ios - PickerView 没有显示

Question

我试图调出一个选择器 View 而不是键盘来放入文本字​​段，但我的选择器 View 没有显示。

#import "SettingsViewController.h"
#import "FindClasses.h"

@interface SettingsViewController ()
@property (weak, nonatomic) IBOutlet UIBarButtonItem *saveButton;
@property (weak, nonatomic) IBOutlet UITextField *classTextField;
@property (strong, nonatomic) UIPickerView *picker;
@property (nonatomic, strong) FindClasses *finder;
@property (nonatomic, strong) NSArray *itemsArray;
@end

@implementation SettingsViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    NSArray *itemsArray = [self.finder findClassesInTimetable];
    // Do any additional setup after loading the view.
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)presentPicker {
    CGRect frame = CGRectMake(0, 40, 0, 0);
    UIPickerView *picker = [[UIPickerView alloc] initWithFrame:frame];
    picker.delegate = self;
    picker.dataSource = self;
    // TODO: animate this on screen
    [self.view addSubview:picker];
}

- (void)textFieldDidBeginEditing:(UITextField *)textField {
    [self presentPicker];
}

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

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    return [self.itemsArray count];  //where items is your array of items
}

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row inComponent:(NSInteger)component {
    return [self.itemsArray objectAtIndex:row];
}

有人可以告诉我我做错了什么吗？我从另一个 Stackoverflow 帖子中拿了这个例子:

Answer 1

这就是我使用UIPickerView的方式，带有示例代码:

UIPickerView* genderPicker = [[UIPickerView alloc] init];

genderPicker.delegate = self;

genderPicker.dataSource = self;

在初始化您的 UITextField 之后(在我的例子中是 registrationGenderField):

registrationGenderField.inputView = genderPicker;

然后是 delegate 和 dataSource:

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

switch (row) {

        case 0:
            return @"Gender";
            break;

        case 1:
            return @"Male";
            break;

        case 2:
            return @"Female";
            break;

        default:
            return @"Gender";
            break;
    }
}

- (void) pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {

    switch (row) {

        case 0:
            registrationGenderField.text = @"";
            break;

        case 1:
            registrationGenderField.text =  @"Male";
            break;

        case 2:
            registrationGenderField.text =  @"Female";
            break;

        default:
            registrationGenderField.text =  @"";
            break;
    }
}



- (NSInteger) numberOfComponentsInPickerView:(UIPickerView *)pickerView {

    return 1;
}

- (NSInteger) pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {

    return 3;
}