文本字段的使用

文本字段是一个用户界面元素,通过应用程序来获取用户输入。

一个UITextfield如下所示:

textfeild

重要的文本字段的属性

  • 在没有任何用户输入时,显示占位符
  • 正常文本
  • 自动更正型
  • 键盘类型
  • 返回键类型
  • 清除按钮模式
  • 对齐方式
  • 委托

更新xib中的属性

可以在Utility area(实用区域,窗口的右侧)更改xib在属性查看器中的文本字段属性。

UITextField_Attribute


文本字段委托

我们可以通过右击 UIElement 界面生成器中设置委托并将它连接到文件的所有者,如下所示:

TextfieldDelegate

使用委托的步骤:

  • 1.设置委托如上图所示
  • 2.添加委托到您的响应类
  • 3.执行文本字段代表,重要的文本字段代表如下:
  • - (void)textFieldDidBeginEditing:(UITextField *)textField
    
    - (void)textFieldDidEndEditing:(UITextField *)textField
    
  • 4.正如其名称所暗示,上述两个委托分别叫做编辑的文本字段和结束编辑
  • 5. 其他的委托请查看 UITextDelegate Protocol 参考手册。


实例

以下我们使用简单的实例来创建UI元素

ViewController 类将采用UITextFieldDelegate,修改ViewController.h文件,如下所示:

将方法addTextField添加到我们的 ViewController.m 文件

然后在 viewDidLoad 方法中调用此方法

在ViewController.m中更新viewDidLoad,如下所示

#import "ViewController.h"
@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    //The custom method to create our textfield is called
    [self addTextField];
    // Do any additional setup after loading the view, typically from a nib.
}

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

-(void)addTextField{
   // This allocates a label 
   UILabel *prefixLabel = [[UILabel alloc]initWithFrame:CGRectZero];
   //This sets the label text
   prefixLabel.text =@"## ";
   // This sets the font for the label
   [prefixLabel setFont:[UIFont boldSystemFontOfSize:14]];
   // This fits the frame to size of the text
   [prefixLabel sizeToFit];

   // This allocates the textfield and sets its frame
   UITextField *textField = [[UITextField  alloc] initWithFrame:
   CGRectMake(20, 50, 280, 30)];

   // This sets the border style of the text field 
   textField.borderStyle = UITextBorderStyleRoundedRect;
   textField.contentVerticalAlignment =
   UIControlContentVerticalAlignmentCenter;
   [textField setFont:[UIFont boldSystemFontOfSize:12]];

   //Placeholder text is displayed when no text is typed
   textField.placeholder = @"Simple Text field";

   //Prefix label is set as left view and the text starts after that
   textField.leftView = prefixLabel;

   //It set when the left prefixLabel to be displayed
   textField.leftViewMode = UITextFieldViewModeAlways;

   // Adds the textField to the view.
   [self.view addSubview:textField];

   // sets the delegate to the current class
   textField.delegate = self;
}

// pragma mark is used for easy access of code in Xcode
#pragma mark - TextField Delegates

// This method is called once we click inside the textField
-(void)textFieldDidBeginEditing:(UITextField *)textField{
   NSLog(@"Text field did begin editing");
}

// This method is called once we complete editing
-(void)textFieldDidEndEditing:(UITextField *)textField{
   NSLog(@"Text field ended editing");
}

// This method enables or disables the processing of return key
-(BOOL) textFieldShouldReturn:(UITextField *)textField{    
    [textField resignFirstResponder];
    return YES;
}

- (void)viewDidUnload {
   label = nil;
   [super viewDidUnload];
}

@end

运行该应用程序会看到下面的输出

TextfieldOutput

委托调用的方法基于用户操作。要知道调用委托时请参阅控制台输出。