最近几年来，地理信息系统无论是在理论上还是应用上都处在一个飞速发展的阶段。 GIS被应用于多个领域的建模和决策支持，如城市管理、区划、环境整治等等，地理信息成为信息时代重要的组成部分之一； “数字地球”概念的提出，更进一步推动了作为其技术支撑的GIS的发展。 与此同时，一些学者致力于相关的理论研究，如空间感知、空间数据误差、空间关系的形式化等等。 这恰好说明了地理信息系统作为应用技术和学科的两个方面，并且这两个方面构成了相互促进的发展过程。
A text field is a user interface element that gets user input through an application.
A UITextfield is as follows:
Properties of important text fields
Displays placeholders when there is no user input
Normal text
Automatic correction type
Keyboard Typ
Returns the key type
Clear button mode
Alignment mode
Entrust
9.9.1. Update properties in xib ¶
You can change the text field properties of xib in the property viewer in Utility area (utility area, on the right side of the window).
9.9.2. Text field delegation ¶
We can set the delegate and connect it to the owner of the file by right-clicking in the UIElement interface generator, as shown below:
To use a delegate:
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:
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
For other delegates, please refer to the UITextDelegate Protocol reference manual.
9.9.3. Example ¶
Let’s use a simple example to create the UI element
The ViewController class will take UITextFieldDelegate and modify the ViewController.h file, as shown below:
Add the method addTextField to our ViewController.m file
Then call this method in the viewDidLoad method
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 Run the application and you will see the following output
The method called by the delegate is based on the user action. To know, refer to the console output when calling the delegate.