UITableView 中的 iPhone 动态 UIButton

Question

我正在为 UITableView 中的每个单元格行创建一个按钮。该按钮充当将所选行添加为 NSUserDefaults 中“收藏夹”的开关。我的问题是，每当我按下此按钮时，就会在旧按钮之上绘制一个新按钮。我如何正确释放/重用它？这就是我的 cellForRowAtIndexPath 方法的样子:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"cellID";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
        cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

    } 

    UIImage *favOn = [UIImage imageNamed:@"favOn.png"];
    UIImage *favOff = [UIImage imageNamed:@"favOff.png"];                   
    UIButton *favButton = [[UIButton alloc] initWithFrame:CGRectMake(230, 0, 54, 54)];


    favButton.tag = viewTag;

    [favButton setImage:favOff forState:UIControlStateNormal];
    [favButton setImage:favOn forState:UIControlStateSelected];

    if([self getFavState:viewTag]) {

        [favButton setSelected:YES];
    }
    else {
        [favButton setSelected:NO];
    }

    [favButton addTarget:self action:@selector(favButtonSwitch:) forControlEvents:UIControlEventTouchUpInside];
    [favButton setBackgroundColor:[UIColor clearColor]];
    [cell.contentView addSubview:favButton];
    [favButton release];

    return cell;
}

此外，我使用三种不同的方法来选择按钮:

- (void) setFavState:(BOOL)state withId:(NSString *)uid {

    NSUserDefaults *savedData = [NSUserDefaults standardUserDefaults];
    [savedData setBool:state forKey:uid];   
}

- (BOOL) getFavState:(NSString *)uid {

    NSUserDefaults *savedData = [NSUserDefaults standardUserDefaults];
    return [savedData boolForKey:uid];
}

- (void) favButtonSwitch:(id) sender {
    NSInteger senderId = [sender tag];
    NSString *senderString = [NSString stringWithFormat:@"%i", senderId];

    NSLog(@"sender:%i",senderId);

    [self getFavState:senderString];

    if([self getFavState:senderString]) {

        [self setFavState:NO withId:senderString];
    }
    else {
        [self setFavState:YES withId:senderString];
    }

    [self.tableView reloadData];
}

Answer 1

您似乎每次都会使用新图像创建一个新按钮，即使它是从缓存中检索的。将创建带有图像的按钮的代码移到第一次创建单元格的代码中。

if (cell == nil) {
    cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease];
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
    // Move all the image and button creation in here...
}