KivaJSON与UIActivityIndi​​cator？

Question

我已经下载了KivaJSON，我尝试在此脚本中添加UIActivityIndi​​cator，但没有成功。

脚本：http://dl.dropbox.com/u/77033905/stackoverflow/KivaJSONDemo.zip

我希望在JSON开始加载时以及何时结束以隐藏指示符时放置UIActivityIndi​​cator。

以下是ViewController.m的代码

#define kBgQueue dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0) //1
#define kLatestKivaLoansURL [NSURL URLWithString: @"http://api.kivaws.org/v1/loans/search.json?status=fundraising"] //2

#import "ViewController.h"

@interface NSDictionary(JSONCategories)
+(NSDictionary*)dictionaryWithContentsOfJSONURLString:(NSString*)urlAddress;
-(NSData*)toJSON;
@end

@implementation NSDictionary(JSONCategories)
+(NSDictionary*)dictionaryWithContentsOfJSONURLString:(NSString*)urlAddress
{
    NSData* data = [NSData dataWithContentsOfURL: [NSURL URLWithString: urlAddress] ];
    __autoreleasing NSError* error = nil;
    id result = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
    if (error != nil) return nil;
    return result;
}

-(NSData*)toJSON
{
    NSError* error = nil;
    id result = [NSJSONSerialization dataWithJSONObject:self options:kNilOptions error:&error];
    if (error != nil) return nil;
    return result;    
}
@end

@implementation ViewController
@synthesize navBar;

- (void)viewDidLoad
{
    [super viewDidLoad];


}

- (void)fetchedData:(NSData *)responseData {
    //parse out the json data
    NSError* error;
    NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData //1
                                                         options:kNilOptions 
                                                           error:&error];
    NSArray* latestLoans = [json objectForKey:@"loans"]; //2

    NSLog(@"loans: %@", latestLoans); //3

    // 1) Get the latest loan
    NSDictionary* loan = [latestLoans objectAtIndex:0];

    // 2) Get the funded amount and loan amount
    NSNumber* fundedAmount = [loan objectForKey:@"funded_amount"];
    NSNumber* loanAmount = [loan objectForKey:@"loan_amount"];
    float outstandingAmount = [loanAmount floatValue] - [fundedAmount floatValue];

    // 3) Set the label appropriately
    humanReadble.text = [NSString stringWithFormat:@"Latest loan: %@ from %@ needs another $%.2f to pursue their entrepreneural dream",
                         [loan objectForKey:@"name"],
                         [(NSDictionary*)[loan objectForKey:@"location"] objectForKey:@"country"],
                         outstandingAmount
                         ];

    //build an info object and convert to json
    NSDictionary* info = [NSDictionary dictionaryWithObjectsAndKeys:
                          [loan objectForKey:@"name"], @"who",
                          [(NSDictionary*)[loan objectForKey:@"location"] objectForKey:@"country"], @"where",
                          [NSNumber numberWithFloat: outstandingAmount], @"what",
                          nil];

    //convert object to data
    NSData* jsonData = [NSJSONSerialization dataWithJSONObject:info 
                                                       options:NSJSONWritingPrettyPrinted
                                                         error:&error];

    //print out the data contents
    jsonSummary.text = [[NSString alloc] initWithData:jsonData
                                             encoding:NSUTF8StringEncoding];

}

- (IBAction)updateJson:(id)sender {



    dispatch_async(kBgQueue, ^{
        NSData* data = [NSData dataWithContentsOfURL: kLatestKivaLoansURL];
        [self performSelectorOnMainThread:@selector(fetchedData:) withObject:data waitUntilDone:YES];
    });


}
- (void)viewDidUnload {
    [self setNavBar:nil];
    [super viewDidUnload];
}
@end

感谢您的帮助。

更新

添加了我的推杆指标。

#define kBgQueue dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0) //1
#define kLatestKivaLoansURL [NSURL URLWithString: @"http://api.kivaws.org/v1/loans/search.json?status=fundraising"] //2

#import "ViewController.h"

@interface NSDictionary(JSONCategories)
+(NSDictionary*)dictionaryWithContentsOfJSONURLString:(NSString*)urlAddress;
-(NSData*)toJSON;
@end

@implementation NSDictionary(JSONCategories)
+(NSDictionary*)dictionaryWithContentsOfJSONURLString:(NSString*)urlAddress
{
    NSData* data = [NSData dataWithContentsOfURL: [NSURL URLWithString: urlAddress] ];
    __autoreleasing NSError* error = nil;
    id result = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
    if (error != nil) return nil;
    return result;
}

-(NSData*)toJSON
{
    NSError* error = nil;
    id result = [NSJSONSerialization dataWithJSONObject:self options:kNilOptions error:&error];
    if (error != nil) return nil;
    return result;    
}
@end


@implementation ViewController{
    UIActivityIndicatorView *activityIndicator;
}

@synthesize navBar;

- (void)viewDidLoad
{
    [super viewDidLoad];


    activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
    self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:activityIndicator];

}

- (void)fetchedData:(NSData *)responseData {
    //parse out the json data
    NSError* error;
    NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData //1
                                                         options:kNilOptions 
                                                           error:&error];
    NSArray* latestLoans = [json objectForKey:@"loans"]; //2

    NSLog(@"loans: %@", latestLoans); //3

    // 1) Get the latest loan
    NSDictionary* loan = [latestLoans objectAtIndex:0];

    // 2) Get the funded amount and loan amount
    NSNumber* fundedAmount = [loan objectForKey:@"funded_amount"];
    NSNumber* loanAmount = [loan objectForKey:@"loan_amount"];
    float outstandingAmount = [loanAmount floatValue] - [fundedAmount floatValue];

    // 3) Set the label appropriately
    humanReadble.text = [NSString stringWithFormat:@"Latest loan: %@ from %@ needs another $%.2f to pursue their entrepreneural dream",
                         [loan objectForKey:@"name"],
                         [(NSDictionary*)[loan objectForKey:@"location"] objectForKey:@"country"],
                         outstandingAmount
                         ];

    //build an info object and convert to json
    NSDictionary* info = [NSDictionary dictionaryWithObjectsAndKeys:
                          [loan objectForKey:@"name"], @"who",
                          [(NSDictionary*)[loan objectForKey:@"location"] objectForKey:@"country"], @"where",
                          [NSNumber numberWithFloat: outstandingAmount], @"what",
                          nil];

    //convert object to data
    NSData* jsonData = [NSJSONSerialization dataWithJSONObject:info 
                                                       options:NSJSONWritingPrettyPrinted
                                                         error:&error];

    //print out the data contents
    jsonSummary.text = [[NSString alloc] initWithData:jsonData
                                             encoding:NSUTF8StringEncoding];

}

- (IBAction)updateJson:(id)sender {



    dispatch_async(kBgQueue, ^{

        [activityIndicator startAnimating];

        NSData* data = [NSData dataWithContentsOfURL: kLatestKivaLoansURL];
        [self performSelectorOnMainThread:@selector(fetchedData:) withObject:data waitUntilDone:YES];

        [activityIndicator stopAnimating];

    });


}
- (void)viewDidUnload {
    [self setNavBar:nil];
    [super viewDidUnload];
}
@end

Answer 1

在初始化UIActivityIndi​​catorView时添加它：

 activityIndicator  = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(150, 150, 30, 30)];
    [activityIndicator setActivityIndicatorViewStyle:UIActivityIndicatorViewStyleGray];
    [self.view addSubview:activityIndicator];

并且应该在调用ispatch_async(kBgQueue, ^{之前开始设置动画，如下所示：

- (IBAction)updateJson:(id)sender {

[activityIndicator startAnimating];
    dispatch_async(kBgQueue, ^{
        NSData* data = [NSData dataWithContentsOfURL: kLatestKivaLoansURL];
        [self performSelectorOnMainThread:@selector(fetchedData:) withObject:data waitUntilDone:YES];

    });
}

并且应该在显示数据后停止动画，即在方法结束时

- (void)fetchedData:(NSData *)responseData