图片异步加载、KVO

图片异步加载

#import "RootTableViewController.h"
#import "MyTableViewCell.h"
#import "Activity.h"
#import "UIImageView+WebCache.h" //SD中的图片异步加载

@interface RootTableViewController ()

@property(nonatomic,strong)NSMutableArray *dataArr;

@end

@implementation RootTableViewController

- (void)viewDidLoad {
    [super viewDidLoad];
   
    [self.tableView registerClass:[MyTableViewCell class] forCellReuseIdentifier:@"cell"];
    self.tableView.separatorStyle = UITableViewCellSeparatorStyleNone;
   
    [self handleData];

}

- (void)handleData{
    self.dataArr = [NSMutableArray array];
    // 准备URL
    NSURL *url = [NSURL URLWithString:@"http://project.lanou3g.com/teacher/yihuiyun/lanouproject/activitylist.php"];
    // 准备请求
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
   
    // 异步请求
    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
        NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil];
        NSArray *arr = [dict objectForKey:@"events"];
        for (NSDictionary *d in arr) {
            Activity *activity = [[Activity alloc]init];
            [activity setValuesForKeysWithDictionary:d];
            [self.dataArr addObject:activity];
            // 刷新数据
            [self.tableView reloadData];
        }
    }];
}



#pragma mark - Table view data source
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    return self.dataArr.count;
}


- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    MyTableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cell" forIndexPath:indexPath];
    cell.activityImage.image = [UIImage imageNamed:@"picholder"];
    cell.activityLabel.text = @"aaa";
    Activity *activity  = [self.dataArr objectAtIndex:indexPath.row];
    cell.activityLabel.text = activity.title;
   
    // 请求图片
    NSURL *url = [NSURL URLWithString:activity.image];
//    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
//[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
//    cell.activityImage.image = [UIImage imageWithData:data];
//}];
   
    // 使用第三方 SDWebImage去实现异步加载
    [cell.activityImage sd_setImageWithURL:url];
    return cell;
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath{
    return [MyTableViewCell heightForCell];
}

KVO

#import "RootViewController.h"
#import "Student.h"

@interface RootViewController ()

@property(nonatomic,strong)UIButton *button;

@property(nonatomic,strong)Student *s;

@end

@implementation RootViewController

 // KVO 键值观察者  他是一种观察者的设计模式  他可以用来检测Model类对象中属性值如果有变化,可以在观察者方法里面做相应处理...

// 由于kvc的设计模式,是由Controller去控制model和View

// model和view 是不直接产生通信的,,但是有了KVO机制  让Controller作为观察者,实现观察者的回调方法,如果model的属性值发生了改变,view也可以做出相应的变化

- (void)viewDidLoad {
    [super viewDidLoad];
   
    self.button = [UIButton buttonWithType:UIButtonTypeSystem];
    self.button.frame = CGRectMake(100, 100, 100, 100);
    [self.button setTitle:@"KVO改值" forState:UIControlStateNormal];
    [self.view addSubview:self.button];
   
    [self.button addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
   
    self.s = [[Student alloc]init];
    self.s.name = @"小明";
    self.s.gender = @"男";
   
    // 添加观察者   
    [self.s addObserver:self forKeyPath:@"gender" options:NSKeyValueObservingOptionNew context:nil];

}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"name改变" message:nil delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles: nil];
    [alert show];
    [self.s removeObserver:self forKeyPath:@"gender"];
}

- (void)buttonAction:(UIButton *)sender{
    self.s.name = @"小红";
    self.s.gender = @"男";
}