Implement a simple calculator of positive numbers that has this UI:
- Two textviews should have these ids:
@+id/tv_formula(formula textview),@+id/tv_result(result textview) - Text inside these two textviews will alight right.
- Formula textview should have textcolor: #757575 in portrait and #b61414 in landscape
- Result textview should have textcolor: #939393 in portrait and #b7339 in landscape
- Background of left-sided buttons: #434343, when pressed: #636363
- Background of right-sided buttons: #636363, when pressed: #838383
- While on landscape: right-sided buttons’ min width is 360px in xhdpi phone screen and 150px in hdpi phone screen.
*and/will have higher priority than+and-- DEL button will clear one right-most character off the current expression.
- If device’s orientation is changed, the current formula and result should be kept.
- Result is calculated when user presses
=button. - Pressing = will move the result from result textview to formula textview and clear result textview.
- Show a dialog with this text “Your expression cannot be calculated” if user presses “=” on an invalid expression.
- Result is calculated on the fly while user inputs operands and operators. If the expression is invalid then the last result should be kept.
- Supports negative numbers.
- Supports more operators if you want.