小编Nic*_*olo的帖子

我的 main.dart 中有一个 TabBarView，每个选项卡都有一个类来显示内容（它是 listview 对象），当我在选项卡之间切换时，listview 页面每次都会刷新，tabbarview 是否正常？我不希望每次在标签之间切换时它都会刷新。

是我班级的问题吗？如何解决这个问题？代码是这样的。

    class ListWidget extends StatefulWidget {
  final catID;

  ListWidget(this.catID);


  _ListWidgetState createState() => new _ListWidgetState(catID);
}

class _ListWidgetState extends State<ListWidget> {

  var catID;

  void initState() {
    super.initState();
    _fetchListData();
  }

  @override

  Widget build(BuildContext context) {
    // TODO: implement build

    return new Scaffold(.......
}

                        new ListView(
                          children: [
                            new SizedBox(
                              height: 100.0,
                              child: ListView(
                                scrollDirection: Axis.horizontal,
                                children: <Widget>[
                                  new Text("hi"),
                                  new Text("hi"),
                                  new Text("hi"),
                                ],
                              ),
                            ),
                          ],
                        ),

我使用了大小的盒子,似乎仍然有错误.

这是我的小部件树:SingleChildScrollView - > Column - > children

Performing hot reload... flutter: ??? EXCEPTION CAUGHT BY RENDERING LIBRARY ?????????????????????????????????????????????????????????? flutter: The following assertion was thrown during performResize(): flutter: Vertical viewport was given unbounded height. flutter: Viewports expand in the scrolling direction to fill their container.In this case, a vertical flutter: viewport was given an unlimited …

我需要在上传到服务器之前调整图像大小。

我正在使用 io 和图像包。

import 'dart:io';  
import 'package:image/image.dart' as Img;

使用这个功能

uploadImages(File image_File) async {

    Img.Image image_temp = Img.decodeImage(image_File.readAsBytesSync());

    Img.Image resized_img = Img.copyResize(image_temp, 800);

    File resized_file = File('resized_img.jpg')
      ..writeAsBytesSync(Img.encodeJpg(resized_img));

    var stream = new http.ByteStream(DelegatingStream.typed(resized_file.openRead()));
    var length = await resized_file.length();

    var uri = Uri.parse("https://myserver.com/upload.php");

    var request = new http.MultipartRequest("POST", uri);
    var multipartFile = new http.MultipartFile('file', stream, length,
        filename: p.basename("resized_image.jpg"));


    request.files.add(multipartFile);
    var response = await request.send();
    print(response.statusCode);
    response.stream.transform(utf8.decoder).listen((value) {
      print(value);
    });
  }

当我运行此代码时，应用程序只是冻结并且图像没有上传到服务器。

我正在尝试通过网络视图为我的 flutter 应用程序集成 PayPal 支付。

return new MaterialApp(\nroutes: {\n"/": (_) => new WebviewScaffold(\n  url: "https://www.paypal.com/cgi-bin/webscr?    business=xxxx.com&cmd=_xclick&item_name=Hot+Sauce-12oz.+Bottle&amount=5.95&currency_code=USD",\n  appBar: new AppBar(\n    title: new Text(\n      "Payment",\n    ),\n  ),\n)\n},\n);\n

当我运行该页面时，应用程序意外关闭并显示错误消息

Unsupported value: <FlutterError: 0x1c422d200> of type FlutterError\nLost connection to device.

这是我的扑动医生。

Running flutter doctor...\nDoctor summary (to see all details, run flutter doctor -v):\n[\xe2\x9c\x93] Flutter (Channel beta, v0.5.1, on Mac OS X 10.13.1 17B1003, locale en-HK)\n[\xe2\x9c\x93] Android toolchain - develop for Android devices (Android SDK 26.0.2)\n[\xe2\x9c\x93] iOS toolchain - develop …

我有一个带有很多特殊字符和表情符号的字符串需要传递给php，特殊字符如&和[]{}，导致php错误，我尝试过

ReplaceAll(new RegExp('&'), '%26');

处理 & ，但是有很多特殊字符也会导致错误，那么在 php 中处理不会导致任何错误的特殊字符的最佳方法是什么？

我正在使用image_picker从图库中获取一些图像，并且将图像的路径保存在列表中，例如

/ private / var / mobile /容器/数据/应用程序/E633FB78-77D3-4913-B37A-496BFBAAD00C/tmp/image_picker_EA6D2836-3EAD-438C-AEEE-21CB3500ED28-9410-00000706FA96031D.jpg

如何从抖动路径中打开图像？

我尝试了Image.file，但是它不起作用，请帮忙。