Same issue. Here is the strings.xml file located @ /platforms/android/res/values/strings.xml with the duplicate entries:

<?xml version='1.0' encoding='utf-8'?>
<resources>
    <string name="app_name">Jasper Government</string>
    <string name="launcher_name">@string/app_name</string>
    <string name="activity_name">@string/launcher_name</string>
    <string name="google_app_id">1:739999999999:android:b738888888888888</string>
    <string name="google_api_key">AIzaSySySySySySySySySySySySySySySySySySy</string>
    <string name="google_app_id">@string/google_app_id</string>
    <string name="google_api_key">@string/google_api_key</string>
</resources>

I am facing also this problem.

Managed to get over the problem. When I run "ionic cordova [build || run] android, the "ionic cordova prepare android" task is writing in the strings.xml file the:

< string name="google_app_id" >[at]string/google_app_id< /string>
< string name="google_api_key" >[at]string/google_api_key< /string>

Because of that the build task fails. I managed to do builds by running "ionic cordova prepare android" task, then I manually delete the two lines from strings.xml. After that I build the apk from Android Studio. And repeat. Develop, prepare, delete, build, install, repeat, :). Hope this helps somebody.

ionic ionfo

cli packages: (C:\Users\userAppData\Roaming\nvm\v6.9.0node_modules)
[at]ionic/cli-utils : 1.18.0
ionic (Ionic CLI) : 3.18.0
global packages:
cordova (Cordova CLI) : 7.1.0
local packages:
[at]ionic/app-scripts : 3.1.0
Cordova Platforms : android 6.3.0 ios 4.5.3
Ionic Framework : ionic-angular 3.9.2
System:
Node : v6.9.0
npm : 3.10.8
OS : Windows 10
Environment Variables:
ANDROID_HOME : not set
Misc:
backend : legacy<

FILES

package.json

{
"name": "project name",
"version": "1.0.0",
"author": "ServusTECH Soft",
"homepage": "http://servustech.com/",
"private": true,
"scripts": {
"clean": "ionic-app-scripts clean",
"build": "ionic-app-scripts build",
"lint": "ionic-app-scripts lint",
"ionic:build": "ionic-app-scripts build",
"ionic:serve": "ionic-app-scripts serve"
},
"dependencies": {
"[at]angular/common": "5.0.0",
"[at]angular/compiler": "5.0.0",
"[at]angular/compiler-cli": "5.0.0",
"[at]angular/core": "5.0.0",
"[at]angular/forms": "5.0.0",
"[at]angular/http": "5.0.0",
"[at]angular/platform-browser": "5.0.0",
"[at]angular/platform-browser-dynamic": "5.0.0",
"[at]ionic-native/camera": "^4.4.0",
"[at]ionic-native/core": "4.3.3",
"[at]ionic-native/firebase": "^4.4.0",
"[at]ionic-native/image-picker": "^4.4.0",
"[at]ionic-native/splash-screen": "4.3.3",
"[at]ionic-native/status-bar": "4.3.3",
"[at]ionic/storage": "2.1.3",
"com.synconset.imagepicker": "~2.1.8",
"cordova-android": "~6.3.0",
"cordova-plugin-camera": "^3.0.0",
"cordova-plugin-device": "^1.1.4",
"cordova-plugin-firebase": "^0.1.24",
"cordova-plugin-ionic-webview": "^1.1.16",
"cordova-plugin-splashscreen": "^4.0.3",
"cordova-plugin-telerik-imagepicker": "^2.1.8",
"cordova-plugin-whitelist": "^1.3.1",
"ionic-angular": "3.9.2",
"ionic-plugin-keyboard": "^2.2.1",
"ionicons": "3.0.0",
"rxjs": "5.5.2",
"sw-toolbox": "3.6.0",
"zone.js": "0.8.18"
},
"devDependencies": {
"[at]ionic/app-scripts": "3.1.0",
"typescript": "2.4.2"
},
"description": "An Ionic project",
"cordova": {
"plugins": {
"cordova-plugin-firebase": {},
"ionic-plugin-keyboard": {},
"cordova-plugin-whitelist": {},
"cordova-plugin-device": {},
"cordova-plugin-splashscreen": {},
"cordova-plugin-ionic-webview": {},
"cordova-plugin-camera": {},
"com.synconset.imagepicker": {
"PHOTO_LIBRARY_USAGE_DESCRIPTION": " needs your permission to access your images."
}
},
"platforms": [
"android",
"ios"
]
}
}<

config.xml

#

>
< ?xml version='1.0' encoding='utf-8'?>
< widget id="" version="0.0.1" xmlns="http://www.w3.org/ns/widgets" xmlns:cdv="http://cordova.apache.org/ns/1.0">
< name>APP NAME
< description>An awesome Ionic/Cordova app.
< author email="hi[at]ionicframework" href="http://ionicframework.com/">Ionic Framework Team
< content src="index.html" />
< access origin="" />
< allow-intent href="http:///" />
< allow-intent href="https:///" />
< allow-intent href="tel:" />
< allow-intent href="sms:" />
< allow-intent href="mailto:" />
< allow-intent href="geo:" />
< preference name="ScrollEnabled" value="false" />
< preference name="android-minSdkVersion" value="16" />
< preference name="BackupWebStorage" value="none" />
< preference name="SplashMaintainAspectRatio" value="true" />
< preference name="FadeSplashScreenDuration" value="300" />
< preference name="SplashShowOnlyFirstTime" value="false" />
< preference name="SplashScreen" value="screen" />
< preference name="SplashScreenDelay" value="3000" />
< platform name="android">
< allow-intent href="market:" />
< icon density="ldpi" src="resources/android/icon/drawable-ldpi-icon.png" />
< icon ...
< splash density="land-ldpi" src="resources/android/splash/drawable-land-ldpi-screen.png" />
< splash ...
< /platform>
< platform name="ios">
< allow-intent href="itms:*" />
< allow-intent ...
< icon height="57" src="resources/ios/icon/icon.png" width="57" />
< icon ...
< splash height="1136" src="resources/ios/splash/Default-568h[at]2x~iphone.png" width="640" />
< splash ...
< /platform>
< engine name="android" spec="~6.3.0" />
< plugin name="cordova-plugin-firebase" spec="^0.1.24" />
< plugin name="ionic-plugin-keyboard" spec="^2.2.1" />
< plugin name="cordova-plugin-whitelist" spec="^1.3.1" />
< plugin name="cordova-plugin-device" spec="^1.1.4" />
< plugin name="cordova-plugin-splashscreen" spec="^4.0.3" />
< plugin name="cordova-plugin-ionic-webview" spec="^1.1.16" />
< plugin name="cordova-plugin-camera" spec="^3.0.0" />
< plugin name="com.synconset.imagepicker" spec="~2.1.8">
< variable name="PHOTO_LIBRARY_USAGE_DESCRIPTION" value=" needs your permission to access your images." />
< /plugin>
< engine name="ios" spec="~4.5.3" />
< /widget >
<

@robertarnesson any ideia how fix it ? any workaround?

@robertarnesson in prepare_after.js

replaced

if (directoryExists(IOS_DIR)) {
    copyKey(PLATFORM.IOS);
} else if (directoryExists(ANDROID_DIR)) {
    copyKey(PLATFORM.ANDROID, updateStringsXml)
}

for

if (directoryExists(IOS_DIR)) {
    copyKey(PLATFORM.IOS);
} 
if (directoryExists(ANDROID_DIR)) {
    copyKey(PLATFORM.ANDROID, updateStringsXml)
}

fixed it!

To fix it:

Edit platforms/android/android.json

Search for 'google_app_id' and you'll find 2 of them. The first with ' translatable=\"false\"' and then 2x more "/resources" objects, one with 'google_app_id' and one with 'google_app_key'. You DON'T need the 2 other ones so leave ONLY the first one (with ' translatable=\"false\"').

Now it'll still not going to work because you need to edit also platforms/android/res/value/strings.xml and do the same: remove the 2 extra google_app_id and google_app_key settings after the first one with ' translatable=\"false\"' in it.

Now you can compile without any errors.