Android Weekly Issue #466

Static analysis tools for Android

Android的靜態(tài)分析工具.

• Android lint
• ktlint
• detekt

各自舉了一個(gè)例子來(lái)說(shuō)如何自定義規(guī)則.

Navigation: Nested graphs and include tag

Navigation graph支持嵌套.

<navigation>標(biāo)簽.
可以放在一個(gè)新的文件中, 再include進(jìn)來(lái).

這樣就可以跨module組織代碼了.

Avoid CI/CD Lock-in — Make Your Builds More Portable

讓CI更具可移植性.

• 把腳本放在代碼庫(kù)里.
• 把gradle任務(wù)放在shell腳本里.
• 盡量使用gradle插件而不是ci插件.
• 使用容器化技術(shù).
• 最小化在ci上的配置.

Assisted Injection With Dagger and Hilt

對(duì)于構(gòu)造一個(gè)對(duì)象, 有些參數(shù)需要DI容器幫忙, 有些參數(shù)你想自己提供的情況.

• 解決方案1: 添加AutoFactory依賴, 和daggeer結(jié)合使用, 會(huì)生成一個(gè)工廠.
• 解決方案2: dagger2.31+之后, 使用@AssistedInject注解, 標(biāo)記在構(gòu)造函數(shù)上, 想要手動(dòng)提供的參數(shù), 標(biāo)記@Assisted. 使用@AssistedFactory創(chuàng)建一個(gè)工廠.

對(duì)ViewModel來(lái)說(shuō), 還需要提供一個(gè)ViewModelProvider.Factory的實(shí)現(xiàn).

Dagger 2 and Jetpack Compose Integration

Dagger2和Jetpack Compose的集成.

首先, 開(kāi)篇定義navigation, 假定每個(gè)屏幕需要一個(gè)ViewModel:

setContent {
   val navController = rememberNavController()

   NavHost(navController, startDestination = NavigationDestination.Screen1.destination) {
       composable(NavigationDestination.Screen1.destination) {
           val viewModel: Screen1ViewModel = viewModel()
           Screen1(viewModel = viewModel)
       }
       composable(NavigationDestination.Screen2.destination) {
           val viewModel: Screen2ViewModel = viewModel()
           Screen2(viewModel = viewModel)
       }
   }
}

后來(lái), 換成這種:

composable(NavigationDestination.Screen1.destination) {
   val viewModel: Screen1ViewModel = hiltNavGraphViewModel()
   Screen1(viewModel = viewModel)
}

hiltNavGraphViewModel()做了什么呢?

• 找ViewModel的owner: Hilt用了LocalViewModelStoreOwner, 可以是Activity, Fragment, 在composable中, 是NavBackStackEntry.

了解Hilt怎么做之后, 看看Dagger 2.

setContent {
   val navController = rememberNavController()

   NavHost(navController, startDestination = NavigationDestination.Screen1.destination) {
       composable(NavigationDestination.Screen1.destination) {
           // option #1 create a component inside NavBackStackEntry,
           // which can be helpful if we need to provide more than one object from DI here
           val component = DaggerScreen1Component.builder().build()

           val viewModel: Screen1ViewModel = daggerViewModel {
               component.getViewModel()
           }

           Screen1(viewModel = viewModel)
       }
       composable(NavigationDestination.Screen2.destination) {
           val viewModel: Screen2ViewModel = daggerViewModel {
               // option #2 create DI component and instantly get ViewModel instance
               DaggerScreen2Component.builder().build().getViewModel()
           }

           Screen2(viewModel = viewModel)
       }
   }
}

Infinite auto-scrolling lists with RecyclerView & LazyLists in Compose

無(wú)限自動(dòng)滾動(dòng)的list, 有點(diǎn)像走馬燈的效果.

Kotlin SharedFlow or: How I learned to stop using RxJava and love the Flow

• RxJava后臺(tái)任務(wù)分步驟進(jìn)行UI顯示 -> Flow.
• 處理熱流:

• PublishSubject -> SharedFlow.
• BehaviorSubject -> StateFlow.

一些特點(diǎn):

• StateFlow是conflated: 如果新的值和舊的值一樣, 不會(huì)傳播.
• SharedFlow需要合理設(shè)置buffer和replay策略.
• StateFlow和SharedFlow永遠(yuǎn)都不會(huì)停止. 不能指望它們的onCompletionCallback.

還有文中提到了一個(gè)觀點(diǎn), 為什么不繼續(xù)用LiveData呢? 因?yàn)長(zhǎng)iveData感覺(jué)是跟Android相關(guān)的一個(gè)類, 而SharedFlow和StateFlow是Kotlin的, 這樣感覺(jué)domain層脫離了對(duì)Android的依賴, 更解耦一些.

From Junior to Master in Kotlin — 1 (Basic Syntax)

一些Kotlin的用法.

Code

• https://github.com/google/modernstorage

News

• #AndroidDevChallenge - It’s a wrap! Jetpack Compose Challenge的總結(jié), 可以訪問(wèn)獲勝者的代碼庫(kù).

Videos

• Staying up to date with new technologies as a Mobile Developer
• Unit Testing Kotlin Channels & Flows
• Navigation: Navigating between modules