今天學什麼？

今天閱讀「適用於 Android 開發人員的 Jetpack Compose」第一章「Compose 基礎知識」的「實作遷移作業」的 6~13 章

學習筆記

1. Compose 不要把整個 ViewModel 傳入，只要傳子項就好
2. LiveData 可以用observeAsState建立觀察，但發出的值可能是 null，所以要做空值判斷

   @Composable
   fun PlantDetailDescription(plantDetailViewModel: PlantDetailViewModel) {
       // Observes values coming from the VM's LiveData<Plant> field
       val plant by plantDetailViewModel.plant.observeAsState()
   
       // If plant is not null, display the content
       plant?.let {
           PlantDetailContent(it)
       }
   }
   

3. Compose 尚不支援轉譯 HTML
4. 真的很想在 Compose 的 text 寫 HTML 的話，可以用AndroidView在 Compose 內建立 TextView
5. 不建議在 Fragment 中使用ComposeView
6. ComposeView 使用DisposeOnViewTreeLifecycleDestroyed
7. 設定主題顏色

   @Composable
   fun SunflowerTheme(
       darkTheme: Boolean = isSystemInDarkTheme(),
       content: @Composable () -> Unit
   ) {
       val lightColors  = lightColors(
           primary = colorResource(id = R.color.sunflower_green_500),
           primaryVariant = colorResource(id = R.color.sunflower_green_700),
           secondary = colorResource(id = R.color.sunflower_yellow_500),
           background = colorResource(id = R.color.sunflower_green_500),
           onPrimary = colorResource(id = R.color.sunflower_black),
           onSecondary = colorResource(id = R.color.sunflower_black),
       )
       val darkColors  = darkColors(
           primary = colorResource(id = R.color.sunflower_green_100),
           primaryVariant = colorResource(id = R.color.sunflower_green_200),
           secondary = colorResource(id = R.color.sunflower_yellow_300),
           onPrimary = colorResource(id = R.color.sunflower_black),
           onSecondary = colorResource(id = R.color.sunflower_black),
           onBackground = colorResource(id = R.color.sunflower_black),
           surface = colorResource(id = R.color.sunflower_green_100_8pc_over_surface),
           onSurface = colorResource(id = R.color.sunflower_white),
       )
       val colors = if (darkTheme) darkColors else lightColors
       MaterialTheme(
           colors = colors,
           content = content
       )
   }