InputMethodManager imm = (InputMethodManager) activity.getSystemService(Context.INPUT_METHOD_SERVICE);
imm.showSoftInput(view, flags)
пример может быть:
InputMethodManager imm = (InputMethodManager) RouteMapActivity.this
.getSystemService(Context.INPUT_METHOD_SERVICE);
imm.showSoftInput(mapView, InputMethodManager.SHOW_IMPLICIT);