Question

我有一个UIPickerView，只要我尝试打开它就会崩溃。我希望用户能够从他们制作的飞机上选择尾号。 这是我的代码：

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

- (NSInteger)pickerView:(UIPickerView *)thePickerView numberOfRowsInComponent:(NSInteger)component {
    NSLog(@"%i", (int)[[NSUserDefaults standardUserDefaults]integerForKey:@"planeNum"]);
    return (NSInteger)[[NSUserDefaults standardUserDefaults]integerForKey:@"planeNum"];
}

NSMutableArray *tailPickerOptions;

- (NSString *)pickerView:(UIPickerView *)thePickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {

    NSInteger num = [[NSUserDefaults standardUserDefaults]integerForKey:@"planeNum"];

    while (num > 0) {
        --num;
        tailPickerOptions = [[NSMutableArray alloc]init];
        NSString *dTailNumber = [NSString stringWithFormat:@"%@", [[NSUserDefaults standardUserDefaults]objectForKey:[NSString stringWithFormat:@"Plane%liTailNumber", (long)num]]];
        [tailPickerOptions addObject:dTailNumber];
        NSLog(@"%@", dTailNumber);
    }

    return tailPickerOptions[row];

}

Answer 1

代码行： tailPickerOptions = [[NSMutableArray alloc]init]; 导致tailPickerOptions多次初始化（每次通过while循环一次），因此只会有一个对象（在索引0处，或者，例如，＆＃34; bounds [ 0..0]＆＃34）。将其移到while循环之外。例如，

tailPickerOptions = [[NSMutableArray alloc]init];
while (num > 0) {
        --num;

        NSString *dTailNumber = [NSString stringWithFormat:@"%@", [[NSUserDefaults standardUserDefaults]objectForKey:[NSString stringWithFormat:@"Plane%liTailNumber", (long)num]]];
        [tailPickerOptions addObject:dTailNumber];
        NSLog(@"%@", dTailNumber);
    }

UIPickerView在打开时崩溃了？

1 个答案: