iOS选择器（Pickers）
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：
