In Android, to see the saved password of all the wifi networks:
1. Install a root browser such as ROM Toolbox Lite' s root browser (you may need to root your phone to be able to use this tool)
2. Using root browser navigate to /data/misc/wifi/. You will see a file name wpa_supplicant.conf. All the wifi networks's information are stored in this file.
3. Open that file with a text editor in your phone. And you will see something like:
The value "MyWifiP@ssword" of "psk" key is the password you need, in plain text.