加载数据时如何显示UIActivityIndi​​cationView

- (void)viewDidLoad {
[super viewDidLoad];
self.title = @\" \";

loadActivityIndicator.hidden = TRUE;  // Hide UIActivityIndicationView at start



[self loadDataIfNeeded];
}

-(void)loadDataIfNeeded {
NSFileManager *fileManager = [NSFileManager defaultManager];

myFileArray = [[NSMutableArray alloc]init];

//======SET THE FILE INPUT NAME======//
qFileTxtName = @\"110615\";
[myFileArray addObject:qFileTxtName];
//===================================//

// CHECK IF THE FILE EXISTS
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:@\"checkQuestionFile.plist\"];

if([fileManager fileExistsAtPath:path]) {
    NSArray *readKeyFileName = [[NSArray alloc] initWithContentsOfFile:path];

    if ([[readKeyFileName objectAtIndex:0] isEqualToString:qFileTxtName]) {
        //==== THERE IS NO UPDATED QUESTION .txt FILE ====//
    }
    else {
        //==== THERE IS AN UPDATED QUESTION .txt FILE ====//

        //  SET UP UIActivityIndicator view to show that work is ongoing
        loadActivityIndicator.hidden = FALSE;
        [loadActivityIndicator startAnimating];


        //==== SET UP PATH FOR ALL FILES====//

        NSString *aString = [[NSString alloc]init];

        aString = [@\"questions_famquiz_hard_\" stringByAppendingString:qFileTxtName];
        NSString *path1 = [[NSBundle mainBundle] pathForResource:aString ofType:@\"txt\"];

        aString = [@\"questions_famquiz_medium_\" stringByAppendingString:qFileTxtName];
        NSString *path2 = [[NSBundle mainBundle] pathForResource:aString ofType:@\"txt\"];

        aString = [@\"questions_famquiz_easy_\" stringByAppendingString:qFileTxtName];
        NSString *path3 = [[NSBundle mainBundle] pathForResource:aString ofType:@\"txt\"];


        AccessQuestionsDB *accessQuestionDataFunction = [AccessQuestionsDB new];
        idCounter = [accessQuestionDataFunction populateTheDatabase: path1 theID:0 firstTime: YES];
        idCounter = [accessQuestionDataFunction populateTheDatabase: path2 theID:idCounter firstTime: NO];
        idCounter = [accessQuestionDataFunction populateTheDatabase: path3 theID:idCounter firstTime: NO];


        //==UPDATE THE PLIST==//
        [myFileArray writeToFile:path atomically: TRUE];

        //  Stop UIActivityIndicator as activity is over
        loadActivityIndicator.hidden = TRUE;
        [loadActivityIndicator stopAnimating];


    }



} else {
    //== If file not found write a new file ==//
    [myFileArray addObject:qFileTxtName];
    [myFileArray writeToFile:path atomically: TRUE];
}
}