http://www.cnblogs.com/andyque/archive/2011/12/30/2307060.html
http://www.raywenderlich.com/6567/uigesturerecognizer-tutorial-in-ios-5-pinches-pans-and-more
本文转自老Zhan博客园博客，原文链接：http://www.cnblogs.com/mybkn/archive/2012/03/31/2427439.html，如需转载请自行联系原作者
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