Does anyone have an opinion on whether it s considered a bad

Question

Does anyone have an opinion on whether it s considered a bad practice to make the ViewModel aware of the screen configuration orientation I have a case where I d like to hide some of the page s content in a tab of a tab bar for phones portrait mode devices while it can be shown on larger devices landscape tablets A list of what tabs to show currently comes from a ViewModel but the ViewModel is not aware of the window configuration In essence it boils down to something like this ```val tabs = if configuration isExpanded Tablet landscape mode listOf TabType Foo TabType Bar else Phone portrait mode listOf TabType Foo TabType Bar TabType MoreInfo ``` Is this something I d better avoid If so what would a better pattern to handle this be In practice the list of tabs is a StateFlow which is collected by a composable but conceptionally this shouldn t really make a difference

Otávio Gabriel (Tavieto) · Answer

In my opinion the UI should have as little knowledge as possible about the data manipulation Your approach is valid and nice but I imagine that can cause some visual bug For example your app is opened in landscape and you switch to another app This other app now is in portrait When you come back to your app your view model will have the information that the screen still in landscape and depends of the screen to inform about the new orientation So is possible to user see the UI change which could not be a good experience You could have 2 data list in your view model about each orientation and leave to UI decide which one to choose I would choose this approach ```val config = LocalConfiguration current val myList = when config orientation androidx compose foundation gestures Orientation Vertical ordinal gt viewModel listPortrait else gt viewModel listLandscape ```

Tom De Decker · Answer

Thanks for the reply that makes sense What makes this difficult however is that I currently store the active tab and its index inside the ViewModel Without information about the orientation the ViewModel can t really know what the active tab is or what the bounds are on the list of tabs e g listPortrait might contain 3 items while listLandscape contains only 2 I feel like this makes it quite difficult to properly use a ViewModel

Otávio Gabriel (Tavieto) · Answer

You can also keep the index list in screen and use the same principle I recommend use rememberSaveable to keep the data across screen orientation and recreation This way the screen will be responsible for handle your lists ```var indexPortrait by rememberSaveable mutableStateOf 0 ``` ```var indexLandscape by rememberSaveable mutableStateOf 0 ``` ``` val index by remember indexPortrait indexLanscape mutableStateOf when config orientation androidx compose foundation gestures Orientation Vertical ordinal gt indexPortrait else gt indexLandscape ```

Otávio Gabriel (Tavieto) · Answer

Here is a reference about rememberSaveable <https developer android com jetpack compose state saving|https developer android com jetpack compose state saving>

Colin T · Answer

```var myOrientation by remember mutableStateOf Configuration ORIENTATION PORTRAIT ```

Colin T · Answer

```LaunchedEffect configuration Save any changes to the orientation value on the configuration object snapshotFlow configuration orientation collectLatest myOrientation = it ```

Colin T · Answer

```when myOrientation Configuration ORIENTATION LANDSCAPE gt YourComposable navController else gt ```