A UIScreenEdgePanGestureRecognizer looks for panning (dragging) gestures that start near an edge of the screen. The system uses screen edge gestures in some cases to initiate view controller transitions. You can use this class to replicate the same gesture behavior for your own actions.

UIScreenEdgePanGestureRecognizer看起來像pan手勢，它是檢測螢幕邊緣的pan手勢的。系統在某些controller轉場的時候會使用這個手勢。你也可以使用這個手勢做其他的事情。

原始碼：

處理手勢：

效果如下圖：

如果想與其他手勢併發操作，實現如下代理即可：

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
    return YES;
}