The situations are:
1. There are access points but android phone has no result in the list.
2. The access point used in the past cannot be listing too.
The solution is, via the reference – HTC Tattoo WIFI 掃描找不到任何 AP 之解法:
IMPORTANT: ONLY FOR A ROOTED USER.
Using any file manager which can access the /data directory for your phone. Then remove a system generated file: /data/misc/wifi/wpa_supplicant.conf.
Because the file is generated by system which can be regenerated after reboot. So after reboot the wifi function works fine. But the secured network connections should be connected by hand again. Enjoy it. 🙂