如何从表格单元格中删除 UIGestureRecognizer

Question

我只想允许滑动删除 UITableView 的第一个单元格。 这一点很简单，但是我想在用户尝试滑动任何其他单元格时显示 UIAlert。我再次通过在除单元格 0 之外的每个单元格上使用 UIGestureRecognizer 来完成此工作。

我遇到的问题是一旦删除了顶行，我希望允许删除新的顶行。 就好像我需要删除分配给单元格的 UIGestureRecognizer ，但我不知道如何操作。

这是我的一些代码

 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    BetCell *cell = [tableView dequeueReusableCellWithIdentifier:@"BetCell"];

    Bet *bet = [self.bets objectAtIndex:([self.bets count]-indexPath.row-1)];
    cell.BFNeedLabel.text = bet.BFNeeded;

    if (indexPath.row != 0) {
    UISwipeGestureRecognizer *swipeRecognizer = [[UISwipeGestureRecognizer alloc]initWithTarget:self action:@selector(swipeDetected:)];
    swipeRecognizer.direction = (UISwipeGestureRecognizerDirectionLeft | UISwipeGestureRecognizerDirectionRight);
    [cell addGestureRecognizer:swipeRecognizer];
    }

    return cell;

}

-(void)swipeDetected:(UIGestureRecognizer *)sender
{
    UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Info" message:@"You can only delete starting from the top cell" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert show];
}

-(BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.row == 0) {
        return YES;
    } else  { 
        return NO;
    }
}

-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    // If the very first row
    if ((editingStyle == UITableViewCellEditingStyleDelete) && (indexPath.row == 0)) {
        Bet *betObj = [self.bets objectAtIndex:([self.bets count]-indexPath.row-1)];
        //Delete from array
        [self.bets removeObjectAtIndex:([self.bets count]-indexPath.row-1)];
        //Delete the row
        [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];

        //Attempt to remove gesture recognizer from cell 0
        UISwipeGestureRecognizer *swipeRecognizer = [[UISwipeGestureRecognizer alloc]initWithTarget:self action:@selector(swipeDetected:)];
        swipeRecognizer.direction = (UISwipeGestureRecognizerDirectionLeft | UISwipeGestureRecognizerDirectionRight);
        [[tableView cellForRowAtIndexPath:0]removeGestureRecognizer:swipeRecognizer];
    }
}

Answer 1

无需删除gestureRecognizer。在您的 swipeDetected 中找出您所在的单元格，并且仅在 indexPath.row != 0 时显示警报。

您的手势识别器将为您提供可以转换为表视图坐标空间的位置，该位置可用于获取该单元格的索引路径。

在swipeDetected中

CGPoint location = [sender locationInView:self.tableView];
NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:location];
if ( indexPath.row != 0 {
// do alert
}

使用示例代码更新：

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return 20;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:@"Test"];
    if ( !cell ) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"test"] autorelease];
        UISwipeGestureRecognizer *gr = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleCellSwipe:)];
        gr.direction = UISwipeGestureRecognizerDirectionRight + UISwipeGestureRecognizerDirectionLeft;
        gr.delegate = self;
        [cell addGestureRecognizer:gr];
        [gr release];
    }
    cell.textLabel.text = [NSString stringWithFormat:@"Cell %d",indexPath.row];
    return cell;
}

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    [tableView deselectRowAtIndexPath:indexPath animated:YES];
}

- (UITableViewCellEditingStyle)tableView:(UITableView *)tableView editingStyleForRowAtIndexPath:(NSIndexPath *)indexPath
{
    if ( indexPath.row == 0 )
        return UITableViewCellEditingStyleDelete;
    else 
        return UITableViewCellEditingStyleNone;
}

- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    return indexPath.row == 0;
}

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
{
    // do stuff
}

- (void)handleCellSwipe:(UIGestureRecognizer *)gestureRecognizer
{
    if ( gestureRecognizer.state == UIGestureRecognizerStateRecognized ) {
        CGPoint location = [gestureRecognizer locationInView:self.tableView];
        NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:location];
        if ( indexPath.row != 0 ) {
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Cell Swipe"
                                                            message:@"Cell in row not equal to 0 swiped"
                                                           delegate:nil 
                                                  cancelButtonTitle:nil
                                                  otherButtonTitles:@"OK", nil];
            [alert show];
            [alert release];
        }
    }
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
    CGPoint location = [touch locationInView:self.tableView];
    NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:location];
    return indexPath.row != 0;
}

Answer 2

当您只需通过 caneditrowatindexpath 显示警报时，为什么要经历手势识别器的麻烦呢？我能看到的唯一问题是，如果您还使用编辑按钮 - 那么您会立即收到很多警报。

-(BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath
{
    if (indexPath.row == 0) {
        return YES;
    } else  { 
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"Info" message:@"You can only delete starting from the top cell" delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];
    }
}

如果您设置使用手势识别器，则只需在删除后在索引 0 上使用 reloadRowsAtIndexPaths:withRowAnimation: 这将重置第一个单元格。然而，您的 cellforrowatindexpath 在您的原始帖子中设置错误，并且无论哪种方式都会导致此设置发生奇怪的事情。

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    BetCell *cell = [tableView dequeueReusableCellWithIdentifier:@"BetCell"];

    if ( !cell ) //this is needed in case a cell was never created in the first place
        cell = [[[BetCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:@"BetCell"] autorelease];

    Bet *bet = [self.bets objectAtIndex:([self.bets count]-indexPath.row-1)];
    cell.BFNeedLabel.text = bet.BFNeeded;

    if (indexPath.row != 0) {
        UISwipeGestureRecognizer *swipeRecognizer = [[UISwipeGestureRecognizer alloc]initWithTarget:self action:@selector(swipeDetected:)];
        swipeRecognizer.direction = (UISwipeGestureRecognizerDirectionLeft | UISwipeGestureRecognizerDirectionRight);
        [cell addGestureRecognizer:swipeRecognizer];
    } else {//this is needed to reset a cell that is being reused (such as when you scroll off the page and return)
        for (UIGestureRecognizer *gesture in cell.gestureRecognizers) {
            [cell removeGestureRecognizer:gesture];
        }
    }

    return cell;

}