Android Basics Quiz

import androidx.compose.ui.unit.dp

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            MiniTheme {
                MiniScreen(stringResource(R.string.screen_title)) {
                    QuizScreen()
                }
            }
        }
    }
}

@Composable
private fun QuizScreen() {
    var questionIndex by rememberSaveable { mutableIntStateOf(0) }
    var selectedIndex by rememberSaveable { mutableIntStateOf(-1) }
    var submitted by rememberSaveable { mutableStateOf(false) }
    var score by rememberSaveable { mutableIntStateOf(0) }
    var finished by rememberSaveable { mutableStateOf(false) }

    if (finished) {
        Text(stringResource(R.string.completed), style = MaterialTheme.typography.headlineSmall)
        Text(stringResource(R.string.final_score, score, quizQuestions.size))

package com.mastercoding.miniprojects.quiz

data class QuizQuestion(
    val id: Int,
    val prompt: Int,
    val options: List<Int>,
    val correctIndex: Int,
    val explanation: Int
)

// Resource IDs keep the question bank localizable without mixing UI into scoring.
val quizQuestions = listOf(
    QuizQuestion(1, R.string.question_1,
        listOf(R.string.q1_a, R.string.q1_b, R.string.q1_c, R.string.q1_d),
        correctIndex = 1, explanation = R.string.explanation_1),
    QuizQuestion(2, R.string.question_2,
        listOf(R.string.q2_a, R.string.q2_b, R.string.q2_c, R.string.q2_d),
        correctIndex = 0, explanation = R.string.explanation_2),
    QuizQuestion(3, R.string.question_3,
        listOf(R.string.q3_a, R.string.q3_b, R.string.q3_c, R.string.q3_d),
        correctIndex = 2, explanation = R.string.explanation_3),
    QuizQuestion(4, R.string.question_4,
        listOf(R.string.q4_a, R.string.q4_b, R.string.q4_c, R.string.q4_d),
        correctIndex = 3, explanation = R.string.explanation_4),
    QuizQuestion(5, R.string.question_5,
        listOf(R.string.q5_a, R.string.q5_b, R.string.q5_c, R.string.q5_d),

/** An answer can be submitted only once and must refer to an existing option. */
fun canSubmitAnswer(selectedIndex: Int, optionCount: Int, submitted: Boolean): Boolean =
    !submitted && selectedIndex in 0 until optionCount

fun scoreAfterAnswer(
    currentScore: Int,
    selectedIndex: Int,
    correctIndex: Int,
    optionCount: Int,
    submitted: Boolean
): Int {
    require(currentScore >= 0)
    require(correctIndex in 0 until optionCount)
    return currentScore + if (
        canSubmitAnswer(selectedIndex, optionCount, submitted) && selectedIndex == correctIndex
    ) 1 else 0
}

@Composable
private fun QuizScreen() {
    var questionIndex by rememberSaveable { mutableIntStateOf(0) }
    var selectedIndex by rememberSaveable { mutableIntStateOf(-1) }
    var submitted by rememberSaveable { mutableStateOf(false) }
    var score by rememberSaveable { mutableIntStateOf(0) }
    var finished by rememberSaveable { mutableStateOf(false) }

    if (finished) {
        Text(stringResource(R.string.completed), style = MaterialTheme.typography.headlineSmall)
        Text(stringResource(R.string.final_score, score, quizQuestions.size))
        Text(stringResource(R.string.review_tip))
        Button(
            onClick = {
                questionIndex = 0
                selectedIndex = -1
                submitted = false
                score = 0
                finished = false
            },
            modifier = Modifier.fillMaxWidth()
        ) { Text(stringResource(R.string.restart)) }
        return
    }

    val question = quizQuestions[questionIndex]

    )
    Column(
        modifier = Modifier.selectableGroup(),
        verticalArrangement = Arrangement.spacedBy(4.dp)
    ) {
        question.options.forEachIndexed { index, option ->
            Row(
                modifier = Modifier.fillMaxWidth()
                    .selectable(
                        selected = selectedIndex == index,
                        enabled = !submitted,
                        role = Role.RadioButton,
                        onClick = { selectedIndex = index }
                    )
                    .padding(vertical = 8.dp, horizontal = 4.dp),
                verticalAlignment = Alignment.CenterVertically
            ) {
                RadioButton(
                    selected = selectedIndex == index,
                    onClick = null,
                    enabled = !submitted
                )
                Text(stringResource(option), modifier = Modifier.padding(start = 12.dp))
            }
        }
    }

        onClick = {
            if (canSubmitAnswer(selectedIndex, question.options.size, submitted)) {
                score = scoreAfterAnswer(
                    score, selectedIndex, question.correctIndex, question.options.size, submitted
                )
                submitted = true
            }
        },
        enabled = canSubmitAnswer(selectedIndex, question.options.size, submitted),
        modifier = Modifier.fillMaxWidth()
    ) { Text(stringResource(R.string.submit_answer)) }

    if (submitted) {
        Column(
            modifier = Modifier.semantics { liveRegion = LiveRegionMode.Polite },
            verticalArrangement = Arrangement.spacedBy(8.dp)
        ) {
            Text(stringResource(
                if (selectedIndex == question.correctIndex) R.string.correct else R.string.incorrect
            ))
            Text(stringResource(R.string.correct_answer, stringResource(question.options[question.correctIndex])))
            Text(stringResource(question.explanation))
        }
        Button(
            onClick = {
                if (questionIndex == quizQuestions.lastIndex) {

        Button(
            onClick = {
                if (questionIndex == quizQuestions.lastIndex) {
                    finished = true
                } else {
                    questionIndex += 1
                    selectedIndex = -1
                    submitted = false
                }
            },
            modifier = Modifier.fillMaxWidth()
        ) {
            Text(stringResource(
                if (questionIndex == quizQuestions.lastIndex) R.string.show_results else R.string.next_question
            ))
        }
    }
}

    }

    @Test fun correctAnswersAddOnePointOnlyBeforeSubmission() {
        assertEquals(3, scoreAfterAnswer(2, 1, 1, 4, false))
        assertEquals(3, scoreAfterAnswer(3, 1, 1, 4, true))
    }

    @Test fun incorrectAndMissingAnswersDoNotAddPoints() {
        assertEquals(2, scoreAfterAnswer(2, 0, 1, 4, false))
        assertEquals(2, scoreAfterAnswer(2, -1, 1, 4, false))
    }
}