你如何让 UIPickerView 组件环绕?

问题描述

我想在 UIPickerView 组件中显示一组连续的数字，但让它像 Clock->Timer 应用程序的秒组件一样环绕.我可以启用的唯一行为类似于 Timer 应用程序的小时组件，您只能在其中向一个方向滚动.

I would like to show a set of consecutive numbers in a UIPickerView component but have it wrap around like the seconds component of the Clock->Timer application. The only behavior I can enable looks like the hours component of the Timer application, where you can scroll in only one direction.

推荐答案

将行数设置为大数，并使其从高值开始一样容易，用户滚动的可能性很小轮子很长一段时间 -- 即便如此，更糟糕的情况是他们会触底.

It's just as easy to set the number of rows to a large number, and make it start at a high value, there's little chance that the user will ever scroll the wheel for a very long time -- And even then, the worse that will happen is that they'll hit the bottom.

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    // Near-infinite number of rows.
    return NSIntegerMax;
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    // Row n is same as row (n modulo numberItems).
    return [NSString stringWithFormat:@"%d", row % numberItems];
}

- (void)viewDidLoad {
    [super viewDidLoad];

    self.pickerView = [[[UIPickerView alloc] initWithFrame:CGRectZero] autorelease];
    // ...set pickerView properties... Look at Apple's UICatalog sample code for a good example.
    // Set current row to a large value (adjusted to current value if needed).
    [pickerView selectRow:currentValue+100000 inComponent:0 animated:NO];
    [self.view addSubview:pickerView];
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
    NSInteger actualRow = row % numberItems;
    // ...
}

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