Android Weekly Notes #484

Android Weekly Issue #484

Don't let ViewModel know about framework level dependencies

ViewModel不应该有framework的依赖.

文章里测试的写法是那种嵌套的, 跟iOS很像的.

代码: https://github.com/PatilShreyas/ViewModelGoodPractice

Testing Hybrid Jetpack Compose Apps

如何测试XML和Compose混合的UI.

Lift on scroll in Jetpack Compose

Top app bar在下面的内容滚动上来以后, 会有一个高度提升显示阴影的效果.

如何在Compose上实现这种liftOnScroll的效果呢.

val LazyListState.elevation: Dp
    get() = if (firstVisibleItemIndex == 0) {
        // For the first element, use the minimum of scroll offset and default elevation
        // i.e. a value between 0 and 4.dp
        minOf(firstVisibleItemScrollOffset.toFloat().dp, AppBarDefaults.TopAppBarElevation)
    } else {
        // If not the first element, always set elevation and show the shadow
        AppBarDefaults.TopAppBarElevation
    }

Composing palettes

Compose的调色板.
可以从Bitmap提取颜色.

demo: https://github.com/tkuenneth/android-demos/tree/master/misc/PaletteDemo

Effective Kotlin Item 50: Eliminate obsolete object references

我们要注意不要持有已经不用的对象的引用.

尤其是这个对象很大或者很多的时候.

Exact alarm improvements-Android12

Android 12对闹钟的改进.

How to master Swipeable and NestedScroll modifiers in Jetpack Compose

要实现一个bottom sheet, 展开后是parent的全部高度, 内容可以滚动, 但是header保持不动.

整体的实现:
https://gist.github.com/arcadefire/7fe138c0ded1a36bee6dd57acdfa3d18

Using WorkManager on Android 12

Android 12加了前台服务的启动限制:
https://developer.android.com/about/versions/12/foreground-services

也就是说, 除了一些特殊情况, Android 12上不允许从后台启动前台服务.

所以在WorkManager 2.7开始, 对紧急的任务( expedited jobs)做了处理.

val request = OneTimeWorkRequestBuilder()       
   .setExpedited(OutOfQuotaPolicy.RUN_AS_NON_EXPEDITED_WORK_REQUEST)   
   .build() 
WorkManager.getInstance(context).enqueue(request)

Controlling TextView MinWidth

关于TextView的最小宽度控制.

Seeing What Talkback Sees

可以查看Talkback看到的文字, debug accessibility的信息.

Code

• https://github.com/kojofosu/Quantitizer
• https://github.com/microsoft/surface-duo-window-manager-samples/tree/main/TravelPlanner
• https://github.com/manueldidonna/waves-timer-animation 倒计时, 有一个水流向下的动画.
• https://github.com/sarnavakonar/Gamebaaz 一个用kotlin做前后端的完整应用.
• https://github.com/square/workflow-kotlin 状态机.

News

• Hilt extensions