Jetpack Compose

Oct 11 2022 Kotlin 1.7.10, Android 13, Android Studio Chipmunk

Part 1: Jetpack Compose Basics

9. Apply Error & Data Handling to the UI

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Previous episode: 8. Build Common UI Components - Part 3 Next episode: 10. Add Actions & Handlers

The student materials have been reviewed and are updated as of September 2022.

In ui/bookReviewDetails/BookReviewDetailsActivity file, within BookRevBookReviewDetailsInformationiewItem() composable function, replace CoilImage() composable by AsyncImage() composable with updated parameters. CoilImage composable is old and not compatible with current Jetpack Compose version.

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Demo

To make sure your forms don’t let the user store empty data, you need a way to disable actions or show errors, when the data is invalid. To do that, you need to apply error and data handling!

InputField(
  value = bookNameState.value,
        ...
  isInputValid = bookNameState.value.isNotEmpty()
)

InputField(
  value = bookDescriptionState.value,
        ...
  isInputValid = bookDescriptionState.value.isNotEmpty()
)

ActionButton(
  ...
  isEnabled = bookNameState.value.isNotEmpty()
      && bookDescriptionState.value.isNotEmpty()
      && _addBookState.value.genreId.isNotEmpty()
)

isInputValid = bookUrl.value.isNotEmpty()

...

isInputValid = bookNotes.value.isNotEmpty()

...

val pickedBook = _bookReviewState.value?.bookAndGenre

isEnabled = bookNotes.value.isNotEmpty() && bookUrl.value.isNotEmpty()
      && pickedBook != null && pickedBook != EMPTY_BOOK_AND_GENRE

private val _bookReviewDetailsState = mutableStateOf(EMPTY_BOOK_REVIEW)
private val _genreState = mutableStateOf(EMPTY_GENRE)

val bookReview = _bookReviewDetailsState.value
val genre = _genreState.value

Column(
  modifier = Modifier
    .fillMaxSize()
    .scrollable(rememberScrollState(), orientation = Orientation.Vertical),
  horizontalAlignment = Alignment.CenterHorizontally,
) {

  Spacer(modifier = Modifier.height(16.dp))

Card(
  modifier = Modifier
    .size(width = 200.dp, height = 300.dp),
  shape = RoundedCornerShape(16.dp),
  elevation = 16.dp
) {
  CoilImage(
    data = bookReview.review.imageUrl,
    contentScale = ContentScale.FillWidth,
    contentDescription = null
  )
}

Spacer(modifier = Modifier.height(16.dp))

Text(
  text = bookReview.book.name,
  fontWeight = FontWeight.Bold,
  fontSize = 18.sp
)

Spacer(modifier = Modifier.height(6.dp))

Text(
  text = genre.name,
  fontSize = 12.sp
)

      Spacer(modifier = Modifier.height(6.dp))

      RatingBar(
        modifier = Modifier.align(CenterHorizontally),
        range = 1..5,
        isSelectable = false,
        isLargeRating = false,
        currentRating = bookReview.review.rating
      )

      Spacer(modifier = Modifier.height(6.dp))

      Text(
        text = stringResource(
          id = R.string.last_updated_date,
          formatDateToText(bookReview.review.lastUpdatedDate)
        ),
        fontSize = 12.sp
      )

      Spacer(modifier = Modifier.height(8.dp))

      Spacer(
        modifier = Modifier
          .fillMaxWidth(0.9f)
          .height(1.dp)
          .background(
            brush = SolidColor(value = Color.LightGray),
            shape = RectangleShape
          )
      )

      Text(
        modifier = Modifier.padding(start = 20.dp, end = 20.dp, top = 8.dp, bottom = 8.dp),
        text = bookReview.review.notes,
        fontSize = 12.sp,
        fontStyle = FontStyle.Italic
      )

      Spacer(
        modifier = Modifier
          .fillMaxWidth(0.9f)
          .height(1.dp)
          .background(
            brush = SolidColor(value = Color.LightGray),
            shape = RectangleShape
          )
      )