修复了 UIPickerView 选择栏中的标签 [英] Fixed labels in the selection bar of a UIPickerView

问题描述

在时钟应用程序中，计时器屏幕显示一个选择器(可能是 UIDatePickerModeCountDownTimer 模式下的 UIPicker)，在选择栏中有一些文本(小时"和分钟")" 在这种情况下).

In the clocks application, the timer screen shows a picker (probably a UIPicker in UIDatePickerModeCountDownTimer mode) with some text in the selection bar ("hours" and "mins" in this case).

(edit) Note that these labels are fixed: They don't move when the picker wheel is rolling.

(edit) Note that these labels are fixed: They don't move when the picker wheel is rolling.

有没有办法在标准 UIPickerView 组件的选择栏中显示这样的固定标签?

Is there a way to show such fixed labels in the selection bar of a standard UIPickerView component?

我没有找到任何可以帮助解决此问题的 API.一个建议是添加一个 UILabel 作为选择器的子视图，但这不起作用.

I did not find any API that would help with that. A suggestion was to add a UILabel as a subview of the picker, but that didn't work.

回答

我遵循了 Ed Marty 的建议(答案如下)，并且有效！不完美，但它应该愚弄人们.作为参考，这是我的实现，请随时改进...

I followed Ed Marty's advice (answer below), and it works! Not perfect but it should fool people. For reference, here's my implementation, feel free to make it better...

- (void)viewDidLoad {
    // Add pickerView
    self.pickerView = [[UIPickerView alloc] initWithFrame:CGRectZero];
    [pickerView release];
    CGSize pickerSize = [pickerView sizeThatFits:CGSizeZero];
    CGRect screenRect = [[UIScreen mainScreen] applicationFrame];
    #define toolbarHeight           40.0
    CGFloat pickerTop = screenRect.size.height - toolbarHeight - pickerSize.height;
    CGRect pickerRect = CGRectMake(0.0, pickerTop, pickerSize.width, pickerSize.height);
    pickerView.frame = pickerRect;

    // Add label on top of pickerView
    CGFloat top = pickerTop + 2;
    CGFloat height = pickerSize.height - 2;
    [self addPickerLabel:@"x" rightX:123.0 top:top height:height];
    [self addPickerLabel:@"y" rightX:183.0 top:top height:height];
    //...
}

- (void)addPickerLabel:(NSString *)labelString rightX:(CGFloat)rightX top:(CGFloat)top height:(CGFloat)height {
#define PICKER_LABEL_FONT_SIZE 18
#define PICKER_LABEL_ALPHA 0.7
    UIFont *font = [UIFont boldSystemFontOfSize:PICKER_LABEL_FONT_SIZE];
    CGFloat x = rightX - [labelString sizeWithFont:font].width;

    // White label 1 pixel below, to simulate embossing.
    UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(x, top + 1, rightX, height)];
    label.text = labelString;
    label.font = font;
    label.textColor = [UIColor whiteColor];
    label.backgroundColor = [UIColor clearColor];
    label.opaque = NO;
    label.alpha = PICKER_LABEL_ALPHA;
    [self.view addSubview:label];
    [label release];

    // Actual label.
    label = [[UILabel alloc] initWithFrame:CGRectMake(x, top, rightX, height)];
    label.text = labelString;
    label.font = font;
    label.backgroundColor = [UIColor clearColor];
    label.opaque = NO;
    label.alpha = PICKER_LABEL_ALPHA;
    [self.view addSubview:label];
    [label release];
}

推荐答案

创建您的选择器，创建一个带有阴影的标签，并将其推送到 selectionIndicator 视图下方的选择器子视图.

Create your picker, create a label with a shadow, and push it to a picker's subview below the selectionIndicator view.

看起来像这样

UILabel *label = [[[UILabel alloc] initWithFrame:CGRectMake(135, 93, 80, 30)] autorelease];
label.text = @"Label";
label.font = [UIFont boldSystemFontOfSize:20];
label.backgroundColor = [UIColor clearColor];
label.shadowColor = [UIColor whiteColor];
label.shadowOffset = CGSizeMake (0,1);
[picker insertSubview:label aboveSubview:[picker.subviews objectAtIndex:5]]; 
//When you have multiple components (sections)...
//you will need to find which subview you need to actually get under
//so experiment with that 'objectAtIndex:5'
//
//you can do something like the following to find the view to get on top of
// define @class UIPickerTable;
// NSMutableArray *tables = [[NSMutableArray alloc] init];
// for (id i in picker.subviews) if([i isKindOfClass:[UIPickerTable class]]) [tables addObject:i];
// etc...

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