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#AskAndroid at Android Dev Summit 2019 - Rough Notes on Jetpack Compose

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This article has been translated by Gemini.

I couldn’t record everything. If there are any mistakes, I would appreciate it if you could point them out.

Video is here: www.youtube.com

Q. When will it be Alpha or Beta?
#

It will be Beta next year.

Q. Is there recycling logic like RecyclerView? (Is it intended only for static Views?)
#

It’s intended for dynamic Views rather than static ones. Current Preview doesn’t have recycling logic, but it’s planned.

Q. When creating an app, is it intended to use only Jetpack Compose instead of XML?
#

  • You can use Jetpack Compose from the stage of building an app from scratch.
  • They also show methods for using existing XML inside Compose functions and vice-versa.
  • They want to make it compatible with existing code.

Reference: www.youtube.com

Q. About Jetpack Compose performance?
#

  • Currently relying entirely on the Experimental Compiler.
  • Sometimes the app might stutter (currently doing allocations for small things).
  • Existing sample apps should feel good.
  • It will get better in the future.

Q. Is it a better/cleaner choice than using LiveData or Data Binding?
#

  • You can use LiveData with Compose.
  • The approach is different regarding Data Binding.
    • Data Binding uses Views.
    • Compose is automatically recomposed.

Q. About replacing existing code like XML in the future?
#

  • Current developers are familiar with android.widget.
  • There are ways completely different from existing ones.
    • Some things don’t have a 1-to-1 correspondence with the existing system.
      • It might not be as easy as converting Java to Kotlin.
  • Replacing existing View code is mixed in terms of appearance and logic.
    • Something like machine translation is needed. It seems interesting to work on, but it’s not a goal at this point.

Q. Can it be incorporated into existing View structures? For example, displaying a WebView in Compose.
#

  • In the existing Compose repository, they are doing something like displaying a WebView on a Compose Wrapper.

Q. Best place to learn Compose at the moment?
#

Requires Android Studio Canary 4.0.

Q. Will it support dynamic View configuration using ConstraintLayout instead of LinearLayout?
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  • ConstraintLayout is not yet supported.
    • Planned for the future.
  • For LinearLayout, Row and Column are the equivalents.

Q. How to send feedback?
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Slack Group
#

Stackoverflow
#

https://stackoverflow.com/questions/tagged/android-jetpack-compose

Issue Tracker
#

https://issuetracker.google.com/issues?q=jetpack%20compose

Bug Reports
#

https://issuetracker.google.com/issues/new?component=612128&template=1253476

They want feedback. Development continues alongside feedback.

Q. Is “Jetpack Compose will be better for UI building” an official answer?
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  • It’s a new means for UI construction.
  • It’s one of the things being proposed to developers as a new means for UI construction.

Q. How will different screen sizes be handled?
#

  • It should be easy to handle in Jetpack Compose.
    • Possible with concise code.
    • Tools will help.
      • Can be easily checked in preview.

Q. Can Navigation Component be used?
#

(I didn’t quite catch this part. Probably Fragment support is difficult?)

  • Navigation Component is not just for Fragments.

Q. Are Compose and Apply Changes related?#

  • Not really.
  • Developers want smooth development.
    • Compose has Preview.

Q. When using Compose, where and how is the Layout rendered? And will these methods change?
#

  • When using XML layouts in a compatible way:
    • Not much different from existing ones.
  • When using only Compose:
    • Initialized at runtime.
  • Completely separate from the existing rendering method.