Summary:
As I was working on mimicking iOS animations for my ongoing work with `react-navigation`, one task I had was to match the "push from right" animation that is common in UINavigationController.
I was able to grab the exact animation values for this animation with some LLDB magic, and found that the screen is animated using a `CASpringAnimation` with the parameters:
- stiffness: 1000
- damping: 500
- mass: 3
After spending a considerable amount of time attempting to replicate the spring created with these values by CASpringAnimation by specifying values for tension and friction in the current `Animated.spring` implementation, I was unable to come up with mathematically equivalent values that could replicate the spring _exactly_.
After doing some research, I ended up disassembling the QuartzCore framework, reading the assembly, and determined that Apple's implementation of `CASpringAnimation` does not use an integrated, numerical animation model as we do in Animated.spring, but instead solved for the closed form of the equations that govern damped harmonic oscillation (the differential equations themselves are [here](https://en.wikipedia.org/wiki/Harmonic_oscillator#Damped_harmonic_oscillator), and a paper describing the math to arrive at the closed-form solution to the second-order ODE that describes the DHO is [here](http://planetmath.org/sites/default/files/texpdf/39745.pdf)).
Though we can get the currently implemented RK4 integration close by tweaking some values, it is, the current model is at it's core, an approximation. It seemed that if I wanted to implement the `CASpringAnimation` behavior _exactly_, I needed to implement the analytical model (as is implemented in `CASpringAnimation`) in `Animated`.
We add three new optional parameters to `Animated.spring` (to both the JS and native implementations):
- `stiffness`, a value describing the spring's stiffness coefficient
- `damping`, a value defining how the spring's motion should be damped due to the forces of friction (technically called the _viscous damping coefficient_).
- `mass`, a value describing the mass of the object attached to the end of the simulated spring
Just like if a developer were to specify `bounciness`/`speed` and `tension`/`friction` in the same config, specifying any of these new parameters while also specifying the aforementioned config values will cause an error to be thrown.
~Defaults for `Animated.spring` across all three implementations (JS/iOS/Android) stay the same, so this is intended to be *a non-breaking change*.~
~If `stiffness`, `damping`, or `mass` are provided in the config, we switch to animating the spring with the new damped harmonic oscillator model (`DHO` as described in the code).~
We replace the old RK4 integration implementation with our new analytic implementation. Tension/friction nicely correspond directly to stiffness/damping with the mass of the spring locked at 1. This is intended to be *a non-breaking change*, but there may be very slight differences in people's springs (maybe not even noticeable to the naked eye), given the fact that this implementation is more accurate.
The DHO animation algorithm will calculate the _position_ of the spring at time _t_ explicitly and in an analytical fashion, and use this calculation to update the animation's value. It will also analytically calculate the velocity at time _t_, so as to allow animated value tracking to continue to work as expected.
Also, docs have been updated to cover the new configuration options (and also I added docs for Animated configuration options that were missing, such as `restDisplacementThreshold`, etc).
Run tests. Run "Animated Gratuitous App" and "NativeAnimation" example in RNTester.
Closes https://github.com/facebook/react-native/pull/15322
Differential Revision: D5794791
Pulled By: hramos
fbshipit-source-id: 58ed9e134a097e321c85c417a142576f6a8952f8
Summary:
* Any animation can be looped on the javascript thread
* Only basic animations supported natively at this stage, loops run
using the native driver cannot contain animations of type sequence,
parallel, stagger, or loop
Motivation: We need a spinner in our app that is displayed and animated while the javascript thread is tied up with other tasks. This means it needs to be offloaded from the javascript thread, so that it will continue to run while those tasks are churning away.
I originally submitted PR #9513, which has served our needs, but brentvatne pointed out a better way to do it. Had hoped his suggestion would be implemented by janicduplessis or another fb employee, but after 5 months I thought I'd give it another push.
I've put together an implementation that basically matches the suggested API. Let me know what you think, and whether others can pick it up from here and get it in to core.
Personal Motivation: I am leaving my current organisation on Feb 10th, so am trying to clean thing
Closes https://github.com/facebook/react-native/pull/11973
Differential Revision: D4704381
fbshipit-source-id: 42a2cdf5d53a7c0d08f86a58485f7f38739e6cd9
Summary:
This change adds support for spring animations to be run off the JS thread on android. The implementation is based on the android spring implementation from Rebound (http://facebook.github.io/rebound/) but since only a small subset of the library is used the relevant parts are copied instead of making RN to import the whole library.
**Test Plan**
Run java tests: `buck test ReactAndroid/src/test/java/com/facebook/react/animated`
Add `useNativeDriver: true` to spring animation in animated example app, run it on android
Closes https://github.com/facebook/react-native/pull/8860
Differential Revision: D3676436
fbshipit-source-id: 3a4b1b006725a938562712989b93dd4090577c48
