First midterm exam

The first midterm exam will be held in class on Wednesday, Oct. 7. The exam will cover the material I have posted on the course web site in the "Introduction to Kotlin" and "Android View Examples" sections.

The exam will mostly focus on key concepts in Android View applications, including

• Activities and their onCreate() methods.
• Click handlers for buttons
• Using findViewById<>(), reading strings from TextFields, and setting the text in TextViews.
• Setting up an Intent to navigate to a new activity, and calling finish() to return from an activity.
• Working with ViewModels
• 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?

interface QuizApi {

    @GET("questions")
    suspend fun getQuestions(@Query("quiz") quizId: Int): Response<Array<Question>>

    @POST("answers")
    suspend fun postAnswer(@Body answer: Answer): Response<Void>

    @GET("quizzes")
    suspend fun getQuizzes(): Response<Array<Quiz>>

    @GET("students")
    suspend fun getStudents(): Response<Array<Student>>
}

2. What does this code do?

companion object {
    const val NAME: String = "edu.lawrence.SecondAndroid.NAME"
}
fun doGreeting(view: View) {
    val nameField = findViewById<EditText?>(R.id.name)
    val name = nameField?.getText().toString()
    val intent: Intent = Intent(this, SecondActivity::class.java)
    intent.putExtra(NAME, name)
    startActivity(intent)
}

What role does the companion object play here?

3. Putting data in an Intent is one way to pass information from one activity to another. An alternative is to use a ViewModel. How would you restructure the example in number two to use a ViewModel to pass the person's name from the first activity to the second?