Below are couple of points on which you may want to improve
Generally when a user clicks something, he/she expects feedback. In your case, this feedback is absent for the amount textbox because when we click it we cannot see a blinking cursor. This may be because you have set the accent color to white.
You can change this property to any suitable color, if you want.
This is a kind of bug/error which I think can be removed with proper validation. Below is the screen recording showing the bug/error
As you can see above, I typed a ‘.’ in the amount textbox and then clicked ‘Covert’.
This resulted in the displayed error.
After dismissing the error(by clicking anywhere outside the error dialogue) the app goes in endless loop(also show in above recording).
Thanks @Vaibhav for your valuable feedback. I have noted your both points.
I have changed accent color to app main color.
The error that shown in video is now fixed, now app will not goes in endless loop.