iOS - 选择器

选择器的使用

选择器由一个可旋转的可滚动视图组成，用于从项目列表中选择一个值。

重要属性

• delegate
• dataSource

重要方法

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

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。 ViewController.h 如下 −

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController
   <UITextFieldDelegate, UIPickerViewDataSource, UIPickerViewDelegate> {
   UITextField *myTextField;
   UIPickerView *myPickerView;
   NSArray *pickerArray;
}
@end

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.textAlignment = UITextAlignmentCenter;
   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;
}

实现委托，如下所示 −

#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 ViewController.m 中的 viewDidLoad 如下 −

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

输出

当我们运行应用程序时，我们会得到以下输出 −

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

❮ iOS - UI 元素