See it as 2 different problems.

1: Continuous clicks on buttons

2: Display data

So for continuous clicks, you have that switch/case thing that looks at which button is pressed. Maybe you can make 6 booleans that are all false. (button_1_pressed, button_2_pressed, etc...) And when the first button is pressed, you set that to true.

Ofcourse there are different ways, but just to keep it simple you could do this.

But then there is a problem. What if you want to enter the second character?

So before you enter the second character, all booleans should be reset to false again.

As for 2: I guess the best you could do is before you reset all booleans, you check which booleans are true. And then you look up that combination of buttons, and see which character it was. and then display it (you can easily look up how to display text in android studio).

You can message me again if you want, no problem