iOS开发关于UITableView从网络中获取到数据源，却在UITableView中不显示的问题

大神就不用看了，对你来说肯定没什么营养，只针对新手朋友！！！

相信在iOS开发中大家会经常的应用到UITableView控件，于此同时我们也少不了与网络打交道，那么问题就产生了：

为什么我从网络获取到了数据源，但是却在UITableView不能成功显示出来？

下面，我用一个例子来给大家展示

首先这是我自己定义的一个类

1. #import "SecondViewController.h"
2. 
   
3. 
   
4. @interface SecondViewController ()
5. 
   
6. @property NSMutableData *mutableData;
7. @property NSString *string;
8. @property NSMutableArray *courses;
9. 
   
10. @end
11. 
    
12. @implementation SecondViewController
13. 
    
14. - (void)viewDidLoad {
15.     NSString *path = @"这是URL地址";
16.     NSURL *url = [NSURL URLWithString:path];
17.     NSURLRequest *request = [NSURLRequest requestWithURL:url];
18.     NSURLConnection *connection = [NSURLConnection connectionWithRequest:request delegate:self];
19.     [connection start];
20.     [super viewDidLoad];
21.     self.classBarItem.badgeValue = nil;
22.     
23. }
24. 
    
25. - (void)didReceiveMemoryWarning {
26.     [super didReceiveMemoryWarning];
27.     // Dispose of any resources that can be recreated.
28. }
29. 
    
30. - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
31.     NSLog(@"%@", response);
32. }
33. 
    
34. - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
35.     if(_mutableData == nil){
36.         _mutableData = [[NSMutableData alloc]init];
37.     }
38.     [_mutableData appendData:data];
39. }
40. 
    
41. - (void)connectionDidFinishLoading:(NSURLConnection *)connection{
42.     _string = [[NSString alloc]initWithBytes:[_mutableData bytes] length:[_mutableData length] encoding:NSUTF8StringEncoding];
43.     NSJSONSerialization *json_courses = [NSJSONSerialization JSONObjectWithData:_mutableData options:0 error:nil];
44.     NSMutableDictionary *json = [NSJSONSerialization JSONObjectWithData:_mutableData options:0 error:nil];
45.     _courses = [[NSMutableArray alloc] init];
46.     for(int i = 0; i < [json count]; i++){
47.         NSString *tag = @"course";
48.         NSString *str_i = [[NSString alloc]initWithFormat:@"%i",i];
49.         tag = [tag stringByAppendingString:str_i];
50.         NSJSONSerialization *json_course = [json_courses valueForKey:tag];
51.         NSString *name = [json_course valueForKey:@"courseName"];
52.         NSLog(@"%@",name);
53.         [_courses addObject:name];
54.     }
55.     NSLog(@"%@",_courses);
56.     //获取NSMuTableArray中第n个元素的值
57.     //NSLog(@"%@", [_courses objectAtIndex:1]);
58.     _mutableData = nil;
59. }
60. 
    
61. - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
62.     return 1;
63. }
64. 
    
65. - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
66.     NSLog(@"Array count is %i",[_courses count]);
67.     return [_courses count];
68. }
69. 
    
70. 
    
71.  - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
72.      UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"courses" forIndexPath:indexPath];
73.      cell.textLabel.text = [_courses objectAtIndex:[indexPath row]];
74.  // Configure the cell...
75.  
76.      return cell;
77.  }
78.  
79. 
    
80. /*
81.  // Override to support conditional editing of the table view.
82.  - (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {
83.  // Return NO if you do not want the specified item to be editable.
84.  return YES;
85.  }
86.  */
87. 
    
88. /*
89.  // Override to support editing the table view.
90.  - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {
91.  if (editingStyle == UITableViewCellEditingStyleDelete) {
92.  // Delete the row from the data source
93.  [tableView deleteRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationFade];
94.  } else if (editingStyle == UITableViewCellEditingStyleInsert) {
95.  // Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
96.  }
97.  }
98.  */
99. 
    
100. /*
101.  // Override to support rearranging the table view.
102.  - (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)fromIndexPath toIndexPath:(NSIndexPath *)toIndexPath {
103.  }
104.  */
105. 
     
106. /*
107.  // Override to support conditional rearranging of the table view.
108.  - (BOOL)tableView:(UITableView *)tableView canMoveRowAtIndexPath:(NSIndexPath *)indexPath {
109.  // Return NO if you do not want the item to be re-orderable.
110.  return YES;
111.  }
112.  */
113. 
     
114. /*
115.  #pragma mark - Navigation
116.  
117.  // In a storyboard-based application, you will often want to do a little preparation before navigation
118.  - (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
119.  // Get the new view controller using [segue destinationViewController].
120.  // Pass the selected object to the new view controller.
121.  }
122.  */
123. 
     
124. @end

程序成功获取到了数据源：

但是，问题就出现了，大家注意到没有，我用来存放网络读取的数据的NSMutableArray的count值为0，但是我也成功获取到了网络数据。

首先，分析，程序先执行输出了盛放我所需数据的长段，然后才从网络获取数据，那么我们就可以推断出，程序必然是先创建了UITableView，之后才获取到了网络数据。

问题产生的原因：程序在获取网络资源时并不会在主线程当中进行，所以程序会先执行之后的代码，然后再来获取网络资源

那么解决这个问题的方法也就明了了，在获取到网络资源后我们需要把它重新加载到tableView上

此时我们只需要在connectionDidFinishLoading末尾添加[self.tableView reloadData];即可

OK，大功告成！

运行结果如下：