How to create complex animation with better performance in iOS?

Question

All the animations mean change of layer.transform or frame properties. There are 2 main questions about performance:

1. I have multiple views which I should animate simultaneously. What is better: to create multiple animateWithDuration blocks or to create one such block and iterate views in it?

2. My animation requires complex calculations and I need to call animateWithDuration enough often. Should I perform all the calculations before the animation block or is there no difference for performance?

Answer 1

Nobody has answered yet. So let I answer my own question and you will correct it if I'm mistaken.

1. I recommend one block only. The usual animateWithDuration:animations: doesn't support simultaneous animations properly (at least in my case it caused some troubles). I suggest to use RZViewActions instead - it uses more complex approach with dispatch_group_t for simultaneous animations (and actions in general). In the last version you don't even need to prepare groups/sequences before the animation start.

2. The only difference I see is the code outside animateWithDuration:animations: is performed in the same NSRunLoop cycle and if I place it inside the animation block it will be calculated in the next cycle. So for example, it will be useful to place the calculations outside the block if sometimes you don't want to start the animation according to the results of these calculations.

   On the other hand it may slow down the current cycle which is usually more critical than than the slower performance of the next cycle. Additionally you should think about variables you need to pass into the block correctly.

   In both cases the animation will not start until the end of the animation block. So if you set some visual variable (for example, view's frame) it is set as usually and you can use it at once. But this value is not rendered until the beginning of the completion block. So you with animateWithDuration:animations: you will see the starting and the ending value only. Even if the animation is interrupted it jumps to the ending value at once (it is default behaviour if you don't specify additional options).