【发布时间】：2020-03-11 23:20:20
【问题描述】：
我想在jetpackcompose 中创建带有hint 文本的textfield。任何示例如何使用jectpack 创建textfield？谢谢
【问题讨论】：
标签： android android-textinputlayout android-jetpack-compose android-compose-textfield
【发布时间】：2020-03-11 23:20:20
【问题描述】：
【讨论】：
-
注意：您需要这两个导入：
import androidx.compose.runtime.getValue和import androidx.compose.runtime.setValue。 Android Studio 当前的金丝雀不会自动添加它们。 -
或者你可以像这样添加
import androidx.compose.runtime.*。
compose_version = '1.0.0-beta07'
使用参数placeholder显示提示
TextField(value = "", onValueChange = {}, placeholder = { Text("Enter Email") })
使用参数label显示浮动标签
TextField(value = "", onValueChange = {}, label = { Text("Enter Email") })
【讨论】：
-
这是正确而优雅的答案。
您可以在jetpackCompose 中创建hintTextField，如下代码所示：
@Composable
fun HintEditText(hintText: @Composable() () -> Unit) {
val state = state { "" } // The unary plus is no longer needed. +state{""}
val inputField = @Composable {
TextField(
value = state.value,
onValueChange = { state.value = it }
)
}
if (state.value.isNotEmpty()) {
inputField()
} else {
Layout(inputField, hintText) { measurable, constraints ->
val inputfieldPlacable = measurable[inputField].first().measure(constraints)
val hintTextPlacable = measurable[hintText].first().measure(constraints)
layout(inputfieldPlacable.width, inputfieldPlacable.height) {
inputfieldPlacable.place(0.ipx, 0.ipx)
hintTextPlacable.place(0.ipx, 0.ipx)
} }
}
}
如下调用@Compose函数：
HintEditText @Composable {
Text(
text = "Enter Email",
style = TextStyle(
color = Color.White,
fontSize = 18.sp
)
)
}
【讨论】：
Jetpack 组合版本：dev08
compose 的好处是我们可以通过组合当前的可组合函数来轻松地创建我们的小部件。
我们可以用当前TextField的所有参数创建一个函数并添加一个
hint: String参数。
@Composable
fun TextFieldWithHint(
value: String,
modifier: Modifier = Modifier.None,
hint: String,
onValueChange: (String) -> Unit,
textStyle: TextStyle = currentTextStyle(),
keyboardType: KeyboardType = KeyboardType.Text,
imeAction: ImeAction = ImeAction.Unspecified,
onFocus: () -> Unit = {},
onBlur: () -> Unit = {},
focusIdentifier: String? = null,
onImeActionPerformed: (ImeAction) -> Unit = {},
visualTransformation: VisualTransformation? = null,
onTextLayout: (TextLayoutResult) -> Unit = {}
) {
Stack(Modifier.weight(1f)) {
TextField(value = value,
modifier = modifier,
onValueChange = onValueChange,
textStyle = textStyle,
keyboardType = keyboardType,
imeAction = imeAction,
onFocus = onFocus,
onBlur = onBlur,
focusIdentifier = focusIdentifier,
onImeActionPerformed = onImeActionPerformed,
visualTransformation = visualTransformation,
onTextLayout = onTextLayout)
if (value.isEmpty()) Text(hint)
}
}
我们可以这样使用它：
@Model
object model { var text: String = "" }
TextFieldWithHint(value = model.text, onValueChange = { data -> model.text = data },
hint= "Type book name or author")
这种方法的缺陷是我们将提示作为字符串传递，因此如果我们想要设置提示的样式，我们应该向TextFieldWithHint 添加额外的参数（例如hintStyle、hintModifier、hintSoftWrap，...）
更好的方法是接受可组合的 lambda 而不是字符串：
@Composable
fun TextFieldWithHint(
value: String,
modifier: Modifier = Modifier.None,
hint: @Composable() () -> Unit,
onValueChange: (String) -> Unit,
textStyle: TextStyle = currentTextStyle(),
keyboardType: KeyboardType = KeyboardType.Text,
imeAction: ImeAction = ImeAction.Unspecified,
onFocus: () -> Unit = {},
onBlur: () -> Unit = {},
focusIdentifier: String? = null,
onImeActionPerformed: (ImeAction) -> Unit = {},
visualTransformation: VisualTransformation? = null,
onTextLayout: (TextLayoutResult) -> Unit = {}
) {
Stack(Modifier.weight(1f)) {
TextField(value = value,
modifier = modifier,
onValueChange = onValueChange,
textStyle = textStyle,
keyboardType = keyboardType,
imeAction = imeAction,
onFocus = onFocus,
onBlur = onBlur,
focusIdentifier = focusIdentifier,
onImeActionPerformed = onImeActionPerformed,
visualTransformation = visualTransformation,
onTextLayout = onTextLayout)
if (value.isEmpty()) hint()
}
}
我们可以这样使用它：
@Model
object model { var text: String = "" }
TextFieldWithHint(value = model.text, onValueChange = { data -> model.text = data },
hint= { Text("Type book name or author", style = TextStyle(color = Color(0xFFC7C7C7))) })
【讨论】：
var textState by remember { mutableStateOf(TextFieldValue()) }
var errorState by remember { mutableStateOf(false) }
var errorMessage by remember { mutableStateOf("") }
TextField(
value = textState,
onValueChange = {
textState = it
when {
textState.text.isEmpty() -> {
errorState = true
errorMessage = "Please Enter Site Code"
}
else -> {
errorState = false
errorMessage = ""
}
}
},
isError = errorState,
label = {
Text(
text = if (errorState) errorMessage
else "You Hint"
)
},
modifier = Modifier
.padding(top = 20.dp, start = 30.dp, end = 30.dp)
.fillMaxWidth())
【讨论】：
这对我有用（我认为它比 Anas 发布的更简单，因为它使用相同的组件：
@Composable
fun TextBox(
loginInput: LoginInput,
hint: String = "enter value",
color: Color = Color.LightGray,
height: Dp = 50.dp
) {
val state = +state { "" }
state.value = if (loginInput.usernameEntered) loginInput.username else hint
Surface(color = color) {
Row {
Container(modifier = Expanded, height = height) {
Clip(shape = RoundedCornerShape(15.dp)) {
Padding(padding = 15.dp) {
TextField(
value = state.value,
keyboardType = KeyboardType.Text,
onFocus = {
if (!loginInput.usernameEntered)
state.value = ""
},
onValueChange = {
loginInput.usernameEntered = true
loginInput.username = it
state.value = loginInput.username
}
)
}
}
}
}
}
}
【讨论】：
如果文本为空，label 参数将显示为文本，并在输入时移动到文本字段上方（作为标签）：
@Composable
fun SearchField() {
val (text, setText) = remember { mutableStateOf(TextFieldValue("")) }
Box(modifier = Modifier.width(180.dp).padding(2.dp)) {
TextField(
modifier = Modifier.fillMaxWidth(),
value = text,
onValueChange = { setText(it) },
label = { Text("quick do:") },
)
}
}
【讨论】：