如何在执行搜索功能期间实现UIActivityIndi​​catorView？

Question

我正在构建一篇阅读app的文章。我以JSON格式从服务器获取数据并加载到UITableViewController。
在用户搜索部分 为搜索输入内容需要时间将数据加载到UITableView中。
我无法在搜索结果加载之间实现UIActivityIndi​​catorView UITableViewController中的数据。

这是我的代码：

           -(void)searchBarSearchButtonClicked:(UISearchBar *)searchBar
              {
          NSString *searchText=searchBar.text;
         [self.mySearchBar resignFirstResponder];

         NSString *trimmedString = [searchText stringByTrimmingCharactersInSet:
                              [NSCharacterSet whitespaceCharacterSet]];
         if (trimmedString.length==0) {
          isFilter=NO;
            UIAlertView *noConn = [[UIAlertView alloc] initWithTitle:@"ERROR" message:@"Please enter your  something in search bar" delegate:self cancelButtonTitle:nil otherButtonTitles:@"ok", nil];
    [noConn show];
           }
         else
           NSString *searchNew = [trimmedString stringByReplacingOccurrencesOfString:@" " withString:@"%20"];
                isFilter=YES;
                  @try {
                          [label removeFromSuperview];
                _Title1 = [[NSMutableArray alloc] init];
                _Author1 = [[NSMutableArray alloc] init];
                _Images1 = [[NSMutableArray alloc] init];
                _Details1 = [[NSMutableArray alloc] init];
                _link1 = [[NSMutableArray alloc] init];
                _Date1 = [[NSMutableArray alloc] init];

                              NSString* myURLString = [NSString  stringWithFormat:@“www.example.com&search=%@", searchNew];

                 NSURL *url = [NSURL URLWithString:myURLString];

                 NSData* data = [NSData dataWithContentsOfURL:url];
                if ((unsigned long)data.length > 3) 
                {
                 NSArray *ys_avatars = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
                    if(ys_avatars){

                     for (int j=0;j<ys_avatars.count;j++)
                 {
                [_Title1 addObject:ys_avatars[j][@"title"]];
                [_Author1 addObject: ys_avatars[j][@"author"]];
                [_Images1 addObject: ys_avatars[j][@"featured_img"]];
                [_Details1 addObject:ys_avatars[j][@"content"]];
                [_link1 addObject:ys_avatars[j][@"permalink"]];
                NSString *newStr=[ys_avatars[j][@"date"] substringToIndex:[ys_avatars[j] [@"date"] length]-3];
                 [_Date1 addObject:newStr];
                   }
                      }
                else
             {
                NSLog(@"error");
                    }
              [self.myTableView reloadData];
              }
                }
               else{
                     [self.myTableView reloadData];
                  self.tableView.separatorColor = [UIColor colorWithRed:255/255.0 green:255/255.0 blue:255/255.0 alpha:1.0];
                   label = [[UILabel alloc] initWithFrame:CGRectMake(90, 100, 200, 100)];
                   label.text=@"No Article Found";
                   label.backgroundColor = [UIColor clearColor];
                   [self.view addSubview:label];
                     }
                }

                 @catch (NSException *exception) {   

                     }         
                  }
            }

Answer 1

您可以在单击searchBarSearchButton后立即执行此操作。 然后在cellForRowAtIndexPath中添加这一行：

-(void)searchBarSearchButtonClicked:(UISearchBar *)searchBar
{
        [_activityIndicator startAnimating];

your code
}

下：

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

     if (indexpath.row == [your_array_of_content count]-1)
     {
         [_activityIndicator stopAnimating];
     }
}

Answer 2

dataWithContentsOfURL是一个同步API。实现所需目标的一种方法是使用NSURLConnection API以异步方式从URL加载日期。您还应该挂钩下面列出的委托方法来启动和停止活动指示器。

connection:didReceiveResponse:
connectionDidFinishLoading:

我还建议你使用像AFNetworking这样的库，它会给你前后钩子作为回调块，这在编码方面会更加清晰。

Answer 3

创建指标：

UIActivityIndicatorView *activityIndicator  = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:
                                               UIActivityIndicatorViewStyleWhiteLarge];

[activityIndicator setCenter:CGPointMake(view.frame.size.width/2.0, view.frame.size.height/2.0)];
activityIndicator.hidesWhenStopped = YES;
activityIndicator.color = [UIColor blackColor];

//add it to the view
[self.view addSubview:activityIndicator];
//start the animation
[activityIndicator startAnimating];

当你想要解雇它时：

[activityIndicator stopAnimating];