Develop Reference

Icon to the edge

I am new to xamarin and android dev. I have created my own app icon. On device install, the icon gets underlaid by a white circle and my icon gets smaller. I use romannurik homepage, here is a screenshot from my homescreen:
I want my icon to be like the icons marked in green. My icon gets like the ones marked in red.
My question is: how can i create an icon like the ones marked in green

SushiHangover is correct, but the better way to do it is to use adaptive icons. The easiest way to deal with Android icons is to download Android Studio. Once that is done, then create a new project. It doesn't matter what the project is.
After it loads and Gradle does it's initial build, in the left hand menu then right click on "res" and select New -> Image Asset. This will launch a new window.
At the top specify the "Icon Type" as "Launcher Icons (Adaptive and Legacy). Then specify a foreground layer and a background layer and hit next. Android studio will generate all the various icons you need for every version of android.
Last step is to transfer all the mipmap folders into your xamarin project and get them added through visual studio.
You should still specify the RoundIcon like SushiHangover mentioned, but if the app is installed on Android 8.0 or greater it will us the adaptive icon to match the look and feel of whatever phone it is installed on.

You are looking for "Round Launcher Icons" available in Android 7.1 and above.
1) You will need to create the various icons and place them in your mipmap-XXXX resource folders
2) Then you need to assign the RoundIcon property either directly in the manifest or via the ActivityAttribute:
[Activity(Label = "Scoreboard",
Icon = "#mipmap/ic_launcher",
RoundIcon="#mipmap/ic_round_launcher",
Theme = "#style/SplashTheme",
MainLauncher = true)]
public class SplashActivity : AppCompatActivity
{
~~~
}
See the blog post for the details:
Blog post: https://devblogs.microsoft.com/xamarin/round-launcher-icons-in-android-7-1/

Use Material Icons in XML

I want to use the new material icons provided by Google. I find it a bit cumbersome to download each icon individually.
Is there a way to do something like:
<ImageButton
android:src="#android:Icon.Material.IconName"
.../>
If not, whats the easiest way to include multiple icons in my project?
Cheers.

Follow these steps to start Vector Asset Studio:
In Android Studio, open an Android app project.
In the Project window, select the Android view.
Right-click the res folder and select New > Vector Asset.
After you open Vector Asset Studio, you can add a material icon as follows:
Select "Material Icon"
Click Choose
Select a material icon

Checkout if this can be helpful:
https://github.com/google/material-design-icons

Is there a default delete icon in Android?

I would like to add a delete icon (trashcan) in my actionbar. Is it a default icon can that an app can use or should the icon be a drawable in the app itself?

You can use #android:drawable/ic_menu_delete in your menu XML. This will show the default delete icon across different versions of Android (meaning it will be different on different OS versions). If you want it to be consistent across all versions, you can also download icons from https://github.com/google/material-design-icons and include them in your project drawables folder.

I would very much recommend this icon pack from Google:
https://github.com/google/material-design-icons/releases
It includes their set of Material design icons.
Navigable here:
https://www.google.com/design/icons/
Update:
This repository is extremely useful, with many Google / Custom icons:
https://materialdesignicons.com/

Where are the drawables or clipart from android.R.drawable stored?

I am integrating ActionBarSherlock in my app and I want to have some menus with some items and its respective icons.
I have looked into samples and documentation, and everything seems to be clear, but when I Inflate the menu, I can see just the text because there are no icons related to each item yet.
I would like to use the icons you see when creating an android project:
But I can't find it, and I don't want to use direct reference to android.R.drawable in order to use those clipart icons, because I have read it is recommended to have the files in drawable folders.

android-sdk/platforms/android-xx/data/res/drawable-yyyy
where xx is your target platform and yyyy is mdpi, hdpi, etc.
Copy the icons you want into the appropriate resource folder in your project.

I generally use Android Asset Studio to create icons for my apps. It has all the standard clipart, and can generate the proper files for all other icons as well.

http://developer.android.com/design/downloads/index.html site has Action Bar Icon Pack

You can use system icons by using "#android:" prefix. The icon is not copied to drawable folders, so the application size is smaller"
Example: android:icon="#android:drawable/ic_menu_preferences"
List of icons at /platforms/android-/data/res/drawable-hdpi
Note 1: If you want to copy the icons to drawable files you can also do it in eclipse by using file /new/other/Anddoid icon set/clipart button/choose button.
Note 2: the icon set could change among platforms. That is why people are suggesting to copy resources. If the applicacion is just at development state you could just link the platform icons

Theming in Android - Eclipse

So I am editing a go launcher template theme and i saw there were some parts i wanted to change that wasn't included in the template. For example the little icons on top of the apps when you want to delete (kill.png kill_light.png etc.) I added this code
<AppIcon text_color="#FFFFFFFF" text_bg_color="#ff3f3f3f" delete_app="kill"
delete_app_highlight="kill_light" new_app_icon="new_install_app"
update_icon="appfunc_app_update" locker_icon="promanage_lock_icon"
close_app_icon="promanage_close_normal" close_app_light="promanage_close_light"/>
With png's with the right names in the drawable hdpi folder but they don't show up when I test it out. Am I missing something? I was able change the media management icons in the app drawer by adding this
<SwitchButtonBean button_galleryicon="appfunc_mediamanagement_switch _button_gallery"
button_gallerylighticon="appfunc_mediamanagement_s witch_button_gallery_light"
button_musicicon="appfunc_mediamanagement_switch_b utton_music"
button_musiclighticon="appfunc_mediamanagement_swi tch_button_music_light"
button_videoicon="appfunc_mediamanagement_switch_b utton_video"
button_videolighticon="appfunc_mediamanagement_swi tch_button_video_light"
button_appicon="appfunc_mediamanagement_switch_but ton_app"
button_appiconlight="appfunc_mediamanagement_switc h_button_app_light"/>
But it didn't work for the other part (the smaller versions of those same icons in the media management menu).
What am I missing?