错误：函数声称它不返回任何东西答案

【问题标题】：Error: Function Claims that it does not Return Anything错误：函数声称它不返回任何东西
【发布时间】：2019-12-23 08:57:24
【问题描述】：

我使用 dart 和返回小部件的颤振框架创建了这个函数：

Widget adjustImage(String weatherPicture, int day) {
    if (weatherPicture == 'images/01n.png' || weatherPicture == 'images/13d.png' || weatherPicture == 'images/13n.png') {
      return Column(
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          Text(
            '${giveWeekday(convertEpochToDate(forecastDay[day]))}',
            style: TextStyle(
              fontFamily: 'Montserrat',
              fontWeight: FontWeight.w600,
              fontSize: 17.0,
            ),
          ),
          Image.asset(
            weatherPicture,
            width: 15.0,
            height: 15.0,
          ),
          Text(
            '${forecastTemperature[day]}°',
            style: TextStyle(
              fontFamily: 'Montserrat',
              fontSize: 15.0,
            ),
          ),
        ],
      );
    } else if (weatherPicture == 'images/01d.png') {
      //sun
      return Column(
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          Text(
            '${giveWeekday(convertEpochToDate(forecastDay[day]))}',
            style: TextStyle(
              fontFamily: 'Montserrat',
              fontWeight: FontWeight.w600,
              fontSize: 17.0,
            ),
          ),
          Image.asset(
            weatherPicture,
            width: 30.0,
            height: 30.0,
          ),
          Text(
            '${forecastTemperature[day]}°',
            style: TextStyle(
              fontFamily: 'Montserrat',
              fontSize: 15.0,
            ),
          ),
        ],
      );
    } else if (weatherPicture == 'images/02d.png' ||
        weatherPicture == 'images/02n.png') {
      Column(
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          Text(
            '${giveWeekday(convertEpochToDate(forecastDay[day]))}',
            style: TextStyle(
              fontFamily: 'Montserrat',
              fontWeight: FontWeight.w600,
              fontSize: 17.0,
            ),
          ),
          Image.asset(
            weatherPicture,
            width: 30.0,
            height: 30.0,
          ),
          Text(
            '${forecastTemperature[day]}°',
            style: TextStyle(
              fontFamily: 'Montserrat',
              fontSize: 15.0,
            ),
          ),
        ],
      );
    } else {
      return Column(
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          Text(
            '${giveWeekday(convertEpochToDate(forecastDay[day]))}',
            style: TextStyle(
              fontFamily: 'Montserrat',
              fontWeight: FontWeight.w600,
              fontSize: 17.0,
            ),
          ),
          Image.asset(
            weatherPicture,
            width: 30.0,
            height: 30.0,
          ),
          Text(
            '${forecastTemperature[day]}°',
            style: TextStyle(
              fontFamily: 'Montserrat',
              fontSize: 15.0,
            ),
          ),
        ],
      );
    }
  }

但是，该函数声称它的返回类型为“Widget”，但没有以 return 语句结束。我不确定为什么会这样，因为我专门用 else 条件结束了它，只是为了确保它总是返回一个小部件。此外，在某些情况下，它会使我的应用程序崩溃并告诉我断言失败。

我不确定是什么原因造成的。

【问题讨论】：

标签： flutter dart

【解决方案1】：

在您的第二个else if 中，您忘记使用return

Widget adjustImage(String weatherPicture, int day) {
  if (weatherPicture == 'images/01n.png' || weatherPicture == 'images/13d.png' || weatherPicture == 'images/13n.png') {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.center,
      children: [
        Text(
          '${giveWeekday(convertEpochToDate(forecastDay[day]))}',
          style: TextStyle(
            fontFamily: 'Montserrat',
            fontWeight: FontWeight.w600,
            fontSize: 17.0,
          ),
        ),
        Image.asset(
          weatherPicture,
          width: 15.0,
          height: 15.0,
        ),
        Text(
          '${forecastTemperature[day]}°',
          style: TextStyle(
            fontFamily: 'Montserrat',
            fontSize: 15.0,
          ),
        ),
      ],
    );
  } else if (weatherPicture == 'images/01d.png') {
    //sun
    return Column(
      crossAxisAlignment: CrossAxisAlignment.center,
      children: [
        Text(
          '${giveWeekday(convertEpochToDate(forecastDay[day]))}',
          style: TextStyle(
            fontFamily: 'Montserrat',
            fontWeight: FontWeight.w600,
            fontSize: 17.0,
          ),
        ),
        Image.asset(
          weatherPicture,
          width: 30.0,
          height: 30.0,
        ),
        Text(
          '${forecastTemperature[day]}°',
          style: TextStyle(
            fontFamily: 'Montserrat',
            fontSize: 15.0,
          ),
        ),
      ],
    );
  } else if (weatherPicture == 'images/02d.png' ||
      weatherPicture == 'images/02n.png') {
    return Column( // you forgot to use return here
      crossAxisAlignment: CrossAxisAlignment.center,
      children: [
        Text(
          '${giveWeekday(convertEpochToDate(forecastDay[day]))}',
          style: TextStyle(
            fontFamily: 'Montserrat',
            fontWeight: FontWeight.w600,
            fontSize: 17.0,
          ),
        ),
        Image.asset(
          weatherPicture,
          width: 30.0,
          height: 30.0,
        ),
        Text(
          '${forecastTemperature[day]}°',
          style: TextStyle(
            fontFamily: 'Montserrat',
            fontSize: 15.0,
          ),
        ),
      ],
    );
  } else {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.center,
      children: [
        Text(
          '${giveWeekday(convertEpochToDate(forecastDay[day]))}',
          style: TextStyle(
            fontFamily: 'Montserrat',
            fontWeight: FontWeight.w600,
            fontSize: 17.0,
          ),
        ),
        Image.asset(
          weatherPicture,
          width: 30.0,
          height: 30.0,
        ),
        Text(
          '${forecastTemperature[day]}°',
          style: TextStyle(
            fontFamily: 'Montserrat',
            fontSize: 15.0,
          ),
        ),
      ],
    );
  }
}

【讨论】：