Mina, I was looking for it these days and saw a very improved solution.
The game designer did 4 semi transparent images, placed them covering all the screen, like slicing the screen in 4 parts. This images are all On Top, so, when you touch your screen, you're touching the buttons.
Figuring out how to use the buttons:
When Touch Screen for Right, simulate control for Right.
The sitting animation need a complex mechanic behind it, so, I'll try to teach you the basic behind this logic. (My sandBOX is a good start to learn complex movements)
Always you create something different from the "Standing" animation, where you player is not pressing any key, you'll need to setup variables to detect these different poses.
Always you have two different poses for the same function, like stand sitting and stand up, you need to setup a variable (like >pose) to make the code know when your gadget is sitting or standing up.
When sitting down, change >pose = "sitting", and make the standing up check if >pose = "standing", so, when different from standing, the code will meet the requisites and will not freeze your animation for sitting down.
The same work when you release (or "not keyDown") the "down" key, setting >pose = "standing", and doing a conditional check for sitting, like the last one.
So, you need a start, middle (in action) and finish for every pose you make. I concern you to use variables with "text" and show them on the screen, to see what is happening "in code".
Good luck ^^