选择器的使用

选择器是一个可滚动视图，用于选取列表项中的值。

重要的属性

• delegate
• dataSource

重要的方法

- (void)reloadAllComponents

- (void)reloadComponent:(NSInteger)component

- (NSInteger)selectedRowInComponent:(NSInteger)component

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

修改 ViewController.h

我们将添加一个文本字段、选择器视图和一个数组。

我们将采用UITextFieldDelegate、UIPickerViewDataSource、UIPickerViewDelegate的协议。ViewController.h文件代码如下所示：

#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-    myPickerView.frame.size.height-50, 320, 50)];    [toolBar setBarStyle:UIBarStyleBlackOpaque];    NSArray *toolbarItems = [NSArray arrayWithObjects:     doneButton, nil];    [toolBar setItems:toolbarItems];    myTextField.inputView = myPickerView;    myTextField.inputAccessoryView = toolBar;}

执行委托，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];}

在ViewController.m修改viewDidLoad，如下所示:

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

输出

现在当我们运行该应用程序我们会看到下面的输出:

文本选择器视图如下所示，我们可以选取我们需要的值：