Question

我在尝试将缩略图从JSON加载到UITableView单元格时遇到问题。单元格的UI是一个xib文件。我无法解析JSON的缩略图部分并将其显示在表视图中。我做了这个已经有一段时间了（我倾向于使用比典型的iOS应用程序更多的游戏），而我最后一次做的是实现略有不同。

JSON：

{
   "data" :
  [

    {
        "user_id" : "3",
        "username" : "Alex Perez",
        "avatar_url" : "http://mywebsite.com/images/alex_avatar.png",
        "message" : "Hello there?"
    },
    {
        "user_id" : "4",
        "username" : "Jon Doe",
        "avatar_url" : "http://mywebsite.com/images/john_avatar.png",
        "message" : "I'm here now"
    },
    {
        "user_id" : "2",
        "username" : "Sam Givens",
        "avatar_url" : "http://mywebsite.com/images/sam_avatar.png",
        "message" : "Can we have a meeting around 2?"
    },

....

Data.h中的数据：

#import <Foundation/Foundation.h>

@interface Data : NSObject

@property (nonatomic, readwrite) int user_id;
@property (nonatomic, strong) NSString *username;
@property (nonatomic, strong) NSString *avatar_url;
@property (nonatomic, strong) NSString *message;

- (void)loadWithDictionary:(NSDictionary *)dict;
@end

Data.m：

#import "Data.h"

@implementation Data


- (void)loadWithDictionary:(NSDictionary *)dict {

  self.user_id = [[dict objectForKey:@"user_id"] intValue];
  self.username = [dict objectForKey:@"username"];
  self.avatar_url = [dict objectForKey:@"avatar_url"];
  self.message = [dict objectForKey:@"message"];
}

@end

在声明属性并将属性分配给数据时，我遇到了问题，然后可以将其传递给将要显示它的View Controller。我收到编译器警告不兼容的指针类型从NSString *分配给UIImage *。我不明白为什么Xcode不抱怨UILabel和UITextView等其他属性。

Cell.m

#import "Cell.h"

@interface Cell ()

@property (nonatomic) int userID;
// UIImageView property created from Interface Builder
@property (strong, nonatomic) IBOutlet UIImageView *avatarImage;
@property (nonatomic, strong) IBOutlet UILabel *usernameLabel;
@property (nonatomic, strong) IBOutlet UITextView *messageTextView;
@end

@implementation Cell


- (void)loadWithData:(Data *)data {

  self.userID = data.user_id;
  // Here I get "Incompatible pointer types assigning to UIImage * from NSString*
  self.avatarImage.image = data.avatar_url;
  self.usernameLabel.text = data.username;
  self.messageTextView.text = data.message;
}
@end

最后显示它的MessagesViewController：

@interface MessagesViewController ()

@property (nonatomic, strong) IBOutlet UITableView *tableView;
@property (nonatomic, strong) NSMutableArray *loadedChatData;
@end

@implementation MessagesViewController

- (void)viewDidLoad {
   [super viewDidLoad];

   self.loadedChatData = [[NSMutableArray alloc] init];
   [self loadJSONData];
}

- (void)loadJSONData {

 NSString *filePath = [[NSBundle mainBundle] pathForResource:@"data" ofType:@"json"];

 NSError *error = nil;

 NSData *rawData = [NSData dataWithContentsOfFile:filePath options:NSDataReadingMappedIfSafe error:&error];

 id JSONData = [NSJSONSerialization JSONObjectWithData:rawData options:NSJSONReadingAllowFragments error:&error];

 [self.loadedChatData removeAllObjects];

if ([JSONData isKindOfClass:[NSDictionary class]]) {

    NSDictionary *jsonDict = (NSDictionary *)JSONData;

    NSArray *loadedArray = [jsonDict objectForKey:@"data"];
    if ([loadedArray isKindOfClass:[NSArray class]])
    {
        for (NSDictionary *chatDict in loadedArray)
        {
            Data *chatData = [[Data alloc] init];
            [chatData loadWithDictionary:chatDict];
            [self.loadedChatData addObject:chatData];
        }
      }
    }

   [self.tableView reloadData];
 }

 - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

 static NSString *cellIdentifier = @"Cell";
 Cell *cell = nil;

 if (cell == nil) {
    NSArray *nib = [[NSBundle mainBundle] loadNibNamed:cellIdentifier owner:self options:nil];
    cell = (Cell *)[nib objectAtIndex:0];
  }

  Data *data = [self.loadedChatData objectAtIndex:[indexPath row]];

 [cell loadWithData:data];

 return cell;
}

Answer 1

你必须修改错误行并将其用作：

self.avatarImage.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:data.avatar_url]]];

Answer 2

为笔尖创建自定义类，然后将特定代码放入其中以从直接URL加载图像...这可以

var stringUrl = "http://mywebsite.com/images/alex_avatar.png"
var url: NSURL = NSURL(string: stringUrl)!;
self.imageView1.sd_setImageWithURL(url, placeholderImage: UIImage(named: "no_image_small.png"));

Answer 3

尝试使用以下代码，它可能会对您有所帮助。

  NSURL *url = [NSURL URLWithString:@"http://mywebsite.com/images/alex_avatar.png"];
   UIImage *thumbnail = [UIImage imageWithData: [NSData dataWithContentsOfURL:url]];
   if (thumbnail == nil) {
       thumbnail = [UIImage imageNamed:@"noimage.jpg"] ; //if no image get from url mean show a dummy one
   }
   CGSize itemSize = CGSizeMake(80, 80);         //your own size can replace with 80
   UIGraphicsBeginImageContext(itemSize);
   CGRect imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height);
   [thumbnail drawInRect:imageRect];
   cell.thumbnailImageView.image = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();

将缩略图图像从JSON加载到UITableView中

3 个答案: