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【已解决】ReactNative中如何实现条件判断显示不同视图

React Native crifan 330浏览 0评论

React Native中,现在代码是:

                          var noticeType = ”;
                          switch (rowData.noticeType) {
                              case "expired":
                                  noticeType = require(‘./img/clock_red.png’);
                                  break;
                              case "normal":
                                  noticeType = require(‘./img/clock_green.png’);
                                  break;
                              case "notEmergent":
                                  noticeType = require(‘./img/clock_gray.png’);
                                  break;
                               default:
                                  noticeType = ”;
                          }
                          console.log("noticeType=" + noticeType);
                          return (
                              <View style={styles.customerRow}>
                                <Image style={styles.intentionLevel} source={levelIcon} />
                                <Text style={styles.customerName}>{rowData.customerName}</Text>
                                <Text style={styles.intentionCar}>{rowData.intentionCar}</Text>
                                <Image style={styles.noticeType} source={noticeType} />
                                <Text style={styles.updateTime}>{rowData.updateTime}</Text>
                              </View>
                              );

导致结果是:

当noticeType为空时,Image的source值就是空,是无效的,非法的,所以会报错:

现在希望实现:

根据条件判断,显示不同的视图,比如

当noticeType为空时,只是加载一个空的view,透明色,占位,即可;

当noticeType不为空时,就加载一个图片。

react native conditional render

Conditional Rendering – React

然后去试试:

function NoticeTypeImage(props){
    const noticeType = props.noticeType;
    switch (noticeType) {
        case "expired":
            return <Image style={styles.noticeType} source={require(‘./img/clock_red.png’)} />;
        case "normal":
            return <Image style={styles.noticeType} source={require(‘./img/clock_green.png’)} />;
        case "notEmergent":
            return <Image style={styles.noticeType} source={require(‘./img/clock_gray.png’)} />;
        case "":
            return <View style={{paddingLeft: 10, width:20, height:20, backgroundColor:’red’}}></View>;
            //return <Image style={{paddingLeft: 10, width:20, height:20, backgroundColor:’transparent’}}></Image>;
    }
}
                          return (
                              <View style={styles.customerRow}>
                                <Image style={styles.intentionLevel} source={levelIcon} />
                                <Text style={styles.customerName}>{rowData.customerName}</Text>
                                <Text style={styles.intentionCar}>{rowData.intentionCar}</Text>
                                <NoticeTypeImage noticeType={rowData.noticeType}/>
                                <Text style={styles.updateTime}>{rowData.updateTime}</Text>
                              </View>
                              );
                          }

真的可以了:

【总结】

此处,想要实现,根据输入的值不同,条件判断后,再决定显示什么

思路是:把要显示返回的内容,封装成一个函数,然后传入参数,函数中,根据参数,用if else或switch case就可以返回所需要显示的内容了。

比如:

function NoticeTypeImage(props){
    const noticeType = props.noticeType;
    switch (noticeType) {
        case "expired":
            return <Image style={styles.noticeType} source={require(‘./img/clock_red.png’)} />;
        case "normal":
            return <Image style={styles.noticeType} source={require(‘./img/clock_green.png’)} />;
        case "notEmergent":
            return <Image style={styles.noticeType} source={require(‘./img/clock_gray.png’)} />;
        case "":
            return <View style={{paddingLeft: 10, width:20, height:20, backgroundColor:’transparent’}}></View>;
    }
}

调用的地方:

                          return (
                              <View style={styles.customerRow}>
                                <Image style={styles.intentionLevel} source={levelIcon} />
                                <Text style={styles.customerName}>{rowData.customerName}</Text>
                                <Text style={styles.intentionCar}>{rowData.intentionCar}</Text>
                                <NoticeTypeImage noticeType={rowData.noticeType}/>
                                <Text style={styles.updateTime}>{rowData.updateTime}</Text>
                              </View>
                              );
                          }

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