Sunday, April 17, 2011

sizeChanged not called

To achieve the Single Jar theory we must deal with handsets fragmentation upfront.
One special piece of these fragments is the orientation change.

Screen orientations are: portrait (height > width) and landscape (width > height).

When the change happens the Java Virtual Machine should notify the running MIDlet with a call to sizeChanged method on the currently displayed Canvas.
Unfortunately this is not guaranteed to happen.

To make sure your application is always presented the right way you can store the last sizeChanged parameter values on attributes and check them on paint method.
Check the code below:

class C extends Canvas {
int lastWidth, lastHeight;
protected void sizeChanged(int w, int h) {
lastWidth = w;
lastHeight = h;
// adjust your user interface to the
// new width and height
// ...
protected void paint(Graphics g) {
if (super.getWidth() != lastWidth
|| super.getHeight() != lastHeight) {
sizeChanged(super.getWidth(), super.getHeight());
// paint your user interface
// ...

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