Build an onscreen keypad in Power Apps
If you use Power Apps on a touch first device, you can access the virtual keyboard to gather input from your app users. But often, for aesthetic or useability reasons, this isn't a choice that fits your objective.
In this video we walk through building a simple keypad to capture a number that would be compatible with touch input. We use UpdateContext, Concatenate, Len, Value, and Left functions to work with the data, and apply If statements in the DisplayMode property to control which aspects of the keypad are active depending on the data already collected. We also use the Self.Text property to make it easy to replicate a working button to enter a different string.
This approach could be applied to any sort of input gathering tool in your apps, and you could even build a full alphanumeric keyboard using a similar approach.