Solved
I was attempting to put a keyboard inside a modal window. When I run the simulator and try to open up my modal window I get "Assertion failed!... Cannot add Drawable multiple times"
void MainScreenView::setVacuumPositionPercentBoxClickHandler(const BoxWithBorder& b, const ClickEvent& evt)
{
// When target vacuum position box is clicked, display modal keypad with numericals
targetPercentModalWindow.setVisible(true);
targetPercentModalWindow.invalidate();
keyboard.setPosition(410, 100, 320, 240);
add(keyboard);
}This is the code where I make the modal window visible and draw the keyboard.