Xamarin.Android: R.java error APT2258 invalid symbol name fix

If you are facing this issue:

R.java : error APT2258: invalid symbol name 'com.companyname.appname:drawable/xxxx'.

You should check for your Resources folder, and look for files with name like a C# or Java keyword. For example: new, public, private, static, class, and so on.

If you rename the file, it will solve your problem.

Xamarin.Android: Missing aapt.exe

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>

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

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/

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

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);
}