UIScrollView 分页在中心选中

Question

我制作了一个 UIScrollView，其中包含四个 UILabel。我希望所选的 UILabel 不是屏幕左侧的，而是中心的。我附上了两张图片来说明我的意思。在第一个图像上，绿色标签将是选定的标签，在下一个图像上，蓝色标签将是选定的标签。

有什么办法可以做到这一点吗？

这是我的代码：

[scrollView setContentSize:CGSizeMake(428, 65)];
[scrollView setDelegate:self];

UILabel *label1 = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 107, 65)];
[label1 setBackgroundColor:[UIColor redColor]];
[label1 setTextAlignment:UITextAlignmentCenter];
[label1 setText:@"Wednesday"];
[scrollView addSubview:label1];
[label1 release];

UILabel *label2 = [[UILabel alloc] initWithFrame:CGRectMake(107, 0, 107, 65)];
[label2 setBackgroundColor:[UIColor greenColor]];
[label2 setTextAlignment:UITextAlignmentCenter];
[label2 setText:@"Thursday"];
[scrollView addSubview:label2];
[label2 release];

UILabel *label3 = [[UILabel alloc] initWithFrame:CGRectMake(214, 0, 107, 65)];
[label3 setBackgroundColor:[UIColor blueColor]];
[label3 setTextAlignment:UITextAlignmentCenter];
[label3 setText:@"Friday"];
[scrollView addSubview:label3];
[label3 release];

UILabel *label4 = [[UILabel alloc] initWithFrame:CGRectMake(321, 0, 107, 65)];
[label4 setBackgroundColor:[UIColor orangeColor]];
[label4 setTextAlignment:UITextAlignmentCenter];
[label4 setText:@"Saturday"];
[scrollView addSubview:label4];
[label4 release];

Answer 1

旋转 UIPickerView 似乎是最简单的。这可以这样完成。

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.

    arrayDays = [[NSMutableArray alloc] init];
    [arrayDays addObject:@"ONSDAG"];
    [arrayDays addObject:@"TORSDAG"];
    [arrayDays addObject:@"FREDAG"];
    [arrayDays addObject:@"LØRDAG"];

    arrayDates = [[NSMutableArray alloc] init];
    [arrayDates addObject:@"29. JUNI"];
    [arrayDates addObject:@"30. JUNI"];
    [arrayDates addObject:@"1. JULI"];
    [arrayDates addObject:@"2. JULI"];

    pickerViewDay = [[UIPickerView alloc] initWithFrame:CGRectZero];
    [pickerViewDay setDelegate:self];
    [pickerViewDay setShowsSelectionIndicator:NO];
    CGAffineTransform rotate = CGAffineTransformMakeRotation(-M_PI/2);
    rotate = CGAffineTransformScale(rotate, 0.25, 2.0);
    [pickerViewDay setTransform:rotate];
    [pickerViewDay setCenter:CGPointMake(self.view.frame.size.width/2, (pickerViewDay.frame.size.height/2)-3)];
    [self.view addSubview:pickerViewDay];

    // Adding selection indicator to pickerview
    UIImage *selectorImage = [UIImage imageNamed:@"DayPickerView_SelectionIndicator.png"];
    UIView *customSelector = [[UIImageView alloc] initWithImage:selectorImage];
    [customSelector setFrame:CGRectMake(0, 0, 120, 74)];
    [customSelector setCenter:CGPointMake(self.view.frame.size.width/2, customSelector.frame.size.height/2)];
    [self.view addSubview:customSelector];
    [customSelector release];

    // Adding background to pickerview
    UIImage *backgroundImage = [UIImage imageNamed:@"DayPickerView_Background.png"];
    UIView *custombackground = [[UIImageView alloc] initWithImage:backgroundImage];
    [custombackground setFrame:CGRectMake(0, 0, 320, 74)];
    // [self.view addSubview:custombackground];
    [custombackground release];
}

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view {
    UIView *viewRow = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 150, 80)];

    CGAffineTransform rotate = CGAffineTransformMakeRotation(3.14/2);
    rotate = CGAffineTransformScale(rotate, 0.25, 2.0);

    // Date
    CGRect rectDate = CGRectMake(30, 0, 150, 80);
    UILabel *date = [[UILabel alloc]initWithFrame:rectDate];
    [date setTransform:rotate];
    [date setText:[arrayDates objectAtIndex:row]];
    [date setFont:[UIFont fontWithName:@"Arial-BoldMT" size:37.0]];
    [date setShadowColor:[UIColor whiteColor]];
    [date setShadowOffset:CGSizeMake(0, -1)];
    [date setTextAlignment:UITextAlignmentCenter];
    [date setBackgroundColor:[UIColor clearColor]];
    [date setClipsToBounds:YES];
    [viewRow addSubview:date];

    // Day
    CGRect rectDay = CGRectMake(-30, 0, 150, 80);
    UILabel *day = [[UILabel alloc]initWithFrame:rectDay];
    [day setTransform:rotate];
    [day setText:[arrayDays objectAtIndex:row]];
    [day setFont:[UIFont fontWithName:@"Arial-BoldMT" size:21.0]];
    [day setTextColor:[UIColor colorWithRed:0.35 green:0.35 blue:0.35 alpha:1]];
    [day setTextAlignment:UITextAlignmentCenter];
    [day setBackgroundColor:[UIColor clearColor]];
    [day setClipsToBounds:YES];
    [viewRow addSubview:day];

    return viewRow;
}

- (NSString *)pickerView:(UIPickerView *)thePickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    return [arrayDays objectAtIndex:row];
}

- (NSInteger)pickerView:(UIPickerView *)thePickerView numberOfRowsInComponent:(NSInteger)component {
    return [arrayDays count];
}