转载:http://blog.csdn.net/jan8705_/article/details/52279533

原理：组件初始化时不设置Text控件的numberOfLines属性，测量一下组件高度（最大高度），然后在设置numberOfLines属性，再次测量一下组件高度（最小高度），若最大高度大与最小高度，表示需要显示“展开”。

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  /*eslintnew-cap:["error",{"capIsNew":false}]*/
 
 importReact,{
 Component,
 PropTypes,
 }from'react';
 
 import{View,Image,StyleSheet,Animated,Text}from'react-native';
 exportdefaultclassCollapsibleTextextendsComponent{
 staticpropTypes={
 style:Text.propTypes.style,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> expandTextStyle:Text.propTypes.style,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> numberOfLines:PropTypes.number
 }
 constructor(props){
 super(props);
 this.state={
 /**文本是否展开*/
 expanded:true,248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> numberOfLines:null,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> /**展开收起文字是否处于显示状态*/
 showExpandText:false,108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> expandText:'展开',248); line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> /**是否处于测量阶段*/
 measureFlag:true
 this.numberOfLines=props.numberOfLines;
 /**文本是否需要展开收起功能：（实际文字内容是否超出numberOfLines限制）*/
 this.needExpand=true;
 this.measureFlag=true;
 }
 _onTextLayout(event){
 if(this.measureFlag){
 if(this.state.expanded){
 this.maxHeight=event.nativeEvent.layout.height;
 this.setState({expanded:false,numberOfLines:this.numberOfLines});
 }else{
 this.mixHeight=event.nativeEvent.layout.height;
 if(this.mixHeight==this.maxHeight){
 this.needExpand=false;
 this.needExpand=true;
 this.setState({showExpandText:true})
 this.measureFlag=false;
 _onPressExpand(){
 if(!this.state.expanded){
 this.setState({numberOfLines:null,expandText:'收起',expanded:true})
 }else{
 this.setState({numberOfLines:this.numberOfLines,expandText:'展开',expanded:false})
 render(){
 const{numberOfLines,onLayout,expandTextStyle,...rest}=this.props;
 letexpandText=this.state.showExpandText?(
 <Text
 style={[this.props.style,styles.expandText,expandTextStyle]}
 onPress={this._onPressExpand.bind(this)}>
 {this.state.expandText}</Text>
 ):null;
 return(
 <View>
 <Text
 numberOfLines={this.state.numberOfLines}
 onLayout={this._onTextLayout.bind(this)}
 {...rest}
 >
 {this.props.children}
 </Text>
 {expandText}
 </View>
 );
 conststyles=StyleSheet.create({
 expandText:{
 color:'blue',108); list-style:decimal-leading-zero outside; color:inherit; line-height:18px; margin:0px!important; padding:0px 3px 0px 10px!important"> marginTop:0
 });
 
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