如何解决无法向python本地服务器发送flutter GET请求
我使用 TextField() 和 Text() 小部件制作了一个简单的 Flutter Web 应用程序。当我按下按钮时,我希望它向使用 python 制作的简单 Flask 应用程序发送一个查询,它会返回反向文本,并在文本小部件上显示它。
注意:反转文本不是实际任务。它只是为了检查我是否 能够获取数据。
Python 代码:
当我在 chrome 上运行时,此代码有效。
#performing flask imports
from flask import Flask,jsonify
from flask.globals import request
app = Flask(__name__) #intance of our flask application
#Route '/' to facilitate get request from our Flutter app
@app.route("/api",methods=["GET"])
def function():
d = {}
text = str(request.args["Query"])
text = text[::-1]
d["query"] = text
return jsonify(d)
if __name__ == "__main__":
app.run()
颤振代码:
main.dart
import 'package:Flutter/material.dart';
import 'api.dart';
import 'dart:convert';
void main() => runApp(MyApp());
class MyApp extends StatefulWidget {
@override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
String url;
var data;
String queryText = "Query";
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Text("PYTHON AND FlutteR"),),body: Column(
children: <Widget>[
Padding(
padding: const EdgeInsets.all(10.0),child: TextField(
onChanged: (value) {
url = "http://10.0.2.2:5000/api?Query=" + value.toString();
},decoration: Inputdecoration(
hintText: "Search Anything Here",suffixIcon: GestureDetector(
onTap: () async {
data = await getData(url);
var decodedData = jsonDecode(data);
setState(() {
queryText = decodedData["Query"];
});
},child: Icon(Icons.search))),Padding(
padding: const EdgeInsets.all(10.0),child: Text(
queryText,style: TextStyle(fontSize: 30.0,fontWeight: FontWeight.bold),],);
}
}
api.dart
import 'package:http/http.dart' as http;
Future getData(url) async {
http.Response response = await http.get(url);
return response.body;
}
我遵循了以下教程:This Youtube Video
我通过命令提示符运行 python 代码,并通过 VScode 运行 Flutter 应用程序。
我收到以下错误:
Error: Expected a value of type 'Uri',but got one of type 'String'
at Object.throw_ [as throw] (http://localhost:50523/dart_sdk.js:5348:11)
at Object.castError (http://localhost:50523/dart_sdk.js:5319:15)
at Object.cast [as as] (http://localhost:50523/dart_sdk.js:5635:17)
at Function.as_C [as as] (http://localhost:50523/dart_sdk.js:5263:19)
at getData (http://localhost:50523/packages/word_prediction/api.dart.lib.js:29:47)
at getData.next (<anonymous>)
at runBody (http://localhost:50523/dart_sdk.js:39211:34)
at Object._async [as async] (http://localhost:50523/dart_sdk.js:39242:7)
at Object.getData (http://localhost:50523/packages/word_prediction/api.dart.lib.js:28:18)
at main._MyAppState.new.<anonymous> (http://localhost:50523/packages/word_prediction/main.dart.lib.js:422:48)
at Generator.next (<anonymous>)
at runBody (http://localhost:50523/dart_sdk.js:39211:34)
at Object._async [as async] (http://localhost:50523/dart_sdk.js:39242:7)
at http://localhost:50523/packages/word_prediction/main.dart.lib.js:421:210
at tap.TapGestureRecognizer.new.invokeCallback (http://localhost:50523/packages/Flutter/src/gestures/recognizer.dart.lib.js:203:18)
at tap.TapGestureRecognizer.new.handleTapUp (http://localhost:50523/packages/Flutter/src/gestures/tap.dart.lib.js:417:40)
at tap.TapGestureRecognizer.new.[_checkUp] (http://localhost:50523/packages/Flutter/src/gestures/tap.dart.lib.js:223:12)
at tap.TapGestureRecognizer.new.acceptGesture (http://localhost:50523/packages/Flutter/src/gestures/tap.dart.lib.js:199:23)
at arena.GestureArenaManager.new.sweep (http://localhost:50523/packages/Flutter/src/gestures/arena.dart.lib.js:222:31)
at binding$5.WidgetsFlutterBinding.new.handleEvent (http://localhost:50523/packages/Flutter/src/gestures/binding.dart.lib.js:402:27)
at binding$5.WidgetsFlutterBinding.new.dispatchEvent (http://localhost:50523/packages/Flutter/src/gestures/binding.dart.lib.js:381:24)
at binding$5.WidgetsFlutterBinding.new.dispatchEvent (http://localhost:50523/packages/Flutter/src/rendering/layer.dart.lib.js:6107:13)
at binding$5.WidgetsFlutterBinding.new.[_handlePointerEventImmediately] (http://localhost:50523/packages/Flutter/src/gestures/binding.dart.lib.js:352:14)
at binding$5.WidgetsFlutterBinding.new.handlePointerEvent (http://localhost:50523/packages/Flutter/src/gestures/binding.dart.lib.js:325:43)
at binding$5.WidgetsFlutterBinding.new.[_flushPointerEventQueue] (http://localhost:50523/packages/Flutter/src/gestures/binding.dart.lib.js:314:14)
at binding$5.WidgetsFlutterBinding.new.[_handlePointerDataPacket] (http://localhost:50523/packages/Flutter/src/gestures/binding.dart.lib.js:304:65)
at Object.invoke1 (http://localhost:50523/dart_sdk.js:185426:7)
at _engine.EnginePlatformdispatcher.__.invokeOnPointerDataPacket (http://localhost:50523/dart_sdk.js:165747:15)
at _engine.PointerBinding.__.[_onPointerData] (http://localhost:50523/dart_sdk.js:166405:49)
at http://localhost:50523/dart_sdk.js:166863:28
at http://localhost:50523/dart_sdk.js:166816:16
at http://localhost:50523/dart_sdk.js:166509:11
我不知道我在这里做错了什么。
解决方法
试试这个:
Future getData(String url) async {
var response = await http.get(Uri.parse(url));
return response.body;
}
,
沿着这个变化 https://stackoverflow.com/a/66517561/13592012 由 Ουιλιαμ Αρκευα 提到。
还有一个问题: 当我使用 Break point 时,它显示了 blinding.dart 的文件调用
这是因为 CORS。
Cross Origin Request(CORS) 错误,这是因为我没有在我的服务器中设置它。
如果您的 Flutter Web 应用程序与运行 api 的服务器不在同一个域中运行,则尤其如此。即使在同一台机器上,您也必须允许来自某些域和端口的请求。
这可以通过在flask代码中添加以下几行来实现:
response.headers.add("Access-Control-Allow-Origin","*")
和
response.headers.add("Access-Control-Allow-Credentials","true")
所以更新后的代码将是:
#performing flask imports
from flask import Flask,jsonify
from flask.globals import request
app = Flask(__name__) #intance of our flask application
#Route '/' to facilitate get request from our flutter app
@app.route("/api",methods=["GET"])
def word_predictor():
d = {}
text = str(request.args["Query"])
text = text[::-1]
d["Query"] = text
response = jsonify(d)
response.headers.add("Access-Control-Allow-Origin","*")
response.headers.add("Access-Control-Allow-Credentials","true")
return response
if __name__ == "__main__":
app.run()
而且,通过这两个更改,代码可以正常工作。
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