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我正在使用下面的代码用数据填充表格视图，它也被填充，但问题是在滚动表格视图时它会挂起，并且在一段时间后它会滚动一小段距离。.h 文件是

#import <UIKit/UIKit.h>
#import "JSON.h"
@interface HomeViewController : UIViewController <UITabBarControllerDelegate,UINavigationControllerDelegate,UIActionSheetDelegate,UIImagePickerControllerDelegate>

@property (strong, nonatomic) IBOutlet UINavigationBar *navigationBar;
@property (strong,nonatomic) IBOutlet UITableView *homeProfileTableview;
@property (nonatomic ,retain) UIImageView *clockImage;
@property (nonatomic,strong) UIImageView *ItemImage;
@property (nonatomic,strong) UIImageView *locationImage;
@property (nonatomic, retain) NSArray *Tableata;

@end

.m 文件

#import "HomeViewController.h"
#import "CameraViewController.h"
#import "JSON.h"
#import "SBJsonParser.h"

@interface HomeViewController ()

@end

@implementation HomeViewController
@synthesize homeProfileTableview,clockImage,Tableata,ItemImage,locationImage;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.tabBarController.delegate=self;
    [self.navigationBar setBackgroundImage:[UIImage imageNamed:@"yellow_bar.png"] forBarMetrics:UIBarMetricsDefault];
    [self.navigationBar setTitleTextAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[UIColor colorWithRed:0.0/255.0 green:0.0/255.0 blue:0.0/255.0 alpha:1.0], UITextAttributeTextColor,[UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0], UITextAttributeTextShadowColor,[NSValue valueWithUIOffset:UIOffsetMake(0, 1)], UITextAttributeTextShadowOffset,[UIFont fontWithName:@"Georgia-BoldItalic" size:25.0], UITextAttributeFont,nil]];

    UIImage *image = [UIImage imageNamed:@"refresh.png"];
    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    [button setBackgroundImage:image forState:UIControlStateNormal];
    button.frame = CGRectMake(0.0, 0.0, image.size.width, image.size.height);
    [button addTarget:self action:@selector(refreshButtonTapped) forControlEvents:UIControlEventTouchUpInside];
    UIView *buttonView = [[UIView alloc] initWithFrame:CGRectMake(0.0, 0.0, image.size.width, image.size.height)];
    [buttonView addSubview:button];
    UIBarButtonItem *backItem = [[UIBarButtonItem alloc] initWithCustomView:buttonView];
    [self.navigationBar.topItem setRightBarButtonItem:backItem];


//    NSString *jsonString = [NSString
//                            stringWithContentsOfURL:[NSURL URLWithString:@"http://izisstechnology.com/garage/index.php?method=login&username=ashu&password=1234"]
//                            encoding:NSStringEncodingConversionAllowLossy
//                            error:nil];
    NSString *jsonString = [NSString
                            stringWithContentsOfURL:[NSURL URLWithString:@"http://izisstechnology.com/garage/index.php?method=home&start=0"]
                            encoding:NSStringEncodingConversionAllowLossy
                            error:nil];

    SBJsonParser *parser=[[SBJsonParser alloc]init];

    NSDictionary *results=[parser objectWithString:jsonString ];

    //NSDictionary *results = [parser objectWithString:jsonString error:nil];
    //[parser release], parser = nil;
    NSLog(@"%@",results);
    // Set tableData
    [self setTableata:[results objectForKey:@"new"]];
    [super viewDidLoad];

}
- (void)refreshButtonTapped {

}
- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{

    // Return the number of sections.
    return 1;
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    return [Tableata count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"homeProfileTableIdentifier";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil) {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] ;
    }
    NSDictionary *item = [Tableata objectAtIndex:[indexPath row]];
    NSURL *url = [NSURL URLWithString:[item objectForKey:@"seller_image"]];


    NSData *data = [[NSData alloc] initWithContentsOfURL:url];
    UIImage *image = [[UIImage alloc] initWithData:data];


    //clock image
    CGRect imageFrame = CGRectMake(240,10, 20, 20);
    self.clockImage = [[UIImageView alloc] initWithFrame:imageFrame];    
    self.clockImage.image = [UIImage imageNamed:@"clock.jpg"];    
    [cell.contentView addSubview:self.clockImage];


    //location image
    CGRect imageFrame1 = CGRectMake(80,20, 20, 20);
    self.locationImage = [[UIImageView alloc] initWithFrame:imageFrame1];
    self.locationImage.image = [UIImage imageNamed:@"location.jpg"];
    [cell.contentView addSubview:self.locationImage];


    //username
    UILabel *username=[[UILabel alloc] initWithFrame:CGRectMake(80,0, 70, 20)];
    username.text=[item objectForKey:@"seller_name"];
    UIFont *myFont = [ UIFont fontWithName: @"futura" size: 18.0 ];
    username.font  = myFont;
    [cell.contentView addSubview:username];

    //user location
    UILabel *userlocation=[[UILabel alloc] initWithFrame:CGRectMake(100,20, 70, 20)];
    userlocation.text=[item objectForKey:@"prod_country"];
    UIFont *myFont2 = [ UIFont fontWithName: @"futura" size: 18.0 ];
    userlocation.font  = myFont2;
    [cell.contentView addSubview:userlocation];

    //item image
    NSURL *url1 = [NSURL URLWithString:[item objectForKey:@"item_image1"]];


    NSData *data1 = [[NSData alloc] initWithContentsOfURL:url1];
    UIImage *image1 = [[UIImage alloc] initWithData:data1];
    CGRect imageFrame2 = CGRectMake(20,40, 280, 320);
    self.ItemImage = [[UIImageView alloc] initWithFrame:imageFrame2] ;

    self.ItemImage.image = image1;

    [cell.contentView addSubview:self.ItemImage];



    UIButton *playButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    playButton.frame = CGRectMake(20, 5, 30, 30);
    [playButton setTitle:@"" forState:UIControlStateNormal];
    playButton.backgroundColor = [UIColor clearColor];
    [playButton setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal ];
    UIImage *buttonImageNormal = image;
    UIImage *strechableButtonImageNormal = [buttonImageNormal stretchableImageWithLeftCapWidth:12 topCapHeight:0];
    [playButton setBackgroundImage:strechableButtonImageNormal forState:UIControlStateNormal];
    [cell.contentView addSubview:playButton];
    return cell;


}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 380;
}
- (void)viewDidUnload {
    [self setNavigationBar:nil];
    [super viewDidUnload];
}
- (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController
{
    if ([viewController isKindOfClass:[CameraViewController class]]) {
        UIActionSheet *actionSheet = [[UIActionSheet alloc]
                                      initWithTitle:@"Choose Source Type?"
                                      delegate:self
                                      cancelButtonTitle:@"Cancel"
                                      destructiveButtonTitle:nil
                                      otherButtonTitles:@"Select From Library", @"Capture From Camera", nil];
        [actionSheet showFromTabBar:tabBarController.tabBar];
        return NO;
    }
    return YES;
}
- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
{
    switch (buttonIndex) {
        case 0:
        {
            CameraViewController *cameraViewController=[self.tabBarController.viewControllers objectAtIndex:2];
            if (!cameraViewController.imagePicker) {
                cameraViewController.imagePicker =[[UIImagePickerController alloc] init];
                cameraViewController.imagePicker.allowsEditing = YES;
            }
            cameraViewController.imagePicker.delegate=self;
            cameraViewController.imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
            [self presentViewController:cameraViewController.imagePicker
                               animated:YES completion:nil];
        }
            break;
        case 1:
        {
            CameraViewController *cameraViewController=[self.tabBarController.viewControllers objectAtIndex:2];
            if (!cameraViewController.imagePicker) {
                cameraViewController.imagePicker =[[UIImagePickerController alloc] init];
                cameraViewController.imagePicker.allowsEditing = YES;
            }
            if ([UIImagePickerController isSourceTypeAvailable:
                 UIImagePickerControllerSourceTypeCamera])
            {
                cameraViewController.imagePicker.delegate=self;
                cameraViewController.imagePicker.sourceType = UIImagePickerControllerSourceTypeCamera;
                [self presentViewController:cameraViewController.imagePicker
                                   animated:YES completion:nil];
            }
        }
            break;
        case 2:
            [self dismissViewControllerAnimated:YES completion:nil];
            break;
        default:
            break;
    }
}
-(void)imagePickerController:
(UIImagePickerController *)picker
didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    CameraViewController *cameraViewController=[self.tabBarController.viewControllers objectAtIndex:2];
    cameraViewController.imageSelected=nil;
    UIImage *image = info[UIImagePickerControllerEditedImage];
    cameraViewController.imageSelected=image;
    cameraViewController.imagePicker.delegate=cameraViewController;
    [self dismissViewControllerAnimated:YES completion:nil];
    self.tabBarController.selectedViewController=cameraViewController;
}

-(void)imagePickerControllerDidCancel:
(UIImagePickerController *)picker
{
    [self dismissViewControllerAnimated:YES completion:nil];
}
@end
4

1 回答 1

1

您的代码充满了同步请求。例如：

 NSString *jsonString = [NSString
                            stringWithContentsOfURL:[NSURL URLWithString:@"http://izisstechnology.com/garage/index.php?method=home&start=0"]
                            encoding:NSStringEncodingConversionAllowLossy
                            error:nil];

或者

NSData *data = [[NSData alloc] initWithContentsOfURL:url];
    UIImage *image = [[UIImage alloc] initWithData:data];

当您执行同步请求时，整个 UI 都会被阻塞，因为请求是在主线程上执行的。基本上，UIKit 的大部分事情都是在主线程上完成的，例如处理触摸、绘制 UI 等。因此，例如触摸在所有数据下载完成之前不会被处理。结果，您的应用程序出现错误。

我最近观看了一个名为“在 iOS 上构建并发用户界面”的 WWDC 2012 会议。这很有趣也很有帮助。主题演讲中的插图使理解材料变得容易。无论如何，关于这个主题有大量的资源，你只需要谷歌“异步 iOS”，你会发现非常有用的教程等。

于 2013-05-20T22:32:14.990 回答