Add reverse functionality to repeat() of AnimationController #25125
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zoechi
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@HansMuller Can you review this? |
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@goderbauer Looks like a nice enhancement. Will review this week. |
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This PR is pretty close to the finish line! Just a few more tweaks, mostly for the corner cases.
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@HansMuller Reworked the PR again with a nicer implementation of the repeating mechanism. Would be cool if you could have a look 😃 |
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LGTM
If you could add just one last comment to the test, I can land this for you.
This is a nice new animation feature. Thanks for the contribution and thanks for hanging in there!
| expect(controller.value, 0.0); | ||
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| controller.repeat(reverse: true); | ||
| tick(const Duration(milliseconds: 0)); |
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It's not clear why this first duration=0 tick is always needed. I assume it's to enable the simulation to figure out which way it's going. Might be helpful to include one comment at the beginning here, to explain what's going on.
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This can also be found in other tests (e.g. test('animateTo sets correct status') or test('after a reverse call animateTo sets correct status'). Every time when starting a new simulation, the first tick is used to initialise the simulation inside the AnimationController. When the line is removed, the elapsed time will always be 0 which means that the simulation will be evaluated at the time 0 and not after x milliseconds.
In the end I didn't comment on that because it is used quite often in the other tests already 😉
…r into add_reverse_to_repeat
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This PR adds a reverse flag to the
repeat()method of the AnimationController. With that feature it will be easier to create 'yoyo' animations like a glowing Flutter logo:AnimationController(vsync: this, duration: Duration(seconds: 1))..repeat(reverse: true);Also have a look at the following Stackoverflow question: https://stackoverflow.com/questions/49604221/how-to-do-yoyo-animation-in-flutter
So right now it's only possible to achieve this by listening to the current status of the AnimationController and alternating between calling
forward()andreverse()or through combining a fade-in animation with a fade-out animation.