Setting an App Icon
An application icon must be provided in many different sizes.
Creating these manually is a tedious task. Fortunately, an application exists to solve this particular problem for app developers. Download Icon Set Creator now.
Open Icon Set Creator once it is downloaded. The first time it runs, you will be prompted to consider financially supporting the developer. If you end up using this app often, I encourage you to do so. For now, click No, Thanks.
Next you may see a dialog mentioning a more capable application that the developer also makes for solving the same problem. That app is more than is necessary for now, so you can dismiss the dialog by pressing No thanks.
You need an image that is at least 1024 pixels wide by 1024 pixels high.
This will typically be a custom-designed icon if you release your app on the public App Store. For your own purposes, any image will do.
I have a nice image of my dog here, but when I open it in Preview, you can see it is not the right size (square).
I'll get a square selection in the image by holding the Shift key down on the keyboard as I move my fingers along the trackpad. To crop the image, I'll use the keyboard shortcut Command-K. Finally, I'll save the image using Command-S.
NOTE: To switch between applications quickly, you can use the keyboard shortcut Command-Tab.
Next, the image must be dragged into Icon Set Creator. Then press the Go button. You can save the output on your Desktop. A folder named iOS will be created. Open this folder, then drag the AppIcon.appiconset folder to the assets folder in Xcode.
The existing placeholder for the app icon is named AppIcon. We can delete this.
Then, we can rename the new app icon we just dragged in, from AppIcon-1 to AppIcon.
That's it! When you next launch the application on a device, you will see that it has an icon!