Android Weekly Issue #450

Using Hilt’s ViewModelComponent

在ViewModelComponent被引入之前, ViewModel的依赖scope只能是: 没有, singleton, activity这三种情况.

在类型上使用注解的时候:

如果所有的ViewModels共享实例, 用@ActivityRetainedScoped.
如果和ViewModel保持一致, 能够configuration change的时候survive, 或者被navigation graph控制, 用@ViewModelScoped.
如果scope和Activity/Fragment一致, configuration change的时候不survive, 用@ActivityScoped或者@FragmentScoped.

在这个例子中:

@ViewModelScoped // Scopes type to the ViewModel
class UserInputAuthData(
  private val handle: SavedStateHandle // Default binding in ViewModelComponent
) { /* Cached data and logic here */ }

class RegistrationViewModel(
  private val userInputAuthData: UserInputAuthData,
  private val validateUsernameUseCase: ValidateUsernameUseCase,
  private val validatePasswordUseCase: ValidatePasswordUseCase
) : ViewModel() { /* ... */ }

class LoginViewModel(
  private val userInputAuthData: UserInputAuthData,
  private val validateUsernameUseCase: ValidateUsernameUseCase,
  private val validatePasswordUseCase: ValidatePasswordUseCase
) : ViewModel() { /* ... */ }

class ValidateUsernameUseCase(
  private val userInputAuthData: UserInputAuthData,
  private val repository: UserRepository
) { /* ... */ }

class ValidatePasswordUseCase(
  private val userInputAuthData: UserInputAuthData,
  private val repository: UserRepository
) { /* ... */ }

每个ViewModel拥有自己的UserInputAuthData实例.
每个ViewModel的UseCase实例依赖的UserInputAuthData(间接依赖), 是各自的ViewModel中的那个实例.

Android Parcelable: There's a better way

介绍这个库: https://github.com/chRyNaN/parcelable

依赖了kotlin serialization来把数据序列化成Parcels.

Why we use Kotlin Multiplatform and Redux

为什么使用了Kotlin Multiplatform和Redux来做一个小app.

文章里的图看起来挺好的(就是没仔细看).

How do we handle multi-modules navigation on our Android app

多module应用的导航.

官方的navigation也支持多module:
https://developer.android.com/guide/navigation/navigation-dynamic?authuser=1
但是和Fragment强相关.

这篇文章提供的解决方案和依赖注入相关.
demo在这里: https://github.com/PhilippeBoisney/android-multi-modules-navigation-demo

Ktor and GraphQL

如何用Ktor写一个GraphQL的server.

Helping You Understand The Syntax of Jetpack Compose

帮你读懂Jetpack Compose的语法.

Epoxy—Build Declarative & Reusable UI Components

每一个View都是一个EpoxyModel.
EpoxyController用来连接models, 类似于Adapter.

优势: ui元素和controller独立, ui元素可以复用.

How runBlocking May Surprise You

关于协程和主线程的一些有趣的讨论, 图不错.

What’s new in Hilt and Dagger 2.31

Hilt的新特性:

HiltAndroidApp.
ApplicationComponent改名为SingleComponent.
引入ViewModelComponent和ViewModelScoped.
Assisted Injection: 一些依赖由依赖注入框架提供, 另一些创建时提供.
Hilt和Navigation以及Compose结合.
HiltWorker.

Sealed goodies coming in Kotlin 1.5

Kotlin1.5推出了sealed interface.

Language Injections in Android Studio / IntelliJ IDEA

同一个文件用不同的语言.

比如Room中的sql语句.

Advanced FP for the Enterprise Bee: Higher Kinded Types

函数式编程系列文章的第三篇.

Code

https://github.com/CRED-CLUB/synth-android 这个样式库的效果还挺好看的.
https://github.com/chRyNaN/serialization-parcelable Android Parcelable support for the Kotlinx Serialization library.
https://github.com/dreipol/multiplatform-redux-sample

Android Weekly Notes #450