我的iOS入门第二课

简介

承上一篇我的iOS入门第一课，本次要记录的是一年前读raywenderlich的基本教程的第二个app，Checklists.主要功能是用来记录个人的一些提醒事项。如下：

主要界面.png

下面主要讲我学到了什么：

一、基本控件
UITableView, UITableView, UITableView!

重点知识：

• 导航控制器的概念 UINavigationController
• 控制器之间的消息回传 delegate
• UITableView的delegate、dataSource
• 操作tableView的cell，删除cell，增加cell
  • 删除cell要做两件事情，一是删除数据，二是删除tableView上的cell

 -(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
   [self.dataModel.lists removeObjectAtIndex:indexPath.row];
   
   [self.tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:(UITableViewRowAnimationAutomatic)];
}

• 动态增加cell，用storyboard的话首先要把tableViewCell布局放好，然后在控制器创建引用，接着就可以用代码操作cell了

在storyboard布局一个隐藏的cell.png

@property (weak, nonatomic) IBOutlet UITableViewCell *datePickerCell;

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    if (section == 1 && _datePickerVisible) {
        return 3;
    }else {
        return [super tableView:tableView numberOfRowsInSection:section];
    }
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    if (indexPath.section == 1 && indexPath.row == 2) {
        return self.datePickerCell;
    }else {
        return [super tableView:tableView cellForRowAtIndexPath:indexPath];
    }
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
    if (indexPath.section == 1 && indexPath.row == 2) {
        return 217;
    }else {
        return [super tableView:tableView heightForRowAtIndexPath:indexPath];
    }
}
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [self.textField resignFirstResponder];
    
    if (indexPath.section == 1 && indexPath.row == 1) {
        if (!self.datePickerVisible) {
            [self showDatePicker];
        }else {
            [self hideDatePicker];
        }
    }
}
- (NSInteger)tableView:(UITableView *)tableView indentationLevelForRowAtIndexPath:(NSIndexPath *)indexPath {
    if (indexPath.section == 1 && indexPath.row == 2) {
        indexPath = [NSIndexPath indexPathForRow:0 inSection:indexPath.section];
    }
    return [super tableView:tableView indentationLevelForRowAtIndexPath:indexPath];
}
- (void)showDatePicker {
    self.datePickerVisible = YES;
    
    NSIndexPath *indexPathDateRow = [NSIndexPath indexPathForRow:1 inSection:1];
    NSIndexPath *indexPathDatePicker = [NSIndexPath indexPathForRow:2 inSection:1];
    
    UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPathDateRow];
    cell.detailTextLabel.textColor = cell.detailTextLabel.tintColor;
    
    [self.tableView beginUpdates];
    [self.tableView insertRowsAtIndexPaths:@[indexPathDatePicker] withRowAnimation:(UITableViewRowAnimationFade)];
    [self.tableView reloadRowsAtIndexPaths:@[indexPathDateRow] withRowAnimation:(UITableViewRowAnimationNone)];
    [self.tableView endUpdates];
    
    [self.datePicker setDate:self.dueDate animated:NO];
}
- (void)hideDatePicker {
    if (self.datePickerVisible) {
        self.datePickerVisible = NO;
        
        NSIndexPath *indexPathDateRow = [NSIndexPath indexPathForRow:1 inSection:1];
        NSIndexPath *indexPathDatePicker = [NSIndexPath indexPathForRow:2 inSection:1];
        
        UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPathDateRow];
        cell.detailTextLabel.textColor = [[UIColor alloc] initWithWhite:0 alpha:0.5];
        
        [self.tableView beginUpdates];
        [self.tableView reloadRowsAtIndexPaths:@[indexPathDateRow] withRowAnimation:(UITableViewRowAnimationNone)];
        [self.tableView deleteRowsAtIndexPaths:@[indexPathDatePicker] withRowAnimation:(UITableViewRowAnimationFade)];
        [self.tableView endUpdates];
    }
}

不得不说动态增加一个cell需要做很多事情。。。

• textField的delegate, 当用户有输入时把done按钮变为可用

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    NSString *oldString = textField.text;
    NSString *newString = [oldString stringByReplacingCharactersInRange:range withString:string];
    self.doneBarButton.enabled = newString.length > 0;
    
    return YES;
}

• 本地通知UILocalNotification
  • 第一次时需要获取本地通知权限

UIUserNotificationSettings *setting = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeSound | UIUserNotificationTypeAlert categories:nil];
        [[UIApplication sharedApplication] registerUserNotificationSettings:setting];

• 设置本地通知

-(void)scheduleNotification {
    UILocalNotification *existingNotification = [self notificationForThisItem];
    if (existingNotification) {
        [[UIApplication sharedApplication] cancelLocalNotification:existingNotification];
    }
    
    if (_shouldRemind && [_dueDate compare:[NSDate new]] != NSOrderedAscending ) {
        UILocalNotification *notification = [UILocalNotification new];
        notification.fireDate = _dueDate;
        notification.timeZone = [NSTimeZone defaultTimeZone];
        notification.alertBody = _text;
        notification.soundName = UILocalNotificationDefaultSoundName;
        notification.userInfo = @{@"ItemID": @(_itemID)};
        
        [[UIApplication sharedApplication] scheduleLocalNotification:notification];
    }
}
-(UILocalNotification *)notificationForThisItem {
    NSArray *notifications = [UIApplication sharedApplication].scheduledLocalNotifications;
    for (UILocalNotification *notification in notifications) {
        NSInteger itemID = (NSInteger)notification.userInfo[@"ItemID"];
        if (itemID == self.itemID) {
            return notification;
        }
    }
    return nil;
}

• 发通知的对象销毁时取消通知

-(void)dealloc {
    if ([self notificationForThisItem]) {
        [[UIApplication sharedApplication] cancelLocalNotification:[self notificationForThisItem]];
    }
}

• 本地存储，使用对象归档为plist文件做本地存储
  • 必须给模型实现NSCoding协议，实现两个方法

 -(instancetype)initWithCoder:(NSCoder *)aDecoder {
    if (self = [super init]) {
        _name = [aDecoder decodeObjectForKey:@"Name"];
        _iconName = [aDecoder decodeObjectForKey:@"IconName"];
        _items = [aDecoder decodeObjectForKey:@"Items"];
    }
    return self;
}
-(void)encodeWithCoder:(NSCoder *)aCoder {
    [aCoder encodeObject:_name forKey:@"Name"];
    [aCoder encodeObject:_iconName forKey:@"IconName"];
    [aCoder encodeObject:_items forKey:@"Items"];
}

• 归档到Document文件夹中

-(void)saveChecklists {
    NSMutableData *data = [NSMutableData data];
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
    [archiver encodeObject:_lists forKey:@"Checklists"];
    [archiver finishEncoding];
    [data writeToFile:[self dataFilePath] atomically:YES];
}
-(NSString *)documentsDirectory {
    return [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
}
-(NSString *)dataFilePath {
    return [[self documentsDirectory] stringByAppendingPathComponent:@"Checklists.plist"];
}

• 程序重新启动时在init方法调用loadChecklists初始化模型加载本地数据

-(void)loadChecklists {
    NSString *path = [self dataFilePath];
    if ([[NSFileManager defaultManager] fileExistsAtPath:path]) {
        NSData *data = [NSData dataWithContentsOfFile:path];
        NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
        _lists = [unarchiver decodeObjectForKey:@"Checklists"];
        [unarchiver finishDecoding];
        [self sortChecklists]; //排序
    }
}

• 在AppDelegate中初始化DataModel, 并在代理方法中保存数据

-(void)applicationDidEnterBackground:(UIApplication *)application {    
    [self saveData];
}
-(void)applicationWillTerminate:(UIApplication *)application {
    [self saveData];
}
-(void)saveData {
    [self.dataModel saveChecklists];
}

总结

此app设计的目的只有一个，就是熟悉tableView的操作，在往后开发的任何一个app里都离不开这个最基本的控件，但现实开发中更多涉及到的是处理动态cell，与xib组合，不同的cell和内容，tableView的header和footer,下拉刷新，如何优化tableView，动态计算cell的高度，MVVM等。革命尚未完成，同志仍需努力。
源代码传送门

卧薪藏胆，三千越甲可吞吴。