Short question, When usb mass storage mode is enabled, I replace a image file in sdcard with another image file with the same name, Then disable usb mass storage mode, Enter gallery, The thumbnail is not updated, This issue exists even in Nexus S device, What's wrong? Thank you!
I think the media scanner service doesn't get the chance to rescan the image. Try rebooting your phone. The media scanner runs on startup by default so it should rescan the SD card then.
Or.. you can just unmount then mount the SDCard. I think MediaScanner also runs when mounting a SDCard.