NSTimer与UIPickerView iOS的链接

Question

I have a UIPickerView with an array in one view controller and an NSTimer in another, i am trying to:

1) link the picker array to NSTimer so a user selects a time on the picker for image to self destruct

2) show time remaining in UILabel so seconds the user selects going down to 0. (ex. select 2 from picker label shows 2 then 1 then 0 and image destucts)

one vc.h

@property (strong, nonatomic) IBOutlet UIPickerView *timePicker;
@property (nonatomic, strong) NSArray *pickerData;

one vc.m 

- (void)viewDidLoad {
    [super viewDidLoad];

    self.pickerData = @[@1,@2,@3,@4,@5,@6,@7];

    self.timePicker.dataSource = self;
    self.timePicker.delegate = self;
}

- (void) viewWillAppear:(BOOL)animated {

    [self.textField setText:self.userText];
}

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

-(long)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return self.pickerData.count;
}


- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    [self.pickerData objectAtIndex:[self.timePicker selectedRowInComponent:0]];
}


two vc.h

@property (weak, nonatomic) IBOutlet UILabel *timeLabel;
@property (nonatomic, assign) int seconds;

two vc.m

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

            [NSTimer scheduledTimerWithTimeInterval:7 target:self selector:@selector(timeout)
                                           userInfo:nil repeats:NO];

    [NSTimer scheduledTimerWithTimeInterval:self.seconds target:self selector:@selector(setTimeToLabel) userInfo:nil repeats:NO];
}

-(void)timeout
{
 // pops to root view
}


- (void)setTimeToLabel
{  
    self.seconds = self.seconds - 1;
    self.timeLabel.text = [NSString stringWithFormat:@"%d", self.seconds];
}

the NSTimer does not respond to the self.seconds and does not pick up the user input from the UIPicker .

any ideas as to how I can link the picker to the timer so that the timer responds to the seconds the user selects in the picker and display the remaining seconds in the label??

my prepareforsegue method below:

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{

    if ([segue.destinationViewController isKindOfClass:[oneViewController class]]) {
        oneViewController * ovc = (oneViewController*)segue.destinationViewController;
        ovc.array = //whatever;
    }

    if  ([segue.destinationViewController isEqual:@"secondVC"]) {
            NSInteger row = [self.timePicker selectedRowInComponent:0];
            twoViewController *tvc = [segue destinationViewController];
            tvc.seconds = [[self.pickerData objectAtIndex:row] intValue];
    }
}

what can be the issue with it, the onviewcontroller method works, whatever i pass it works, but for the tvc.seconds nothing is passed to it.

Answer 1

You are creating a new instance of the controller rather than the actual one that would be used. You should be using the prepareForSegue method to do this, and get a reference to the destinationViewController, like so:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if ([segue.identifier isEqual: @"nextScreen"]) {
        NSInteger row = [self.timePicker selectedRowInComponent:0];
        SecondViewController *tvc = [segue destinationViewController];
        tvc.seconds = [[self.pickerData objectAtIndex:row] intValue];
    }
}

// First View Controller
//.h
#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

@property (weak, nonatomic) IBOutlet UITextField *textField;
@property (weak, nonatomic) IBOutlet UIPickerView *timePicker;
@property (nonatomic, strong) NSArray *pickerData;
@property (weak, nonatomic) IBOutlet UIButton *next;

@end

//.m
#import "ViewController.h"
#import "SecondViewController.h"

@interface ViewController () <UIPickerViewDataSource, UIPickerViewDelegate>

@end

@implementation ViewController

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

    self.pickerData = @[@1,@2,@3,@4,@5,@6,@7];

    self.timePicker.dataSource = self;
    self.timePicker.delegate = self;
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

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

-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return self.pickerData.count;
}

- (NSString*)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    return [NSString stringWithFormat: @"%@", self.pickerData[row]];
}


- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    [self.pickerData objectAtIndex:[self.timePicker selectedRowInComponent:0]];
}

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if ([segue.identifier isEqual: @"nextScreen"]) {
        NSInteger row = [self.timePicker selectedRowInComponent:0];
        SecondViewController *tvc = [segue destinationViewController];
        tvc.seconds = [[self.pickerData objectAtIndex:row] intValue];
    }
}

@end

// SecondViewController
//.h
#import "ViewController.h"

@interface SecondViewController : ViewController

@property (nonatomic) int seconds;
@property (weak, nonatomic) IBOutlet UILabel *timeLabel;

@end


//.m
#import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

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

    [NSTimer scheduledTimerWithTimeInterval:7 target:self selector:@selector(timeout)
                                   userInfo:nil repeats:NO];

    [NSTimer scheduledTimerWithTimeInterval:self.seconds target:self selector:@selector(setTimeToLabel) userInfo:nil repeats:NO];
}

-(void)timeout
{
    // pops to root view
}


- (void)setTimeToLabel
{
    self.seconds = self.seconds - 1;
    self.timeLabel.text = [NSString stringWithFormat:@"%d", self.seconds];
}

@end