UITextField 控件丢失委托引用 ID

Question

我正在通过代码（不是 XIB）向 ViewController 添加控件。

Form 有两个 UITextfield 控件，它们在 .h 文件中定义为 IBOutlet

@interface ConditionsViewController : UIViewController <UITabBarDelegate, UITextFieldDelegate,UIPickerViewDelegate,UIPickerViewDataSource>
{
id tfDelegate;  
IBOutlet UITextField *tfOAT;
IBOutlet UITextField *tfWind;
}
- (void) setTextFieldAttributes:(UITextField *)tf;
...

在viewDidLoad中的.m中，UITextField都是init和alloc

    [super viewDidLoad];

    tfDelegate = self;

//create OAT textfield

 frame = CGRectMake( xRightSide-boxWidth*1.5-5, 200, boxWidth*0.75, boxHeight );

        tfOAT = [[UITextField alloc] initWithFrame:frame];
        [tfOAT setFont:font];
        [self setTextFieldAttributes:tfOAT];
        [[self view] addSubview:tfOAT];

NSLog(@"OAT after addSubview is: %@",tfOAT);

//create Wind textfield

 frame = CGRectMake( xRightSide-boxWidth*1.5-5, 400, boxWidth*0.75, boxHeight );

               UITextField *tfWind = [[UITextField alloc] initWithFrame:frame];
               [tfWind setFont:font];
               [self setTextFieldAttributes:tfWind];
               //[tfWind setText:@"1"];
               [[self view] addSubview:tfWind];

NSLog(@"WindField after addSubview is: %@",tfWind);

在视图中会出现

// OAT is returned 

    float t = [pModel OAT];  //t returns 12

    if( t == 0 )
        [tfOAT setText:@""];
    else
        [tfOAT setText:[NSString stringWithFormat:@"%.0f", t]];    


NSLog(@"OAT within viewWillAppear is: %@",tfOAT);   
NSLog(@"OAT text is: %@",tfOAT.text);


// Wind component is returned

    int w = [pModel wind];  //w does return an integer 8

    if(w==0)
        [tfWind setText:@"0"];
    else
        [tfWind setText:[NSString stringWithFormat:@"%d",w]];


NSLog(@"WindField in viewDidAppear: %@",tfWind);
NSLog(@"Windfield text is: %@",tfWind.text);

这里是setTextAttributes函数，没什么特别的。

- (void) setTextFieldAttributes:(UITextField *)tf
{

    tf.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
    tf.borderStyle = UITextBorderStyleRoundedRect;
    [tf setDelegate:self];
    tf.clearsOnBeginEditing = YES;
    [tf setKeyboardType:UIKeyboardTypeNumbersAndPunctuation];
    [tf setReturnKeyType:UIReturnKeyDone];

}

NSLog 会这样打印出来。请注意，对象的指针/引用号为 0x7fccad7219a0 和 0x7fccb041beb0。

//NSLogs within viewDidLoad

OAT after addSubview is: <UITextField: 0x7fccad7219a0; frame = (510.5 200; 71.25 55); text = ''; opaque = NO; layer = <CALayer: 0x60000328f0e0>>

WindField after addSubview is: <UITextField: 0x7fccb041beb0; frame = (510.5 400; 71.25 55); text = ''; opaque = NO; layer = <CALayer: 0x600003284860>>

//NSLogs within viewWillAppear

OAT within viewWillAppear is: <UITextField: 0x7fccad7219a0; frame = (510.5 200; 71.25 55); text = '12'; opaque = NO; tag = 3; layer = <CALayer: 0x60000328f0e0>>

OAT text is:12


WindField within viewDidAppear: (null)
Windfield text is: (null)

请注意，指向 tfWind 的指针或引用在 viewDidLoad 和 viewWillAppear 之间的某处消失了。在 tfWind 对象下的导航器窗口中，条目 _delegate = (id) 0x0 在 vi​​ewWillAppear 中断后出现，但显示了 tfOAT 的参考编号。两个控件仍在屏幕上，但 tfWind 已“断开连接”。

如果我取消注释 //[tfWind setText:@"1"]; viewDidLoad 中的行（重新启动应用程序），我确实让“1”出现在文本字段中。

这是一个真正的谜。有人有任何想法或以前见过吗？

Answer 1

啊……

它“断开连接”的原因是因为您在viewDidLoad() 中创建了一个新变量：

- (void)viewDidLoad {

    [super viewDidLoad];

    // creates a text field object for the class property tfOAT
    tfOAT = [[UITextField alloc] initWithFrame:frame];
    ...

    // creates a NEW LOCAL text field object
    UITextField *tfWind = [[UITextField alloc] initWithFrame:frame];
    ...

    // end of viewDidLoad, the LOCAL tfWind goes out-of-scope
}

看到区别了吗？