SongFuZhen/Android Error.md

## Android Error.md

      
    Raw
  

              Android Error.md
            
          
    Execution failed for task ':app:transformDexArchiveWithExternalLibsDexMergerForDebug'.

Android 运行的时候会报错
解决方案

在android的app层的build.gradle里面添加如下内容:
android {
  defaultConfig {
    multiDexEnabled true
    ...
  }
}

dependencies {
  ...
  implementation 'com.android.support:multidex:1.0.3'
}

Execution failed for task ':app:transformClassesAndResourcesWithProguardForRelease

Android 在开发的时候没有报错，但是在打包的时候，报错如上
解决方案

在proguard-rules.pro文件中添加代码
 -ignorewarnings 

添加完毕之后，再次运行即可正常打包

  
## async await.md

      
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              async  await.md
            
          
    async & await 相关信息


## Config.md

      
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              Config.md
            
          
    Flutter的一些配置

1. Resolving dependencies... 很慢

解决方案

打开Flutter SDK：xx/flutter/packages/flutter_tools/gradle/flutter.gradle
修改内容如下
  buildscript {
    repositories {
        // google()
        // jcenter()

        maven{ url 'https://maven.aliyun.com/repository/google' }
        maven{ url 'https://maven.aliyun.com/repository/jcenter' }
        maven{url 'http://maven.aliyun.com/nexus/content/groups/public'}
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.2.1'
    }
}

2.precache 很慢


Downloading android-arm64-profile/windows-x64 tools... 下载不下来

解决方案

修改环境变量如下
Tips: 注意linux系统和windows的不同配置方式;
Windows尽量配置在系统变量中, 然后将之添加到Path中,最好重启电脑

PUB_HOSTED_URL=https://pub.flutter-io.cn
FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn

3.android-licenses 长时间没反应


Downloading android-arm64-profile/windows-x64 tools... 下载不下来

解决方案

执行命令如下:
flutter doctor --android-licenses


## Container OnTap.md

      
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              Container OnTap.md
            
          
    在Container上添加事件

在Container上包裹一层GestureDetector
GestureDetector(
  onTap:(){
    print('click');
  },
  child: Container(
    child: Text("文本")
  )
)


## cookbook.md

      
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              cookbook.md
            
          
    flutter 相关packages, 里面有很多优秀和常用的库

/// List of Awesome Flutter Packages
///
/// A curated list 📄 of awesome 🌟 Flutter packages. These are some of the most valuable gems 💎 of the Flutter community.
/// Is your favourite 😍 package missing? Let me know or create a pull request...
/// Please read the contribution guidelines before opening a pull request 👍

https://github.com/leisim/awesome-flutter-packages
一个UI框架

/// Flutter Screens
///
/// A collection of Login Screens, Buttons, Loaders and Widgets with attractive UIs, built with Flutter, ready to be used in your applications.

https://github.com/samarthagarwal/FlutterScreens
一个UI框架
UI设计, 一些通用界面的UI设计，可以参考参考

/// flutter-ui-nice

https://github.com/nb312/flutter-ui-nice
一些Flutter Demo的集合

/// Flutter-Notebook
///
/// lutetr_note_book有许多flutter相关功能demo的集合，它能够帮助您快速学习一些零碎的知识，本项目将会不定期更新

https://github.com/OpenFlutter/Flutter-Notebook

  
## flutter Waiting for another flutter command to release the startup lock.md

      
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              flutter Waiting for another flutter command to release the startup lock.md
            
          
    flutter Waiting for another flutter command to release the startup lock

Flutter 报错如上
解决方案

# windows 
taskkill /F /IM dart.exe


## mac os config flutter.md

      
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              mac os config flutter.md
            
          
    在mac os 下配置 flutter 环境变量

下载 flutter 到指定目录

# 从 github 下载
git clone https://github.com/flutter/flutter.git
pwd

设置到全局 profile 里面

使用管理员权限打开文件

sudo vim /etc/profile

添加以下内容到文件末尾

export PATH_TO_FLUTTER_GIT_DIRECTORY=/Volumes/Extreme\ SSD/Mac_Softwares/flutter
export PUB_HOSTED_URL=https://pub.flutter-io.cn #国内用户需要设置
export FLUTTER_STORAGE_BASE_URL=https://storage.flutter-io.cn #国内用户需要设置
export PATH=PATH_TO_FLUTTER_GIT_DIRECTORY/flutter/bin:$PATH


Tips: 内容里面如果有空格，需要加\转义；只能用 # 注释；=两边不能有空格；

使配置生效

source /etc/profile


## Parent Child Params.md

      
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              Parent Child Params.md
            
          
    Widget 父子传值

父组件传值给子组件

父组件调用子组件
  BarCode(fromWhere: "cc");

子组件接收父组件传递过来的值
class Barcode extends StatefulWidget {
  final String fromWhere;
  Barcode({Key key, this.fromWhere}) : super(key: key);

  @override
  _BarcodeState createState() => _BarcodeState();
}

子组件使用父组件传递过来的值
  String fromWhere = widget.fromWhere


## TextField Remove Focus.md

      
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              TextField Remove Focus.md
            
          
    TextField 怎么Remove Focus, 关闭软键盘

FocusScope.of(context).requestFocus(FocusNode());


## Widget Params.md

      
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              Widget  Params.md
            
          
    Widget 之间传值

使用Event Bus进行消息的传递

定义EventBus

新建../common/EventBus.dart文件
import 'package:event_bus/event_bus.dart';

EventBus eventBus = new EventBus();

class BarcodeInEvent {
  List<String> barcodeLists = List<String>();
  BarcodeInEvent(this.barcodeLists);
}
发送消息

  import '../common/EventBus.dart'; // 要使用这种方式引入，不能用package
  ...
  
  eventBus.fire(new BarcodeInEvent(barCodeLists)); // 此处的eventBus是上面文件定义的全局变量
  

接收消息

  import '../common/EventBus.dart';
  ...
  
  // 在 initState 添加监听事件，监听特定的事件
  @override
  void initState() {
    super.initState();

    eventBus
        .on<BarcodeInEvent>()
        .listen((BarcodeInEvent data) => _setBarCode(data.barcodeLists));
  }
  
  void _setBarCode(list) {
    setState(() {
      barCodeLists = list;
    });
  }