本文转载至 http://kyfxbl.iteye.com/blog/2147888
从iOS8开始,controller之间的跳转特效,需要用新的API UIPresentationController来实现。比如希望实现这样一个特效:显示一个模态窗口,大小和位置是自定义的,遮罩在原来的页面上。在iOS8之前,可以在viewWillAppear里设置superview的frame:
- - (void)presentModal:(NSDictionary*)result
- {
- YLSCheckoutSignatureController *controller = [[YLSCheckoutSignatureController alloc] initWithModel:result];
- if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) {
- controller.modalPresentationStyle = UIModalPresentationCustom;
- }else{
- controller.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
- controller.modalPresentationStyle = UIModalPresentationFormSheet;
- }
- [self presentViewController:controller animated:YES completion:nil];
- }
- -(void) viewWillAppear:(BOOL)animated
- {
- // in iOS8, handle by UIPresentationController
- if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) {
- return;
- }
- self.view.superview.layer.cornerRadius = 10;
- self.view.superview.layer.borderColor = [UIColor darkGrayColor].CGColor;
- self.view.superview.clipsToBounds = YES;
- self.view.superview.frame = CGRectMake(62, 114, 900, 540);
- }
但是以上的代码,在iOS8里就不再生效了,要用UIPresentationController来实现
首先明确一点,从Controller A->B,B的样式和跳转特效,还是由B来控制的。只不过以前是直接在Controller的生命周期方法里操作,而现在有专门的API来完成而已。这种设计也是合理的,否则如果从A可以跳转到B和C,但是样式和特效不一样,就只能通过在A里面设置实例变量来区分了,容易出错也很别扭。所以把跳转的行为由目标Controller来控制是很合理的
不过这组API的文档不太全,后续SDK升级可能会逐渐完善。以下介绍实现步骤:
目标Controller实现特定protocol
首先目标Controller要实现特定的协议,创建一个UIPresentationController
- @interface YLSCheckoutSignatureController : UIViewController
- self.transitioningDelegate = self;
- - (UIPresentationController *)presentationControllerForPresentedViewController:(UIViewController *)presented presentingViewController:(UIViewController *)presenting sourceViewController:(UIViewController *)source
- {
- return [[YLSMainPresentationController alloc] initWithPresentedViewController:presented presentingViewController:presenting];
- }
当条件满足时,iOS系统会调用这个方法,于是可以实例化自定义的UIPresentationController子类,定义跳转的样式和特效
自定义UIPresentationController
然后就要实现自定义的UIPresentationController,下面这段实例代码,实现居中展示一个自定义frame的模态页面,同时有半透明背景遮住原来的页面
- @implementation YLSMainPresentationController
- {
- UIView *dimmingView;
- }
- -(id) initWithPresentedViewController:(UIViewController *)presentedViewController presentingViewController:(UIViewController *)presentingViewController
- {
- self = [super initWithPresentedViewController:presentedViewController presentingViewController:presentingViewController];
- if(self){
- dimmingView = [[UIView alloc] init];
- dimmingView.backgroundColor = [UIColor grayColor];
- dimmingView.alpha = 0.0;
- }
- return self;
- }
- - (void)presentationTransitionWillBegin
- {
- dimmingView.frame = self.containerView.bounds;
- [self.containerView addSubview:dimmingView];
- [self.containerView addSubview:self.presentedView];
- id
coordinator = self.presentingViewController.transitionCoordinator; - [coordinator animateAlongsideTransition:^(id
context) { - dimmingView.alpha = 0.5;
- } completion:nil];
- }
- - (void)presentationTransitionDidEnd:(BOOL)completed
- {
- if(!completed){
- [dimmingView removeFromSuperview];
- }
- }
- - (void)dismissalTransitionWillBegin
- {
- id
coordinator = self.presentingViewController.transitionCoordinator; - [coordinator animateAlongsideTransition:^(id
context) { - dimmingView.alpha = 0.0;
- } completion:nil];
- }
- - (void)dismissalTransitionDidEnd:(BOOL)completed
- {
- if(completed){
- [dimmingView removeFromSuperview];
- }
- }
- - (CGRect)frameOfPresentedViewInContainerView
- {
- return CGRectMake(62.f, 114.f, 900.f, 540.f);
- }
- @end
代码确实比以前复杂了一点,但是其实每个生命周期方法都是比较明确的,开发者可控的粒度也更细了。比如设置presented frame,就有专门的方法,只要返回CGRect就可以了,还是比较方便的
原始的ViewController发起跳转动作
经过前面2步,当自定义跳转发生时,就可以很细致地控制样式和跳转行为。接下来就是由原始controller(presenting view controller)来发起跳转动作:
- - (void)presentModal:(NSDictionary*)result
- {
- YLSCheckoutSignatureController *controller = [[YLSCheckoutSignatureController alloc] initWithModel:result];
- if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 8.0) {
- controller.modalPresentationStyle = UIModalPresentationCustom;
- }else{
- controller.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
- controller.modalPresentationStyle = UIModalPresentationFormSheet;
- }
- [self presentViewController:controller animated:YES completion:nil];
- }
关键是设置modalPresentationStyle为UIModalPresentationCustom,然后当presentViewController方法调用时,iOS系统就会创建出UIPresentationController的实例,来控制跳转的行为