在iOS 7还没有发布的时候，各种App实现各种的swipe to pop效果，比如这里有一份简单的demo。
在iOS 7上，只要是符合系统的导航结构：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
// Override point for customization after application launch.
self.viewController = [[[ViewController alloc] initWithNibName:@"ViewController" bundle:nil] autorelease];
self.navController = [[[UINavigationController alloc] initWithRootViewController:self.viewController] autorelease];
self.window.rootViewController = self.navController;
[self.window makeKeyAndVisible];
return YES;
}
就能够拥有原生的漂亮效果：
遗憾的是目前项目代码里没有遵循iOS系统的导航结构，使得无法利用这点好处。所以我考虑使用新增的UIScreenEdgePanGestureRecognizer手势：
if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"7.0")) {
UIScreenEdgePanGestureRecognizer *left2rightSwipe = [[[UIScreenEdgePanGestureRecognizer alloc]
initWithTarget:self
action:@selector(handleSwipeGesture:)]
autorelease];
[left2rightSwipe setDelegate:self];
[left2rightSwipe setEdges:UIRectEdgeLeft];
[self.view addGestureRecognizer:left2rightSwipe];
}
}
- (void)handleSwipeGesture:(UIScreenEdgePanGestureRecognizer *)gestureRecognizer
{
[self.navigationController popViewControllerAnimated:YES];
}
刚加上去的时候各种无法触发，很郁闷——毕竟是在既有代码添加，而不是在一个干净的工程上。
后来发现现有代码实现了是否开始解释touch的代理函数，稍作修改得以生效：
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"7.0")) {
if ([gestureRecognizer isKindOfClass:[UIScreenEdgePanGestureRecognizer class]]) {
return YES;
}
}
生效了以后但是体验不好，感觉不灵敏。原来是已经添加过tapGesture，受了影响，又做了进一步修改：
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
BOOL result = NO; if ([gestureRecognizer isKindOfClass:[UIScreenEdgePanGestureRecognizer class]]) {
result = YES;
} return result;
}
如此一番才觉得尚可。
上面这个代理函数的描述如下：
Asks the delegate if a gesture recognizer should be required to fail by another gesture recognizer.
gestureRecognizer和otherGestureRecognizer之间到底是怎样的一个影响关系呢？