Animations in Xamarin Forms (XF)

(Part 7 of the Panzer General Portable Project)

Granted, there are not a lot of animations in Panzer General – which is one of the reasons I thought it would be a good candidate for Fabulous and XF.  However, there is 1 place where there is a 6 frame animation – when there is a battle and a unit takes damage.  The images look like this:


and animated like this

When I did Panzer General in Windows Phone 6/7 using WPF, it was very simple to use a a storyboard and an ObjectAnimation class like this

1 <Storyboard x:Name="ExplodeStoryboard"> 2 <ObjectAnimationUsingKeyFrames 3 Storyboard.TargetName="ExplodeTranslateTransform" 4 Storyboard.TargetProperty="X" Duration="0:0:1" Completed="ObjectAnimationUsingKeyFrames_Completed"> 5 <DiscreteObjectKeyFrame KeyTime="0:0:0" Value="0" /> 6 <DiscreteObjectKeyFrame KeyTime="0:0:.2" Value="-60" /> 7 <DiscreteObjectKeyFrame KeyTime="0:0:.4" Value="-120" /> 8 <DiscreteObjectKeyFrame KeyTime="0:0:.6" Value="-180" /> 9 <DiscreteObjectKeyFrame KeyTime="0:0:.8" Value="-240" /> 10 <DiscreteObjectKeyFrame KeyTime="0:0:1" Value="100" /> 11 </ObjectAnimationUsingKeyFrames> 12 </Storyboard>

In XF, it looks like there is only 1 timer available so I need to hook into it like this

1 module ChickenSoftware.PanzerGeneral.ExplodeDemo 2 3 open Xamarin.Forms 4 5 let addContent (layout:AbsoluteLayout) = 6 let image = new Image() 7 image.Source <- ImageSource.FromResource("explode0") 8 let x = 50.0 9 let y = 50.0 10 let height = 50.0 11 let width = 60.0 12 let rectangle = new Rectangle(x,y,width,height) 13 layout.Children.Add(image , rectangle) 14 15 let mutable index = 1 16 let callback = new System.Func<bool>(fun _ -> 17 match index with 18 | 1 -> image.Source <- ImageSource.FromResource("explode1"); index <- 2 19 | 2 -> image.Source <- ImageSource.FromResource("explode2"); index <- 3 20 | 3 -> image.Source <- ImageSource.FromResource("explode3"); index <- 4 21 | 4 -> image.Source <- ImageSource.FromResource("explode4"); index <- 5 22 | 5 -> image.Source <- ImageSource.FromResource("explode0"); index <- 99 23 | _ -> () 24 true) 25 Device.StartTimer(System.TimeSpan.FromSeconds(20.25),callback) 26 27 let populateImage = 28 let layout = new AbsoluteLayout() 29 layout.HeightRequest <- 5000.0 30 layout.WidthRequest <- 5000.0 31

The key lines is 16, where I create the callback function that gets called each time the timer triggers and then line 25 when the Device class has a method called “StartTimer”

This works


since there is no other animation in the game, I *think* this will work.  I guess I will see soon enough


Handling User Interaction Using Xamarin Forms (XF)

(Part 6 of the Panzer General Portable Project)

Now that I have a rudimentary board in place, I need to understand basic user interaction with the board. The most common gesture is the tap. When I creted the Windows Phone 6/7 version of this game using native WPF, it was very easy to work with these concepts. The Xamarin Forms (XF), not so much.

In XF, capturing a user’s tap on the screen is done via the TapGestureRecognizer class. For example, to see if a person taps on an given game hex you can write some code like this (lines 1 and 19 are the important ones below):

1 let tapRecognizer = new TapGestureRecognizer() 2 3 let getTerrainFrame (tile: Tile) (scale:float) = 4 let baseTile = getBaseTile tile 5 let baseTerrain = getBaseTerrainFromTerrain baseTile.Terrain 6 let tileId = baseTerrain.Id 7 let locatorPrefix = 8 match baseTerrain.Condition with 9 | LandCondition.Dry -> "tacmapdry" 10 | LandCondition.Frozen -> "tacmapfrozen" 11 | LandCondition.Muddy -> "tacmapmuddy" 12 let frame = new TileFrame(tile) 13 let terrainImageLocator = locatorPrefix + tileId.ToString() 14 let image = getImage terrainImageLocator 15 image.Scale <- (scale + 0.6) 16 frame.BackgroundColor <- Color.Transparent 17 frame.BorderColor <- Color.Transparent 18 frame.Content <- image 19 frame.GestureRecognizers.Add(tapRecognizer) 20 frame 21

The getTerrainFrame is called for each hex that is created for the game board

Since there can be multiple frames layered on top of the base terrain image (like units, nation flags, etc..) we need a way for those frames to not capture the tap event. Enter the InputTransparent property (line 8 below)

1 let getSingleUnitFrame (iconId:int) (scale:float) = 2 let frame = new Frame() 3 let path = "tacicons" + iconId.ToString() 4 let image = getImage path 5 image.Scale <- (scale + 0.6) 6 frame.BackgroundColor <- Color.Transparent 7 frame.BorderColor <- Color.Transparent 8 frame.InputTransparent <- true 9 frame.Content <- image 10 Some frame 11

With each hex’s base frame now wired up to this tap recognizer, I need a way to send data into the event and a way to get the data out of the event.

My first thought was to use the eventArgs – which is the way I have done it 100% of the time before this project. I was thinking code like this:

1 type TapEventArgs(tileId:int) = 2 inherit EventArgs() 3 member this.TileId = tileId 4

Where I have an custom event type that inherits from EventArgs and can can put whatever data I want into the additional properities – in this case the unique Id for the Hex/Tile

I could then create an event handler that handles the event and gets the needed data from the event args:

1 let handleTapEvent (sender:Object) (e:TapEventArgs) = 2 app.MainPage.DisplayAlert(e.TileId.ToString(), "OK") |> ignore 3 () 4

And then to wire things together, I would use an EventHandler class

1 let tapEventHandler = new EventHandler<TapEventArgs>(handleTapEvent) 2 tapRecognizer.Tapped.AddHandler(tapEventHandler :> EventHandler<EventArgs>) 3

Unfortunately, this does not work!  When doing a simple cast, I get

The type ‘EventArgs’ is not compatible with the type ‘TapEventArgs’

and if I try and force it into the event handler

1 let tapEventHandler = new EventHandler<TapEventArgs>(handleTapEvent)

I get this error

This expression was expected to have type ‘EventHandler’ but here has type ‘EventHandler<TapEventArgs>’

You can see my trail of tears on stack overflow here

So instead of spending my time fighting with the compiler, I decided to use the other event arg: object

1 let handleTapEvent (sender:Object) (e:EventArgs) = 2 let tileFrame = sender 😕> TileFrame 3 let tile = tileFrame.Tile 4 let baseTile = getBaseTile tile 5 let tileId = baseTile.Id.ToString() 6 app.MainPage.DisplayAlert("Tile Pressed", tileId, "OK") |> ignore 7 () 8

with the TileFrame inheriting from Frame like so

1 type TileFrame(tile:Tile) = 2 inherit Frame() 3 member this.Tile = tile 4

and I get what I need


removing files part of a later-added git ignore

Dear Future Jamie

When you add a gitignore to an existing project, to force git to release the files you don’t want, run the following from the directory where the project is located (note the extra period at the end of the 2st two commands)

1 git rm -r –cached . 2 3 git add . 4 5 git commit -am "Remove ignored files" 6


Past Jamie

Creating an Initial Game Board

(Part 5 of the Panzer General Portable Project)

The first game-like task I wanted to accomplish was to set up the base game board – like I did here seven years ago.  I fired up the F# Xamarin Forms (XF) project I was working on last post and open the app.fs file.  Following the “Full-On Monty” Elm pattern, I am not going to do any of this app in markup so there are no XAML files to deal with.

Inside the app.fs file, I first created a record type to keep track of the tiles and units for each hex (later in this series, I will create a proper domain model – for now this is a just a spike to see what it takes to render the game board – I named it ContentData).  Notice that ContentData always had a Tile, Row and Column, but it does not always have a unit on it – so I used an option type. for Unit.  I also needed a type for the Tile, the Unit, and the Equipment – starting with image then moving out to additional data to make the game work.  Enter type providers – all I needed to do was to point to the files that were already part of the solution to get the types

1 type TileContext = JsonProvider<"Data//Scenario_Tile.json"> 2 type UnitContext = JsonProvider<"Data//Scenario_Unit.json"> 3 type EquipmentContext = JsonProvider<"Data//Equipment.json"> 4 type ContentData = {TileId: int; ColumnNumber: int; RowNumber: int; UnitId: int option} 5

I then created three functions to get the data for each instance of those types

1 let getTiles (scenarioId:int) = 2 let assembly = IntrospectionExtensions.GetTypeInfo(typeof<App>).Assembly 3 let stream = assembly.GetManifestResourceStream("scenariotile"); 4 let reader = new StreamReader(stream) 5 let json = reader.ReadToEnd() 6 let scenarioTile = TileContext.Parse(json) 7 scenarioTile.Dataroot.ScenarioTile 8 |> Array.filter(fun st -> st.ScenarioId = scenarioId) 9 10 let getUnits (scenarioId: int) = 11 let assembly = IntrospectionExtensions.GetTypeInfo(typeof<App>).Assembly 12 let stream = assembly.GetManifestResourceStream("scenariounit"); 13 let reader = new StreamReader(stream) 14 let json = reader.ReadToEnd() 15 let unit = UnitContext.Parse(json) 16 unit.Dataroot.ScenarioUnit 17 |> Array.filter(fun su -> su.ScenarioId = scenarioId) 18 19 let getEquipments = 20 let assembly = IntrospectionExtensions.GetTypeInfo(typeof<App>).Assembly 21 let stream = assembly.GetManifestResourceStream("equipment"); 22 let reader = new StreamReader(stream) 23 let json = reader.ReadToEnd() 24 let equipment = EquipmentContext.Parse(json) 25 equipment.Dataroot.Equipment

You first thought is “this screams refactoring to a high order function” and I would agree.  I will do that in next iteration

In any event, I needed a way to create the actual image from the file path and then a way of hydrating the ContentData

1 let createImage path = 2 let image = new Image() 3 image.Source <- ImageSource.FromResource(path) 4 image 5 6 let createTileContentData (tile:TileContext.ScenarioTile) (units: UnitContext.ScenarioUnit seq) (equipments: EquipmentContext.Equipment seq) = 7 let scenarioUnit = 8 units 9 |> Seq.tryFind(fun u -> u.StartingScenarioTileId = tile.ScenarioTileId) 10 let unitId = 11 match scenarioUnit with 12 | Some u -> 13 let equipment = equipments |> Seq.find(fun e -> e.EquipmentId = u.EquipmentId) 14 Some equipment.Icon 15 | None -> None 16 17 {TileId = tile.TerrainId; 18 ColumnNumber = tile.ColumnNumber; 19 RowNumber = tile.RowNumber; 20 UnitId = unitId}

With this function ready to return the image, I needed a way to put it in the correct place on the board.  In XF, this is accomplished via the Rectangle type

1 let createRectangle columnIndex rowIndex scale = 2 let height = 50.0 * scale 3 let width = 60.0 * scale 4 let yOffsetPlug = 25.0 * scale 5 let xOffsetPlug = -15.0 * scale 6 let columnIndex' = float columnIndex 7 let rowIndex' = float rowIndex 8 let yOffset = 9 match columnIndex % 2 = 0 with 10 | true -> yOffsetPlug 11 | false -> yOffsetPlug + yOffsetPlug 12 let xOffset = (columnIndex' * xOffsetPlug) + xOffsetPlug 13 let x = xOffset + columnIndex' * width 14 let y = yOffset + rowIndex' * height 15 new Rectangle(x,y,width,height)

With the individual hex functions ready, I was ready to put them onto the screen.  In XF, there is a type called layout that seems what I need to position images in absolute positions

1 let createLayout numberOfTiles scale = 2 let width = 60.0 * scale 3 let height = 50.0 * scale 4 let layout = new AbsoluteLayout() 5 layout.WidthRequest <- 12.0 * width 6 let rows = numberOfTiles % 20 |> float 7 layout.HeightRequest <- rows * height 8 layout

With the layout ready, I could create a function that takes in the layout, an individual hex’s contentdata, find it in the image files, and put it on the board.  I used the Children property of the Layout type to push multiple images on the same hex – I am not sure about Z-ordering yet, so I put the unit image after the tile

1 let addTileContent (layout:AbsoluteLayout) (contentData: ContentData) (scale: float) = 2 let rectangle = createRectangle contentData.ColumnNumber contentData.RowNumber scale 3 let terrainImageLocator = "tacmapdry" + contentData.TileId.ToString() 4 layout.Children.Add(createImage terrainImageLocator, rectangle) 5 match contentData.UnitId with 6 |Some i -> 7 let unitImageLocator = "tacicons" + i.ToString() 8 layout.Children.Add(createImage unitImageLocator, rectangle) 9 |None -> ()

With the individual hex functions ready, I could iterate through the first scenario and populate its initial board.  Notice that I put the Content control inside a ScrollView type that then put into a ContentPage that is then put into the Page.  I think the common convention is right – UX is very much OO in nature

1 let populateBoard = 2 let tiles = getTiles 0 3 let units = getUnits 0 4 let equipments = getEquipments 5 let numberOfTiles = tiles |> Seq.length 6 let scale = 1.0 7 let layout = createLayout numberOfTiles scale 8 tiles 9 |> t -> createTileContentData t units equipments) 10 |> Array.iter(fun cd -> addTileContent layout cd scale) 11 let scrollView = new ScrollView() 12 scrollView.Orientation <- ScrollOrientation.Both 13 scrollView.Content <- layout 14 base.MainPage <- ContentPage(Content = scrollView) 15 16 do 17 populateBoard

So when I fired up the emulator, I got some pretty good first results

Screen Shot 2018-11-08 at 8.22.57 PM

Out of the box with Win Phone, I could pinch and spread a location and the screen images would automatically adjust and get bigger/smaller.  No such luck with XF – so I need to see how to do that.  In any event, zooming into the bottom left corner, all Panzer General fans will immediate recognize this layout. 


And it looks pretty good compared to the winphone


and the original game


Lots to do, but I am happy with the progress

Gist is here

Creating File Reference For An XF Shared .FSProj File

(Part 4 of the Panzer General Portable Project)

As I talked about in the last post, I have about 700 images to be referenced from the Panzer General Portable game.  When dealing with images in Xamarin Forms (XF), there are two choices:  make the image an embedded resource in the shared project or create a stub in the shared project and have the image in both the iOS and Android project.  Following Occam’s Razor, I opted for one file in the shared project.

Going back to the project, I opened the shared project and added the folder that contained all of the images.  A demo project looks like this:

Screen Shot 2018-11-08 at 6.15.01 PM

So far so good. 

I then high-lighted all of the images (that took a bit) and right clicked –> Build Action –> EmbeddedResource

Screen Shot 2018-11-08 at 6.16.20 PM

Visual Studio then tagged each of the files with a ResourceId of the file name:

Screen Shot 2018-11-08 at 6.15.29 PM

So far, so bad.  When I tried to reference these files in my code, the app could not find the images

So it turns out that when you are doing cross-platform development, Xamarin tries to reconcile any problems to the lowest level.  In this case, Android has some very specific opinions about naming and the file names that I used did not match.  iOS does not seem to have such limitations.   The frustrating thing for me is that Visual Studio for Mac let me assign illegal values and did not issue any warnings so it took way too long of trial and error to figure this out.  In my case, I used an underscore “_", which is an illegal character.

When I renamed a test image and followed the same steps, I got it working

Screen Shot 2018-11-08 at 6.15.48 PM

So I then went back and changed the naming of the photo parsing script.  But then I realized that highlighting all of the files in the solution explorer is a drag, so I wrote a new script that gave the correct file name and ResourceId for the fsproj file:

1 let createBlock (resource:string) (logicalName:string)= 2 ""\"><LogicalName>" + logicalName + "</LogicalName></EmbeddedResource>"

I then looped though all of the images files and created a text file

1 let getOutput path = 2 let resources = getResources path 3 let logicalNames = getLogicalNames path 4 resources 5 |> logicalNames 6 |> (r,ln) -> createBlock ln r) 7 |> s -> " " + s)

the getLogicalNames function makes the ResourceId (Logical name in the .fsproj) acceptable to Android

1 let getLogicalNames path = 2 subDirectoryInfos path 3 |> Array.collect(fun sdi -> sdi.GetFiles()) 4 |> f -> f.Name) 5 |> n -> n.ToLowerInvariant()) 6 |> n -> n.Replace(".jpeg",String.Empty)) 7 |> n -> n.Replace("_",String.Empty))

I took the contents of that file, open the Panzer General project .fsproj file, pasted it in, and I got my images working

Gist is here

Parsing Photos

(Part 3 of the Panzer General Portable Project)

When I created Panzer General Portable (PGP) for the windows phone, I had to deal with creating a game board based on a a single image file that looks like this:


There are 12 rows and 20 columns of images – each image is 60 pixels wide and 50 pixels wide.  Each image represents a hex on the game board.  When I did the Windows Phone app, I loaded this image each time in needed a hex – not the most efficient use of resources to be sure.  In addition to these game board images, there are similar composite images of units, country flags, etc..  The game board is a series of overlaid images for a given hex. The application keeps track of the correct image to be used via the x/y coordinates of the hex.  For example, the top left fix has a x/y of 0,0.



In other parts of the app, an index is used so the 0,0 hex is also index 0 with the 1,19 hex having an index value of 20.



You will also note that each image is a rectangle, and the area outside of the hex is a pink color.  Apparently, back in the old days, that color meant “transparent” to windows.  However, it does not to the iOS and Android, so that color needs to be converted into transparent

I fired up a new FSharp project in Visual Studio for Mac and created a F# script

I created a function that takes in the path to this composite image on my file system, a target directory where I want the small image to be written to, the name of that file, and the x y coordinates to locate the smaller image in the composite image:

1 let createHexImage sourcePath targetDirectory (fileName:string) x y = 2 let width = 60 3 let height = 50 4 let index = x + (y * 20) 5 use sourceImage = Image.FromFile(sourcePath) 6 use bitmap = new Bitmap(width,height) 7 use graphics = Graphics.FromImage(bitmap) 8 let targetRectangle = new Rectangle(0,0,width,height) 9 let sourceRectangle = new Rectangle(width*x,height*y,width,height) 10 graphics.DrawImage(sourceImage,targetRectangle,sourceRectangle,GraphicsUnit.Pixel) 11 graphics.Flush() 12 let transparentBitmap = createTransparentBitmap bitmap 13 let fileName = fileName.Replace("_",String.Empty) 14 let fileName' = targetDirectory + "//" + fileName + index.ToString() + ".jpeg" 15 transparentBitmap.Save(fileName') 16

The code is pretty straight forward File I/O and image creation.  Notice on line 12 a function called “createTransparentBitmap” is called to turn the pink into transparent.  That function is actually step 0 of a function chain like this (BTW: read from the bottom up in F# world):

1 let updateColor (color:Color) = 2 match color.R, color.G, color.B with 3 | 255uy,225uy,225uy -> Color.FromArgb(0x00FFFFFF) 4 | _,_,_ -> color 5 6 let getCoordinates index (bitmap:Bitmap) = 7 let y = index / bitmap.Width 8 let x = index % bitmap.Width 9 x,y 10 11 let adjustColor index (bitmap:Bitmap) = 12 let coordinates = getCoordinates index bitmap 13 let x = fst coordinates 14 let y = snd coordinates 15 let color = bitmap.GetPixel(x,y) 16 let updatedColor = updateColor color 17 bitmap.SetPixel(x,y,updatedColor) 18 19 let createTransparentBitmap (bitmap:Bitmap) = 20 let totalPixels = bitmap.Height * bitmap.Width 21 [0 .. totalPixels - 1] 22 |> Seq.iter(fun i -> adjustColor i bitmap) 23 bitmap

  • updateColor looks at a given pixel and if it is “pink”, it returns a new pixel of transparent, else it returns the pixel that came in (note that System drawing uses Pixel and Color interchangeably, which can be confusing)
  • getCordinates gets the pixel from the x,y coordinate of the bitmap
  • adjustColor takes in a bitmap and an index – it uses the index to locate the targeted pixel, updates the color if needed, and then sets a new pixel into the bitmap with the updated pixel.
  • createTransparentBitmap takes in the bitmap, calculates the total pixels, creates an array of integers, and then calls the adjustColor function

So after running this script, you can see my file system has a list of all of the images that the game needs:


The gist is here






Setting Up The Environment For Mobile Development

(Part 2 of the Panzer General Portable Project)

I tried, I really did, to use my ultra-hyped personal computer running Win10 and Visual Studio 2017 to create a Xamarin phone app.  Things were actually OK until I tried to launch the emulator for iOS and Android.  The machine just fell on its face and after waiting several minutes for the simulator to launch… and then crash, I gave up.

Also, since you need a Mac to publish to the Apple store, it made sense to go out and get a MacBook.  I know that you can “rent a Mac” for Apple store deployment using services like Azure Dev Ops, but:

  • I would have to develop on a PC (see the paragraph above)
  • I couldn’t debug on a real device
  • Everyone, I mean everyone, I talked to about writing a phone app said to get a Mac to reduce friction
  • I could finally look like a hipster hacker at the local Starbucks

Getting started with a MacBook wasn’t particular hard – though I had to retrain some muscle memory for the keyboard shortcuts.  Visual Studio for Mac certainly has some quirks that are worth mentioning (some of which I documented here):

1) VS sits on top of XCode.  If XCode has an update, VS may not recognize it, so it will break.  A rule of thumb is to manually update XCode whenever there is a VS update, and manually update VS whenever there is an XCode Update

2) Managing files in the .fsproj file is not seamless.  F# requires the files to be in a certain order for dependency management which allows the awesomeness of inferred typing when compiling.  In Visual Studio for the PC, you can hold down the shift key and move your files up and down.  There is no such feature in VS for Mac so you need to open the .fsproj file and manually move things as demonstrated here

3) Some some random reason, my solution would stop building and I would get the following errors.

Screen Shot 2018-11-07 at 3.22.01 PM

I put it into User Voice here – until then, I just recreate a new project.  Obviously once I start coding for real, this is not a good solution,