Animated.loop doesn't work as expected in combination with Animated.sequence

[sokki]

Environment

  React Native Environment Info:
    System:
      OS: macOS High Sierra 10.13.6
      CPU: x64 Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
      Memory: 720.97 MB / 16.00 GB
      Shell: 5.3 - /bin/zsh
    Binaries:
      Node: 8.9.4 - ~/.nvm/versions/node/v8.9.4/bin/node
      Yarn: 1.6.0 - /usr/local/bin/yarn
      npm: 6.1.0 - ~/.nvm/versions/node/v8.9.4/bin/npm
      Watchman: 4.9.0 - /usr/local/bin/watchman
    SDKs:
      iOS SDK:
        Platforms: iOS 11.4, macOS 10.13, tvOS 11.4, watchOS 4.3
      Android SDK:
        Build Tools: 25.0.3, 26.0.1, 27.0.3
        API Levels: 23, 26
    IDEs:
      Xcode: 9.4.1/9F2000 - /usr/bin/xcodebuild
    npmPackages:
      react: ^16.4.2 => 16.4.2
      react-native: ^0.56.0 => 0.56.0
    npmGlobalPackages:
      create-react-native-app: 1.0.0
      react-native-cli: 2.0.1

Description

Currently, Animated.loop calls animation.reset() before each iteration. That makes sense in most cases. However, when looping a Animated.sequence one might want to loop between the animations in the sequence without falling back to the initial value on each iteration.

Some people faced the same issue:

• Animated.loop resets animatedValue #18028
• https://stackoverflow.com/questions/48135919/how-to-chain-multiple-animations-together-in-react-native

I would propose to add a new a config to Animated.loop like:

Animated.loop(Animated.sequence(animations), {resetBeforeIteration:false})

Reproducible Demo

MCVE: https://snack.expo.io/@sokki/animated-loop

  state = {
    animated: new Animated.Value(0),
  };

  animate() {
    // What I want:
    // 0-1-2-1-2-1-2 etc.
    // What I get:
    // 0-1-2-0-1-2 etc.
    Animated.loop(
      Animated.sequence([
        Animated.timing(this.state.animated, {
          toValue: 1,
        }),
        Animated.timing(this.state.animated, {
          toValue: 2,
        }),
      ])
    ).start();
  }

[stale]

Hey there, it looks like there has been no activity on this issue recently. Has the issue been fixed, or does it still require the community's attention? This issue may be closed if no further activity occurs. You may also label this issue as "For Discussion" or "Good first issue" and I will leave it open. Thank you for your contributions.

[stale]

Closing this issue after a prolonged period of inactivity. If this issue is still present in the latest release, please feel free to create a new issue with up-to-date information.