Jetpack Compose
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Notes: 05. Decouple Composables
In ui/addBook/AddBookActivity, within AddBookTopBar() composable function, the method onBackPressed() is deprecated and is replaced by onBackPressedDispatcher.onBackPressed() method.
In ui/composeUi/InputField, the statement backgroundColor = Color.White is added to make the background color of OutlinedTextField as white instead of the default theme color.
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Demo
One of the most important things about writing good and clean code is decoupling different components, to make them more reusable.
@Composable
@Preview
fun ActionButton(
modifier: Modifier = Modifier,
text: String = "Librarian",
isEnabled: Boolean = true,
enabledColor: Color = colorResource(id = R.color.colorPrimary),
disabledTextColor: Color = Color.Gray,
onClick: () -> Unit = {}
) {
}
val backgroundColor = if (isEnabled) enabledColor else Color.LightGray
TextButton(
shape = RoundedCornerShape(16.dp),
enabled = isEnabled,
colors = ButtonDefaults.textButtonColors(
backgroundColor = backgroundColor,
contentColor = Color.White,
disabledContentColor = disabledTextColor
),
modifier = modifier
.padding(16.dp),
content = { Text(text = text) },
onClick = onClick
)
@Composable
@Preview
fun BackButton(
modifier: Modifier = Modifier,
onBackAction: () -> Unit = {}
) {
IconButton(
modifier = modifier,
content = {
Icon(
Icons.Default.ArrowBack,
tint = Color.White,
contentDescription = "Back"
)
},
onClick = { onBackAction() }
)
}
@Composable
@Preview
fun InputField(
modifier: Modifier = Modifier,
value: String = "",
label: String = stringResource(id = R.string.app_name),
keyboardType: KeyboardType = KeyboardType.Text,
isInputValid: Boolean = true,
imeAction: ImeAction = ImeAction.Next,
onStateChanged: (String) -> Unit = {}
) {
val focusedColor = colorResource(id = R.color.colorPrimary)
val unfocusedColor = colorResource(id = R.color.colorPrimaryDark)
}
OutlinedTextField(
value = value,
onValueChange = { newValue -> onStateChanged(newValue) },
label = { Text(label) },
modifier = modifier
.fillMaxWidth()
.padding(
start = 16.dp,
end = 16.dp,
top = 4.dp,
bottom = 4.dp
),
keyboardOptions = KeyboardOptions(keyboardType = keyboardType, imeAction = imeAction),
visualTransformation = getVisualTransformation(keyboardType),
isError = !isInputValid,
colors = ...
)
colors = TextFieldDefaults.textFieldColors(
focusedIndicatorColor = focusedColor,
focusedLabelColor = focusedColor,
unfocusedIndicatorColor = unfocusedColor,
unfocusedLabelColor = unfocusedColor,
cursorColor = focusedColor,
backgroundColor = Color.White
)
private fun getVisualTransformation(keyboardType: KeyboardType) =
if (keyboardType == KeyboardType.Password || keyboardType == KeyboardType.NumberPassword)
PasswordVisualTransformation()
else VisualTransformation.None
@Composable
@Preview
fun TopBar(
modifier: Modifier = Modifier,
title: String = "Add a new review",
actions: @Composable RowScope.() -> Unit = {},
onBackPressed: (() -> Unit)? = null
) {
}
val backButtonAction: (@Composable () -> Unit)? = if (onBackPressed != null) {
@Composable { BackButton(onBackAction = { onBackPressed() }) }
} else {
null
}
TopAppBar(
modifier = modifier,
title = { Text(title) },
navigationIcon = backButtonAction,
actions = actions,
backgroundColor = colorResource(id = R.color.colorPrimary),
contentColor = Color.White
)
@Composable
fun AddBookTopBar() {
TopBar(
title = stringResource(id = R.string.add_book_title),
onBackPressed = { onBackPressedDispatcher.onBackPressed() })
}
InputField(
value = bookNameState.value,
onStateChanged = { newValue ->
bookNameState.value = newValue
_addBookState.value = _addBookState.value?.copy(name = newValue)
},
label = stringResource(id = R.string.book_title_hint)
)
InputField(
value = bookDescriptionState.value,
onStateChanged = { newValue ->
bookDescriptionState.value = newValue
_addBookState.value = _addBookState.value?.copy(description = newValue)
},
label = stringResource(id = R.string.book_description_hint)
)
ActionButton(
text = stringResource(id = R.string.add_book_button_text),
onClick = { onAddBookTapped() }
)
@Composable
fun BooksTopBar() {
TopBar(
title = stringResource(id = R.string.my_books_title),
actions = { FilterButton() })
}
@Composable
fun FilterButton() {
IconButton(onClick = {
// TODO
}) {
Icon(Icons.Default.Edit, tint = Color.White, contentDescription = "Filter")
}
}