in my app i am trying to make a slider using the LWSlideShow LWSlideShow
the source of images are fetched from my server after trying the solution here i stuck with error that said unbalanced call and it means that i am presenting a modal view on a view that did not completed his animation after solving this problem by putting animation to no the splashView that i present will be dismissed before the images are downloaded here is my code for further explanation:
- (IBAction)goDownload {
UIViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:#"Splash"];
[self.navigationController presentViewController:vc animated:YES completion:nil];
dispatch_async(dispatch_get_main_queue(), ^{
NSMutableArray *array = [#[] mutableCopy];
LWSlideItem *item = [LWSlideItem itemWithCaption:#""
imageUrl:#"http://code-bee.net/geeks/images/cover-1.jpg"];
[array addObject:item];
item = [LWSlideItem itemWithCaption:#""
imageUrl:#"http://code-bee.net/geeks/images/cover-2.jpg"];
[array addObject:item];
item = [LWSlideItem itemWithCaption:#""
imageUrl:#"http://code-bee.net/geeks/images/cover-3.jpg"];
[array addObject:item];
LWSlideShow *slideShow = [[LWSlideShow alloc] initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.view.bounds), 120)];
slideShow.autoresizingMask = UIViewAutoresizingFlexibleWidth;
//slideShow.delegate = self;
[self.view addSubview:slideShow];
slideShow.slideItems = array;
if ([slideShow.slideItems count] == [array count]) {
[self dismissViewControllerAnimated:YES completion:nil];
}
});
}
//
//-(void)viewWillAppear:(BOOL)animated
//{
//
// UIViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:#"Splash"];
// [self.navigationController presentViewController:vc animated:YES completion:nil];
//}
- (void)viewDidLoad {
[super viewDidLoad];
[self goDownload];
}
also you can see from the code that also i try to use viewWillAppear same thing happened what i want is when the images are downloaded the splashView need to be dismissed i dont know what i am doing wrong
Running that code from a VC anytime before viewDidAppear (like viewDidLoad, viewWillAppear) will cause the problem you describe. But you probably don't want the slide show view to appear - even for an instant - until you're done fetching the assets. This is a common problem.
The solution is to realize that the "splash screen" and the network tasks aren't just preamble, they are as much a part of your application as the slide show.
EDIT
Make that Splash vc the app's initial view controller in storyboard. Right now, the slide show vc probably looks like this:
Uncheck the "Is Initial View Controller" checkbox, find your splash view controller (in the same storyboard, I hope) and check it's box to be the initial view controller. Now your app will start up on the splash vc, like you want it.
When the splash vc done, it can present the slide show vc, or it can even replace itself (with the slide show ) as the app window's root.
To replace the UI, I use variations of this snippet...
// in the splash vc, after all of the asset loading is complete
// give what used to be your initial view controller a storyboard id
// like #"MySlideShowUI"
UIViewController *vc = [self.storyboard instantiateViewControllerWithIdentifier:#"MySlideShowUI"];
UIWindow *window = [UIApplication sharedApplication].delegate.window;
window.rootViewController = vc;
[UIView transitionWithView:window
duration:0.3
options:UIViewAnimationOptionTransitionCrossDissolve
animations:nil
completion:nil];
I don't know how to load my page as it is, When i press back button. I have two type of pages storyboard and xib. Which display all information, When i click go button it will taken to new page. All these working good, But my problem is when i press back button i need my storyboard and xib file should be display in same view. When i run my app it display only storyboard page xib didn't load.
Thanks for advance here's my code:
- (IBAction)back:(id)sender {
Recharge *view = [self.storyboard instantiateViewControllerWithIdentifier:#"Recharge"];
[self presentViewController:view animated:YES completion:nil];
self.recharge = [[mobileViewcontroller alloc]init];
self.recharge.view.frame = CGRectMake(0,100, 400, 400);
[self addChildViewController:self.recharge];
[self.view addSubview:self.recharge.view];
}
Replace your code with
- (IBAction)back:(id)sender {
Recharge *rechargeView = [self.storyboard instantiateViewControllerWithIdentifier:#"Recharge"];
[self presentViewController:rechargeView animated:YES completion:nil];
self.recharge = [[mobileViewcontroller alloc]init];
self.recharge.view.frame = CGRectMake(0,100, 400, 400);
[rechargeView addChildViewController:self.recharge];
[rechargeView.view addSubview:self.recharge.view];
}
And it will work.
As you are adding your mobileViewcontroller view on your current viewController which is not visible to user, instead you should add your mobileViewcontroller to the the recharge viewController which is in hierarchy and visible to user.
I'm assuming that Recharge is the view controller from the storyboard and mobileViewController is the view controller from the xib.
You're calling the wrong constructor to load mobileViewController. You need to use (instancetype)initWithNibName:(NSString *)nibName bundle:(NSBundle *)nibBundle to load it with a xib file. See https://developer.apple.com/library/ios/Documentation/UIKit/Reference/UIViewController_Class/index.html#//apple_ref/occ/instm/UIViewController/initWithNibName:bundle:
when ever you call new viewcontroller with passing somthing you have do code like this put all code before[self presentViewController:view animated:YES completion:nil];
try this:
(IBAction)back:(id)sender
{
Recharge *view = [self.storyboard instantiateViewControllerWithIdentifier:#"Recharge"];
self.recharge = [[mobileViewcontroller alloc]init];
self.recharge.view.frame = CGRectMake(0,100, 400, 400);
[view addChildViewController:self.recharge];
[view addSubview:self.recharge.view];
[self presentViewController:view animated:YES completion:nil];
}
I'm developing for iPad and I have the following problem:
I'm trying to show a modal with his own size and his own UINavigationController, I already done that, but when I present the modal with his UINavigationController, I get this:
I want the UINavigationController to fit to modal size. I leave the code of how I'm presenting the modal:
- (void)createANewEvent:(id)sender
{
AddEditEventViewController *addEditEventViewController = [[(ScheduleViewController *)self.viewContainer storyboard] instantiateViewControllerWithIdentifier:#"AddEditEventViewControllerID"];
addEditEventViewController.modalPresentationStyle = UIModalPresentationFormSheet;
addEditEventViewController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:addEditEventViewController];
[self.viewContainer presentViewController:navigationController animated:YES completion:nil];
}
How I resize the modal:
AddEditEventViewController.m
// Resize the view
- (void)viewWillLayoutSubviews
{
[super viewWillLayoutSubviews];
self.view.superview.bounds = CGRectMake(0, 0, 548, 768);
self.view.superview.backgroundColor = [UIColor clearColor];
}
Hope you can help me!
Thanks in advance! :)
A view should never modify its superview's size or position.
The problem is that you're setting modalPresentationStyle on the root view controller instead of the view controller you're presenting, navigationController.
Delete:
addEditEventViewController.modalPresentationStyle = UIModalPresentationFormSheet;
addEditEventViewController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
Delete the viewWillLayoutSubviews method you posted.
Add:
navigationController.modalPresentationStyle = UIModalPresentationFormSheet;
navigationController.modalTransitionStyle = UIModalTransitionStyleCrossDissolve;
I would sub-class UINavigationController and implement the method:
preferredContentSize
Something like
- (CGSize) perferredContentSize {
return CGSizeMake(548,768);
}
That's all you should need to do to have properly resized modal views.
and have it return a CGSize structure with the size that you want the modal to be. This is the 'correct' way to do it per Apple documentation.
In conjunction, remove the viewWillLayoutSubviews method, that's just going to cause problems sometime in the future.
After [self.viewContainer presentViewController....] add:
navigationController.view.superview.bounds = CGRectMake(0, 0, 548, 768);
and get rid of your viewWillLayoutSubviews
I am trying to debug a really weird issue in the following code:
if(condition1) {
ImageViewController* imageViewer = [[ImageViewController alloc] initWithImageData:tappedItem];
[self presentViewController:imageViewer animated:YES completion:^{
[imageViewer loadImage];
}];
}
else if(condition2) {
DocumentViewController* docViewer = [[DocumentViewController alloc] init];
[self presentViewController:docViewer animated:YES completion:nil];
}
In other words, depending on the state of condition1 and condition2, one of two subclasses of UIViewController will be displayed modally to the user.
In the second case all is well, but in the first the view controller is not presented with the usual animation that shows it sliding in from the bottom of the screen. Instead, after a brief delay, it just shows up all of a sudden, covering the entire screen. Another oddity is that in the dismissal animation, the image view inside the view controller is transparent.
Removing the completion block has no effect. Replacing my view controller with an instance of UIViewController also has no effect, other than demonstrating that for some reason, animations don't work for UIViewController instances either.
Thinking that maybe I did something wrong in viewDidLoad etc, I tried commenting out the view load/appear methods but to no avail.
Pushing the view controller onto the nav stack is not an option because the app has a tab bar and I don't want to be visible.
update
Replacing my instance of ImageViewController with a DocumentViewController does result in an animation. The question now becomes: what could I have done in ImageViewController to mess up the animation?
I've found a solution but I still have no idea what the real cause was.
The fix was to set a background color for the view of the UIViewController being displayed modally in its viewDidload method e.g.
self.view.backgroundColor = [UIColor grayColor];
If I ever figure out what really happened, I will post here.
How about presenting the view controller on the tab bar controller:
if(condition1) {
ImageViewController* imageViewer = [[ImageViewController alloc] initWithImageData:tappedItem];
[self.tabBarController presentViewController:imageViewer animated:YES completion:^{
[imageViewer loadImage];
}];
}
else if(condition2) {
DocumentViewController* docViewer = [[DocumentViewController alloc] init];
[self.tabBarController presentViewController:docViewer animated:YES completion:nil];
}
It happened to me as well.. changing the background colour didn't really help.
I did the following - it turns up to be quite nice:
-(void) viewWillAppear:(BOOL)animated
{
[super viewWillAppear:NO];
self.view.userInteractionEnabled = FALSE;
self.view.hidden = TRUE;
self.navigationController.navigationBar.alpha = 0;
}
-(void) viewDidAppear:(BOOL)animated
{
[super viewDidAppear:NO];
float width = self.view.frame.size.width;
float height = self.view.frame.size.height;
self.view.frame = CGRectMake(0, height, width, height);
self.view.hidden = FALSE;
[UIView animateWithDuration:0.7f animations:^{
self.view.frame = CGRectMake(0, 0, width, height);
self.navigationController.navigationBar.alpha = 1;
} completion:^(BOOL finished){
self.view.userInteractionEnabled = TRUE;
}];
}
Setting the background color works for me in iOS 8.
Also uncheck the opaque setting in the Interface Builder works!
I am displaying a modal view with
[self presentModalViewController:controller animated:YES];
When the view moves up the screen it is transparent as per the setting in the xib file it is created from, but once it fills the screen it goes opaque.
Is there anyway of keeping the view transparent?
I suspect that the view it is being placed over is not being rendered rather then that the modal view is becoming opaque.
After iOS 3.2 there is a method to do this without any “tricks” – see the documentation for the modalPresentationStyle property. You have a rootViewController which will present the viewController.
So here's the code to success:
viewController.view.backgroundColor = [UIColor clearColor];
rootViewController.modalPresentationStyle = UIModalPresentationCurrentContext;
[rootViewController presentModalViewController:viewController animated:YES];
With this method the viewController's background will be transparent and the underlying rootViewController will be visible. Please note that this only seems to work on the iPad, see comments below.
Your view is still transparent, but once your modal controller is at the top of the stack, the view behind it is hidden (as is the case with any top-most view controller). The solution is to manually animate a view yourself; then the behind-viewController won't be hidden (since you won't have 'left' it).
What I needed to get this to work:
self.window.rootViewController.modalPresentationStyle = UIModalPresentationCurrentContext;
For those who want to see some code, here's what I added to my transparent view's controller:
// Add this view to superview, and slide it in from the bottom
- (void)presentWithSuperview:(UIView *)superview {
// Set initial location at bottom of superview
CGRect frame = self.view.frame;
frame.origin = CGPointMake(0.0, superview.bounds.size.height);
self.view.frame = frame;
[superview addSubview:self.view];
// Animate to new location
[UIView beginAnimations:#"presentWithSuperview" context:nil];
frame.origin = CGPointZero;
self.view.frame = frame;
[UIView commitAnimations];
}
// Method called when removeFromSuperviewWithAnimation's animation completes
- (void)animationDidStop:(NSString *)animationID
finished:(NSNumber *)finished
context:(void *)context {
if ([animationID isEqualToString:#"removeFromSuperviewWithAnimation"]) {
[self.view removeFromSuperview];
}
}
// Slide this view to bottom of superview, then remove from superview
- (void)removeFromSuperviewWithAnimation {
[UIView beginAnimations:#"removeFromSuperviewWithAnimation" context:nil];
// Set delegate and selector to remove from superview when animation completes
[UIView setAnimationDelegate:self];
[UIView setAnimationDidStopSelector:#selector(animationDidStop:finished:context:)];
// Move this view to bottom of superview
CGRect frame = self.view.frame;
frame.origin = CGPointMake(0.0, self.view.superview.bounds.size.height);
self.view.frame = frame;
[UIView commitAnimations];
}
The Apple-approved way to do this in iOS 8 is to set the modalPresentationStyle to 'UIModalPresentationOverCurrentContext'.
From the UIViewController documentation:
UIModalPresentationOverCurrentContext
A presentation style where the content is displayed over only the
parent view controller’s content. The views beneath the presented
content are not removed from the view hierarchy when the presentation
finishes. So if the presented view controller does not fill the screen
with opaque content, the underlying content shows through.
When presenting a view controller in a popover, this presentation
style is supported only if the transition style is
UIModalTransitionStyleCoverVertical. Attempting to use a different
transition style triggers an exception. However, you may use other
transition styles (except the partial curl transition) if the parent
view controller is not in a popover.
Available in iOS 8.0 and later.
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIViewController_Class/
The 'View Controller Advancements in iOS 8' video from WWDC 2014 goes into this in some detail.
Be sure to give your presented view controller a clear background color (otherwise, it will still appear opaque).
There is another option: before showing the modal controller, capture a screenshot of the whole window. Insert the captured image into an UIImageView and add the image view to the controller's view you're about to show.
Then send to back.
Insert another view above the image view (background black, alpha 0.7).
Show your modal controller and it looks like it was transparent.
Just tried it on iPhone 4 running iOS 4.3.1. Like charm.
this is quite old, but i solved the same problem as follows:
Since i need to present a navigation controller in iPhone, adding a subview wasn't a viable solution.
So what i did:
1) Before presenting the view controller, take a screenshot of your current screen:
UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, self.view.opaque, 0.0);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage * backgroundImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
2) Create the view controller you want to present, and add the background as a subview, sending it to back.
UIViewController * presentingVC = [UIViewController new];
UIImageView * backgroundImageOfPreviousScreen = [[UIImageView alloc] initWithImage:backgroundImage];
[presentingVC.view addSubview:backgroundImageOfPreviousScreen];
[presentingVC.view sendSubviewToBack:backgroundImageOfPreviousScreen];
3) Present your view controller, but before that in the new view controller, add a transparent view in the viewDidLoad (i used ILTranslucentView)
-(void)viewDidLoad
{
[super viewDidLoad];
ILTranslucentView * translucentView = [[ILTranslucentView alloc] initWithFrame:self.view.frame];
[self.view addSubview:translucentView];
[self.view sendSubviewToBack:translucentView];
}
And that's all!
I wrote down my findings about this in a different question, but the gist of it is that you have to call modalPresentationStyle = UIModalPresentationCurrentContext on whatever owns the full screen at the moment. Most of the time, it's whatever is the [UIApplication sharedApplication].delegate.window's rootViewController. It could also be a new UIViewController that was presented with modalPresentationStyle = UIModalPresentationFullScreen.
Please read my other much more detailed post if you're wondering how I specifically solved this problem. Good luck!
This appears to be broken in IOS 8, I am using a navigation controller and the context that is being displayed is the Navigation menus context which in our case is a sliding Menu controller.
We are using pod 'TWTSideMenuViewController', '0.3' have not checked to see if this is an issue with the library yet or the method described above.
This worked to me in iOS 8-9:
1- Set your view controller's background with an alpha
2- add this code:
TranslucentViewController *tvc = [[TranslucentViewController alloc] init];
self.providesPresentationContextTransitionStyle = YES;
self.definesPresentationContext = YES;
[tvc setModalPresentationStyle:UIModalPresentationOverCurrentContext];
[self.navigationController presentViewController:tvc animated:YES completion:nil];
I know this is pretty old question. I was stuck on this issue and I was able to get a lead from this thread. So putting here how I got it worked :) .
I am using storyboard and I have segue to the ViewController which is to be presented. The view controller have a transparent background colour. Now in the Attributes inspector of the segue I set the presentation to "Over current context".And it worked for me. I am developing for iPhone.
I've created open soruce library MZFormSheetController to present modal form sheet on additional UIWindow. You can use it to present transparency modal view controller, even adjust the size of the presented view controller.
In my condition i am having view on same viewController. So make a new view controller for holding UIView. Make that view transparent by setting it's alpha property.
Then on a button click i wrote this code. It looks good.
UIGraphicsBeginImageContext(objAppDelegate.window.frame.size);
[objAppDelegate.window.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIViewController *controllerForBlackTransparentView=[[[UIViewController alloc] init] autorelease];
[controllerForBlackTransparentView setView:viewForProfanity];
UIImageView *imageForBackgroundView=[[UIImageView alloc] initWithFrame:CGRectMake(0, -20, 320, 480)];
[imageForBackgroundView setImage:viewImage];
[viewForProfanity insertSubview:imageForBackgroundView atIndex:0];
[self.navigationController presentModalViewController:controllerForBlackTransparentView animated:YES];
And it shows what i want. hope it help some one.
Here's a category I've created that will solve the problem.
//
// UIViewController+Alerts.h
//
#import <UIKit/UIKit.h>
#interface UIViewController (Alerts)
- (void)presentAlertViewController:(UIViewController *)alertViewController animated:(BOOL)animated;
- (void)dismissAlertViewControllerAnimated:(BOOL)animated;
#end
//
// UIViewController+Alerts.m
//
#import "UIViewController+Alerts.h"
#implementation UIViewController (Alerts)
- (void)presentAlertViewController:(UIViewController *)alertViewController animated:(BOOL)animated
{
// Setup frame of alert view we're about to display to just off the bottom of the view
[alertViewController.view setFrame:CGRectMake(0, self.view.frame.size.height, alertViewController.view.frame.size.width, alertViewController.view.frame.size.height)];
// Tag this view so we can find it again later to dismiss
alertViewController.view.tag = 253;
// Add new view to our view stack
[self.view addSubview:alertViewController.view];
// animate into position
[UIView animateWithDuration:(animated ? 0.5 : 0.0) animations:^{
[alertViewController.view setFrame:CGRectMake(0, (self.view.frame.size.height - alertViewController.view.frame.size.height) / 2, alertViewController.view.frame.size.width, alertViewController.view.frame.size.height)];
}];
}
- (void)dismissAlertViewControllerAnimated:(BOOL)animated
{
UIView *alertView = nil;
// find our tagged view
for (UIView *tempView in self.view.subviews)
{
if (tempView.tag == 253)
{
alertView = tempView;
break;
}
}
if (alertView)
{
// clear tag
alertView.tag = 0;
// animate out of position
[UIView animateWithDuration:(animated ? 0.5 : 0.0) animations:^{
[alertView setFrame:CGRectMake(0, self.view.frame.size.height, alertView.frame.size.width, alertView.frame.size.height)];
}];
}
}
#end
After a lot of research looks like this will solve our issue and serve our purpose.
create a segue from source VC to destination VC with an identifier.
for example "goToDestinationViewController"
okay to makes lives easy let's consider the current view controller i.e, the one you want behind your transparent view as source and the destination as destination
Now in source VC in viewDidLoad: or view
performSegueWithIdentifier("goToDestinationViewController", sender: nil)
good we are half way through.
Now go to your storyboard. Click on the segue. which should look like this:
segue
change the options to what are shown.
Now comes the real solution.
in your destination view controller's viewDidLoad add this code.
self.modalPresentationStyle = .Custom
.........................................................................THAT EASY..................................................................
Alternate way is to use a "container view". Just make alpha below 1 and embed with seque.
XCode 5, target iOS7.
can't show image, not enough reputation)))
Container view available from iOS6.
This code works fine on iPhone under iOS6 and iOS7:
presentedVC.view.backgroundColor = YOUR_COLOR; // can be with 'alpha'
presentingVC.modalPresentationStyle = UIModalPresentationCurrentContext;
[presentingVC presentViewController:presentedVC animated:YES completion:NULL];
But along this way you loose 'slide-from-the-bottom' animation.
I found this elegant and simple solution for iOS 7 and above!
For iOS 8 Apple added UIModalPresentationOverCurrentContext, but it does not work for iOS 7 and prior, so I could not use it for my case.
Please, create the category and put the following code.
.h file
typedef void(^DismissBlock)(void);
#interface UIViewController (Ext)
- (DismissBlock)presentController:(UIViewController *)controller
withBackgroundColor:(UIColor *)color
andAlpha:(CGFloat)alpha
presentCompletion:(void(^)(void))presentCompletion;
#end
.m file
#import "UIViewController+Ext.h"
#implementation UIViewController (Ext)
- (DismissBlock)presentController:(UIViewController *)controller
withBackgroundColor:(UIColor *)color
andAlpha:(CGFloat)alpha
presentCompletion:(void(^)(void))presentCompletion
{
controller.modalPresentationStyle = UIModalPresentationCustom;
UIWindow *keyWindow = [UIApplication sharedApplication].keyWindow;
__block UIView *overlay = [[UIView alloc] initWithFrame:keyWindow.bounds];
if (color == nil) {
color = [UIColor blackColor];
}
overlay.backgroundColor = color;
overlay.alpha = alpha;
if (self.navigationController != nil) {
[self.navigationController.view addSubview:overlay];
}
else if (self.tabBarController != nil) {
[self.tabBarController.view addSubview:overlay];
}
else {
[self.view addSubview:overlay];
}
self.modalPresentationStyle = UIModalPresentationCurrentContext;
[self presentViewController:controller
animated:true
completion:presentCompletion];
DismissBlock dismissBlock = ^(void) {
[self dismissViewControllerAnimated:YES completion:nil];
[UIView animateWithDuration:0.25
animations:^{
overlay.alpha = 0;
} completion:^(BOOL finished) {
[overlay removeFromSuperview];
}];
};
return dismissBlock;
}
#end
Note: it works also for navigationContoller, tabBarController.
Example of usage:
// Please, insure that your controller has clear background
ViewController *controller = [ViewController instance];
__block DismissBlock dismissBlock = [self presentController:controller
withBackgroundColor:[UIColor blackColor]
andAlpha:0.5
presentCompletion:nil];
// Supposed to be your controller's closing callback
controller.dismissed = ^(void) {
dismissBlock();
};
Enjoy it! and please, leave some feedbacks.
This is the best and cleanest way I found so far:
#protocol EditLoginDelegate <NSObject>
- (void)dissmissEditLogin;
#end
- (IBAction)showtTransparentView:(id)sender {
UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:#"foo bar"
delegate:self
cancelButtonTitle:#"cancel"
destructiveButtonTitle:#"destructive"
otherButtonTitles:#"ok", nil];
[actionSheet showInView:self.view];
}
- (void)willPresentActionSheet:(UIActionSheet *)actionSheet{
UIStoryboard *loginStoryboard = [UIStoryboard storyboardWithName:#"Login" bundle:nil];
self.editLoginViewController = [loginStoryboard instantiateViewControllerWithIdentifier:#"EditLoginViewController"];
self.editLoginViewController.delegate = self;
[self.editLoginViewController viewWillAppear:NO];
[actionSheet addSubview:self.editLoginViewController.view];
[self.editLoginViewController viewDidAppear:NO];
}
The best solution I have come across is to use the addChildViewController method.
Here is an excellent example : Add a child view controller's view to a subview of the parent view controller
I try to use multiple methods to solve but still failed, the follow code implemented finally.
The resolution by Swift:
// A.swift init method
modalPresentationStyle = .currentContext // or overCurrentContent
modalTransitionStyle = .crossDissolve // dissolve means overlay
then in B view controller：
// B.swift
let a = A()
self.present(a, animated: true, completion: nil)