ios - 是否可以使用淡入淡出将 ui 元素从一个位置移动到另一个位置？

Question

我希望能够从位置 A 淡出 UIView 并同时在位置 B淡入。这在 iOS 上可行吗？

Answer 1

是的，沿着这些思路：

    [UIView animateWithDuration:0.25 animations:^{

    self.viewA.frame = CGRectMake... // middle point
    self.viewA.alpha = 0.0f;

    }completion:^ (BOOL finished) 
 {
    [UIView animateWithDuration:0.25 animations:^{

    self.viewA.frame = CGRectMake... // final point
    self.viewA.alpha = 1.0f;
    }];
 }];

Answer 2

一种方法是创建视图的图像，将其放在屏幕上（在图像视图中）而不是实际视图，将视图的 alpha 设置为 0，设置其框架（或调整布局约束）以将其置于新位置，然后启动一个使图像淡出并在实际视图中淡出的动画。

像这样的东西应该工作：

#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>

@interface ViewController ()
@property (weak,nonatomic) IBOutlet UIView *fadingView;
@property (weak,nonatomic) IBOutlet NSLayoutConstraint *topCon;
@property (strong,nonatomic) UIImageView *iv;
@end

@implementation ViewController

-(IBAction)moveView:(id)sender {
    UIImage *viewimage = [self imageWithView:self.fadingView];
    self.iv = [[UIImageView alloc] initWithFrame:self.fadingView.frame];
    self.iv.image = viewimage;
    [self.view addSubview:self.iv];
    self.fadingView.alpha = 0;
    self.topCon.constant = 200; // topCon is IBOutlet to the top constraint to the superview

    [UIView animateWithDuration:1 animations:^{
        self.fadingView.alpha = 1;
        self.iv.alpha = 0;
    } completion:^(BOOL finished) {
        [self.iv removeFromSuperview];
    }];
}

- (UIImage *)imageWithView:(UIView *)view {
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(view.bounds.size.width, view.bounds.size.height), view.opaque, [[UIScreen mainScreen] scale]);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage * img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return img;
}