修复UIPickerView的选择栏中的标签 [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 UIPicker 在 UIDatePickerModeCountDownTimer 模式）

（编辑）请注意，这些标签是固定的：

有一种方法可以在标准的 UIPickerView的选择栏中显示这样的固定标签组件？

我没有找到任何有用的API。建议添加 UILabel 作为选择器的子视图，但这不起作用。

---

回答

我按照Ed Marty的建议（下面的答案）不完美，但它应该愚弄人。作为参考，这里是我的实现，随意让它更好...

   - （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; 
 
 //在pickerView的顶部添加标签
 CGFloat top = pickerTop + 2; 
 CGFloat height = pickerSize.height  -  2; 
 [self addPickerLabel：@xrightX：123.0 top：top height：height]; 
 [self addPickerLabel：@yrightX：183.0 top：top height：height]; 
 // ... 
} 
 
  - （void）addPickerLabel：（NSString *）labelString rightX：（CGFloat）rightX top：（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; 
 
 //白色标签下面1个像素，用于模拟压纹。 
 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]; 
 
 //实际标签。 
 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]; 
} 
  

解决方案

创建您的选择器，标签与阴影，并推送到pickIndicator视图下面的选择器的子视图。

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]]; 
 //当你有多个组件（部分）... 
 //你需要找到你需要实际获得
 //下的子视图，所以实验'objectAtIndex：5 '
 // 
 //你可以像下面这样找到视图来获取
 // define @class UIPickerTable; 
 // NSMutableArray * tables = [[NSMutableArray alloc] init]; 
 // for（id i in picker.subviews）if（[i isKindOfClass：[UIPickerTable class]]）[tables addObject：i]; 
 //等... 
 
  

p>

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.

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

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.

---

Answer

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];
}

解决方案

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

It would look something like this

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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