IOS 6下拉刷新

苹果在IOS 6 API中加入了下拉刷新控件；并且IOS 6之后，UITableViewController中增加了一个refreshControl属性，这个属性保持了UIRefreshControl的一个对象指针。UIRefreshControl是IOS 6为表视图实现下拉刷新而提供的类，目前该类只应用于表视图界面。UIRefreshControl的refreshControl属性与UITableViewController配合使用，关于下拉刷新布局等问题可以不必考虑，UITableViewController会将其自动放入表视图中。

下面是一个简单的下拉刷新实现：

//  ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UITableViewController

@property (strong,nonatomic) NSMutableArray *data;

@end

//  ViewController.m

#import "ViewController.h"

@interface ViewController ()
{
    NSDateFormatter *dateFormater;
}
@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
	
    dateFormater=[[NSDateFormatter alloc] init];
    [dateFormater setDateFormat:@"yyyy-MM-dd HH:mm:ss zzz"];
    
    self.data=[NSMutableArray arrayWithObject:[[NSDate alloc] init]];
    //UIRefreshControl
    UIRefreshControl *refreshCtrl=[[UIRefreshControl alloc] init];
    //The styled title text to display in the refresh control.
    refreshCtrl.attributedTitle=[[NSAttributedString alloc] initWithString:@"下拉刷新"];
    //A touch dragging or otherwise manipulating a control, causing it to emit a series of different values.
    [refreshCtrl addTarget:self action:@selector(refresh) forControlEvents:UIControlEventValueChanged];
    self.refreshControl=refreshCtrl;
}

-(void) refresh
{
    //A Boolean value indicating whether a refresh operation has been triggered and is in progress. (read-only)
    if(self.refreshControl.refreshing){
        self.refreshControl.attributedTitle=[[NSAttributedString alloc] initWithString:@"正在加载..."];
        NSDate *date=[[NSDate alloc] init];
        [self performSelector:@selector(finishLoad:) withObject:date afterDelay:5];
    }
}

-(void) finishLoad:(id) obj
{
    [self.refreshControl endRefreshing];
    self.refreshControl.attributedTitle=[[NSAttributedString alloc] initWithString:@"下拉刷新"];
    [self.data addObject:obj];
    [self.tableView reloadData];
}

-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return [self.data count];
}

-(UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *cellIdentifier=@"cell";
    UITableViewCell *cell=[tableView dequeueReusableCellWithIdentifier:cellIdentifier];
    if(!cell){
        cell=[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIdentifier];
    }
    cell.textLabel.text=[dateFormater stringFromDate:[self.data objectAtIndex:indexPath.row]];
    cell.accessoryType=UITableViewCellAccessoryDisclosureIndicator;
    return cell;
}

-(void)didReceiveMemoryWarning
{
    dateFormater=nil;
    self.refreshControl=nil;
    [self.data removeAllObjects];
    self.data=nil;
}

@end