Xamarin Native, Xamarin Forms and native mobile

I hear many misunderstandings of what Xamarin is and how it differs from native mobile.

There are two flavours of Xamarin: Xamarin Native and Xamarin Forms. They are very different.

The first offers a native mobile experience with the UI written in the native language for the device type. Therefore an understanding of the native tooling, languages, OSs and devices is required to do this type of mobile development. The advantage here is that Xamarin Native developers typically know native development but can also work across both iOS and Android in their respective native languages.

The second is an abstraction, does not have access to all native features and has more shared code between the device types than Xamarin Native. Forms is more suited to prototypes and line of business apps rather than consumer apps.

For an excellent overview of what Xamarin Native and Xamarin forms are and how they differ from native mobile, have a quick read of this:

https://www.altexsoft.com/blog/mobile/the-good-and-the-bad-of-xamarin-mobile-development/

Adding a spotlight overlay in Android

Often there's a need to provide an overlay to your view with a spotlight to highlight a particular area. These are commonly used in the context of map views or tutorials.

First subclass RelativeLayout:

public class MaskView extends RelativeLayout
{
Paint _paint;
Button _spotlightButton;
PorterDuffXfermode _blender;
LayoutParams _spotlightButtonLayout;
Matrix _matrix;
Context _context;

int _spotlightX;
int _spotlightY;
float _scale;

public MaskView(Context context)
{
super(context);
_context = context;
}

public MaskView(Context context, AttributeSet attrs)
{
super(context, attrs);
_context = context;
}

public MaskView(Context context, AttributeSet attrs, int defStyleAttr)
{
super(context, attrs, defStyleAttr);
_context = context;
}
}

Set your X,Y and set up your paint object:

public void init(Point point, String buttonText, float scale)
{
SetHardwareAccelerated(true);

_spotlightX = point.x;
_spotlightY = point.y;
_scale = scale;

_blender = new PorterDuffXfermode(PorterDuff.Mode.CLEAR);
_paint = new Paint();
_paint.setColor(getResources().getColor(android.R.color.white));
_paint.setAlpha(0);
_paint.setXfermode(_blender);
_paint.setAntiAlias(true);

addButton(buttonText);
}

Then override the dispatchDraw method and draw your circle:

@Override
protected void dispatchDraw(Canvas canvas)
{
canvas.drawColor(Color.parseColor("#8C000000"));

_matrix = new Matrix();
_matrix.postScale(_scale, _scale, _spotlightX, _spotlightY);
canvas.setMatrix(_matrix);

canvas.drawCircle(_spotlightX, _spotlightY, 200, _paint);

canvas.setMatrix(new Matrix());

super.dispatchDraw(canvas);
}

Using your new layout:

_maskView = new MaskView(this);
_maskView.init(new Point(width / 2, height / 2), "Dismiss mask view", 1f);

_maskView.getMaskButton().setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View view)
{
_maskView.setVisibility(View.GONE);
}
});

And that is it! Full code on GitHub at https://github.com/pricimus/Mask

Using the iOS AVFoundation sdk in Xamarin to take a picture and save to the image gallery

Using the AVFoundation you can capture still images from your app, convert to a CIImage, obtain a mutable copy of its metadata (you can add custom properties), then save to the device's image gallery:

async void TakePhotoButtonTapped(UIButton sender)
{
var videoConnection = stillImageOutput.ConnectionFromMediaType(AVMediaType.Video);

var sampleBuffer = await stillImageOutput.CaptureStillImageTaskAsync(videoConnection);

var jpegImageAsNsData = AVCaptureStillImageOutput.JpegStillToNSData(sampleBuffer);

var image = CIImage.FromData(jpegImageAsNsData);

var metaData = image.Properties.Dictionary.MutableCopy() as NSMutableDictionary;

var library = new ALAssetsLibrary();

library.WriteImageToSavedPhotosAlbum(jpegImageAsNsData, metaData, (assetUrl, error) => 
{
Console.WriteLine ("assetUrl:"+assetUrl);
});

}