如何知道UITableView动画何时完成？

Question

我想对某些UITableView动画的结尾做一系列反应。例如，我希望表格视图单元格通过scrollToRowAtIndexPath滚动后突出显示（通过selectRowAtIndexPath）。

这怎么办？

Answer 1

那么如果你想在scrollToRowAtIndexPath被触发时执行一个动作。

- (void)scrollToRowAtIndexPath:(NSIndexPath *)indexPath atScrollPosition:(UITableViewScrollPosition)scrollPosition animated:(BOOL)animated 

你需要创建一个CAAnimation指针像

CAAnimation *myAnimation; 

然后delgate设置为自

myAnimation.delegate = self; 

一旦你这样做，这些下面的委托方法应该启动，你可以把您的代码：

- (void)animationDidStart:(CAAnimation *)theAnimation 

- (void)animationDidStop:(CAAnimation *)theAnimation finished:(BOOL)flag 

Answer 2

基本模板：

[UIView animateWithDuration:0.2 animations:^{ 
    //do some animations, call them with animated:NO 
} completion:^(BOOL finished){ 
    //Do something after animations finished  
}]; 

示例：滚动到行100完成后，在该行获得的细胞，并与标签单元格内容视图= 1至firstResponder：

[UIView animateWithDuration:0.2 animations:^{ 
     [self.tableView scrollToRowAtIndexPath:[NSIndexPath indexPathForRow:100 inSection:0] atScrollPosition:UITableViewScrollPositionTop animated:NO]; 
    } completion:^(BOOL finished){ 
     //Do something after scrollToRowAtIndexPath finished, e.g.: 
     UITableViewCell *nextCell = [self.tableView cellForRowAtIndexPath:[NSIndexPath indexPathForRow:100 inSection:0]]; 
     [[nextCell.contentView viewWithTag:1] becomeFirstResponder];   
    }]; 

Answer 3

我意识到这是一个旧帖子，但我遇到了类似的问题，并创建了一个适用于我的解决方案。我将NSCookBook上使用的技术用于创建带有块的UIAlertView。我之所以这样做是因为我想使用内置的动画而不是UIView的+ animateWithDuration：动画：completion :.这些动画与iOS 7的更改有较大的区别。

您为UITableView创建一个类别，并在实现文件中创建一个内部私有类，该类将通过将其分配为您的tableview委托来回调该块。可以肯定的是，在块被调用之前，原来的委托将会“丢失”，因为新委托是调用块的对象。这就是为什么当调用块重新分配原始UITableViewDelegate时，我会通知发送消息。这段代码已经过测试，并且正在处理我的工作。

// Header file 
@interface UITableView (ScrollDelegateBlock) 

-(void)scrollToRowAtIndexPath:(NSIndexPath *)indexPath 
      atScrollPosition:(UITableViewScrollPosition)scrollPosition 
        animated:(BOOL)animated 
       scrollFinished:(void (^)())scrollFinished; 

@end 


// Implementation file 
#import "UITableView+ScrollDelegateBlock.h" 
#import <objc/runtime.h> 

NSString *const BLOCK_CALLED_NOTIFICATION = @"BlockCalled"; 

@interface ScrollDelegateWrapper : NSObject <UITableViewDelegate> 

@property (copy) void(^scrollFinishedBlock)(); 

@end 

@implementation ScrollDelegateWrapper 

-(void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView { 
    if (self.scrollFinishedBlock) { 
     [[NSNotificationCenter defaultCenter] postNotificationName:BLOCK_CALLED_NOTIFICATION object:nil]; 
     self.scrollFinishedBlock(); 
    } 
} 

@end 

static const char kScrollDelegateWrapper; 

static id<UITableViewDelegate>previousDelegate; 

@implementation UITableView (ScrollDelegateBlock) 

-(void)scrollToRowAtIndexPath:(NSIndexPath *)indexPath 
      atScrollPosition:(UITableViewScrollPosition)scrollPosition 
        animated:(BOOL)animated 
       scrollFinished:(void (^)())scrollFinished { 
    previousDelegate = self.delegate; 
    ScrollDelegateWrapper *scrollDelegateWrapper = [[ScrollDelegateWrapper alloc] init]; 
    scrollDelegateWrapper.scrollFinishedBlock = scrollFinished; 
    self.delegate = scrollDelegateWrapper; 

    objc_setAssociatedObject(self, &kScrollDelegateWrapper, scrollDelegateWrapper, OBJC_ASSOCIATION_RETAIN_NONATOMIC); 

    [self scrollToRowAtIndexPath:indexPath atScrollPosition:scrollPosition animated:animated]; 

    [[NSNotificationCenter defaultCenter] addObserver:self 
              selector:@selector(blockCalled:) 
               name:BLOCK_CALLED_NOTIFICATION 
               object:nil]; 
} 

/* 
* Assigns delegate back to the original delegate 
*/ 
-(void) blockCalled:(NSNotification *)notification { 
    self.delegate = previousDelegate; 
    [[NSNotificationCenter defaultCenter] removeObserver:self 
                name:BLOCK_CALLED_NOTIFICATION 
                object:nil]; 
} 

@end 

然后，您可以调用像任何其他与块的方法：

[self.tableView scrollToRowAtIndexPath:self.currentPath 
          atScrollPosition:UITableViewScrollPositionMiddle 
            animated:YES 
          scrollFinished:^{ 
           NSLog(@"scrollFinished"); 
          } 
];