Jetpack Compose
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Notes: 06. Build Common UI Components - Part 1
The student materials have been reviewed and are updated as of September 2022.
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Intro
[Slide 1 - Material Design]
Demo
Let’s start off by making more of your components reusable. Open the AddBookActivity. Now let’s move the DropdownMenu from the class to a separate file in the composeUi package, to make it reusable:
@Composable
fun GenrePicker(
genres: List<Genre>,
selectedGenreId: String,
onItemPicked: (Genre) -> Unit
) {
...
}
DropdownMenu(expanded = isGenresPickerOpen.value,
onDismissRequest = { isGenresPickerOpen.value = false }) {
for (genre in genres) {
DropdownMenuItem(onClick = {
onItemPicked(genre)
isGenresPickerOpen.value = false
}) {
Text(text = genre.name)
}
}
}
GenrePicker(genres = genres, onItemPicked = {
_addBookState.value = _addBookState.value.copy(genreId = it.id)
}, selectedGenreId = _addBookState.value.genreId ?: "")
private val _addBookState = mutableStateOf(AddBookState())
private val _genresState = mutableStateOf(emptyList<Genre>())
@Composable
fun BooksContent() {
val bookFilterDrawerState = rememberBottomDrawerState(initialValue = BottomDrawerValue.Closed)
Scaffold(topBar = { BooksTopBar(bookFilterDrawerState) },
floatingActionButton = { AddNewBook(bookFilterDrawerState) }) {
BookFilterModalDrawer(bookFilterDrawerState = bookFilterDrawerState)
}
}
@Composable
fun BooksTopBar(bookFilterDrawerState: BottomDrawerState) {
TopBar(
actions = { FilterButton(bookFilterDrawerState) })
}
@Composable
fun FilterButton(bookFilterDrawerState: BottomDrawerState) {
val scope = rememberCoroutineScope()
IconButton(onClick = {
scope.launch {
if (!bookFilterDrawerState.isClosed) {
bookFilterDrawerState.close()
} else {
bookFilterDrawerState.expand()
}
}
}) {
Icon(Icons.Default.Edit, tint = Color.White, contentDescription = "Filter")
}
}
@Composable
fun AddNewBook(bookFilterDrawerState: BottomDrawerState) {
val scope = rememberCoroutineScope()
FloatingActionButton(
content = { Icon(Icons.Filled.Add, contentDescription = "Add Book") },
onClick = {
scope.launch {
bookFilterDrawerState.close()
showAddBook()
}
},
)
}
@ExperimentalMaterialApi
@Composable
fun BookFilterModalDrawer(bookFilterDrawerState: BottomDrawerState) {
val books = _booksState.value ?: emptyList()
BottomDrawer(
drawerState = bookFilterDrawerState,
drawerContent = {
BookFilterModalDrawerContent(Modifier.align(CenterHorizontally), bookFilterDrawerState)
},
content = { BooksList(books) })
}
@ExperimentalMaterialApi
@Composable
fun BookFilterModalDrawerContent(
modifier: Modifier,
bookFilterDrawerState: BottomDrawerState
) {
val scope = rememberCoroutineScope()
val genres = _genresState.value ?: emptyList()
BookFilter(modifier, filter, genres, onFilterSelected = { newFilter ->
scope.launch {
bookFilterDrawerState.close()
filter = newFilter
loadBooks()
}
})
}
@Composable
fun BookFilter(
modifier: Modifier,
filter: Filter?,
genres: List<Genre>,
onFilterSelected: (Filter?) -> Unit
) {
val currentFilter = remember {
mutableStateOf(
when (filter) {
null -> 0
is ByGenre -> 1
is ByRating -> 2
}
)
} // 0 - no filter, 1 - ByGenre, 2 - By Rating
val currentGenreFilter = remember { mutableStateOf<Genre?>(null) }
val currentRatingFilter = remember { mutableStateOf(0) }
Column(
modifier = modifier,
horizontalAlignment = Alignment.CenterHorizontally
) {
Column {
}
}
Row {
RadioButton(
selected = currentFilter.value == 0,
onClick = { currentFilter.value = 0 },
modifier = Modifier.padding(8.dp)
)
Text(
text = stringResource(id = R.string.no_filter),
modifier = Modifier.align(Alignment.CenterVertically)
)
}
Row {
RadioButton(
selected = currentFilter.value == 1,
onClick = { currentFilter.value = 1 },
modifier = Modifier.padding(8.dp)
)
Text(
text = stringResource(id = R.string.filter_by_genre),
modifier = Modifier.align(Alignment.CenterVertically)
)
}
Row {
RadioButton(
selected = currentFilter.value == 2,
onClick = { currentFilter.value = 2 },
modifier = Modifier.padding(8.dp)
)
Text(
text = stringResource(id = R.string.filter_by_rating),
modifier = Modifier.align(Alignment.CenterVertically)
)
}
val currentlySelectedGenre = currentGenreFilter.value
if (currentFilter.value == 2) {
RatingBar(
range = 1..5,
currentRating = currentRatingFilter.value,
isLargeRating = true,
onRatingChanged = { newRating -> currentRatingFilter.value = newRating })
}
if (currentFilter.value == 1) {
GenrePicker(
genres = genres,
selectedGenreId = currentlySelectedGenre?.id ?: "",
onItemPicked = {
currentGenreFilter.value = it
}
)
}
ActionButton(
modifier = Modifier.fillMaxWidth(),
text = stringResource(id = R.string.confirm_filter),
onClick = {
val newFilter = when (currentFilter.value) {
0 -> null
...
}
}
)
1 -> ByGenre(currentGenreFilter.value?.id ?: "")
2 -> ByRating(currentRatingFilter.value)
else -> throw IllegalArgumentException("Unknown filter!")
}
onFilterSelected(newFilter)