我想为文本字段提供一个初始值,并重新绘制一个空值以清除文本。用Flutter的api实现这一点的最佳方法是什么?
我想为文本字段提供一个初始值,并重新绘制一个空值以清除文本。用Flutter的api实现这一点的最佳方法是什么?
我安装了Flutter并设置了Android Studio。然后我在GitHub (https://github.com/flutter/flutter)上克隆了一个flutter的例子,并在Android Studio中启动它,但它警告我“Dart SDK未配置”,这也发生在我的同事身上。但如果我在Android Studio中创建一个新项目,就完全没有问题。
我所做的:
安装了颤振 安装了Android Studio,以及Flutter插件,包括Dart插件 在命令行中颤振运行正常,所有五个测试都通过了。(见下文)
[✓] Flutter (on Mac OS X 10.13.3 17D47, locale en-US, channel dev) • Flutter version 0.0.22 at /Users/katelyn/flutter • Framework revision 3001b3307d (7 days ago), 2018-01-30 11:37:15 -0800 • Engine revision 8f2d72b183 • Tools Dart version 2.0.0-dev.16.0 • Engine Dart version 2.0.0-edge.7af4db0ea091dddca6b2da851e6dda8d7f9467e8 [✓] Android toolchain - develop for Android devices (Android SDK 27.0.3) • Android SDK at /Users/katelyn/Library/Android/sdk • Android NDK location not configured (optional; useful for native profiling support) • Platform android-27, build-tools 27.0.3 • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b08) [✓] iOS toolchain - develop for iOS devices (Xcode 9.2) • Xcode at /Applications/Xcode.app/Contents/Developer • Xcode 9.2, Build version 9C40b • ios-deploy 1.9.2 • CocoaPods version 1.4.0 [✓] Android Studio (version 3.0) • Android Studio at /Applications/Android Studio.app/Contents • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-915-b08) [✓] Connected devices • Android SDK built for x86 • emulator-5554 • android-x86 • Android 7.1.1 (API 25) (emulator)
上周,我可以通过命令行运行他们的例子(在那个目录下),
flutter run
但现在我显示一些错误与Gradle。
Launching lib/main.dart on Android SDK built for x86 in debug mode... Initializing gradle... 0.7s Resolving dependencies... Error running Gradle: Exit code 1 from: /Users/katelyn/AndroidStudioProjects/flutter/examples/flutter_gallery/android/gradlew app:properties: FAILURE: Build failed with an exception. Where: Build file '/Users/katelyn/AndroidStudioProjects/flutter/examples/flutter_gallery/android/app/build.gradle' line: 20 What went wrong: A problem occurred evaluating project ':app'. 3 Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Get more help at https://help.gradle.org BUILD FAILED in 0s Please review your Gradle project setup in the android/ folder.
我有一个DateTime的实例,我想将其格式化为字符串。我怎么做呢?我想把日期转换成一个字符串,类似于“2013-04-20”。
我在WAMP上使用xdebug (php_xdebug-2.1.2-5.3-vc9.dll)。当我在一个大对象或变量上使用var_dump时,它不会显示完整的变量。
array
'node' =>
array
'my_form' =>
array
'form' =>
array
...
如果不进行xdebug,就会显示出预期的结果。我查看了文档,但没有找到解决方案。有人知道我如何解决这个问题,以便xdebug var_dump显示完整的对象吗?
如你所见,我的按钮在刑台的身体里。但是我得到了这个异常:
使用不包含脚手架的上下文调用Scaffold.of()。
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: HomePage(),
);
}
}
class HomePage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('SnackBar Playground'),
),
body: Center(
child: RaisedButton(
color: Colors.pink,
textColor: Colors.white,
onPressed: _displaySnackBar(context),
child: Text('Display SnackBar'),
),
),
);
}
}
_displaySnackBar(BuildContext context) {
final snackBar = SnackBar(content: Text('Are you talkin\' to me?'));
Scaffold.of(context).showSnackBar(snackBar);
}
编辑:
我找到了这个问题的另一个解决方案。如果我们给Scaffold一个键GlobalKey<ScaffoldState>,我们就可以像下面那样显示SnackBar,而不需要在Builder小部件中包装我们的主体。返回脚手架的小部件应该是一个有状态的小部件。
_scaffoldKey.currentState.showSnackBar(snackbar);
我试图为我的扑动应用程序构建一个简单的登录页面。我已经成功构建了TextFields和登录/登录按钮。我想添加一个水平的ListView。运行代码时,元素消失了,如果没有ListView,也没问题。我怎样才能正确地做到这一点呢?
return new MaterialApp(
home: new Scaffold(
appBar: new AppBar(
title: new Text("Login / Signup"),
),
body: new Container(
child: new Center(
child: new Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new TextField(
decoration: new InputDecoration(
hintText: "E M A I L A D D R E S S"
),
),
new Padding(padding: new EdgeInsets.all(15.00)),
new TextField(obscureText: true,
decoration: new InputDecoration(
hintText: "P A S S W O R D"
),
),
new Padding(padding: new EdgeInsets.all(15.00)),
new TextField(decoration: new InputDecoration(
hintText: "U S E R N A M E"
),),
new RaisedButton(onPressed: null,
child: new Text("SIGNUP"),),
new Padding(padding: new EdgeInsets.all(15.00)),
new RaisedButton(onPressed: null,
child: new Text("LOGIN"),),
new Padding(padding: new EdgeInsets.all(15.00)),
new ListView(scrollDirection: Axis.horizontal,
children: <Widget>[
new RaisedButton(onPressed: null,
child: new Text("Facebook"),),
new Padding(padding: new EdgeInsets.all(5.00)),
new RaisedButton(onPressed: null,
child: new Text("Google"),)
],)
],
),
),
margin: new EdgeInsets.all(15.00),
),
),
);
我已经使用Flutter create testapp创建了应用程序。 现在,我想将应用程序名称从“testapp”更改为“My Trips Tracker”。我该怎么做呢?
我已经尝试从AndroidManifest.xml进行更改,它已经更改,但是Flutter提供了一种方法来做到这一点吗?
我无法找到一种方法来创建一个输入字段颤振,将打开一个数字键盘,应该采取数字输入。这是可能的颤振材料部件?一些GitHub讨论似乎表明这是一个受支持的功能,但我无法找到任何关于它的文档。
我试图创建一行,其中中心文本有一个最大大小,如果文本内容太大,它适合大小。
我插入TextOverflow。属性来缩短文本并插入三个点…但这并不奏效。
main.dart
import 'package:flutter/material.dart';
void main() {
runApp(new MyApp());
}
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
home: new HomePage(),
);
}
}
class HomePage extends StatelessWidget {
@override
Widget build(BuildContext context) => new Scaffold(
appBar: new AppBar(
backgroundColor: new Color(0xFF26C6DA),
),
body: new ListView (
children: <Widget>[
new Card(
child: new Container(
padding: new EdgeInsets.symmetric(horizontal: 16.0, vertical: 18.0),
child: new Row(
children: <Widget>[
new Container(
padding: new EdgeInsets.only(right: 24.0),
child: new CircleAvatar(
backgroundColor: new Color(0xFFF5F5F5),
radius: 16.0,
)
),
new Container(
padding: new EdgeInsets.only(right: 13.0),
child: new Text(
'Text lar...',
overflow: TextOverflow.ellipsis,
style: new TextStyle(
fontSize: 13.0,
fontFamily: 'Roboto',
color: new Color(0xFF212121),
fontWeight: FontWeight.bold,
),
),
),
new Container(
child: new Column(
crossAxisAlignment: CrossAxisAlignment.end,
children: <Widget>[
new Row(
children: <Widget>[
new Text(
'Bill ',
style: new TextStyle(
fontSize: 12.0,
fontFamily: 'Roboto',
color: new Color(0xFF9E9E9E)
),
),
new Text(
'\$ -999.999.999,95',
style: new TextStyle(
fontSize: 14.0,
fontFamily: 'Roboto',
color: new Color(0xFF212121)
),
),
],
),
new Row(
children: <Widget>[
new Text(
'Limit ',
style: new TextStyle(
fontSize: 12.0,
fontFamily: 'Roboto',
color: new Color(0xFF9E9E9E)
),
),
new Text(
'R\$ 900.000.000,95',
style: new TextStyle(
fontSize: 14.0,
fontFamily: 'Roboto',
color: new Color(0xFF9E9E9E)
),
),
],
),
]
)
)
],
),
)
),
]
)
);
}
结果:
预期:
如何调试PHP脚本?
我知道基本的调试,如使用错误报告。PHPEclipse中的断点调试也非常有用。
在phpStorm或任何其他IDE中调试的最佳方法(就快速和简单而言)是什么?