1 前言
UITextField用來接受用戶輸入的文本，在開發中十分常見，今天我們來學習一下該控件。

2 代碼實例
ZYViewController.h：


#import <UIKit/UIKit.h> 
 
@interface ZYViewController : UIViewController 
 
@property (nonatomic,strong)UITextField *myTextField; 
 
@end 

#import <UIKit/UIKit.h>

@interface ZYViewController : UIViewController

@property (nonatomic,strong)UITextField *myTextField;

@end
ZYViewController.m：






@synthesize myTextField; 
 
- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view, typically from a nib. 
    self.view.backgroundColor = [UIColor whiteColor]; 
    CGRect textFieldFrame = CGRectMake(0.0f, 0.0f, 200.0f, 31.0f); 
    self.myTextField = [[UITextField alloc] initWithFrame:textFieldFrame];//繪制控件模型 
    self.myTextField.borderStyle = UITextBorderStyleRoundedRect;//設置如何顯示邊框 
    self.myTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;//設置縱向居中 
    self.myTextField.textAlignment = UITextAlignmentCenter;//設置水平居中 
    self.myTextField.text = @"Sir Archy Develop_Zhang";//設置輸入框內容 
    self.myTextField.center = self.view.center;//設置UITextField位置 
    [self.view addSubview:self.myTextField]; 
} 

@synthesize myTextField;

- (void)viewDidLoad
{
    [super viewDidLoad];
 // Do any additional setup after loading the view, typically from a nib.
    self.view.backgroundColor = [UIColor whiteColor];
    CGRect textFieldFrame = CGRectMake(0.0f, 0.0f, 200.0f, 31.0f);
    self.myTextField = [[UITextField alloc] initWithFrame:textFieldFrame];//繪制控件模型
    self.myTextField.borderStyle = UITextBorderStyleRoundedRect;//設置如何顯示邊框
    self.myTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;//設置縱向居中
    self.myTextField.textAlignment = UITextAlignmentCenter;//設置水平居中
    self.myTextField.text = @"Sir Archy Develop_Zhang";//設置輸入框內容
    self.myTextField.center = self.view.center;//設置UITextField位置
    [self.view addSubview:self.myTextField];
}
ZYUITextFieldViewController.h：




#import <UIKit/UIKit.h> 
 
@interface ZYUITextFieldViewController : UIViewController<UITextFieldDelegate> 
 
@property(nonatomic,strong) UITextField *myTextField; 
 
@property(nonatomic,strong) UILabel *labelCounter; 
 
@end 

#import <UIKit/UIKit.h>

@interface ZYUITextFieldViewController : UIViewController<UITextFieldDelegate>

@property(nonatomic,strong) UITextField *myTextField;

@property(nonatomic,strong) UILabel *labelCounter;

@end
ZYUITextFieldViewController.m：


@synthesize myTextField; 
 
@synthesize labelCounter; 
 
- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    // Do any additional setup after loading the view. 
    self.view.backgroundColor = [UIColor whiteColor]; 
    CGRect textFieldFrame = CGRectMake(38.0f, 30.0f, 220.0f, 31.0f); 
    self.myTextField = [[UITextField alloc] initWithFrame:textFieldFrame]; 
    self.myTextField.delegate = self; 
    self.myTextField.borderStyle = UITextBorderStyleRoundedRect; 
    self.myTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter; 
//    self.myTextField.text = @"Sir Archy Developer_Zhang"; 
    self.myTextField.placeholder = @"Enter text here......";//當UITextField裡面沒有字符的時候，默認顯示的內容 
    [self.view addSubview:myTextField]; 
     
    CGRect labelCounterFrame = self.myTextField.frame; 
    labelCounterFrame.origin.y += textFieldFrame.size.height+10; 
    self.labelCounter = [[UILabel alloc] initWithFrame:labelCounterFrame]; 
    [self.view addSubview:labelCounter]; 
    [self calculateAndDisplayTextFieldLengthWithText:self.myTextField.text]; 
     
    UILabel *currencyLabel = [[UILabel alloc] initWithFrame:CGRectZero];//CGRectZero相當於CGRectMake(0,0,0,0) 
    currencyLabel.text = [[[NSNumberFormatter alloc] init] currencySymbol];//初始化Label內容返回接受者的本地貨幣符號 
    currencyLabel.font = self.myTextField.font; 
    [currencyLabel sizeToFit];//調整和移動接收者的視圖,它只是包含它自己的視圖。 
    self.myTextField.leftView = currencyLabel; 
    self.myTextField.leftViewMode = UITextFieldViewModeAlways;//設置左視圖一直顯示 
    /* 
     typedef enum{ 
     UITextFieldViewModeNever,//從不顯示 
     UITextFieldViewModeWhileEditing,//編輯時候顯示 
     UITextFieldViewModeUnlessEditing,//編輯結束時候顯示 
     UITextFieldViewModeAlways//一直顯示 
     }UITextFieldViewMode; 
      
      
     */ 
     
} 
 
//計算UITextField裡面字符的長度 
-(void)calculateAndDisplayTextFieldLengthWithText:(NSString *)paramText{ 
    NSString *characterOrCharacters = @"Characters"; 
    if ([paramText length]==1) { 
        characterOrCharacters = @"Character"; 
    } 
    self.labelCounter.text = [NSString stringWithFormat:@"%lu %@",(unsigned long)[paramText length],characterOrCharacters]; 
} 
 
//當UITextField輸入文字後觸發的事件 
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{ 
    BOOL result = YES; 
    if ([textField isEqual:self.myTextField]) { 
        NSString *wholeText = [textField.text stringByReplacingCharactersInRange:range withString:string];//追加後輸入的字符串 
        [self calculateAndDisplayTextFieldLengthWithText:wholeText];//重新計算字符長度 
    } 
    return result; 
} 
//當單擊返回按鈕觸發的事件 
-(BOOL)textFieldShouldReturn:(UITextField *)textField{ 
    [textField resignFirstResponder];//關閉鍵盤 
    return YES; 
} 

@synthesize myTextField;

@synthesize labelCounter;

- (void)viewDidLoad
{
    [super viewDidLoad];
 // Do any additional setup after loading the view.
    self.view.backgroundColor = [UIColor whiteColor];
    CGRect textFieldFrame = CGRectMake(38.0f, 30.0f, 220.0f, 31.0f);
    self.myTextField = [[UITextField alloc] initWithFrame:textFieldFrame];
    self.myTextField.delegate = self;
    self.myTextField.borderStyle = UITextBorderStyleRoundedRect;
    self.myTextField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;
//    self.myTextField.text = @"Sir Archy Developer_Zhang";
    self.myTextField.placeholder = @"Enter text here......";//當UITextField裡面沒有字符的時候，默認顯示的內容
    [self.view addSubview:myTextField];
   
    CGRect labelCounterFrame = self.myTextField.frame;
    labelCounterFrame.origin.y += textFieldFrame.size.height+10;
    self.labelCounter = [[UILabel alloc] initWithFrame:labelCounterFrame];
    [self.view addSubview:labelCounter];
    [self calculateAndDisplayTextFieldLengthWithText:self.myTextField.text];
   
    UILabel *currencyLabel = [[UILabel alloc] initWithFrame:CGRectZero];//CGRectZero相當於CGRectMake(0,0,0,0)
    currencyLabel.text = [[[NSNumberFormatter alloc] init] currencySymbol];//初始化Label內容返回接受者的本地貨幣符號
    currencyLabel.font = self.myTextField.font;
    [currencyLabel sizeToFit];//調整和移動接收者的視圖,它只是包含它自己的視圖。
    self.myTextField.leftView = currencyLabel;
    self.myTextField.leftViewMode = UITextFieldViewModeAlways;//設置左視圖一直顯示
    /*
     typedef enum{
     UITextFieldViewModeNever,//從不顯示
     UITextFieldViewModeWhileEditing,//編輯時候顯示
     UITextFieldViewModeUnlessEditing,//編輯結束時候顯示
     UITextFieldViewModeAlways//一直顯示
     }UITextFieldViewMode;
    
    
     */
   
}

//計算UITextField裡面字符的長度
-(void)calculateAndDisplayTextFieldLengthWithText:(NSString *)paramText{
    NSString *characterOrCharacters = @"Characters";
    if ([paramText length]==1) {
        characterOrCharacters = @"Character";
    }
    self.labelCounter.text = [NSString stringWithFormat:@"%lu %@",(unsigned long)[paramText length],characterOrCharacters];
}

//當UITextField輸入文字後觸發的事件
-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    BOOL result = YES;
    if ([textField isEqual:self.myTextField]) {
        NSString *wholeText = [textField.text stringByReplacingCharactersInRange:range withString:string];//追加後輸入的字符串
        [self calculateAndDisplayTextFieldLengthWithText:wholeText];//重新計算字符長度
    }
    return result;
}
//當單擊返回按鈕觸發的事件
-(BOOL)textFieldShouldReturn:(UITextField *)textField{
    [textField resignFirstResponder];//關閉鍵盤
    return YES;
}

運行結果：