Second midterm exam

The second midterm exam will be held in class on Wednesday, Nov. 4. The exam will cover the material I have posted on the course web site in the "Jetpack Compose" section.

The exam will mostly focus on key concepts in Jetpack Compose applications, including

• Setting up and working with state variables.
• Basic components such as Text(), TextField(), and Button()
• How navigation works and what roles the NavController, NavHost, and composable play in navigation.
• What a Scaffold does, and what you use its topBar for.
• How to use a ViewModel in Jetpack Compose
• Working with Retrofit

Sample questions

I will ask two types of questions. In the first type of question I will show you a chunk of code and ask you to explain what the code is doing. In the second type of question I will ask you to explain how you would accomplish a particular task: for this type of question you can answer with a mix of written explanation and a few relevant snippets of code.

Here are some sample questions:

1. What does this code do?

@Composable
fun CalculatorScreen(code : String, toOptions: () -> Unit,modifier: Modifier) {
    Scaffold(topBar = {
        TopAppBar(
            title = {
                Text(
                    "Travel Money",
                )
            },
            actions = {
                IconButton(onClick = toOptions) {
                    Icon(
                        imageVector = Icons.Default.Settings,
                        contentDescription = "Settings"
                    )
                }
            },
        )
    },
        modifier = Modifier.fillMaxSize())
    { innerPadding ->
        Calculator(code,modifier.padding(innerPadding))
    }
}

2. What does this code do?

@Composable
fun WeatherApp(modifier : Modifier) {
    val vm : WeatherModel = viewModel()
    vm.getForecast()
    val navController = rememberNavController()
    NavHost(navController,startDestination="forecast") {
        composable(route="forecast") {
            WeatherScreen(vm,toOptions = { navController.navigate("location")}, modifier = modifier)
        }
        composable(route="location") {
            LocationScreen(vm,back = { navController.navigate("forecast")}, modifier = modifier)
        }
    }
}

3. To implement navigation we use a NavController with a NavHost. The NavHost consists of a list of routes implemented via composable(), and each route contains a component for the view that that route displays. Suppose we made an app with two views, viewA() and viewB(). Suppose further that we wanted to add a Close button in viewB() that would take us back to viewA(). How would you implenent something like this?