For our second Android app project, we will create the most pointless but addictive game in the world…a cookie clicker! A basic version of it will look like the image shown below, but you can extend this game as much as you like. You will also learn how to add image buttons to your app screens.

Watch the video below or scroll down to read the step-by-step instructions and view the sample code.

Video

Step 1

You will need to create a new Android App solution in Xamarin called CookieClicker. Click on New Solution (or File > New Solution) to get started.

Step 2

Choose Android App as the type of new solution and then click Next.

Step 3

Set the App Name to CookieClicker (one word – no spaced). Choose Modern Development as the Targeted Platform using the default theme and click on Next.

Step 4

Keep the project and solution names as CookieClicker, select a project location to store your files in and click on Create.

Step 5

Open the MainActivity.cs file (if it does not automatically open) and delete the lines of code highlighted below. These lines of code won’t be needed for this project.

Step 6

Now open the Main.axml file located in the Resources > layout folder.

Step 7

Click on the button that says “Hello World, Click Me!”. We won’t need this button so it can be deleted. Either click on it and press the Delete key on your keyboard, or right-click the button and select Delete.

Step 8

From the Toolbox (if you don’t see it, you can search for the Toolbox from the search bar), scroll down under Images & Media and drag an ImageButton element on to the phone screen.

Step 9

Now you will need to download a cookie image to your computer (preferably a PNG image file with a transparent background). A free public-domain image has been provided below. Click on the image to open the full-size version and then save the image to a folder on your computer and name it cookie.png.

Step 10

Select the ‘drawable’ folder inside the Resources folder and click on the small cog icon. Then select Add > Add Files from Folder.

Step 11

Select the folder that contains the cookie image file and click on Open.

Step 12

Select the cookie.png file (or whatever yours is called) and make sure the checkbox is checked. Then click on OK.

Step 13

Make sure you select Copy the file to the directory and then click on OK.

Step 14

Now you should see cookie.png in the drawable folder.

Step 15

Click on the ImageButton element on the phone screen and change the Src property to @drawable/cookie (you do not need to include the .png file extension).

Step 16

Now we need to make sure the image fits properly on the screen. Click on the drop-down arrow next to the Scale Type property and change it to fitCenter.

You can then also click on the ImageButton and drag the little circle up to change the height of the image. You can also change the width of the image this way. Alternatively, go to the Layout tab on the Properties panel and change the width and height values there eg. 435dp for the height. Note: sizes of elements are measured using the ‘dp’ unit on Android.

If you go to the Source tab, your code for the Main.axml file might look like the code shown below. However, your code could be a little different so don’t change the code here unless you are sure you know what you are doing.

Step 17

In the Designer view, drag a Text (Large) element on to the phone screen under the ImageButton. This will be used to display the number of clicks.

Step 18

From the Widget tab on the Properties panel, change the Text value from Large Text to 0 clicks. At the same time, change its Id from @+id/textView1 to @+id/cookieTextView . You can also change the Gravity value to center so the text is centered.

Step 19

Click on the ImageButton element (the cookie) and change its Id from @+id/imageButton1 to @+id/cookieImageButton – now you need to save the Main.axml file.

Step 20

Now we can add the code! Open the MainActivity.cs file and create an integer variables called clicks that is given an initial integer value of 0. This variable will be created inside the MainActivity class, as highlighted below.

Step 21

We also need to define the ImageButton element and the TextView element in the code. This is highlighted in the lines below. Make sure to use the correct names for each element.

Step 22

Inside the OnCreate method (under the SetContentView (Resource.Layout.Main); line), we need to now setup the ImageButton and TextView element.

Step 23

The next thing you need to do is create a click event for the cookie ImageButton by adding the line cookieImageButton.Click+= CookieImageButton_Click; – this will create a new method called CookieImageButton_Click which will contain the code that will increase the number of clicks and display the number of clicks each time the ImageButton is tapped.

Step 24 

Inside the CookieImageButton_Click method, add the following two highlighted lines of code. The clicks++; line will increase the clicks variable by 1 each time the button is tapped, and the next line of code is responsible for converting the clicks variable value to a string and displaying the clicks variable’s value on the screen as well as the text “clicks!” at the end eg. 25 clicks!

Now save your work. All of the coding is done! Now you could extend this app by adding extra buttons to purchase items when a certain number of cookies are clicked (using if statements) or increase the number of cookies by a different amount. You could add extra text labels or buttons too. However, let’s test that this app works properly first. Click on the Build button after selecting a virtual device to run the app on (if you don’t know how to do this, refer to the previous tutorial – Creating your first Android app with Xamarin).

Here is the source code for the MainActivity.cs file:

using Android.App;
using Android.Widget;
using Android.OS;

namespace CookieClicker
{
  [Activity (Label = "CookieClicker", MainLauncher = true, Icon = "@midmap-hdpi/icon")]
  public class MainActivity : Activity
  {
    int clicks = 0;

    ImageButton cookieImageButton;
    TextView cookieTextView;

    protected override void OnCreate (Bundle savedInstanceState)
    {
      base.OnCreate (savedInstanceState);

      // Set our view from the "main" layout resource
      SetContentView (Resource.Layout.Main);

      cookieImageButton = FindViewById<ImageButton> (CookieClicker.Resource.Id.cookieImageButton);
      cookieTextView = FindViewById<TextView> (CookieClicker.Resource.Id.cookieTextView);

      cookieImageButton.Click+= CookieImageButton_Click;

    }

    void CookieImageButton_Click (object sender, System.EventArgs e)
    {
      clicks++;
      cookieTextView.Text = clicks.ToString () + " clicks!";
    }
  }
}