为什么我的NSLog会崩溃？ （NSMutable Array和UIPickerView相关）

Question

我有一个带有2个组件的UIPickerView。

这是加载到其中的数组：

pickerArray = [[NSMutableArray alloc] initWithCapacity:700];
for ( int i = 0 ; i <= 1000 ; ++i)
    [pickerArray addObject:[NSString stringWithFormat:@"%d", i]];    
pickerArrayHalf = [[NSMutableArray alloc]initWithCapacity:2];
[pickerArrayHalf addObject:@".0 lb"];
[pickerArrayHalf addObject:@"1/2 lb"];

以下是委托方法：

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)thePickerView 
{
    if (thePickerView.tag==1)
    {
    return 2;
    }
    else
        return 1;
}

- (NSInteger)pickerView:(UIPickerView *)thePickerView numberOfRowsInComponent:(NSInteger)component 
{
    if (thePickerView.tag==1)
    {
        if (component == 0)
            return [pickerArray count];
        if (component == 1)
            return [pickerArrayHalf count];
    }
    else
        return [pickerArray count];
}

- (void)pickerView:(UIPickerView *)thePickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component 
{
    if (thePickerView.tag==1)
    {
        NSLog(@"Selected weight 1: %@. Index of  array: %i", [pickerArray objectAtIndex:row], row);
        NSLog(@"Selected weight 2: %@. Index of  array: %i", [pickerArrayHalf objectAtIndex:row], row);
    }
    else
    {
        NSLog(@"Selected rep number: %@. Index of array: %i", [pickerArray objectAtIndex:row], row);
    }
}

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view
{
    if (pickerView.tag==1)
    {
        if (component == 0)
        {
            UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 300, 37)];
            int weight = [[pickerArray objectAtIndex:row] intValue];
            label.text = [NSString stringWithFormat:@"%d", weight];

            label.textAlignment = UITextAlignmentCenter;
            label.backgroundColor = [UIColor clearColor];
            label.font = [UIFont boldSystemFontOfSize:30];
            [label autorelease];
            return label;
        }

        else
        {
            UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 300, 37)];
            label.text = [pickerArrayHalf objectAtIndex:row];
            label.textAlignment = UITextAlignmentCenter;
            label.backgroundColor = [UIColor clearColor];
            label.font = [UIFont boldSystemFontOfSize:30];
            [label autorelease];
            return label;
        }
    }

滚动时，应用程序在第NSLog(@"Selected weight 2: %@. Index of array: %i", [pickerArrayHalf objectAtIndex:row], row);

行崩溃

任何想法为什么？

Answer 1

您的选择器视图有两个组件/列。您必须分别处理每个组件的滚动。在您的情况下，即使该方法特定于组件，您也会在两个组件的行索引处打印出值。

因此，如果我要滚动到第一列中的第十行，您将尝试打印两个数据源的第十个元素。鉴于第二列的数据源似乎只有2个元素，只要第一列滚动超过前两个值，您的应用程序就会崩溃。

您需要像在numberOfRowsInComponent：方法中那样基于给定的组件实现逻辑。