参数类型'Future<String>函数()‘不能分配给参数类型'double?’

Question

我正在尝试使用runJavascriptReturningResult获取webview高度

child: Container(
         height: () async => await webViewController.runJavascriptReturningResult("document.body.scrollHeight"),
 ...
)

总是得到错误的The argument type 'Future<String> Function()' can't be assigned to the parameter type 'double?'.，我如何才能在容器中获得这个网页的高度？

Answer 1

我认为runJavascriptReturningResult函数返回一个字符串值。首先，通过将其写入控制台或调试来检查它返回的内容。如果是正确的字符串值，则转换为双值。那么，您应该将其解析为：

String retVal = await webViewController.runJavascriptReturningResult("document.body.scrollHeight").then(),

double val = double.parse(retVal);

Answer 2

您需要提取您的方法：

Future<double> getHeight() async {
    String retVal = await webViewController
        .runJavascriptReturningResult("document.body.scrollHeight");
    // 0.0 is a fallback value in case it doesn't parse your string, you can set it whatever you want
    double height = double.tryParse(retVal) ?? 0.0;
    return height;
  }

因此，您可以像这样在FutureBuilder中使用它：

FutureBuilder(
  future: getHeight(),
  builder: (context, snap) {
    return SizedBox(
      height: snap.data as double?,
    );
  },
)