That's pretty much what the internet says.
1. Set options under Tools, then click Reload under Menu Packages
2. Then the list will be installed at the point install
But there's also an error when it comes to updating.
To solve a mistake like this I have found a lot of methods, but others can update the success. I think the difference between me and others is that the first time I downloaded the SDK was not from the official,
Instead of looking for a link.
So I went back to the official Internet War (https://developer.android.com/sdk/index.html) to download this
And then with the new incredibly successful.
So most of the settings and online methods, but still unsuccessful, reported a variety of errors, may be you originally downloaded the SDK is not from the official download.
* If you can't open the official network War can download a blue light jailbreak
Http://pan.baidu.com/s/1eRnidME Password: 5nvq*
Android SDK update failure problem resolution