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Improve your user experience through simple animation. Explore the fundamentals of iOS UIView animation as well as the building blocks of Core Animation - unlocking loads of versatility using very little code.
Updated Code Samples
Compatible with Xcode 8 & Swift 3
Links
Code - Before
- (IBAction)mute{
self.alpha = .25;
}
- (IBAction)delete{
[self removeFromSuperview];
}
- (IBAction)upgrade{
CGPoint from = self.center;
CGPoint to = CGPointMake(750, 584);//Plug for simplicity
self.layer.position = to;
CABasicAnimation *slide = [CABasicAnimation animationWithKeyPath:@"position"];
slide.fromValue = [NSValue valueWithCGPoint:from];
slide.toValue = [NSValue valueWithCGPoint:to];
slide.duration = 2.0;
[self.layer addAnimation:slide forKey:@"position"];
}
- (IBAction)flag{
UIImageView *flagView = [[UIImageView alloc]initWithFrame:CGRectMake(25, 15, 40, 40)];
[flagView setImage:[UIImage imageNamed:@"bombIcon"]];
[self addSubview:flagView];
}
Code - After
- (IBAction)mute{
[UIView animateWithDuration:1.0 delay:0.0 options:0 animations:^{
self.alpha = .25;
}completion:nil];
}
- (IBAction)delete{
CGPoint current = CGPointMake(self.frame.origin.x, self.frame.origin.y);
[self.layer setAnchorPoint:CGPointMake(0, 0)];
self.layer.position = current;
CABasicAnimation *swing = [CABasicAnimation animationWithKeyPath:@"transform.rotation"];
swing.fromValue = [NSNumber numberWithInt:0];
swing.toValue = [NSNumber numberWithInt:1.5];
swing.duration = 1.5;
swing.autoreverses = YES;
swing.repeatCount = 3;
swing.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
[self.layer addAnimation:swing forKey:@"rotation"];
CABasicAnimation *drop = [CABasicAnimation animationWithKeyPath:@"position"];
CGPoint dropTo = CGPointMake(self.frame.origin.x, self.superview.frame.size.height);
drop.fromValue = [NSValue valueWithCGPoint:current];
drop.toValue = [NSValue valueWithCGPoint:dropTo];
drop.duration = 3.0;
drop.beginTime = CACurrentMediaTime() + 3.5;
[self.layer addAnimation:drop forKey:@"position"];
[self performSelector:@selector(removeFromSuperview) withObject:nil afterDelay:6.5];
}
- (IBAction)upgrade{
CGPoint from = self.center;
CGPoint corner = CGPointMake(750, self.center.y);
CGPoint to = CGPointMake(750, 584);//Plug for simplicity
self.layer.position = to;
CAKeyframeAnimation *rightTurn = [CAKeyframeAnimation animationWithKeyPath:@"position"];
[rightTurn setValues:[NSArray arrayWithObjects:[NSValue valueWithCGPoint:from], [NSValue valueWithCGPoint:corner], [NSValue valueWithCGPoint:to], nil]];
rightTurn.duration = 2.0;
[self.layer addAnimation:rightTurn forKey:@"position"];
}
- (IBAction)flag{
CATextLayer *flagLayer = [CATextLayer layer];
flagLayer.position = CGPointMake(25, 20);
flagLayer.bounds = CGRectMake(0, 0, 30, 30);
flagLayer.backgroundColor = [[UIColor redColor] CGColor];
flagLayer.string = @"!";
flagLayer.fontSize = 24;
flagLayer.alignmentMode = @"center";
[self.bgView.layer addSublayer:flagLayer];
CABasicAnimation *pulse = [CABasicAnimation animationWithKeyPath:@"opacity"];
pulse.fromValue = [NSNumber numberWithFloat:1];
pulse.toValue = [NSNumber numberWithFloat:.2];
pulse.duration = 1.0;
pulse.autoreverses = YES;
pulse.repeatCount = HUGE_VALF;
[flagLayer addAnimation:pulse forKey:@"opacity"];
}
Now let's turn to our upgrade function. 0:00 As it stands, 0:02 we're using a CABasicAnimation to move the sticky diagonally from its 0:03 original position to the lowest empty spot on the high priority side of our screen. 0:07 Now the code should look pretty familiar to you. 0:12 We have to and from points, then use those as our to and 0:15 from values in an animation on the position key path. 0:18 Also, if this hard coded to position is setting off alarm bells, raise your hand. 0:22 Okay, good. 0:27 Now put your hand down because I can't see you. 0:28 In a real app, we would want to employ some reusable logic 0:31 to determine the destination, given any arrangement of the stickies, or 0:33 even use a more sophisticated super view class to handle the repositioning, 0:37 though here, we're just trying to illustrate how these animations work, so 0:41 I didn't want to confuse matters with that. 0:44 Now, the diagonal movement works, but I think it would look better 0:47 if it slides to the right, then down the high priority column. 0:50 More importantly, 0:53 it'll give us a perfect opportunity to try out CAKeyframe animations. 0:54 To do that, we'll need to use three points to act as our keyframes. 0:59 The from point, the to point, and that corner point 1:03 in the middle where we switch from horizontal to vertical movement. 1:06 That corner is pretty easy to figure out, as it shares an x-value with the to, 1:09 and a y-value with the from. 1:13 Now, we can create a CAKeyframeAnimation for position, and set the duration. 1:16 Next, we have to feed the animation an array of values, namely, our three points. 1:21 Lastly, we apply the animation to the layer. 1:27 Okay, that looks quite different. 1:39 The animation looked all right, but at the end, 1:42 the sticky snapped back to its original position. 1:44 That, of course, just won't do, and coincidentally, 1:47 is probably the number one mistake iOS animators make. 1:49 The reason this happens is that the animation is simply changing 1:53 the appearance of the layer. 1:56 The underlying position doesn't actually change. 1:58 The same would be true for other animated properties like opacity. 2:00 Just to repeat, and this is really important, the animation is changing 2:04 the appearance of the properties, but not the underlying values. 2:08 So when the animation ends, 2:11 the user again sees the actual original unchanged position. 2:13 Luckily, we can fix that pretty easily 2:18 by simply setting the actual position of the layer to the final key frame. 2:20 In this case, the point we called to. 2:24 Let's try it again. 2:27 There we go. 2:37 Now, because we gave our animation three key values but no key times, 2:39 core animation will default and assume that each leg of the animation, that is, 2:44 the journey between key frames, gets an equal chunk of the time to execute. 2:48 This works just fine, since the legs of our journey are more or 2:52 less the same size, but you could very easily give the animation an array of key 2:55 times to specify exactly how long each leg should take. 2:59 If you decide to do this, remember that you won't be specifying key times in 3:02 seconds, but rather in fractions of the total duration. 3:06 So for our example, the three key times would be 0, 0.5, and 1. 3:10 This brings us to your last animation, the flag. 3:16 Right now, we're just creating a little UIImageView, 3:19 filling it with the image of flag, and adding it as a sub-view to the sticky. 3:22 Instead, let's create a flag made up of a white exclamation point 3:26 on a red background, and then have that flag fade in and out continuously. 3:30 For this, we'll use one of those subclasses of CALayer we saw before, 3:34 specifically, CATextLayer. 3:39 We'll create a discreet CATextLayer called flagLayer. 3:42 We'll set its position and bounds, that's very important by the way. 3:46 Don't forget this part or it won't show up at all. 3:49 Set the background color, set the string, much like you would a UILabel, 3:52 the font size, the alignment mode, and then add it as a sub-layer. 3:57 You'll note here that we're adding it as a sub-layer on the bgView, and 4:01 that's because we want to make sure it appears on top of the image of the sticky, 4:05 which resides inside the bgView. 4:09 If we simply added it to self.layer It would appear in the sticky, but 4:12 behind the image of the yellow paper. 4:16 Next, we'll create a CABasicAnimation to handle the opacity change. 4:19 We'll set the fromValue to 1, the toValue to 0.2, 4:24 that's almost transparent We'll set the duration, the auto reverse to yes, 4:29 and the repeat count to HUGE_VALF, which is essentially a float proxy for 4:34 infinity, so it'll repeat over, and over, and over. 4:39 We add the animation, and we're ready to run it. 4:43 Voila, we see the CATextLayer created on the fly, and pulse in and out. 4:52 We can even delete the sticky, and watch the flag go along for the ride. 4:57 Today we've seen some of the simple yet 5:05 powerful things we can do with UI views and core animation. 5:07 We've used CA basic animations both individually and sequentially, 5:10 and also tried our hands at creating discreet CA layers on the fly. 5:13 We've also gotten tripped up by some of the common animation mistakes and 5:17 learn how to fix them. 5:20 If there's one thing I hope that you take away from this, is that the animation for 5:21 iOS is fairly simple to begin using, yet extremely dynamic. 5:24 You can get an incredible amount of variety and 5:28 have a lot of fun just using the basics I've shown today. 5:30 Start combining this functionalities and 5:33 scanning through the documentation, you'll find countless things to experiment with, 5:35 or better yet, ways to improve the apps you're working on right now. 5:39 I've added some links in the teacher's notes for 5:43 further reading if you're interested in learning more. 5:44 You'll also find the Objective C code we views today, along with both Swift 1.3 and 5:47 2.0 versions. 5:51 See you next time. 5:52
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