导航控制器与表格视图中的详细视图控制器实现

### 导航控制器与表格视图中的详细视图控制器实现 在开发过程中，导航控制器和表格视图是常见的组件。本文将详细介绍如何实现一个用于编辑总统信息的详细视图控制器。 #### 1. 视图即将出现时的操作 在视图即将出现时，我们需要重新加载表格数据，以确保显示的是最新信息。代码如下： ```objc - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; [self.tableView reloadData]; } ``` #### 2. 创建详细视图控制器 当用户点击 `BIDPresidentsViewController` 表格中的某一行时，会将一个新的控制器推送到导航栈上，以便为该总统进行数据录入。下面是创建详细视图控制器的步骤。 ##### 2.1 修改头文件 `BIDPresidentDetailController.h` ```objc #import <UIKit/UIKit.h> @class BIDPresident; #define kNumberOfEditableRows 4 #define kNameRowIndex 0 #define kFromYearRowIndex 1 #define kToYearRowIndex 2 #define kPartyIndex 3 #define kLabelTag 4096 @interface BIDPresidentDetailController : UITableViewController <UITextFieldDelegate> @property (strong, nonatomic) BIDPresident *president; @property (strong, nonatomic) NSArray *fieldLabels; @property (strong, nonatomic) NSMutableDictionary *tempValues; @property (strong, nonatomic) UITextField *currentTextField; - (IBAction)cancel:(id)sender; - (IBAction)save:(id)sender; - (IBAction)textFieldDone:(id)sender; @end ``` 这里定义了一些常量，用于表示可编辑的行数、每行对应的索引以及标签的 `tag` 值。该类遵循了 `UITextFieldDelegate` 协议，以便在用户对文本字段进行更改时得到通知并保存字段的值。 各属性的作用如下： - `president`：指向要编辑的 `BIDPresident` 对象。 - `fieldLabels`：包含与各索引对应的标签数组。 - `tempValues`：用于临时存储用户更改的值，避免直接修改 `president` 对象，方便处理取消操作。 - `currentTextField`：指向当前正在编辑的文本字段，解决保存和取消操作时的数据保存问题。 ##### 2.2 修改实现文件 `BIDPresidentDetailController.m` ```objc #import "BIDPresidentDetailController.h" #import "BIDPresident.h" @implementation BIDPresidentDetailController @synthesize president; @synthesize fieldLabels; @synthesize tempValues; @synthesize currentTextField; - (IBAction)cancel:(id)sender { [self.navigationController popViewControllerAnimated:YES]; } - (IBAction)save:(id)sender { if (currentTextField != nil) { NSNumber *tagAsNum = [NSNumber numberWithInt:currentTextField.tag]; [tempValues setObject:currentTextField.text forKey:tagAsNum]; } for (NSNumber *key in [tempValues allKeys]) { switch ([key intValue]) { case kNameRowIndex: president.name = [tempValues objectForKey:key]; break; case kFromYearRowIndex: president.fromYear = [tempValues objectForKey:key]; break; case kToYearRowIndex: president.toYear = [tempValues objectForKey:key]; break; case kPartyIndex: president.party = [tempValues objectForKey:key]; default: break; } } [self.navigationController popViewControllerAnimated:YES]; NSArray *allControllers = self.navigationController.viewControllers; UITableViewController *parent = [allControllers lastObject]; [parent.tableView reloadData]; } - (IBAction)textFieldDone:(id)sender { [sender resignFirstResponder]; } #pragma mark - - (void)viewDidLoad { [super viewDidLoad]; NSArray *array = [[NSArray alloc] initWithObjects:@"Name:", @"From:", @"To:", @"Party:", nil]; self.fieldLabels = array; UIBarButtonItem *cancelButton = [[UIBarButtonItem alloc] initWithTitle:@"Cancel" style:UIBarButtonItemStylePlain target:self action:@selector(cancel:)]; self.navigationItem.leftBarButtonItem = cancelButton; UIBarButtonItem *saveButton = [[UIBarButtonItem alloc] initWithTitle:@"Save" style:UIBarButtonItemStyleDone target:self action:@selector(save:)]; self.navigationItem.rightBarButtonItem = saveButton; NSMutableDictionary *dict = [[NSMutableDictionary alloc] init]; self.tempValues = dict; } #pragma mark - #pragma mark Table Data Source Methods - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return kNumberOfEditableRows; } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *PresidentCellIdentifier = @"PresidentCellIdentifier"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier: PresidentCellIdentifier]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:PresidentCellIdentifier]; UILabel *label = [[UILabel alloc] initWithFrame: CGRectMake(10, 10, 75, 25)]; label.textAlignment = UITextAlignmentRight; label.tag = kLabelTag; label.font = [UIFont boldSystemFontOfSize:14]; [cell.contentView addSubview:label]; UITextField *textField = [[UITextField alloc] initWithFrame: CGRectMake(90, 12, 200, 25)]; textField.clearsOnBeginEditing = NO; [textField setDelegate:self]; textField.returnKeyType = UIReturnKeyDone; [textField addTarget:self action:@selector(textFieldDone:) forControlEvents:UIControlEventEditingDidEndOnExit]; [cell.contentView addSubview:textField]; } NSUInteger row = [indexPath row]; UILabel *label = (UILabel *)[cell viewWithTag:kLabelTag]; UITextField *textField = nil; for (UIView *oneView in cell.contentView.subviews) { if ([oneView isMemberOfClass:[UITextField class]]) textField = (UIText ```