Preview Driven Development

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Rikin Marfatia — Android @ Pinterest — @heyrikin Preview Driven Development™ Avoid build times at all cost!

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Agenda Compose + Previews 101 Previews —> Isolated Features Dependency Fakes Gradle Strategy for Previews Real World Example

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Compose + Previews

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Jetpack Compose Declarative UI @Composable functions Previews for visualization Android is fun again

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@Previews

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Deploy Previews to Device

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Powerful in-IDE Support

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Faster UI Development

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Isolated Features

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Isolated Features Built “isolated” from the rest of the application Simulate inputs Stub out side effects + outputs

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Mini Apps (Sample Apps) Run each feature as an app Composition of features Setup for modularization

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Other Benefits Feature Teams Easy Testing + Refactoring Non-engineers can play with Previews

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Faking Dependencies

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Control your Environment Real Application Real Application - No Internet Fake Feature

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Real Dependencies are Expensive 💰💰💰 import InnocentDependency Retrofit OkHttp Room SqlLite KAPT

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Interface + Implementation

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Gradle Strategy

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Gradle Modules — Before App Feature Common Feature Feature Network

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Gradle Modules — After App Feature NetworkLive Common Feature Feature Network FeaturePreview FeaturePreview FeaturePreview

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Interface + Live Modules App Feature NetworkLive Common Feature Feature Network FeaturePreview FeaturePreview FeaturePreview

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Full Application App Feature NetworkLive Common Feature Feature Network FeaturePreview FeaturePreview FeaturePreview

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Feature Preview App Feature NetworkLive Common Feature Feature Network FeaturePreview FeaturePreview FeaturePreview

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Demo

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Takeways Previews are extremely powerful, start using them Separate interface/fakes + implementation in Gradle Having fast deployable features is AWESOME Long build times SUCK

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How to apply this today? - Gradle structure works without Compose / Previews - Ralf Wondratschek — Android at Square - Start Creating Fakes - Preparing for Compose - Adam Bennet — Migrating your design system

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Credits / Resources - Point-Free - Designing Dependencies - Modeled my talk after this series - Amazing resource - Attacking Build Times with Sample Apps - Bill Phillips @ Cash App - Demo Application Code - https:#//github.com/Rahkeen/Hail

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Thanks @heyrikin