ios 中的半屏幕底部弹出框

static UIView *modalView;
if (modalView) {
        [modalView removeFromSuperview];
        modalView = nil;
        return;
    }

    CGRect screen = [[UIScreen mainScreen] bounds];
    CGRect bounds = CGRectMake(screen.origin.x, screen.origin.y, screen.size.width, screen.size.height/);
    modalView = [[UIView alloc] initWithFrame:bounds];
    modalView.opaque = NO;
    modalView.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.5f];

    UILabel *label = [[UILabel alloc] init];
    label.text = @"Modal View";
    label.textColor = [UIColor whiteColor];
    label.backgroundColor = [UIColor clearColor];
    label.opaque = NO;
    [label sizeToFit];
    [label setCenter:CGPointMake(modalView.frame.size.width / , modalView.frame.size.height / )];
    [modalView addSubview:label];

    [self.view addSubview:modalView];

若要从xib众加载UI的外观，则：

if (popupViewController) {
        [popupViewController.view removeFromSuperview];
        popupViewController = nil;
        return;
    }

    popupViewController = [[UIViewController alloc] initWithNibName:@"View" bundle:nil];
    [self.view addSubview:popupViewController.view];

如果需要从底部的动画向上slide in的动画：

UIView *popView = popupViewController.view;
    CGRect orig = popView.bounds;
    CGRect screen = [[UIScreen mainScreen] bounds];
    [popView setFrame:CGRectMake(, screen.size.height, orig.size.width, orig.size.height)];
    [UIView beginAnimations:@"animatePopView" context:nil];
    [UIView setAnimationDuration:0.4];
    [popView setFrame:CGRectMake(, screen.size.height-orig.size.height, orig.size.width, orig.size.height)];
    [UIView commitAnimations];

Add a UIView above all, even the navigation bar

UIView* myView = /* Your custom view */;
UIWindow* currentWindow = [UIApplication sharedApplication].keyWindow;
[currentWindow addSubview:myView];

或者：

[self.navigationController.view addSubview:overlayView];