First call of app not working http requests (only on first call)

On first call (when installed) or when I clear data of the app on Android devices, then the http request not works, returning unknown error. So, when I remove de app from memory (not from device) and call again the app, the http request works fine.

The http request is in app.component.ts:

this.httpProvider.getUsuario().subscribe(data => { . . . }, err => { . . . })

"getUsuario" is a function:

getUsuario(tipo, valor) {
return this.http.get(url);
}

I am using HttpClient:
import { HttpClient } from '@angular/common/http';

Can anyone help me, please??
Ionic 3


IONIC INFO:

Ionic:

   ionic (Ionic CLI)  : 4.8.0 (/usr/lib/node_modules/ionic)
   Ionic Framework    : ionic-angular 3.9.2
   @ionic/app-scripts : 3.2.2

Cordova:

   cordova (Cordova CLI) : 8.0.0
   Cordova Platforms     : android 7.1.4
   Cordova Plugins       : cordova-plugin-ionic-keyboard 2.1.3, cordova-plugin-ionic-webview 1.2.1, (and 12 other plugins)

System:

   Android SDK Tools : 26.1.1 (/home/daniel/Android/Sdk)
   NodeJS            : v10.16.0 (/usr/bin/node)
   npm               : 6.9.0
   OS                : Linux 5.1

PACKAGE.JSON (some lines):

"dependencies": {
    "@angular/animations": "5.2.9",
    "@angular/common": "5.2.9",
    "@angular/compiler": "5.2.9",
    "@angular/compiler-cli": "5.2.9",
    "@angular/core": "5.2.9",
    "@angular/forms": "5.2.9",
    "@angular/http": "5.2.9",
    "@angular/platform-browser": "5.2.9",
    "@angular/platform-browser-dynamic": "5.2.9",
    "@ionic-native/app-version": "4.10.0",
    "@ionic-native/camera": "4.10.0",
    "@ionic-native/core": "^4.20.0",
    "@ionic-native/diagnostic": "^3.14.0",
    "@ionic-native/geolocation": "4.10.0",
    "@ionic-native/google-maps": "^4.21.0",
    "@ionic-native/network": "^4.20.0",
    "@ionic-native/push": "^4.20.0",
    "@ionic-native/splash-screen": "4.6.0",
    "@ionic-native/status-bar": "^4.20.0",
    "@ionic-native/unique-device-id": "^4.20.0",
    "@ionic/pro": "1.0.20",
    "@ionic/storage": "2.1.3",
    "cordova-android": "7.1.4",
    "cordova-plugin-app-version": "^0.1.9",
    "cordova-plugin-camera": "^4.0.3",
    "cordova-plugin-device": "^2.0.2",
    "cordova-plugin-geolocation": "^4.0.1",
    "cordova-plugin-googlemaps": "^2.6.2",
    "cordova-plugin-ionic": "^4.2.0",
    "cordova-plugin-ionic-keyboard": "^2.1.3",
    "cordova-plugin-ionic-webview": "^1.2.1",
    "cordova-plugin-network-information": "^2.0.1",
    "cordova-plugin-splashscreen": "^5.0.2",
    "cordova-plugin-statusbar": "^2.4.2",
    "cordova-plugin-uniquedeviceid": "^1.3.2",
    "cordova-plugin-whitelist": "^1.3.3",
    "cordova-support-google-services": "^1.1.0",
    "crypto-js": "^3.1.9-1",
    "ionic-angular": "3.9.2",
    "ionicons": "3.0.0",
    "phonegap-plugin-multidex": "^1.0.0",
    "phonegap-plugin-push": "^2.2.3",
    "rxjs": "^5.5.12",
    "sw-toolbox": "3.6.0",
    "zone.js": "0.8.20"
  },
  "devDependencies": {
    "@ionic/app-scripts": "^3.2.2",
    "typescript": "~2.6.2"
  },
  "description": "An Ionic project",
  "cordova": {
    "plugins": {
      "cordova-plugin-whitelist": {},
      "cordova-plugin-device": {},
      "cordova-plugin-splashscreen": {},
      "cordova-plugin-ionic-keyboard": {},
      "cordova-plugin-camera": {},
      "cordova-plugin-statusbar": {},
      "cordova-plugin-googlemaps": { REMOVED API },
      "cordova-plugin-geolocation": {},
      "cordova-plugin-uniquedeviceid": {},
      "cordova-plugin-network-information": {},
      "cordova-plugin-app-version": {},
      "phonegap-plugin-push": {},
      "cordova-plugin-ionic-webview": {}
    },
    "platforms": [
      "android"
    ]
  }

The problem is solved.
After this thread Ionic3 + HTTP call + Android 9.0.4 I am able to configure my app and server.

Just use HTTPS on server side.

Its a new security feature to Android devices.

:wink: