iOS - 选择器

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  选择器的使用

  选择器由一个旋转的可滚动视图组成，用于从项目列表中选择一个值。
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  重要属性

  • delegate
  • dataSource
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  重要方法

  
  - (void)reloadAllComponents
  - (void)reloadComponent:(NSInteger)component
  - (NSInteger)selectedRowInComponent:(NSInteger)component
  - (void)selectRow:(NSInteger)row inComponent:(NSInteger)component animated:(BOOL)animated
  

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  更新 ViewController.h

  我们将为文本字段、选择器视图和数组添加实例。我们将采用UITextFieldDelegate, UIPickerViewDataSource 和 UIPickerViewDelegate协议。这ViewController.h 如下 -

  
  #import <UIKit/UIKit.h>
  @interface ViewController : UIViewController
     <UITextFieldDelegate, UIPickerViewDataSource, UIPickerViewDelegate> {
     UITextField *myTextField;
     UIPickerView *myPickerView;
     NSArray *pickerArray;
  }
  @end
  

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  添加自定义方法 addPickerView

  
  -(void)addPickerView {
     pickerArray = [[NSArray alloc]initWithObjects:@"Chess", 
     @"Cricket",@"Football",@"Tennis",@"Volleyball", nil];
     myTextField = [[UITextField alloc]initWithFrame:
     CGRectMake(10, 100, 300, 30)];
     myTextField.borderStyle = UITextBorderStyleRoundedRect;
     myTextField.textMoognment = UITextMoognmentCenter;
     myTextField.delegate = self;
     [self.view addSubview:myTextField];
     [myTextField setPlaceholder:@"Pick a Sport"];
     myPickerView = [[UIPickerView alloc]init];
     myPickerView.dataSource = self;
     myPickerView.delegate = self;
     myPickerView.showsSelectionIndicator = YES;
     UIBarButtonItem *doneButton = [[UIBarButtonItem alloc] 
     initWithTitle:@"Done" style:UIBarButtonItemStyleDone 
     target:self action:@selector(done:)];
     UIToolbar *toolBar = [[UIToolbar alloc]initWithFrame:
     CGRectMake(0, self.view.frame.size.height-
     myDatePicker.frame.size.height-50, 320, 50)];
     [toolBar setBarStyle:UIBarStyleBlackOpaque];
     NSArray *toolbarItems = [NSArray arrayWithObjects: 
     doneButton, nil];
     [toolBar setItems:toolbarItems];
     myTextField.inputView = myPickerView;
     myTextField.inputAccessoryView = toolBar;
  }
  

  实现如下所示的代理 -

  
  #pragma mark - Text field delegates
  -(void)textFieldDidBeginEditing:(UITextField *)textField {
     if ([textField.text isEqualToString:@""]) {
        [self dateChanged:nil];
     }
  }
  #pragma mark - Picker View Data source
  -(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
     return 1;
  }
  -(NSInteger)pickerView:(UIPickerView *)pickerView 
     numberOfRowsInComponent:(NSInteger)component {
     return [pickerArray count];
  }
  #pragma mark- Picker View Delegate
  -(void)pickerView:(UIPickerView *)pickerView didSelectRow:
     (NSInteger)row inComponent:(NSInteger)component {
     [myTextField setText:[pickerArray objectAtIndex:row]];
  }
  - (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:
     (NSInteger)row forComponent:(NSInteger)component {
     return [pickerArray objectAtIndex:row];
  }
  

  更新 viewDidLoad 在 ViewController.m 如下 -

  
  (void)viewDidLoad {
     [super viewDidLoad];
     [self addPickerView];
  }
  

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  输出

  当我们运行应用程序时，我们将获得以下输出 -

  

  在选择文本字段时，选择器视图将显示如下所示，我们可以在其中选择我们的选择 -