将 UILabel 滑到视图控制器上

Question

我正在尝试以平滑的幻灯片类型动画从 UIViewController 顶部的起始位置移动 UILabel，以便在视图加载时它从顶部向下滑动，然后在 y 位置停止大约 10 秒. 10 秒后，我想再次滑出视图。

-(void) animateInstructionLabel
{
float newX = 50.0f;
float newY = 100.0f;

[UIView transitionWithView:self.lblInstruction
                  duration:10.0f
                   options:UIViewAnimationCurveEaseInOut
                animations:^(void) {
                    lblInstruction.center = CGPointMake(newX, newY);
                }
                completion:^(BOOL finished) {
                    // Do nothing
                }];
} 

但我不知道如何进行 10 秒延迟，然后在上述方法中返回。最终结果是我希望这是一个看起来像通知的标签，然后再次移出屏幕。

谁能帮我把上面描述的这些部分放在一起？

编辑

我根据以下答案添加此内容：

-(void) animateInstructionLabel
{
float newX = lblInstruction.frame.origin.x;
float newY = 20.0f;

lblInstruction.center = CGPointMake(lblInstruction.frame.origin.x, -20.0f);
lblInstruction.bounds = CGRectMake(lblInstruction.frame.origin.x, -20.0f, 650.0f, 40.0f);

[UIView animateWithDuration:3.0f
                      delay:0
                    options:UIViewAnimationCurveEaseInOut
                 animations:^(void) {
                     lblInstruction.center = CGPointMake(newX, newY);
                 }
                 completion:^(BOOL finished) {
                     [UIView animateWithDuration:5.0f
                                           delay:5.0
                                         options:UIViewAnimationCurveEaseInOut
                                      animations:^(void) {
                                          lblInstruction.center = CGPointMake(newX, -20);
                                      }
                                      completion:^(BOOL finished) {
                                          // Do nothing
                                      }
                      ];
                 }
 ];
}

但即使我在动画开始之前将 label.center 设置在屏幕之外，我还是看到它从 viewcontroller 的左上角移动到 viewcontroller 的中心。它没有保持动画开始之前应该设置的 x 位置。

Answer 1

尝试在动画块之后添加这个（oldX,oldY 是旧坐标，在为标签设置动画之前）：

double delayInSeconds = 10.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    [UIView transitionWithView:self.lblInstruction
                      duration:10.0f
                       options:UIViewAnimationCurveEaseInOut
                    animations:^(void) {
                        lblInstruction.center = CGPointMake(oldX, oldY);
                    }
                    completion:^(BOOL finished) {
                        // Do nothing
                    }];
});

Answer 2

这样的事情应该可以工作：

-(void) animateInstructionLabel {
    float newX = 50.0f;
    float newY = 100.0f;

    labelInstruction.center = CGPointMake(newX, -20); // start off screen

    [UIView animateWithDuration:10.0f
                delay:0
                options:UIViewAnimationCurveEaseInOut
                animations:^(void) {
                    lblInstruction.center = CGPointMake(newX, newY);
                }
                completion:^(BOOL finished) {
                    [UIView animateWithDuration:10.0f
                                delay:10.0
                                options:UIViewAnimationCurveEaseInOut
                                animations:^(void) {
                                    lblInstruction.center = CGPointMake(newX, -20);
                                }
                                completion:^(BOOL finished) {
                                    // Do nothing
                                }
                    ];
                }
    ];
}

Answer 3

如果它可以帮助其他人，这是有效的。我必须使用 .frame 而不是 .center 来设置初始位置，然后将后续动画设置回该位置。

-(void) animateInstructionLabel
{

lblInstruction.frame = CGRectMake(lblInstruction.frame.origin.x, -40.0f, 650.0f, 40.0f);
[self.view addSubview:lblInstruction];
lblInstruction.hidden = NO;

float newX = lblInstruction.frame.origin.x;
float newY = 20.0f;

[UIView animateWithDuration:3.0f
                      delay:0
                    options:UIViewAnimationCurveEaseInOut
                 animations:^(void) {
                     lblInstruction.center = CGPointMake(newX, newY);
                 }
                 completion:^(BOOL finished) {
                     [UIView animateWithDuration:3.0f
                                           delay:5.0
                                         options:UIViewAnimationCurveEaseInOut
                                      animations:^(void) {
                                          lblInstruction.frame = CGRectMake(lblInstruction.frame.origin.x, -40.0f, 650.0f, 40.0f);
                                      }
                                      completion:^(BOOL finished) {
                                          lblInstruction.hidden = YES;
                                      }
                      ];
                 }
 ];
}

这可以平滑地使标签从视图中滑下，停止 5 秒，然后将其平滑地垂直移回视图之外。

感谢之前的回答，让我找到了上述最终解决方案。