xamarin android

Xamarin.Android : Google Play app target level error solution

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If you are uploading an application to the Google Play, and it gives the following error:

Your app currently targets API level 28 and must target at least API  level 29 to ensure it is built on the latest APIs optimized for security  and performance. Change your app's target API level to at least 29

You have to change the target framework and the target android version in your androidmanifest.xml or in the UI editor of the manifest. To change it, set the Target Framework in the properties tab of your android application

Changing target framework

Then Navigate to Android Manifest option, and set target android version

Setting Target Android version

If you are re archive your application, it will upload successfully.

This content has 2 years. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.

Xamarin.Android: Missing aapt.exe

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When trying to deploy an application to simulator or device, Visual Studio gives the following error:

Cannot find `aapt.exe`. Please install the Android SDK Build-Tools package with the `C:\Program Files (x86)\Android\android-sdk\tools\android.bat` program.

To solve this problem you sould go to Visual Studio’s Tools then Android and select SDK Manager option.

Navigate to this option

It will give an error dialog, that the SDK tool files are corrupted. Click repair.

Click on Repair

The mentioned batch command in the error message is deprecated by the way.

Microsoft Windows [Version 10.0.19042.804]
(c) 2020 Microsoft Corporation. All rights reserved.

C:\Users\banditoth>cd C:\Program Files (x86)\Android\android-sdk\tools\

C:\Program Files (x86)\Android\android-sdk\tools>android.bat
**************************************************************************
The "android" command is deprecated.
For manual SDK, AVD, and project management, please use Android Studio.
For command-line tools, use tools\bin\sdkmanager.bat
and tools\bin\avdmanager.bat
**************************************************************************

Invalid or unsupported command ""

Supported commands are:
android list target
android list avd
android list device
android create avd
android move avd
android delete avd
android list sdk
android update sdk

C:\Program Files (x86)\Android\android-sdk\tools>
This content has 2 years. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.

Xamarin.Forms: Bypass SSL Certificate validation on Android

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Disclaimer: Bypassing SSL Certificate validation in production releases are not recommended. It can make your application vulnerable by hackers and reverse engineers, and your users will be unprotected from the bad guys. Consider to use the following codes with compile directives.

But in the other hand, it can be handful to just ignore the certification errors in development enviroment. Local machines has self signed certificates, and it is easier to just bypass the validation method, rather than set the self signed certificate acceptance in our client applications.

In Xamarin.Android (Lower than Android 10) and Xamarin.iOS, use the ServicePointManager in order to make your own certificate validator algorithm. The code below just accepts every cert.

ServicePointManager.ServerCertificateValidationCallback =
            (message, certificate, chain, sslPolicyErrors) => true;

To bring Android 10 also to work, construct your HttpClient with the following constructor:

            var httpClientHandler = new HttpClientHandler();
#if DEBUG
            httpClientHandler.ServerCertificateCustomValidationCallback =
                (message, certificate, chain, sslPolicyErrors) => true;
#endif
            var httpClient= new HttpClient(httpClientHandler);
This content has 2 years. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.

[Xamarin.Android]: Cleartext HTTP traffic to not permitted

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If your Android application gives the following error, when trying to use a HttpClient:

Java.IO.IOException: 'Cleartext HTTP traffic to 192.168.0.10 not permitted'

Set usesClearTraffic property to true in the AndroidManifest.xml:

<application android:label="MobileSolution.Android" 
	     android:theme="@style/MainTheme"
             android:usesCleartextTraffic="true">
		
</application>

The restriction was introduced in Android 8. More explanation: https://koz.io/android-m-and-the-war-on-cleartext-traffic/

This content has 2 years. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.

Xamarin Android: Dismiss lock screen or show activity on lock screen

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To gain an Activity to be showed on the lock screen, or bypass the phone’s lock screen (aka Keyguard) for important notification handling, for example an Incoming VOIP call, you need to do the following:

Set the permission for disabling keyguard. Add the following permission to the AndroidManifest.xml:

  <uses-permission android:name="android.permission.DISABLE_KEYGUARD"/>

Add flags to the Activity’s Window in order to show the activity on the lock screen, or to bypass the lock screen.

this.Window.AddFlags(WindowManagerFlags.DismissKeyguard | WindowManagerFlags.ShowWhenLocked);

Dismiss the keyguard if needed. (CrossCurrentActivity plugin is used to get the current activity):

KeyguardManager keyguardManager = (KeyguardManager)CrossCurrentActivity.Current.Activity?.GetSystemService(Context.KeyguardService);
if (keyguardManager != null)
{	
	keyguardManager.RequestDismissKeyguard(CrossCurrentActivity.Current.Activity, null);
}

This content has 2 years. Some of the information in this post may be out of date or no longer work. Please, read this page keeping its age in your mind.