How to reduce the speed at which a row is selected in PickerView?

Question

My goal is to create a slotmachine in which rows rotate and one after another, they need to stop spinning one after another. However, in order to make it look beautiful, the rows should rotate for at least 3 seconds. I think PickerView is the best option for this, since I have no idea how to make this work differently.

If this is my code:

self.slotMachine.selectRow(99, inComponent: 1, animated: true) 

PickerView will go to line 99, but after 1 second. How can I control this second (and expand the row selection process)? One of the conditions is that it should look beautiful and feel that you are playing a slot machine. I tried this:

  UIView.animate(withDuration: 3.0, delay: 0, animations: { () -> Void in self.slotMachine.selectRow(99, inComponent: 1, animated: true) }, completion: nil ) 

But that did not work.

Thanks.

Answer 1

You can use the timer and select cells one by one as follows:

 var timer = Timer() var currentRow = 0 override func viewDidLoad() { super.viewDidLoad() timer = Timer.scheduledTimer(timeInterval: 0.2, target: self, selector: #selector(timerAction), userInfo: nil, repeats: true) } func timerAction() { currentRow += 1 self.slotMachine.selectRow(currentRow, inComponent: 1, animated: true) if(currentRow == 99){ timer.invalidate() } } 

Answer 2

Quick version:

 import UIKit class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate { var picker: UIPickerView! override func viewDidLoad() { super.viewDidLoad() picker = UIPickerView(frame: CGRect(x: 0, y: 100, width: 100, height: 375)); view.addSubview(picker) picker.dataSource = self picker.delegate = self let button = UIButton(frame: CGRect(x: 50, y: 50, width: 100, height: 100)) button.backgroundColor = .red button.addTarget(self, action: #selector(trigger), for: .touchUpInside) view.addSubview(button) } func trigger() { let timer = Timer.scheduledTimer(timeInterval: 0.25, target: self, selector: #selector(scrollRandomly), userInfo: nil, repeats: true); //call the block 3 seconds later DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + Double(Int64(3*NSEC_PER_SEC))/Double(NSEC_PER_SEC)) { timer.invalidate() //always select 500 finally self.picker.selectRow(500, inComponent: 0, animated: true) } } func scrollRandomly() { let row:Int = Int(arc4random() % 1000); picker.selectRow(row, inComponent: 0, animated: true) } func numberOfComponents(in pickerView: UIPickerView) -> Int { return 1 } func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int { return 1000 } func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? { return row.description } } 

OC Version:

 #import "ViewController.h" @interface ViewController () <UIPickerViewDelegate, UIPickerViewDataSource> @property (weak, nonatomic) UIPickerView *picker; @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; UIPickerView *picker = [[UIPickerView alloc] initWithFrame:CGRectMake(0, 100, 100, 375)]; self.picker = picker; [self.view addSubview:picker]; picker.delegate = self; picker.showsSelectionIndicator = true; UIButton *b = [[UIButton alloc] initWithFrame:CGRectMake(50, 50, 100, 100)]; b.backgroundColor = [UIColor redColor]; [self.view addSubview:b]; [b addTarget:self action:@selector(bbbb) forControlEvents:UIControlEventTouchUpInside]; } - (void)bbbb { NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:0.25 repeats:true block:^(NSTimer * _Nonnull timer) { NSInteger row = arc4random()%1000; [self.picker selectRow:row inComponent:0 animated:true]; }]; dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ [timer invalidate]; [self.picker selectRow:500 inComponent:0 animated:true]; }); } - (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component { return 1000; } - (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView { return 1; } - (nullable NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component { return [NSString stringWithFormat:@"%ld",row]; } @end