调用Google plus GPPSignInButton 的方

<pre><code> UIControlEvents en =[_GPPSignInButton allControlEvents];
NSArrayArr= [_GPPSignInButton actionsForTarget:_GPPSignInButton forControlEvent:en];
NSStringaction = Arr[0];
[_GPPSignInButton performSelector:NSSelectorFromString(action) withObject:_GPPSignInButton afterDelay:0];
</code></pre>