iosobjective-cxcodeswiftuipickerview

How to set a default Value of a UIPickerView


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);


}

Solution

  • 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: