundamental issue with use of drawRect: Any advice would be greatly appreciated.
The application needs to draw a variety of .png images at different times, sometimes with animation, sometimes without.
A design goal that I was hoping to adhere to is to have the code inside drawRect: very simple and "dumb" - i.e. just do drawing and no other application logic.
To draw the image I am using the drawAtPoint: method of UIImage. Since this method does not take a CGContext as a parameter, it can only be called within the drawRect: method. So I have:
- (void)drawRect:(CGRect)rect {
[firstImage drawAtPoint:CGPointMake(firstOffsetX, firstOffsetY)];
}
All fine and dandy for one image. To draw multiple images (over time) the approach I have taken is to maintain an array of dictionaries with each dictionary containing an image, the point location to draw at and a flag to enable/suppress drawing for that image. I add dictionaries to the array over time and trigger drawing via the setNeedsDisplay: method of UIView. Use of an array of dictionaries allows me to completely reconstruct the entire display at any time. drawRect: now becomes:
- (void)drawRect:(CGRect)rect {
for (NSMutableDictionary *imageDict in [self imageDisplayList]) {
if ([[imageDict objectForKey:#"needsDisplay"] boolValue]) {
[[imageDict objectForKey:#"image"] drawAtPoint:[[imageDict objectForKey:#"location"] CGPointValue]];
[imageDict setValue:[NSNumber numberWithBool:NO] forKey:#"needsDisplay"];
}
}
}
Still OK. The code is simple and compact. Animating this is where I run into problems. The first problem is where do I put the animation code? Do I put it in UIView or UIViewController? If in UIView, do I put it in drawRect: or elsewhere? Because the actual animation depends on the overall state of the application, I would need nested switch statements which, if put in drawRect:, would look something like this:
- (void)drawRect:(CGRect)rect {
for (NSMutableDictionary *imageDict in [self imageDisplayList]) {
if ([[imageDict objectForKey:#"needsDisplay"] boolValue]) {
switch ([self currentState]) {
case STATE_1:
switch ([[imageDict objectForKey:#"animationID"] intValue]) {
case ANIMATE_FADE_IN:
[self setAlpha:0.0];
[UIView beginAnimations:[[imageDict objectForKey:#"animationID"] intValue] context:nil];
[UIView setAnimationDelegate:self];
[UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
[UIView setAnimationDuration:2];
[self setAlpha:1.0];
break;
case ANIMATE_FADE_OUT:
[self setAlpha:1.0];
[UIView beginAnimations:[[imageDict objectForKey:#"animationID"] intValue] context:nil];
[UIView setAnimationDelegate:self];
[UIView setAnimationCurve:UIViewAnimationCurveEaseOut];
[UIView setAnimationDuration:2];
[self setAlpha:0.0];
break;
case ANIMATE_OTHER:
// similar code here
break;
default:
break;
}
break;
case STATE_2:
// similar code here
break;
default:
break;
}
[[imageDict objectForKey:#"image"] drawAtPoint:[[imageDict objectForKey:#"location"] CGPointValue]];
[imageDict setValue:[NSNumber numberWithBool:NO] forKey:#"needsDisplay"];
}
}
[UIView commitAnimations];
}
In addition, to make multiple sequential animations work correctly, there would need to be an outer controlling mechanism involving the animation delegate animationDidStop: callback that would set the needsDisplay entries in the dictionaries to allow/suppress drawing (and animation).
The point that we are at now is that it all starts to look very ugly. More specifically:
drawRect: starts to bloat quickly and contain code that is not "just drawing" code
the UIView needs implicit awareness of the application state
the overall process of drawing is now spread across three methods at a minimum
And on to the point of this post: how can I do this better? What would the experts out there recommend in terms of overall structure? How can I keep application state information out of the view? Am I looking at this problem from the wrong direction. Is there some completely different approach that I should consider?
I'd start off by not re-inventing Core Animation…
Bill Dudney's is probably the best: Core Animation for Mac OS X and the iPhone: Creating Compelling Dynamic User Interfaces