如何降低PickerView中选择行的速度？

我的目标是创建一个slotmachine，其中行是一个接一个地旋转，他们需要一个接一个地停止旋转。 然而，为了使它看起来不错，行需要至少旋转3秒。 我认为PickerView是最好的选择，因为我不知道如何以不同的方式使这项工作。

这是我的代码：

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

PickerView将进入第99行，但是在1秒内。 如何控制第二个（并扩展选择行过程）？ 一个条件是它应该看起来不错，感觉你在玩老虎机。 我试过这个：

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

但这没效果。

谢谢。

Answer 1

您可以使用计时器并逐个选择单元格，如下所示：

 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

Swift版本：

 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版：

 #import "ViewController.h" @interface ViewController ()  @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