多个组件崩溃的uppicker

Question

我试图创建一个应用程序使用UIPickerView与三个组件。第一个组件有3行。第二个组件有6行，第三个组件有12行。每次滚动到组件2或3中的第3行之后，应用程序就会崩溃并指向第一个组件数组。我相信这很容易解决，但我迷路了。提前谢谢。

-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row
  inComponent:(NSInteger)component
{    
{
    NSString *resultString0 = [[NSString alloc] initWithFormat:
                              @"Sensor: %@",
                              [modelArray objectAtIndex:row]];        
    modelLabel.text = resultString0;
    [resultString0 release];   
}
{
    NSString *resultString1 = [[NSString alloc] initWithFormat:
                              @"Pixels: %@",
                              [memoryArray objectAtIndex:row]];
    memoryLabel.text = resultString1;
    [resultString1 release];
    NSString *firstString = horizFaceRecLabel.text;
    float horizontalFace = [[horizontalArray objectAtIndex:row] floatValue];
    float requiredFace = 100;
    output1 = [firstString floatValue];
    output1 = horizontalFace / requiredFace;
    horizFaceRecLabel.text = [NSString stringWithFormat:(@"%.1f ft"), output1];
    NSString *secondString = horizLicensePlateLabel.text;
    float horizontalLicense = [[horizontalArray objectAtIndex:row] floatValue];
    float requiredLicense = 45;
    output2 = [secondString floatValue];
    output2 = horizontalLicense / requiredLicense;
    horizLicensePlateLabel.text = [NSString stringWithFormat:(@"%.1f ft"), output2];
    NSString *thirdString = horizVisualIdLabel.text;
    float horizontalVisual = [[horizontalArray objectAtIndex:row] floatValue];
    float requiredVisual = 30;
    output3 = [thirdString floatValue];
    output3 = horizontalVisual / requiredVisual;
    horizVisualIdLabel.text = [NSString stringWithFormat:(@"%.1f ft"), output3];
}
{
    NSString *resultString2 = [[NSString alloc] initWithFormat:
                              @"Lens: %@",
                              [lensArray objectAtIndex:row]];
    lensLabel.text = resultString2;
    [resultString2 release];
    {
        NSString *firstDistString = faceRecLabel.text;
        float angle = [[anglesArrayA objectAtIndex:row] floatValue];
        float densityOne;
        float densityTwo;
        densityOne = [firstDistString floatValue];
        densityTwo = (output1/2)/(sin(angle/2));
        faceRecLabel.text = [NSString stringWithFormat:(@"%.1f ft"), densityTwo];
    }
}
}

Answer 1

看起来你缺少一些if语句来控制何时调用每个代码块

每个组件大概有三个独立的代码块，但由于没有控制流的条件，因此每当选择任何组件中的一行时，所有代码块都会执行。(第三个代码块里面还有另一个代码块——不知道你为什么这样写。)

当您在第二和第三个组件中超过第3行时，第一个组件的代码运行并在试图获取组件1(不存在)的数组中的第4行时崩溃。

由于组件索引是从零开始的，所以条件应该是这样的:

if (component == 0)
{
    //code for 1st component here...
}
else if (component == 1)
{
    //code for 2nd component here...
}
else if (component == 2)
{
    //code for 3rd component here...
}

您也可以使用switch语句。