我想渲染一个需要HTTP调用的小部件来收集一些数据.
得到以下代码(简化)
import 'package:flutter/material.dart';
import 'dart:async';
import 'dart:convert';
void main() {
runApp(new MyApp());
}
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'async demo'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
var …有没有办法在函数return语句中返回多个值(除了返回一个对象),就像我们可以在Go(或其他一些语言)中做的那样？
例如,在Go中我们可以做到:
func vals() (int, int) {
return 3, 7
}
这可以在Dart完成吗？像这样的东西:
int, String foo() {
return 42, "foobar";
}
我有一个应用程序,您需要登录才能继续(例如使用Google).
我想在需要验证时重定向用户.
但是,当我跑一个Navigator.of(context).pushNamed("myroute").我收到以下错误:
??? EXCEPTION CAUGHT BY WIDGETS LIBRARY ????????????????????????????????????????????????????????????
I/flutter ( 5624): The following assertion was thrown building _ModalScopeStatus(active):
I/flutter ( 5624): setState() or markNeedsBuild() called during build.
I/flutter ( 5624): This Overlay widget cannot be marked as needing to build because the framework is already in the
I/flutter ( 5624): process of building widgets. A widget can be marked as needing to be built during the build phase
I/flutter ( 5624): only if one of its …正在开发一个扑腾的应用程序,并从一些Firebase数据动态构建一些容器.我想知道是否有办法为容器(或任何不是按钮的小部件)获取onTap方法？
这是一个代码示例:
child: new Container(
//INSERT ONTAP OR ONPRESSED METHOD HERE
margin: const EdgeInsets.symmetric(vertical: 10.0),
child: new Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
new Container(
margin: const EdgeInsets.only(right: 16.0),
child: new GoogleUserCircleAvatar(snapshot.value['images'][0]),
),
new Column(
crossAxisAlignment: CrossAxisAlignment.start,
children : [
new Container(
padding: const EdgeInsets.only(bottom: 8.0),
child: new Text("${snapshot.value['name']}",
style: new TextStyle(
fontWeight: FontWeight.bold,
),
),
),
new Text("${snapshot.value['description']}",
style: new TextStyle(
color: Colors.grey[500],
),
),
]
)
],
),
我是Flutter的新手,刚刚完成了入门教程.我想创建一个侧边菜单,当您滑动时,它会从左侧显示(如Android上的Gmail).
不幸的是,我在文档上找不到这样的布局,而且来自颤动画廊的例子有点乱.
有人可以解释一下如何实现这样的Widget吗？
我正在构建一个页面,动态地生成一些视图.在我的情况下,显示的列表将根据用户输入(用作过滤器)进行更新.
当使用Text Widget进行动态渲染时,一切都运行得很好,但是当我尝试切换到Column或Gridview时,一切都出错并且出现了下面的错误
The following assertion was thrown building ServerGrid(dirty; state: _ServerGridState#59211289()):
I/flutter (14351): setState() or markNeedsBuild() called during build.
I/flutter (14351): This Overlay widget cannot be marked as needing to build because the framework is already in the
I/flutter (14351): process of building widgets. A widget can be marked as needing to be built during the build phase
I/flutter (14351): only if one of its ancestors is currently building. This exception is allowed because the framework
I/flutter (14351): builds …我有一个列，它包含许多不同大小的文本条目，我想让它们扩展到与最大文本相同的宽度。
我的文本条目被包裹在一个带有颜色的容器中，我想将它们与容器对齐，以便可以用直边框呈现。
我如何在 Flutter 中指示这个？
我使用的是 Windows 7，并且使用 R Studio 0.99.902 和 R3.3.1。当我尝试安装软件包时，我收到警告：
Warning: unable to access index for repository http://cran.rstudio.com/src/contrib:
cannot open URL 'http://cran.rstudio.com/src/contrib/PACKAGES'
Warning: unable to access index for repository http://www.stats.ox.ac.uk/pub/RWin/src/contrib:
cannot open URL 'http://www.stats.ox.ac.uk/pub/RWin/src/contrib/PACKAGES'
这是我第一次看到它，我无法解决它。谁能帮我 ？
我正在开发一个 Flutter 应用程序，它使用 Textfield.
我声明TextField如下：
new TextField(
controller : _controller,
decoration : new InputDecoration(
hintText: 'Message...'
)
)
该TextField显示在我的窗口小部件，但是当我在上面敲击时，键盘会自动关闭，以下错误出现在控制台
E/SpannableStringBuilder(17860): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length
我在 Android（三星 Galaxy Grand Prime，Android 5.1）上使用 IntelliJ 中的 Flutter 插件运行它。
我怎么能解决这个问题？
编辑：正如在这个答案中看到的（Android - SPAN_EXCLUSIVE_EXCLUSIVE 跨度不能为零长度），我试过切换键盘（谷歌和三星），仍然相同
我想使用Java和HBase API连接到docker中独立运行的HBase
我用这段代码连接:
Configuration config = HBaseConfiguration.create();
config.set("hbase.zookeeper.quorum", "163.172.142.199");
config.set("hbase.zookeeper.property.clientPort","2181");
HBaseAdmin.checkHBaseAvailable(config);
这是我的/ etc/hosts文件
127.0.0.1 localhost
XXX.XXX.XXX.XXX hbase-srv
这是我的docker中的/ etc/hosts文件(名为hbase-srv)
XXX.XXX.XXX.XXX hbase-srv
使用此配置,我收到连接拒绝错误:
INFO | Initiating client connection, connectString=163.172.142.199:2181 sessionTimeout=90000 watcher=hconnection-0x6aba2b860x0, quorum=163.172.142.199:2181, baseZNode=/hbase
INFO | Opening socket connection to server 163.172.142.199/163.172.142.199:2181. Will not attempt to authenticate using SASL (unknown error)
INFO | Socket connection established to 163.172.142.199/163.172.142.199:2181, initiating session
INFO | Session establishment complete on server 163.172.142.199/163.172.142.199:2181, sessionid = 0x15602f8d8dc0002, negotiated timeout = 40000
INFO | Closing zookeeper sessionid=0x15602f8d8dc0002
INFO | …