QA-flutter

6.android studio打开flutter项目android下面的java文件import标红问题。

flutter插件太烂了，它需要在另外一个studio实例里根目录打开android.右键android->flutter->Open android module in android studio.

5.Could not resolve all artifacts for configuration ‘:fluttertoast:classpath’.

打开\flutter_sdk\.pub-cache\hosted\pub.flutter-io.cn\fluttertoast-x.x.x\android\build.gradle修改repositories为国内镜像或者翻墙

4.flutter upgrade报unable to access 'https://github.com/flutter/flutter.git/'

git config --global http.sslVerify false

3.isolate、linke2

• 1.由于dart是单线程，而async、await运行在event队列，所以async、await并不是并发。
• 2.isolate创建步骤(引入'dart:isolate'包)
  • 1.通过Isolate.spawn创建isolate

    //1,创建ReceivePort，因为SendPort需要通过ReceivePort来获取
    ReceivePort receivePort = ReceivePort();
      
    //2,创建isolate
    //  dataLoader是入口函数，必须且是static
    //  receivePort.sendPort是传入给dataLoader的参数
    await Isolate.spawn(dataLoader, receivePort.sendPort);
  

  • 2.发送数据

      //1,获取sendPort用于发送数据（dataLoader函数中的relyTo）
      SendPort sendPort = await receivePort.first;//这个receivePort就是1中创建的receivePort
      //2,创建用于接收消息的ReceivePort,在返回消息时需要用到(dataloader中的relayTo)
      ReceivePort response = ReceivePort();
      //3,发送数据
      //  [msg, response.sendPort]:发送的消息
      sendPort.send([msg, response.sendPort]);
      //4,获取返回数据
      response.first;
    

  • 3.isolate入口函数

      //创建isolate必须要的参数
      static void dataLoader(SendPort sendPort){
    final port = new ReceivePort();
    //1,绑定发送来的port
    sendPort.send(port.sendPort);
          
    //2,监听消息
    port.listen((message){
      //获取数据并解析
      final data = message[0] as String;  //对应发送时的数组元素1
      final replyTo = message[1] as SendPort;
      //3,返回结果
      replyTo.send(xxxx);
    });
      }
    

  • 4.完整例子

    loadData2() async {
      ReceivePort receivePort = ReceivePort();
      await Isolate.spawn(dataLoader, receivePort.sendPort);
      print("spanw....");
  
      // The 'echo' isolate sends its SendPort as the first message
      SendPort sendPort = await receivePort.first;
      print("await receivePort.first....");
  
      List msg = await sendReceive(sendPort, "https://jsonplaceholder.typicode.com/posts");
      print("sendReceive!!");
      setState(() {
        widgets = msg;
      });
    }
  
    // the entry point for the isolate
    static dataLoader(SendPort sendPort) async {
      // Open the ReceivePort for incoming messages.
      ReceivePort port = ReceivePort();
  
      // Notify any other isolates what port this isolate listens to.
      sendPort.send(port.sendPort);
  
      await for (var msg in port) {
        String data = msg[0];       //对应sendReceive 中port.send([msg, response.sendPort]);
        SendPort replyTo = msg[1];
  
        String dataURL = data;
        http.Response response = await http.get(dataURL);
        // Lots of JSON to parse
        replyTo.send(json.decode(response.body));
      }
    }
  
    Future sendReceive(SendPort port, msg) {
      print("sendReceive...");
      ReceivePort response = ReceivePort();
      port.send([msg, response.sendPort]);
      return response.first;
    }
  }
  

• 3.isolate的简化调用方法compute引入package:flutter/foundation.dart'包

 loadData() async{
    List msg =  await compute(_httpReq, "https://jsonplaceholder.typicode.com/posts");
    setState(() {
      widgets = msg;
    });
  }

  static Future<List> _httpReq(String dataURL) async{
        http.Response response = await http.get(dataURL);
        return json.decode(response.body);
  }

2.配置国内镜像

• mac 打开~/.bash_profile添加

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

检查~/.zlogin是否存在一下配置

if [ -f ~/.bash_profile ]; then
   source ~/.bash_profile
fi

• windows添加到环境变量

1.flutter Running Gradle task ‘assmebleDebug’

• 1.修改flutter sdk目录的/packages/flutter_tools/gradle/flutter.gradle

    repositories {
//       google()
//       jcenter()
        maven{url 'https://maven.aliyun.com/repository/google'}
        maven{url 'https://maven.aliyun.com/repository/public' }
        //maven{url 'https://maven.aliyun.com/repository/gradle-plugin'}
        //mavenLocal()
        //mavenCentral()
    }

• 2.修改项目目录下/android/build.gradle 同上
• 3.检查flutter.gradle中的classpath 'com.android.tools.build:gradle:xxx'和项目中的是否一致（很多疑难杂症都是版本不一致导致的）