7.7.3 Double Buffering
As we've already seen, double buffering is supported by using the
lock() and unlock() methods of the Graphics class. The Symbian
OS implementation of the MIDP Canvas class is double buffered by
default, or you use an offscreen image context to create your own double
buffer. This is not a major problem and changing your code base to deal
with it should be fairly easy.
DoJa uses the Dialog class in place of MIDP's Alert class. A Dialog
is a fixed-function, very simple modal dialog and the following MIDP
functionality is not available:
automatic re-direction to a specified Displayable when the dialog
playing an appropriate (and device dependent) alert sound on display
using your own images - DoJa dialogs do not have any images
adding your own command buttons and listeners
timeouts - all dialogs are modal
All you can do is simplify your alert management code to address this.
Applications that rely on post-dismissal re-directions are likely to require
the most re-engineering.
DoJa allows any screen to specify up to two softkeys and there is no
equivalent of the Command class, therefore there is no support for menus.
Depending on your application, this may require a careful re-design of
your application's navigation flows.
7.7.6 Text Positioning
The anchor point concept used extensively in MIDP is not used in DoJa.
When drawing text on a graphics context at a specified point, that point
is always relative to the left edge of the text and its baseline. Working
around this is a simple exercise in mathematics.