Question

我有两个UIViews我想在屏幕上关闭动画。两者都应该从屏幕开始定位。顶部向下动画，向下动画。没有约束，它按预期工作。但是，使用UIViews在应用启动时可见（带有轻微的动画可见）。但它们会在屏幕上制作动画。

对于顶部UIView，我有一个前导空间，尾随空间，顶部空间和高度。

对于底部UIView，我有一个前导空间，尾随空间，底部空间和高度。

我应该如何调整代码和/或约束以获得所需的动画？

这是我的代码：

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    [self animateViewsIn];
}

- (void)viewWillLayoutSubviews {
    [super viewWillLayoutSubviews];

    self.topView.frame = CGRectMake(16.0, -self.topView.frame.size.height, self.topView.frame.size.width, self.topView.frame.size.height);

    self.bottomView.frame = CGRectMake(16.0, self.view.bounds.size.height, self.bottomView.frame.size.width, self.bottomView.frame.size.height);
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)animateViewsIn {
    [UIView animateWithDuration:0.5
                      delay:1.0
                    options: UIViewAnimationOptionCurveEaseIn
                 animations:^{
                     self.topView.frame = CGRectMake(16.0, 
    self.topView.frame.size.height/8.0, self.topView.frame.size.width, 
    self.topView.frame.size.height);
                     self.bottomView.frame = CGRectMake(16.0, (self.view.bounds.size.height-self.bottomView.frame.size.height)-20.0, self.bottomView.frame.size.width, self.bottomView.frame.size.height);
                 }
                 completion:^(BOOL finished){
                     NSLog(@"Done!");
                 }];
}

- (IBAction)animateViewsOut:(id)sender {
    CGRect basketTopFrame = self.topView.frame;
    basketTopFrame.origin.y = -basketTopFrame.size.height;

    CGRect basketBottomFrame = self.bottomView.frame;
    basketBottomFrame.origin.y = self.view.bounds.size.height;


    [UIView animateWithDuration:0.5
                      delay:1.0
                    options: UIViewAnimationOptionCurveEaseOut
                 animations:^{
                     [self.view layoutIfNeeded];

                     self.topView.frame = basketTopFrame;
                     self.bottomView.frame = basketBottomFrame;
                 }
                 completion:^(BOOL finished){
                     NSLog(@"Done!");
                 }];
}

Answer 1

使用约束时，不应调整帧。您应该修改约束的constant属性（或者取消一个约束并激活另一个约束）。

以下是从顶部为顶部视图设置动画的示例，假设您在视图@IBOutlet的顶部约束中添加了一个名为topConstraint的{{1}}：

在Objective-C中：

topView

在斯威夫特：

- (void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];

    self.topConstraint.constant = -self.topView.frame.size.height;  // or whatever you want
    [self.view layoutIfNeeded];
    [UIView animateWithDuration:0.5 delay:1 options:0 animations:^{
        self.topConstraint.constant = 0;
        [self.topView layoutIfNeeded];
    } completion:nil];
}

如何为具有约束的UIView制作动画？

1 个答案: