关于React Native的下拉刷新,虽然官方出了一个控件RefreshControl,但可定制性太差,基本上样式固定了.最近将公司的Android端用RN重写一下,之前用的是PullToRefresh,于是准备用React Native写一套该效果出来.
效果图:
与
PullToRefresh类似,不光是ListView控件可以下拉刷新,任一控件都可以.
实现原理
PanResponder
在React Native的API中有一个PanResponder,它能检测到用户的手势,与Android中的 事件分发机制的作用类似.可以捕获到用户的touch down,touch move,touch up事件. 然后根据用户按下的距离,对整个View进行y轴的移动.
setNativeProps
在捕获到用户的下拉轨迹后,需要 子控件 跟随用户手势,这里可以改变子控件的marginTop或者translateY的值.
这里比较适合用setNativeProps来直接改变值,如果用state状态机来动态更改,会造成 View的多次重复render,造成不必要的性能损耗.
LayoutAnimation
当用户刷新动作完成之后,需要程序自动将 正在刷新的布局恢复原状,这里使用LayoutAnimation可以很简单的做到.
shouldComponentUpdate
该函数 可用来比较哪些状态的更改需要重新render,用当前的state与将要改变的state比较是否一致.
完整源码:
'use strict'
import React, { Component } from 'react';
import {
AppRegistry,
StyleSheet,
View,
PanResponder,
LayoutAnimation,
ProgressBarAndroid,
Dimensions,
Text,
AsyncStorage,
Image
} from 'react-native';
let self;
/**ref的引用*/
const PULL_REFRESH_LAYOUT="pullLayout";
/**屏幕宽度*/
const deviceWidth = Dimensions.get('window').width;
/**下拉阻力系数*/
const factor=1.8;
/**最大下拉高度*/
const MAX_PULL_LENGTH=170;
/**Loading的高度*/
const REFRESH_PULL_LENGTH=70;
/**动画时长*/
const BACK_TIME=400;
/**存储最后刷新时间的Key*/
const REFRESH_LAST_TIME_KEY="refresh_last";
const RefreshStatus={
Refresh_NONE:0,
Refresh_Drag_Down:1,
Refresh_Loading:2,
Refresh_Reset:3,
};
const ShowLoadingStatus={
SHOW_DOWN:0,
SHOW_UP:1,
SHOW_LOADING:2,
};
class PullToRefreshLayout extends Component{
_panResponder:{}
// 构造
constructor(props) {
super(props);
// 初始状态
this.state = {
currentDistance:0,
pullRefreshStatus:RefreshStatus.Refresh_NONE,
showPullStatus:ShowLoadingStatus.SHOW_DOWN,
showPullLastTime:'NONE',
};
this.resetHeader=this.resetHeader.bind(this);
this.refreshStateHeader=this.refreshStateHeader.bind(this);
this.getTime=this.getTime.bind(this);
this.addZeroAtFront=this.addZeroAtFront.bind(this);
}
//要求成为响应者
_handleStartShouldSetPanResponder(e: Object, gestureState: Object): boolean {
return true;
}
_handleMoveShouldSetPanResponder(e: Object, gestureState: Object): boolean {
return true;
}
//touch down 开始手势操作。给用户一些视觉反馈，让他们知道发生了什么事情！
_handlePanResponderGrant(e: Object, gestureState: Object){
}
//touch move 响应滑动事件
_handlePanResponderMove(e: Object, gestureState: Object) {
if(self.state.currentDistance>REFRESH_PULL_LENGTH){
if(self.state.showPullStatus===ShowLoadingStatus.SHOW_DOWN){
self.setState({
showPullStatus:ShowLoadingStatus.SHOW_UP,
});
}
}
else{
if (self.state.showPullStatus===ShowLoadingStatus.SHOW_UP){
self.setState({
showPullStatus:ShowLoadingStatus.SHOW_DOWN,
});
}
}
if (self.state.pullRefreshStatus===RefreshStatus.Refresh_Loading){
self.setState({
currentDistance:REFRESH_PULL_LENGTH+gestureState.dy/factor,
// refreshStateHeader:2,
});
self.refs[PULL_REFRESH_LAYOUT].setNativeProps({
style:{
marginTop:self.state.currentDistance,
}
});
return;
}
if (gestureState.dy>0&&self.state.currentDistance<MAX_PULL_LENGTH){
self.setState({
currentDistance:gestureState.dy/factor,
pullRefreshStatus:RefreshStatus.Refresh_Drag_Down,
});
self.refs[PULL_REFRESH_LAYOUT].setNativeProps({
style:{
marginTop:self.state.currentDistance,
}
});
}
else if(gestureState.dy>0&&self.state.currentDistance>MAX_PULL_LENGTH){//则不再往下移动
self.setState({
currentDistance:MAX_PULL_LENGTH,
pullRefreshStatus:RefreshStatus.Refresh_Drag_Down,
});
self.refs[PULL_REFRESH_LAYOUT].setNativeProps({
style:{
marginTop:self.state.currentDistance,
}
});
}
}
resetHeader(){
LayoutAnimation.configureNext({
duration: BACK_TIME,
update: {
type: 'linear',
}
});
self.refs[PULL_REFRESH_LAYOUT].setNativeProps({
style:{
marginTop:0,
}
});
self.setState({
currentDistance:0,
pullRefreshStatus:RefreshStatus.Refresh_Reset,
showPullStatus:ShowLoadingStatus.SHOW_DOWN,
});
}
refreshStateHeader(){
self.setState({
pullRefreshStatus:RefreshStatus.Refresh_Loading,
currentDistance:REFRESH_PULL_LENGTH,
showPullStatus:ShowLoadingStatus.SHOW_LOADING,
},()=>{
if(self.props.onRefresh){
self.props.onRefresh();
}
});
LayoutAnimation.configureNext({
duration: BACK_TIME,
update: {
type: 'linear',
}
});
self.refs[PULL_REFRESH_LAYOUT].setNativeProps({
style:{
marginTop:REFRESH_PULL_LENGTH,
}
});
}
addZeroAtFront(count){
if (count<10){
count="0"+count;
}
return count;
}
getTime(){
let date=new Date();
let mMonth=this.addZeroAtFront(date.getMonth()+1);
let mDate=this.addZeroAtFront(date.getDate());
let mHours=this.addZeroAtFront(date.getHours());
let mMinutes=this.addZeroAtFront(date.getMinutes());
return mMonth+"-"+mDate+" "+mHours+":"+mMinutes;
}
stopRefresh(){
let savedDate=this.getTime();
self.setState({
showPullLastTime:savedDate,
});
AsyncStorage.setItem(REFRESH_LAST_TIME_KEY,savedDate,()=>{
});
this.resetHeader();
}
_handlePanResponderEnd(e: Object, gestureState: Object) {
if (self.state.currentDistance>=REFRESH_PULL_LENGTH){
self.refreshStateHeader();
}
else{
self.resetHeader();
}
}
componentDidMount() {
AsyncStorage.getItem(REFRESH_LAST_TIME_KEY,(err,result)=>{
if (result){
self.setState({
showPullLastTime:result,
});
}
});
}
componentWillMount() {
self=this;
this._panResponder=PanResponder.create({
onStartShouldSetPanResponder: this._handleStartShouldSetPanResponder,
onMoveShouldSetPanResponder: this._handleMoveShouldSetPanResponder,
onPanResponderGrant: this._handlePanResponderGrant,
onPanResponderMove: this._handlePanResponderMove,
onPanResponderRelease: this._handlePanResponderEnd,
onPanResponderTerminate: this._handlePanResponderEnd,
});
}
shouldComponentUpdate(nextProps,nextState) {
if (nextState.showPullStatus!==self.state.showPullStatus){
return true;
}
if (self.state.showPullLastTime!==nextState.showPullLastTime){
return true;
}
return false;
}
render(){
let pullText;
let indicatorView;
if (this.state.showPullStatus===ShowLoadingStatus.SHOW_DOWN){
indicatorView=<Image
style={{height:30,width:30,marginRight:10}}
source={require('./img/ptr_rotate_arrow.png')}
resizeMode={Image.resizeMode.contain}
/>;
pullText="下拉刷新";
}
else if (this.state.showPullStatus===ShowLoadingStatus.SHOW_UP){
indicatorView=<Image
style={{height:30,width:30,marginRight:10,transform:[{rotate:"180deg"}]}}
source={require('./img/ptr_rotate_arrow.png')}
resizeMode={Image.resizeMode.contain}
/>;
pullText="释放刷新";
}
else if(this.state.showPullStatus===ShowLoadingStatus.SHOW_LOADING){
indicatorView=<ProgressBarAndroid style={{marginRight:10,width:30,height:30}} />
pullText="刷新中......";
}
return (
<View style={styles.base}>
<View style={{backgroundColor:'white',position:'absolute',}}>
<View style={{justifyContent:'center',alignItems:'center',width:deviceWidth,height:REFRESH_PULL_LENGTH,flexDirection:'row'}}>
{indicatorView}
<View style={{height:REFRESH_PULL_LENGTH,justifyContent:'center',alignItems:'center',marginLeft:10}}>
<Text style={{fontSize:12,color:'#666',marginBottom:1}}>{pullText}</Text>
<Text style={{fontSize:12,color:'#666',marginTop:1}}>最后更新: {this.state.showPullLastTime}</Text>
</View>
</View>
</View>
<View
ref={PULL_REFRESH_LAYOUT}
style={{flex:1,position:'absolute'}} {...this._panResponder.panHandlers} >
{this.props.children}
</View>
</View>
);
}
}
export default PullToRefreshLayout;
var styles = StyleSheet.create({
base: {
flex: 1,
position :'relative'
},
});
使用代码
