How to change Gmail account on Android without hard reset
1. Go to google apps
2. click "Clear Data"
After that there will be a message "All information you've saved in this application Will be deleted Permanently",
click OK
4. After that click
"Back" and type "Synchronize Data", or go to
Home> Menu> Settings> Data synchronization
5. After synchronize
Data will display a wizard to input data to a new Google account. This wizard also arise when we just bought a new android handset or when we just do the wipe through hardreset.
Note: For more safety, u can change account by going to Settings> Applications> Manage Applications> Gmail. Click the "Clear Data".
This will clear the previous Gmail account information.