如何在React-Native中创建下拉菜单？

Question

从'React'导入React，{useState}；//导入useState从'react-native-dropdown-picker'中导入DropDownPicker；从“React-Native”导入{样式表、文本、视图、文本输入、状态条、安全视图、图像、按钮、警报}；

    export default function App() {
    
        const [search, setSearch] = useState(''); //add this line
        
      return (      
        
        <SafeAreaView>
          <View style={styles.container}>
            <TextInput 
              onChangeText={(text) => setSearch(text)}
              
              placeholder="Search"
              style={styles.searchbox}                        
            ></TextInput>   
    
          <View style={styles.makecentral} >   
            {search.length < 1 ? <Image               
                style={styles.tinyLogo}
                source={require('./assets/icons8_search_200px_3.png')}        
              /> : ( 
                  null  //add clear text image and clear search text
                  
              )}
          
          </View>
                <View style={{flexDirection:'row'}}>
    
                  <View elevation={2}  style={{flex:3,backgroundColor:'#ffffff',height:40,marginTop:10,marginLeft:'2.5%',borderBottomLeftRadius:5,borderTopLeftRadius:5}}>
                    <Text style={{textAlign:'center',fontSize:20,color:'#FF7B00',marginTop:7}}>
                      Category
                    </Text>
                  </View>
                  
                  <View elevation={2} style={{backgroundColor:'#FF7B00',height:40,flex:5,marginTop:10,borderTopRightRadius:5,borderBottomRightRadius:5,marginRight:'2.5%'}}>

                   //here..I want to add a dropdown..
       
                  </View>
    
                
                </View>
    
        </View>
        </SafeAreaView>
      );
    }
    
    
    const styles = StyleSheet.create({
      container: {    
        backgroundColor: '#fff',    
        
      },
    
      searchbox:{
        backgroundColor:'#f2f2f2',
        marginTop : StatusBar.currentHeight+5,
        height : 50,
        marginLeft:10,
        marginRight : 10,
        borderRadius : 20,
        textAlignVertical:'center',
        textAlign : 'center',
        alignItems:'center',        
      },
    
      tinyLogo: {
        position : 'absolute',
        width: 30,
        height: 30,
        opacity: 0.5,
        marginTop: -40,    
      },
    
      makecentral: {
        alignItems:'center',
        marginRight:80,    
      },
    
      category:{
        backgroundColor:'#f2f2f2',
        height:50,
        width:'90%',
        alignContent:'center',
    
    
      }
    });

Answer 1

从您的回答来看，您似乎没有向下拉选择器提供项，因此它崩溃了。你不能只给出一个空的组件。

根据文档，它应该类似于：

<DropDownPicker
    items={[
        {label: 'USA', value: 'usa', icon: () => <Icon name="flag" size={18} color="#900" />, hidden: true},
        {label: 'UK', value: 'uk', icon: () => <Icon name="flag" size={18} color="#900" />},
        {label: 'France', value: 'france', icon: () => <Icon name="flag" size={18} color="#900" />},
    ]}
    defaultValue={this.state.country}
    containerStyle={{height: 40}}
    style={{backgroundColor: '#fafafa'}}
    onChangeItem={item => this.setState({
        country: item.value
    })}
/>

items实际上是唯一需要的道具。