react-native 滚动头部置顶

/**

* Create by lutn on 2018-04-17

*

*/

'use strict';

import React,{ Component } from 'react'

import {

Text,

View,

BackHandler,

ScrollView,

StyleSheet,

AlertIOS,

RefreshControl,

TouchableOpacity,

Image,

TextInput,

Platform,

Dimensions,

ActivityIndicator,

Animated

} from 'react-native'

import px2dp from '../../utils/Px2dp'

const isIOS = Platform. OS == "ios"

const { width,height } = Dimensions. get( 'window')

const headH = px2dp( isIOS? 140: 120)

const InputHeight = px2dp( 28)

export default class HomePage3 extends Component {

constructor( props){

super( props)

this. state = {

location: "三里屯SOHO",

scrollY: new Animated. Value( 0),

searchView: new Animated. Value( 0),

modalVisible: false,

searchBtnShow: true,

isRefreshing: false

}

this. SEARCH_BOX_Y = px2dp( isIOS? 48: 43)

this. SEARCH_FIX_Y = headH- px2dp( isIOS? 64: 44)

this. SEARCH_KEY_P = px2dp( 58)

this. SEARCH_DIFF_Y = this. SEARCH_FIX_Y- this. SEARCH_BOX_Y

}

componentDidMount(){

BackHandler. addEventListener( 'hardwareBackPress',function () {

BackHandler. exitApp( 0)

return true

})

}

_renderHeader(){

let searchY = this. state. scrollY. interpolate({

inputRange: [ 0,this. SEARCH_BOX_Y,this. SEARCH_FIX_Y,this. SEARCH_FIX_Y],

outputRange: [ 0,0,this. SEARCH_DIFF_Y,this. SEARCH_DIFF_Y]

})

let lbsOpaticy = this. state. scrollY. interpolate({

inputRange: [ 0,this. SEARCH_BOX_Y],

outputRange: [ 1,0]

})

let keyOpaticy = this. state. scrollY. interpolate({

inputRange: [ 0,this. SEARCH_KEY_P],1,0]

})

return (

< View style= { styles. header } >

< Animated.View style= {[ styles. lbsWeather,{ opacity: lbsOpaticy}] } >

< Text >头 </ Text >

</ Animated.View >

< Animated.View style= {{

marginTop: px2dp( 15),

transform: [{

translateY: searchY

}]} } >

< Text >中 </ Text >

</ Animated.View >

< Animated.View style= {[ styles. keywords,{ opacity: keyOpaticy}] } >

< Text >底 </ Text >

</ Animated.View >

</ View >

)

}

_renderFixHeader(){

let showY = this. state. scrollY. interpolate({

inputRange: [ 0,

outputRange: [- 9999,- 9999,0]

})

return (

< Animated.View style= {[ styles. header,{

position: "absolute",

left: 0,

right: 0,

top: 0,

bottom: 0,

height: px2dp( isIOS? 64: 44),

paddingTop: px2dp( isIOS? 25: 10),

transform: [

{ translateY: showY}

]

}] } >

< Text >中 </ Text >

</ Animated.View >

)

}

_onRefresh(){

this. setState({ isRefreshing: true});

setTimeout(() => {

this. setState({ isRefreshing: false});

},2000)

}

render(){

return (

< View style= {{ flex: 1,backgroundColor: "#f3f3f3"} } >

< ScrollView

onScroll= { Animated. event(

[{ nativeEvent: { contentOffset: { y: this. state. scrollY}}}]

) }

scrollEventThrottle= { 16 }

refreshControl= {

< RefreshControl

refreshing= {this. state. isRefreshing }

onRefresh= {this. _onRefresh. bind( this) }

colors= {[ '#ddd','#0398ff'] }

progressBackgroundColor= "#ffffff"

/>

}

>

{this. _renderHeader() }

< View style= {{ backgroundColor: "#fff",paddingBottom: 10} } >

< Text >头 </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >sdlkfsdklsfkldflskdsdlkkds </ Text >

< Text >底部 </ Text >

</ View >

</ ScrollView >

{this. _renderFixHeader() }

</ View >

)

}

}

const styles = StyleSheet. create({

header: {

backgroundColor: "#0398ff",

height: headH,

paddingTop: px2dp( isIOS? 30: 10),

paddingHorizontal: 16

},

lbsWeather: {

height: InputHeight,

overflow: "hidden",

flexDirection: "row",

justifyContent: "space-between"

},

keywords: {

marginTop: px2dp( 14),

flexDirection: "row"

},

})

'use strict';

import { Dimensions} from 'react-native'

const deviceH = Dimensions. get( 'window'). height

const deviceW = Dimensions. get( 'window'). width

const basePx = 375

export default function px2dp( px) {

return px * deviceW / basePx

}