UIPIckerView显示奇怪的行为

Question

我是iOS开发的新手，我有一个任务，我需要实现一个UITextfield，点击它，带来一个国家选择器UIPickerView。

我经历了一些在线教程，并以某种方式让它工作。但它显示了一些我似乎无法弄清楚的奇怪行为。

出现了一些奇怪的黑条，每次滚动时选择器内容都会明显重复。

我相信我在代码中犯了一个错误，原谅我缺乏知识，但似乎无法弄清楚代码中的错误。

你能告诉我出了什么问题吗？

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField {

    if ([textField isEqual:self.countryTextField]) {
        countryPicker = [[UIPickerView alloc] initWithFrame:CGRectZero];
        countryPicker.showsSelectionIndicator = YES;
        self.countryPicker.delegate = self;
        self.countryPicker.dataSource = self;
       // [self.countryPicker reloadAllComponents];
       countryPicker.showsSelectionIndicator = YES;
   //     [countryPicker init:self];

        textField.inputView = countryPicker;
    }

    return YES;
}

- (UIView * ) pickerView: (UIPickerView * ) pickerView viewForRow: (NSInteger) row forComponent: (NSInteger) component reusingView: (UIView * ) view {


        UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, pickerView.frame.size.width, 44)];
    label.text =   [NSString stringWithFormat:@"%@", [[self.countries objectAtIndex:row] objectForKey:@"name"]];


    [label setTextAlignment:UITextAlignmentLeft];
    [label setBackgroundColor:[UIColor clearColor]];
    [label setFont:[UIFont boldSystemFontOfSize:15]];

        return label;
    }

Answer 1

似乎代码中很少有东西需要更改 1.每次编辑文本字段时都不要为UIPickerView分配内存-textFieldShouldBeginEditing

if(self.countryPicker == nil)
{
   self.countryPicker = [[UIPickerView alloc] initWithFrame:CGRectZero];
   self.countryPicker.showsSelectionIndicator = YES;
    self.countryPicker.delegate = self;
    self.countryPicker.dataSource = self;
   self.countryPicker.showsSelectionIndicator = YES;
}

2.使用self.countrypicker - ＆gt; class属性或countrypicker不会互换使用它们。

Answer 2

每次都可以初始化，而不是每次初始化，检查UIPicker是否已经初始化

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField {

    if ([textField isEqual:self.countryTextField]) {

       if(! countryPicker){
        countryPicker = [[UIPickerView alloc] initWithFrame:CGRectZero];
        countryPicker.showsSelectionIndicator = YES;
        self.countryPicker.delegate = self;
        self.countryPicker.dataSource = self;
        countryPicker.showsSelectionIndicator = YES;
       }
        textField.inputView = countryPicker;
    }

    return YES;
}

Answer 3

好吧，我终于找到了这个问题。在numberOfComponentsInPickerView

中定义错误数量的组件是一个愚蠢的错误