如何在按下按钮后显示UIPickerView动画？

我想在按下按钮后为我的UIPickerView设置动画。我已经将我的UIPickerView编码为隐藏在viewDidLoad上，而不是在按下按钮后隐藏，但它没有像默认情况下ModalViewController动画的动画。我只是希望我的UIPickerView能够像默认情况下的ModalViewController动画一样动画。

I want to animate my UIPickerView after pressing the button. I already have coded my UIPickerView to be hidden on viewDidLoad and not hidden after pressing a button, but it doesn't animate like how a ModalViewController animates by default. I just want my UIPickerView to be animated just like a ModalViewController animates by default.

我已经在网站和网络上进行过研究，但我不能似乎做得很好。

I've researched already on the site, and on the web, but I can't seem to do it properly.

这是我的代码：

#pragma mark - Picker View 

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

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    return 4;
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    timersArray = [[NSMutableArray alloc] init];
    [timersArray addObject:@"No timer"];
    [timersArray addObject:@"15 seconds"];
    [timersArray addObject:@"30 seconds"];
    [timersArray addObject:@"60 seconds"];

    return [timersArray objectAtIndex:row];
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component
{
    if ([[timersArray objectAtIndex:row] isEqual:@"No timer"])
    {
        timerIndication.text = @"No timer selected";
        timersPickerView.hidden = YES;
        // Animation code to dismiss picker should go here
    }
    else if ([[timersArray objectAtIndex:row] isEqual:@"15 seconds"])
    {
        timerIndication.text = @"15 seconds selected";
        timersPickerView.hidden = YES;
        // Animation code to dismiss picker should go here
    }
    else if ([[timersArray objectAtIndex:row] isEqual:@"30 seconds"])
    {
        timerIndication.text = @"30 seconds selected";
        timersPickerView.hidden = YES;
        // Animation code to dismiss picker should go here
    }
    else if ([[timersArray objectAtIndex:row] isEqual:@"60 seconds"])
    {
        timerIndication.text = @"60 seconds selected";
        timersPickerView.hidden = YES;
        // Animation code to dismiss picker should go here
    }
}

#pragma mark - Delay method

// This is where Send button should be enabled
- (IBAction)selectTimer
{
    timersPickerView.hidden = NO;
    // Animation code to present picker view should go here
}