如何设置UIPickerView的默认值 [英] How to set a default Value of a UIPickerView

问题描述

我的UIPickerView出了问题。
我在EU AP和NA中有3个值。
当我启动应用程序时，欧盟似乎被选中，但当我创建一个 NSLog（@％@，[regions objectAtIndex：row]）; 我只有现在回到（null），
当我触摸UIPickerView时，选择了EU值，我得到EU从NSLog返回。

我的问题是：

如何我可以定义一个默认值，当用户只启动应用程序并且什么都不接触时，该默认值被选中（不仅是标签）。

编辑：以下是获取所选项目的代码：

  #pragma mark  -  
 #pragma mark PickerView DataSource 
 
  - （NSInteger）numberOfComponentsInPickerView：
（UIPickerView *）pickerView 
 {
 return 1; 
} 
  - （NSInteger）pickerView：（UIPickerView *）pickerView 
 numberOfRowsInComponent：（NSInteger）component 
 {
 return [regions count]; 
} 
  - （NSString *）pickerView：（UIPickerView *）pickerView 
 titleForRow：（NSInteger）row 
 forComponent：（NSInteger）component 
 {
 return [regions objectAtIndex：row]; 
} 
 
 #pragma mark  -  
 #pragma mark PickerView Delegate 
  - （void）pickerView：（UIPickerView *）pickerView didSelectRow：（NSInteger）row 
 inComponent：（NSInteger）组件
 {
 
 selectedRegion = [[NSString alloc] initWithFormat：
 @％@，[regions objectAtIndex：row]]; 
 NSLog（@％@，selectedRegion）; 
 
 
} 
  

解决方案

TL：DR版本：

  // Objective-C 
 [self。 picker selectRow：2 inComponent：0 animated：YES]; 
 // Swift 
 picker.selectRow（2，inComponent：0，animated：true）
  

---

要么你没有设置你的选择器来选择行（你说你似乎已经完成但无论如何）：

   - （void）selectRow :( NSInteger）inComponent :( NSInteger）组件动画：（BOOL）动画
  

或者您没有使用以下方法从您的选择器中获取所选项目

   - （NSInteger）selectedRowInComponent：（NSInteger）组件
  

这将得到从您的选择器中选择行作为整数，并随意使用它。
这应该可以解决问题。祝你好运。

无论如何阅读参考：

I have a problem with my UIPickerView. I have 3 values in it EU AP and NA. When I start the app EU seems to be selected but when I make a NSLog(@"%@", [regions objectAtIndex:row]); I only get back (null), now when I touch the UIPickerView the EU value is selected and I get "EU" back from a NSLog.

My question is:

How can I define a default value which is selected (not only the label) when the user only starts the app and touches nothing.

Edit: Here is my code to get the selected item:

#pragma mark -
#pragma mark PickerView DataSource

- (NSInteger)numberOfComponentsInPickerView:
(UIPickerView *)pickerView
{
    return 1;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView
numberOfRowsInComponent:(NSInteger)component
{
    return [regions count];
}
- (NSString *)pickerView:(UIPickerView *)pickerView
             titleForRow:(NSInteger)row
            forComponent:(NSInteger)component
{
    return [regions objectAtIndex:row];
}

#pragma mark -
#pragma mark PickerView Delegate
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row
      inComponent:(NSInteger)component
{

                selectedRegion = [[NSString alloc] initWithFormat:
                              @"%@", [regions objectAtIndex:row]];
    NSLog(@"%@", selectedRegion);


}

解决方案

TL:DR version:

//Objective-C
[self.picker selectRow:2 inComponent:0 animated:YES];
//Swift
picker.selectRow(2, inComponent:0, animated:true)

---

Either you didn't set your picker to select the row (which you say you seem to have done but anyhow):

- (void)selectRow:(NSInteger)row inComponent:(NSInteger)component animated:(BOOL)animated

OR you didn't use the the following method to get the selected item from your picker

- (NSInteger)selectedRowInComponent:(NSInteger)component

This will get the selected row as Integer from your picker and do as you please with it. This should do the trick for yah. Good luck.

Anyhow read the ref: https://developer.apple.com/documentation/uikit/uipickerview

---

EDIT:

An example of manually setting and getting of a selected row in a UIPickerView:

the .h file:

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController <UIPickerViewDelegate, UIPickerViewDataSource>
{
    UIPickerView *picker;
    NSMutableArray *source;
}

@property (nonatomic,retain) UIPickerView *picker;
@property (nonatomic,retain) NSMutableArray *source;

-(void)pressed;

@end

the .m file:

#import "ViewController.h"

@interface ViewController ()

@end
@implementation ViewController

@synthesize picker;
@synthesize source;

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

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return YES;
}

- (void) viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    self.view.backgroundColor = [UIColor yellowColor];

    self.source = [[NSMutableArray alloc] initWithObjects:@"EU", @"USA", @"ASIA", nil];

    UIButton *pressme = [[UIButton alloc] initWithFrame:CGRectMake(20, 20, 280, 80)];
    [pressme setTitle:@"Press me!!!" forState:UIControlStateNormal];
    pressme.backgroundColor = [UIColor lightGrayColor];
    [pressme addTarget:self action:@selector(pressed) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:pressme];

    self.picker = [[UIPickerView alloc] initWithFrame:CGRectMake(20, 110, 280, 300)];
    self.picker.delegate = self;
    self.picker.dataSource = self;
    [self.view addSubview:self.picker];

    //This is how you manually SET(!!) a selection!
    [self.picker selectRow:2 inComponent:0 animated:YES];
}

//logs the current selection of the picker manually
-(void)pressed
{
    //This is how you manually GET(!!) a selection
    int row = [self.picker selectedRowInComponent:0];

    NSLog(@"%@", [source objectAtIndex:row]);
}

- (NSInteger)numberOfComponentsInPickerView:
(UIPickerView *)pickerView
{
    return 1;
}

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

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

#pragma mark -
#pragma mark PickerView Delegate
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row
      inComponent:(NSInteger)component
{
//    NSLog(@"%@", [source objectAtIndex:row]);
}

@end

---

EDIT for Swift solution (Source: Dan Beaulieu's answer)

Define an Outlet:

@IBOutlet weak var pickerView: UIPickerView!  // for example

Then in your viewWillAppear or your viewDidLoad, for example, you can use the following:

pickerView.selectRow(rowMin, inComponent: 0, animated: true)
pickerView.selectRow(rowSec, inComponent: 1, animated: true)

If you inspect the Swift 2.0 framework you'll see .selectRow defined as:

func selectRow(row: Int, inComponent component: Int, animated: Bool) 

option clicking .selectRow in Xcode displays the following:

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