滚动UITableview会更改UIButton，UITableview滚动问题的图像

Question

我正在做的是，我有一个UITableview ，我添加了UIButton作为自定义视图。 我给每个按钮添加标签，并在动作方法中收到标签 。 当我按下按钮时，它会更改所选和未选择按钮的图像，但是当我滚动它时，它将进入正常状态。

这是我在索引方法行的单元格

static NSString *CellIdentifier = @"Cell4";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
    cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];
}
followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
[followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];
[followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
[cell.contentView addSubview:followingButton];
NSLog(@"row--%d",indexPath.row);
followingButton.tag=indexPath.row;
NSLog(@"followingButton.tag--%d",followingButton.tag);
[self configureCellFollowing:cell forIndexPath:indexPath];
return cell;
}

==================

//Here is the action method

-(void)followingButtonpressed:(id)sender
{
    NSLog(@"sender tag --%d",[sender tag]);
    UIButton *btnPly = (UIButton *)sender;
    if([btnPly isSelected])
    {
        [btnPly setSelected:NO];
        [btnPly setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
    }
    else
    {
        [btnPly setSelected:YES];
        [btnPly setImage:[UIImage imageNamed:@"following_off12.png"] forState:UIControlStateNormal];
    }
}

Answer 1

注意：此代码为每行数据创建单元格（不重用单元格）

您只需按描述进行更改，可能对您有所帮助

NSString *CellIdentifier = [NSString stringWithFormat:@"S%1dR%1d",indexPath.section,indexPath.row];

UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];

可能会解决你的问题:)

Answer 2

您的按钮“重置”的原因是因为tableView：cellForRowAtIndexPath被多次调用（每当一个单元格即将可见时）。

每次调用此按钮时，您都会重新初始化按钮并将图像重置为following12.png（默认状态）。 这就是滚动按钮时出现重置的原因。

您不能依赖单元本身来保留状态，因为单元格每次都会重置。 您需要将状态移动到其他位置（例如在数组实例变量中）。 然后，当您必须在tableView：cellForRowAtIndexPath中配置新单元格时，可以将其初始化为正确的状态（基于数组）。

因此，创建一个名为myStateArray（或其他）的NSMutableArray实例变量来存储您的按钮状态，然后您的cellForRowAtIndexPath看起来应该更像：

static NSString *CellIdentifier = @"Cell4";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
    cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];
}
followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
[followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];

// -- Fetch the state from your array
BOOL buttonPressed = [[self.myStateArray objectAtIndex:indexPath.row] boolValue];

// -- Initialize the button state correctly
[followingButton setSelected:buttonPressed];
if (buttonPressed) {
    [followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
} else {
    [followingButton setImage:[UIImage imageNamed:@"following_off12.png"] forState:UIControlStateNormal];
}



followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
[cell.contentView addSubview:followingButton];
NSLog(@"row--%d",indexPath.row);
followingButton.tag=indexPath.row;
NSLog(@"followingButton.tag--%d",followingButton.tag);
[self configureCellFollowing:cell forIndexPath:indexPath];
return cell;
}

然后按下按钮确保保存状态：

-(void)followingButtonpressed:(id)sender
{
    // -- Save the state
    [self.myStateArray insertObject:[NSNumber numberWithBool:[btnPly isSelected]] atIndex:[sender tag]];

    NSLog(@"sender tag --%d",[sender tag]);
    UIButton *btnPly = (UIButton *)sender;
    if([btnPly isSelected])
    {
        [btnPly setSelected:NO];
        [btnPly setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
    }
    else
    {
        [btnPly setSelected:YES];
        [btnPly setImage:[UIImage imageNamed:@"following_off12.png"] forState:UIControlStateNormal];
    }
}

Answer 3

据我所知，每当UITableView请求单元格时，您都会创建UIButton。 在这两种情况下，如果您创建一个新单元格或使用出列单元格。 然后，每次在已创建的按钮上创建并添加一个按钮。 if您的cellForRowAtIndexPath方法应该如此， if按钮创建移动到单元格创建

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"Cell4";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil)
    {
        cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];
        followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];
        [followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
        followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
        [cell.contentView addSubview:followingButton];
    }
    NSLog(@"row--%d",indexPath.row);
    followingButton.tag=indexPath.row;
    NSLog(@"followingButton.tag--%d",followingButton.tag);
    [self configureCellFollowing:cell forIndexPath:indexPath];
    return cell;
}

但这不会成为您问题的竞争解决方案。 您可能知道UITableView使用“可重用”单元来减少系统内存使用量。 它只使用当前需要显示的细胞数量。 因此，在具有100个单元格的表格中，它实际上将创建大约10个。并且它们都不会存储所有按下/未按下按钮的正确状态。 要实现正确的行为，您必须拒绝使用标记并使用某些模型逻辑。 最简单的方法 - NSMutableArray，您将存储按钮状态。 在followingButtonpressed:方法中，您将正确的对象设置为YES / NO，在cellForRowAtIndexPath您将读取此值。 检查下面的代码

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    static NSString *CellIdentifier = @"Cell4";
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil)
    {
        cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];
        followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];
        [followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
        followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
        [cell.contentView addSubview:followingButton];

        BOOL isSelected = [[statesArray objectAtIndex:btnPly.tag] boolValue];
        [self setState:isSelected forButton:followingButton];
    }
    NSLog(@"row--%d",indexPath.row);
    followingButton.tag=indexPath.row;
    NSLog(@"followingButton.tag--%d",followingButton.tag);
    [self configureCellFollowing:cell forIndexPath:indexPath];
    return cell;
}

-(void)followingButtonpressed:(id)sender
{
    NSLog(@"sender tag --%d",[sender tag]);
    UIButton *btnPly = (UIButton *)sender;

    BOOL isSelected = [[statesArray objectAtIndex:btnPly.tag] boolValue];
    [statesArray replaceObjectAtIndex:btnPly.tag withObject:[NSNumber numberWithBool:!isSelected]];

    if(isSelected)
    {
        [self setState:NO forButton:btnPly];
    }
    else
    {
        [self setState:YES forButton:btnPly];
    }
}

- (void) setState:(BOOL)state forButton:(UIButton *)button
{
    if(state)
    {
        [button setSelected:NO];
        [button setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];
    }
    else
    {
        [button setSelected:YES];
        [button setImage:[UIImage imageNamed:@"following_off12.png"] forState:UIControlStateNormal];
    }
}

statesArray在哪里

NSMutableArray *statesArray = [NSMutableArray new];

你必须在课堂上的某个地方创建并初始化它。 statesArray的对象计数必须与tableView的单元格数相同。

Answer 4

这是因为每次滚动时都会调用此代码

[followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];

所以现在检查

static NSString *CellIdentifier = @"Cell4";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
    cell = [self tableviewCellWithReuseIdentifierFollowing:CellIdentifier];

followingButton = [UIButton buttonWithType:UIButtonTypeCustom];
[followingButton addTarget:self action:@selector(followingButtonpressed:)forControlEvents:UIControlEventTouchUpInside];

[followingButton setImage:[UIImage imageNamed:@"following12.png"] forState:UIControlStateNormal];

followingButton.frame = CGRectMake(220.0 ,20.0, 100, 40.0);
[cell.contentView addSubview:followingButton];

[self configureCellFollowing:cell forIndexPath:indexPath];
}
return cell;
}