Carrier: Sprint
Network: CDMA
Manufacturer: Sanyo
Programming Language: J2ME
I ran into an issue trying to download jpg data to a J2ME application recently, and I figured it warranted a blog post.
The data the comes over the air is a bunch of meta data about the image, followed by all the bytes that are the contents of the image. When the request comes in I find where the Image starts and try to load it into an Image object. The Image object has a method:
Image.createImage(byte[] buffer, int start, int length)
which is perfect. I figured I could just pass in the whole response with the right start index and length, and it would work perfect. When I tested it, it worked great on IDEN phones, and some sprint phones, but on a number of them, Sanyo phones in particular, it would only work a small fraction of the time. Most of the time it would return a IOException with a null message.
After debugging this for a few hours, I found that the data being sent from the server was being received right by the phone, and that the phone was using the correct start index and length. Then I found that if the same contents were sent to two different phones, one would work and one would fail. I couldn't figure out why it would fail, and it really didn't make any sense.
Fortunately I was able to come up with a workaround that I haven't seen on the Internet yet, hence this blog...
Instead of passing in the whole buffer, with start and length values, I just the image bytes into a new array and pass in 0 for start and the length of the array for the length.
This solved the problem, but blew my mind. :)
Original Code that crashed:
Image img = null;
try {
img = Image.createImage(output, imageStartIdx, length)
} catch(Exception e) {
throw new Exception("The map returned was not valid.");
}
After The Fix:
byte[] imageBytes = new byte[length];
System.arraycopy(output, imageStartIdx, imageBytes, 0, length);
Image img = null;
try {
img = Image.createImage(imageBytes, 0, imageBytes.length);
// img = Image.createImage(output, imageStartIdx, length)
} catch(Exception e) {
throw new Exception("The map returned was not valid.");
}
This is nothing too impressive, but I figured someone might not figure it out on their own, so there it is...
Happy Coding!
