如何在elm中实现滑块-Java 学习之路

我想链接一个滑块和一个输入文本区域，这样当我更改一个时，另一个会自动更新 . 我找到了elm-reactor的实现，它使用本机JavaScript并使用回调 . 移动滑块时会调用回调，但是当从文本区域更改值时，我无法移动它 .

4 回答

事实并非那么难 . 此代码显示如何设置两种输入类型的值 .

import Html exposing (div, text, input)
import Html.Attributes as H exposing (..)
import Html.Events as E 

mbox = 
  Signal.mailbox "0"

view v =
  let 
    evth = E.on "change" E.targetValue (Signal.message mbox.address)
  in
  div [] 
    [ input 
      [ type' "range"
      , H.min "0"
      , H.max "20"
      , value v
      , evth
      ] []
    , input
      [ type' "text", value v, evth ] []
    ]


main =
  Signal.map view mbox.signal

Update for 0.17

import Html exposing (Attribute, div, text, input)
import Html.App as Html
import Html.Attributes as H exposing (..)
import Html.Events exposing (on, onInput)
import Json.Decode exposing (string, map)
import String

type alias Model = Int

type Msg
    = Update String

update : Msg -> Model -> Model
update (Update v) model =
    String.toInt v |> Result.withDefault 0

view model =
  div []
    [ input
      [ type' "range"
      , H.min "0"
      , H.max "20"
      , value <| toString model
      , onInput Update
      ] []
    , text <| toString model
    ]

main =
  Html.beginnerProgram
    { model = 0
    , view = view
    , update = update
    }

Update for 0.18

import Html exposing (Attribute, div, text, input)
import Html.Attributes as H exposing (..)
import Html.Events exposing (on, onInput)
import Json.Decode exposing (string, map)
import String

type alias Model = Int

type Msg
    = Update String

update : Msg -> Model -> Model
update (Update v) model =
    String.toInt v |> Result.withDefault 0

view model =
  div []
    [ input
      [ type_ "range"
      , H.min "0"
      , H.max "20"
      , value <| toString model
      , onInput Update
      ] []
    , text <| toString model
    ]

main =
  Html.beginnerProgram
    { model = 0
    , view = view
    , update = update
    }

见runelm example

回复于 2024-04-26T04:26:25+08:00

18

基本思想是在模型中使用一个数字的规范表示 . 每当它发生变化时（这将是一个动作），你不关心变化的来源，你只需要更新模型 . 然后根据模型中数字的值渲染文本区域和滑块 . （我们说的只是一个单独的文本字段，而不是一个自由形式的段落框，对吧？）

希望有所帮助！

回复于 2024-04-26T04:26:25+08:00

来自Simon H的原始答案， Update for Elm 0.18:

import Html exposing (Attribute, div, text, input, beginnerProgram)
import Html.Attributes as H exposing (..)
import Html.Events exposing (on, onInput)

type alias Model = Int

type Msg
    = Update String

update : Msg -> Model -> Model
update (Update v) model =
    String.toInt (Debug.log "" v) |> Result.withDefault 0

view model =
  div []
    [ input
      [ type_ "range"
      , H.min "0"
      , H.max "20"
      , value <| toString model
      , onInput Update
      ] []
    , text <| toString model
    ]

main =
  Html.beginnerProgram
    { model = 0
    , view = view
    , update = update
    }

回复于 2024-04-26T04:26:25+08:00

Updated to Elm 0.19 来自banncee 's update to 0.18 from Simon H'的原始答案

import Browser
import Html exposing (Attribute, div, text, input)
import Html.Attributes as H exposing (..)
import Html.Events exposing (on, onInput)

type alias Model = Int

type Msg
    = Update String

init : Model
init = 0

update : Msg -> Model -> Model
update (Update v) model =
    case String.toInt v of
        Just i -> i
        Nothing -> model

view model =
  div []
    [ input
      [ type_ "range"
      , H.min "0"
      , H.max "20"
      , value  <| String.fromInt model
      , onInput Update
      ] []
    , text <|String.fromInt model
    ]

main =
    Browser.sandbox
        { init = init
        , view = view
        , update = update
        }

回复于 2024-04-26T04:26:25+08:00

如何在elm中实现滑块

4 回答

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