我是iOS开发人员的新手（现在已经有2个星期了），我正在开发一个iOS应用，我希望用UIPickerView填写国家/地区列表。
这是我到目前为止所做的：
1-创建了选择器视图
2-将我的视图控制器定义为选择器视图的委托
3-将这些代码行添加到我的.m视图控制器文件中:(方法：viewdidload，numberOfComponentsInPickerView，titleForRow）
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
NSMutableArray *countries = [NSMutableArray arrayWithCapacity: [[NSLocale ISOCountryCodes] count]];
for (NSString *countryCode in [NSLocale ISOCountryCodes])
{
NSString *identifier = [NSLocale localeIdentifierFromComponents: [NSDictionary dictionaryWithObject: countryCode forKey: NSLocaleCountryCode]];
NSString *country = [[NSLocale currentLocale] displayNameForKey: NSLocaleIdentifier value: identifier];
[countries addObject: country];
}
NSArray *sortedCountries = [countries sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];
}
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView{
return 1;// or the number of vertical "columns" the picker will show...
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
if (sortedCountries!=nil) {
return [sortedCountries count];//this will tell the picker how many rows it has - in this case, the size of your loaded array...
}
return 0;
}
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
//you can also write code here to descide what data to return depending on the component ("column")
if (sortedCountries!=nil) {
return [sortedCountries objectAtIndex:row];//assuming the array contains strings..
}
else
{
NSLog(@"Register tab empty?");
}
return @"empty";//or nil, depending how protective you are
}
这是我的.h文件：
#import <UIKit/UIKit.h>
@interface RegisterViewController_iPhone : UIViewController <UIPickerViewDelegate> {
NSArray * sortedCountries;
}
@property (strong, nonatomic) IBOutlet UIPickerView *pickerView;
@end
当我跑步时，它会给我一个空UIpickerView，感谢您的帮助，谢谢。
答案 0 :(得分：2)
此行不正确：
NSArray *sortedCountries = [countries sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];
您正在重新排序sortedCountries而不是使用头文件中定义的那个。删除NSArray *。
您的viewDidLoad方法应如下所示：
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
NSMutableArray *countries = [NSMutableArray arrayWithCapacity: [[NSLocale ISOCountryCodes] count]];
for (NSString *countryCode in [NSLocale ISOCountryCodes])
{
NSString *identifier = [NSLocale localeIdentifierFromComponents: [NSDictionary dictionaryWithObject: countryCode forKey: NSLocaleCountryCode]];
NSString *country = [[NSLocale currentLocale] displayNameForKey: NSLocaleIdentifier value: identifier];
[countries addObject: country];
}
sortedCountries = [countries sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];
}
答案 1 :(得分：1)
#pragma mark - pickerview
-(void)pickerview:(id)sender
{
pickerView=[[UIPickerView alloc] initWithFrame:CGRectMake(0,[Util window_height]-260,[Util window_width],300)];
// pickerView.transform = CGAffineTransformMakeScale(0.75f, 0.75f);
// pickerView.transform = CGAffineTransformMakeScale(0.85f, 0.85f);
pickerView.delegate = self;
pickerView.dataSource = self;
pickerView.showsSelectionIndicator = YES;
pickerView.backgroundColor = [UIColor lightGrayColor];
[pickerView selectRow:1 inComponent:0 animated:YES];
[self.view addSubview:pickerView];
// [contentView addSubview:pickerView];
}
- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView;
{
return 1;
}
- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component;
{
return [_items count];
}
- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
return[_items objectAtIndex:row];
}
-(void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component{
[pickerView removeFromSuperview];
[Txt_SecurityQue setText:[_items objectAtIndex:row]];
NSLog(@"Did select");
}
#pragma mark - securityQuestionsArray
-(void)securityQuestionsArray {
_items =[[NSArray alloc]initWithObjects:
@"Where do you want to retire?",
@"Where did you vacation last year?",
@"What is your personal address",
@"What is your employer name",
@"Who is your nearest relative",
@"What is your best friend phone number",
@"In what city were you born?",
@"What was your childhood nickname?",
@"Type your own question.",
@"What was the make and model of your first car?",
@"What time of the day was your first child born?",
@"What is your oldest sibling’s birthday month and year?",
@"What was your childhood nickname?",
@"What is the name of your favorite childhood friend?",
@"In what city or town did your mother and father meet?",
@"What is the middle name of your oldest child?",
@"What is your favorite team?",
@"What is your favorite movie?",
@"What was your favorite sport in high school?",
@"What was your favorite food as a child?",
@"What is the first name of the boy or girl that you first kissed?",
@"What was the make and model of your first car?",
@"What was the name of the hospital where you were born?",
@"Who is your childhood sports hero?",
@"What school did you attend for sixth grade?",
@"What was the last name of your third grade teacher?",
@"what town was your first job?",
@"What was the name of the company where you had your first job?",
nil];
}
答案 2 :(得分：0)
我读了这一行：
if (sortedCountries!=nil) {
我发现你遇到了麻烦。因为您没有遵循Objective-C编码约定。您有一个名为sortedCountries的实例变量。实例变量应该以_sortedCountries之类的下划线开头，这样它们就可以与属性区分开来。令人困惑的实例变量和属性通常会导致人们出现问题。首先，将sortedCountries更改为属性。
一般情况下，我不会将这种代码放入loadView。我为sortedCountries编写了一个访问器，如下所示：
- (NSArray*)sortedCountries
{
if (_sortedCountries == nil)
{
.... code to set _sortedCountries to non-nil value
}
return _sortedCountries;
}
现在，如果您更改排序顺序，只需将_sortedCountries设置为nil并确保更新UI。它还将创建此列表的任务与loadView必须执行的所有其他操作完全分开。
PS。当你还声明了一个名为sortedCountries的局部变量时，遇到麻烦的那个位。这就是为什么这些编码约定很重要的原因：因为如果你遵循编码约定，那么代码中的问题就很明显了。