Android SDK cannot be updated

1. Open the settings of SDK manager in tools> options under SDK manager, and select "Force https ://... Sources to be fetched using http ://...", Use http.
2. Modify the host file and add the following two lines

# Google_android update
203.208.46.146 dl.google.com
203.208.46.146 dl-ssl.google.com

In addition:
How to Modify host in Windows
Open the c: \ windows \ system32 \ drivers \ etc \ hosts file in windows and directly modify the file.

How to change the host on Mac
1. Open the terminal and enter sudo VI/etc/hosts.
2. Enter the system password.
3. Enter I to enter the editing mode.
4. After editing, Press ESC and enter: WQ