XCode:当用户点击UITextbox时显示UIDatePicker

Question

我已经研究了这个话题死亡,发现有人发帖对一些网站,包括权完全一样的问题,这里的计算器.

我已经尝试了所有的建议但是无法让UIDatePicker实际显示.我采取什么方法似乎并不重要.我尝试使用继承模型,我继承UITextBox控件并覆盖它的默认方法以显示UIDatePicker然后我确保在StoryBoard中我将我的UITextView控件的类设置为该自定义类.我已尝试以编程方式生成UIDatePicker,并尝试将其拖到StoryBoard中的视图上.当我尝试编程方法时,没有显示任何内容,当我尝试将其拖到StoryBoard上时,它总是会显示.当我将它的属性设置为"隐藏"时,它会隐藏但是当我尝试将代码添加到textboxDidBeginEditing应取消隐藏的方法时,我无法显示它.我确保将UITextView的inputView属性设置为等于我的UIDatePicker控件.

什么都行不通!我不明白为什么Apple不只是将UIDatePicker作为UITextView控件的Attributes Inspector下拉列表中的默认选项之一.这会让这更容易.

下面是我的实现类文件中的一些代码.

#import "AddTasksViewController.h"

@implementation AddTasksViewController

@synthesize dueDate;
@synthesize description;
@synthesize shortTitle;
@synthesize datePicker;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
        self.dueDate.inputView = datePicker;

    }
    return self;
}

- (IBAction)dueDateDidBeginEditing:(UITextView *)textField 
{  
    [textField resignFirstResponder];
    [datePicker setFrame:CGRectMake(0,200,320,120)];
    [datePicker addTarget:self action:@selector(done) forControlEvents:UIControlEventValueChanged];
    [self.view addSubview:datePicker];
}

这是我的头文件的样子......

#import <UIKit/UIKit.h>

@interface AddTasksViewController : UIViewController

@property (nonatomic, copy) IBOutlet UITextView      *dueDate;
@property (nonatomic, copy) IBOutlet UITextView      *description;
@property (nonatomic, copy) IBOutlet UITextView      *shortTitle;
@property (nonatomic, retain) IBOutlet UIDatePicker    *datePicker;

- (IBAction)doneEditing:(id)sender;
- (IBAction)dateChanged:(id)sender;
- (IBAction)dueDateDidBeginEditing:(UITextView *)textField;

@end

正如我已经提到的,我采用的另一种方法(即子类化UITextView)也不起作用.我完全复制了这里提供的代码.然后我将名为"DateField"的自定义类添加到我的项目(标题和实现文件)中,然后在我的AddTaskViewController.h和AddTaskViewController.m文件中用DateField替换dueDate的UITextBox声明,并确保StoryBoard引用通过在Identity Inspector中为控件的类选择DateField来更新.

无论我做什么,我都无法在点击UITextView时显示UIDatePicker.当我设置一个断点时,它确实击中了dueDateDidBeginEditing方法,因此我知道某些东西正在被触发.问题是我不明白为什么没有使用UIDatePicker显示subView.

任何帮助都会受到高度赞赏,因为这个看似简单的任务似乎需要花费很多时间.我可以做这种事情,闭着眼睛,双手绑在我的背后用Java和C#,但是当谈到Objective-C时,一切都是如此不必要的复杂.语法真的让我很恼火.

这么多方括号!!! Arghhhh!

Answer 1

呈现出UIDatePicker了inputView一个UITextField比较硬比较显示键盘,但比起你们有过的麻烦相对容易.

我注意到你的代码中遇到的第一个问题之一是,对于那些刚接触iOS/Mac开发的人来说,这是一个非常常见的问题,就是你试图设置一个尚不存在的对象的属性.由于视图尚未加载,因此self.dueDate.inputView = datePicker;在您的文档中放置" " initWithNibName:bundle:将无效,并且dueDate是您视图的一部分.在objective-c中,使用alloc&init实例化一个对象.Init是对任何对象的第一个实际方法调用.此时,在视图控制器的生命周期中,尚未创建视图.方法调用where self.dueDate.inputView = datePicker;属于viewDidLoad方法.当它听起来像是被调用的时候dueDate就会被调用,并且你的属性将在那时被正确加载.无需使用自定义子类UITextField来显示文本字段的日期选择视图.以下是自定义输入视图类的一个非常基本的示例:

ExampleBasicDateInputView.h:

#import <UIKit/UIKit.h>

@interface ExampleBasicDateInputView : UIView
@property (strong,nonatomic) UIDatePicker *datePicker;
@end

ExampleBasicDateInputView.m:

#import "ExampleBasicDateInputView.h"

@implementation ExampleBasicDateInputView{
    UITextField *_inputField; // ivar to store the textfield currently being edited
}
@synthesize datePicker = _datePicker;
// TARGET METHODS
-(void)pickerValueChanged:(UIDatePicker *)picker{
    _inputField.text = self.datePicker.date.description; // set text to date description
}
-(void)viewDoubleTapped:(UITapGestureRecognizer *)tapGR{
    [_inputField resignFirstResponder]; // upon double-tap dismiss picker
}
-(void)textFieldBeganEditing:(NSNotification *)note{
    _inputField = note.object; // set ivar to current first responder
}
-(void)textFieldEndedEditing:(NSNotification *)note{
    _inputField = nil; // the first responder ended editing CRITICAL:avoids retain cycle
}
// INITI METHODS
-(void)initializationCodeMethod{
    _datePicker = [[UIDatePicker alloc] initWithFrame:CGRectMake(0, 0, 320, 0)];// All pickers have preset height
    self.bounds = _datePicker.frame; // Make our view same size as picker
    [self addSubview:_datePicker];
    [_datePicker addTarget:self action:@selector(pickerValueChanged:) forControlEvents:UIControlEventValueChanged]; // register to be notified when the value changes
        // As an example we'll use a tap gesture recognizer to dismiss on a double-tap
    UITapGestureRecognizer *tapGR = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(viewDoubleTapped:)];
    tapGR.numberOfTapsRequired = 2; // Limit to double-taps
    [self addGestureRecognizer:tapGR];
    NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
    [center addObserver:self selector:@selector(textFieldBeganEditing:) name:UITextFieldTextDidBeginEditingNotification object:nil]; // Ask to be informed when any textfield begins editing
    [center addObserver:self selector:@selector(textFieldEndedEditing:) name:UITextFieldTextDidEndEditingNotification object:nil]; // Ask to be informed when any textfield ends editing
}
-(id)init{
    if ((self = [super init])){
        [self initializationCodeMethod];
    }
    return self;
}
-(id)initWithFrame:(CGRect)frame{
    if ((self = [super initWithFrame:frame])){
        [self initializationCodeMethod];
    }
    return self;
}
-(id)initWithCoder:(NSCoder *)aDecoder{
    if ((self = [super initWithCoder:aDecoder])){
        [self initializationCodeMethod];
    }
    return self;
}
-(void)dealloc{
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UITextFieldTextDidBeginEditingNotification object:nil];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UITextFieldTextDidEndEditingNotification object:nil];
}
@end

然后在视图中加载你将使用这样的类:

ExampleBasicDateInputView *dateEntryView = [[ExampleBasicDateInputView alloc] init];
self.dueDate.inputView = datePickerView;

正如您在.h文件中看到的那样,我们已将日期选择器实例公开为属性,因此您可以设置样式.等等:

dateEntryView.datePicker.datePickerMode = UIDatePickerModeDate;

显然这是一个非常基本的例子,但我认为它显示了可以做的事情.

Answer 2

我使用Storyboard时遇到了同样的问题.以下是我如何解决它:

概述:我在viewDidLoad中分配并初始化我的UIDatePicker属性:然后我将textfield的inputView属性设置为我的datepicker属性.

这是我的代码:在TripViewController.h中:

@property (nonatomic,strong) IBOutlet UIDatePicker *datePicker;

在TripViewController.m中:

@synthesize datePicker;
...
-(void)viewDidLoad {
...
self.datePicker = [[UIDatePicker alloc]init];
[self.datePicker addTarget:self action:@selector(dateChanged) forControlEvents:UIControlEventValueChanged];
self.dateField.inputView = self.datePicker;
}

然后我实现我的方法dateChanged,这样每当日期选择器轮停止移动时,我的文本字段就会更新.

- (void)dateChanged
{
NSDate *date = self.datePicker.date;
NSDateFormatter *dateFormat = [[NSDateFormatter alloc]init];
[dateFormat setDateStyle:NSDateFormatterMediumStyle];
self.dateField.text = [dateFormat stringFromDate:date];
}