试图在UITableView中加载大量的JSON数据需要花费很多时间

Question

I'm new to iOS and have been trying to load JSON data in UITableView (within a UIViewController, which are in a Tab bar controller). The JSON data is huge and I have tried using AFNetworking library as well. But still the data takes more that 15 secs. to load.

Here is what I've tried: Approach #2

@implementation AppDelegate


- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
// Override point for customization after application launch.


[self saveData];



return YES;
}
-(void) saveData
{
NSString * userType= @"3" ; 
NSString * userID= @"33" ;
NSString * URLString = [NSString stringWithFormat:@"http://<some_url>/%@/%@/",userType,userID];
AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
manager.responseSerializer =[AFHTTPResponseSerializer serializer];
[manager GET:leadsURLString parameters:nil progress:nil success:^(NSURLSessionTask *task, NSData* responseObject) {
    NSError * error = nil;
    NSArray * lData = [NSJSONSerialization JSONObjectWithData:responseObject options:NSJSONReadingAllowFragments error:&error];
    NSLog(@"Leads:%@",lData);


    if (error != nil) {
        NSLog(@"JSON Error: %@", [error localizedDescription]);
    }
    // Write the file .
    NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString * docDirectory = [paths objectAtIndex:0];
    NSString * lFilePath = [NSString stringWithFormat:@"%@",[docDirectory stringByAppendingPathComponent:@"leads"]]; // File

    if (![leadsData writeToFile:lFilePath atomically:YES]) {
        NSLog(@"Couldn't save leads data.");
    }

} failure:^(NSURLSessionTask *operation, NSError *error) {
    NSLog(@"Error: %@", error);
}];

}
@end
Code for tableView
@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];

// Uncomment the following line to preserve selection between presentations.
// self.clearsSelectionOnViewWillAppear = NO;

// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem;

NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString * docDirectory = [paths objectAtIndex:0];
NSString * projFilePath = [NSString stringWithFormat:@"%@",[docDirectory stringByAppendingPathComponent:@"leads"]]; // file
if ([[NSFileManager defaultManager] fileExistsAtPath:projFilePath])
{
    _projects = [[NSMutableArray alloc] initWithContentsOfFile:projFilePath];

}
else
{
    _projects = [NSMutableArray arrayWithObject:[NSDictionary dictionaryWithObject:@"No Project" forKey:@"project_name"]];
}
[self.tableView reloadData];

}

1. Initially tried loading data when the view controllers load, took too long.

2. Then tried loading data in Appdelegate and saving it, and loading it when the view controllers load, still took long enough.

3. Tried loading data in Appdelegate and then setting it in the respective view controllers, but couldn't achieve it.

Could anyone suggest the best way to accomplish it?

Answer 1

Try to follow below steps to reduce the time.

Step: 1 Try to load data from below check how time it will take.

                 AFHTTPSessionManager *managerFB = [AFHTTPSessionManager manager];
                 [managerFB GET:WEB_SERIVCE_URL parameters:dicData progress:^(NSProgress * _Nonnull downloadProgress) {
                     <#code#>
                 } success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
                     NSLog(@"%@",responseObject);
                 } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
                     <#code#>
                 }];

Step: 2: Don't try to save data into local file. Create one global variable in AppDelegate and stored directly into it.

Step: 3: Try to call service in background thread, so your main application UI won't be stuck.

[self performSelector:@selector(yourMethodName) withObject:nil afterDelay:0.2];

Also, you can check your web-service response time in Postman which is extension of Chrome. So you can get response time from service.

Answer 2

if data is much larger(as you mentioned in comment) then you can manage your api something like you can send last index to server and server returns data from that index and you can define total number of records should be return in one call. then you can frequently call api as user scrolls your table view!

For example you could consider facebook app's time line or Quora app's read tab!