Ionic 4 Http failure response for (unknown url): 0 Unknown Error. when calling api on real device

问题

I have an ionic 4 application which calls a .NET Core backend api. It works correctly on chrome browser, but when I run apk on android device, the response is:

{"headers":{"normalizedNames":{},"lazyUpdate":null,"headers":{}},"status":0,"statusText":"Unknown Error","url":null,"ok":false,"name":"HttpErrorResponse","message":"Http failure response for (unknown url): 0 Unknown Error","error":{"isTrusted":true}}

regarding to header I appended these options:

const httpOptions = {
    headers: new HttpHeaders({
        "Content-Type": "application/x-www-form-urlencoded; charset=utf-8" , 
        "Access-Control-Allow-Origin": "*", 
        "Access-Control-Allow-Headers": "Origin, Content-Type, X-Auth-Token, Accept, Authorization, X-Request-With",
        "Access-Control-Allow-Credentials" : "true",
        "Access-Control-Allow-Methods" : "GET, POST, DELETE, PUT, OPTIONS, TRACE, PATCH, CONNECT"  
       }) 
};

I have already installed plugin: cordova-plugin-ionic-webview

and using HttpClient from "@angular/common/http"

My API hosted remotely, no ssl certificate used !

I googled all solutions, but none of them solve my problem

回答1:

Certain things I would advice you to check:

1) CORS enable at your server side

2) If your APIs is not https, make sure android webview is not blocking the traffic. Enforce enable of cleartextTraffic, which is disabled by default. Add a security config in your app like below. Setup reference here

<edit-config file="app/src/main/AndroidManifest.xml" mode="merge" target="/manifest/application" xmlns:android="http://schemas.android.com/apk/res/android">
            <application android:usesCleartextTraffic="true" />
</edit-config>

回答2:

Finally, I could resolve problem after two days hardwork ! I migrated API calling from '@angular/common/http' to native http '@ionic-native/http/ngx' with this header:

        // create headers data
        const headers = {
          "Content-Type": "application/x-www-form-urlencoded; charset=utf-8", 
          'Accept': 'application/json, text/plain',
          "cache-control": "no-cache", 
          "Access-Control-Allow-Origin": "*", 
          "Access-Control-Allow-Headers": "Origin, Content-Type, X-Auth-Token, Accept, Authorization, X-Request-With, Access-Control-Request-Method, Access-Control-Request-Headers",
          "Access-Control-Allow-Credentials" : "true",
          "Access-Control-Allow-Methods" : "GET, POST, DELETE, PUT, OPTIONS, TRACE, PATCH, CONNECT",  
          };

The cons for me, For now on I have to test on a real device.

来源：https://stackoverflow.com/questions/57061417/ionic-4-http-failure-response-for-unknown-url-0-unknown-error-when-calling-a

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