Question

以下是我的控制器的代码，我在标签栏上的每个选项卡中都有四个。我有两个问题。

我得到一个阵列出界但我无法追逐它。我在这里遗漏了什么吗？

当我的应用启动时，它需要5到8秒才能加载标签栏的第一个视图。加载后我单击另一个选项卡，选项卡不会变为蓝色，应用程序在那里停留3秒钟然后最终切换。我是一个菜鸟，我在这里挣扎。我认为可以通过在另一个线程或其他东西中获取数据来解决此问题？我确信这个控制器充满了bug。

import "AllMackTableViewController.h"
import "PostDetailViewController.h"
import "MackdabMobileAppDelegate.h"
import <QuartzCore/QuartzCore.h>
import "Post.h"

define FONT_SIZE 14.0f
define CELL_CONTENT_WIDTH 254.0f
define CELL_CONTENT_MARGIN 5.0f



@implementation AllMackTableViewController

@synthesize jsonArray;
@synthesize localJsonArray;
@synthesize postDetailViewController;
@synthesize allPostsTableView;
@synthesize fetchedResultsController, managedObjectContext;



@synthesize minuteTimer;
@synthesize regionsTimer;

pragma mark 
pragma mark View lifecycle


 (void)viewDidLoad {
    [super viewDidLoad];

    self.title = NSLocalizedString(@"Feed", @"You're Matching Posts");

    UIBarButtonItem *refreshButton = [[UIBarButtonItem alloc]
                                      initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh
                                      target:self
                                      action:@selector(refresh)];
    self.navigationItem.rightBarButtonItem = refreshButton;
    allPostsTableView.delegate = self;
    [refreshButton release];

    [self refresh];




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

 (void)scrollViewDidScroll:(UIScrollView *) scrollView;
{
    CGFloat scrollHeight = scrollView.contentSize.height;
    CGPoint p = scrollView.contentOffset; 

    //NSLog(@"x = %f, y = %f", p.x, p.y);
}



 (void)viewWillAppear:(BOOL)animated {


    /*
     Set up two timers, one that fires every minute, the other every fifteen minutes.

     1/ The time displayed for each time zone must be updated every minute on the minute.
     2/ Time zone data is cached. Some time zones are based on 15 minute differences from GMT, so update the cache every 15 minutes, on the "quarter".
     */

    NSTimer *timer;
    NSDate *date = [NSDate date];

    /*
     Set up a timer to update the table view every minute on the minute so that it shows the current time.
     */
    NSDate *oneMinuteFromNow = [date dateByAddingTimeInterval:60];

    NSCalendarUnit unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit;
    NSDateComponents *timerDateComponents = [calendar components:unitFlags fromDate:oneMinuteFromNow];
    // Add 1 second to make sure the minute update has passed when the timer fires.
    [timerDateComponents setSecond:1];
    NSDate *minuteTimerDate = [calendar dateFromComponents:timerDateComponents];

    timer = [[NSTimer alloc] initWithFireDate:minuteTimerDate interval:60 target:self selector:@selector(updateTime:) userInfo:nil repeats:YES];
    [[NSRunLoop currentRunLoop] addTimer:timer forMode:NSDefaultRunLoopMode];
    self.minuteTimer = timer;   
    [timer release];



}



pragma mark 
pragma mark Table view data source

 (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    // Return the number of sections.
    return 1;
}


 (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
   // return [self.localJsonArray count];

    NSLog(@"Setting numberOfRowsInSection to %i",[self.localJsonArray count]);
    if ( [jsonArray count] < 9 ) {
        return [self.localJsonArray count];
        NSLog(@"Setting numberOfRowsInSection to %i inside of non add one.",[self.localJsonArray count]);

    } else {
        return [self.localJsonArray count] + 1;
    } 


}

 (void)updateTime:(NSTimer *)timer {
    /*
     To display the current time, redisplay the time labels.
     Don't reload the table view's data as this is unnecessarily expensive  it recalculates the number of cells and the height of each item to determine the total height of the view etc.  The external dimensions of the cells haven't changed, just their contents.
     */
    NSArray *visibleCells = self.tableView.visibleCells;
    for (PostTableCustomCellController *cell in visibleCells) {
        [cell redisplay];
    }

    [self updateRegions];
}



(NSString *)dateDiff:(NSString *)origDate {
    NSDateFormatter *df = [[NSDateFormatter alloc] init];
    [df setFormatterBehavior:NSDateFormatterBehavior10_4];
    [df setDateFormat:@"EEE, dd MMM yy HH:mm:ss VVVV"];
    NSDate *convertedDate = [df dateFromString:origDate];
    [df release];
    NSDate *todayDate = [NSDate date];
    double ti = [convertedDate timeIntervalSinceDate:todayDate];
    ti = ti * 1;
    if(ti < 1) {
        return @"never";
    } else      if (ti < 60) {
        return @"less than a minute ago";
    } else if (ti < 3600) {
        int diff = round(ti / 60);
        return [NSString stringWithFormat:@"%d minutes ago", diff];
    } else if (ti < 86400) {
        int diff = round(ti / 60 / 60);
        return[NSString stringWithFormat:@"%d hours ago", diff];
    } else if (ti < 2629743) {
        int diff = round(ti / 60 / 60 / 24);
        return[NSString stringWithFormat:@"%d days ago", diff];
    } else {
        return @"never";
    }   
}


 (void)updateRegions {
    /*
     The following sets the date for the regions, hence also for the time zone wrappers. This has the sideeffect of "faulting" the time zone wrappers (see TimeZoneWrapper's setDate: method), so can be used to relieve memory pressure.
     */
    NSDate *date = [NSDate date];
    for (Post *post in localJsonArray) {
        post.timeRemaining = [self dateDiff:post.deadline];
    }
}




// Customize the appearance of table view cells.
 (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    UILabel *distance;
    UIImage *image = [UIImage imageNamed:@"imageA.png"];
    static NSString *CellIdentifier = @"customCell"; // This is identifier given in IB jason set this.

    PostTableCustomCellController *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (indexPath.row != [localJsonArray count] ) {
        if (cell == nil) {

            NSLog(@"Cell created");

            NSArray *nibObjects = [[NSBundle mainBundle] loadNibNamed:@"PostTableCustomCellController" owner:nil options:nil];

            for(id currentObject in nibObjects)
            {
                if([currentObject isKindOfClass:[PostTableCustomCellController class]])
                {
                    cell = (PostTableCustomCellController *)currentObject;  
                }
            }
        }

        Post *post = [localJsonArray objectAtIndex:indexPath.row];

        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        [formatter setDateFormat:@"yyyy"];

        //Optionally for time zone converstions
        //[formatter setTimeZone:[NSTimeZone timeZoneWithName:@"..."]];

        NSString *stringFromDate = [formatter stringFromDate:post.deadline];

        cell.authorName.text = post.author;
        cell.deadline.text = stringFromDate;
        cell.budget.text = post.budget;
        cell.description.text = post.description;
        [[cell avatar] setImage:[UIImage imageNamed:@"butterfly.jpeg"]];
        [stringFromDate release];

        NSLog([NSString stringWithFormat:@"%@", post.distance]);
        if([@"" isEqualToString: post.distance] || nil == post.distance) {
            cell.distance.text = @"1 mi.";
        }else{
            cell.distance.text = @"25 mi.";
        }

        Post *myPost = [localJsonArray objectAtIndex:[indexPath row]];

        // Might can remove these
        UILabel *locationLabel = (UILabel *) [cell distance];
        UITextView *postTextView = (UITextView *) [cell description];

        //CGSize maximumLabelSize = CGSizeMake(254,88.0f);

        NSString *text;
        CGSize constraint;
        CGSize size;    
        CGFloat height;
        CGFloat realHeight;
        CGSize expectedLabelSize;

        text = myPost.description;

        constraint = CGSizeMake(CELL_CONTENT_WIDTH  (CELL_CONTENT_MARGIN * 2), 88.0f);

        size = [text sizeWithFont:[UIFont systemFontOfSize:FONT_SIZE] constrainedToSize:constraint lineBreakMode:UILineBreakModeWordWrap];

        height = MAX(size.height, 35.0f);

        realHeight = height + 36.0f  (10); 

        expectedLabelSize = [text sizeWithFont:[UIFont boldSystemFontOfSize:18.0f] constrainedToSize:CGSizeMake(252.0f, CGFLOAT_MAX) lineBreakMode:UILineBreakModeWordWrap];

        CGRect newFrame = postTextView.frame;
        newFrame.size.height = expectedLabelSize.height;
        newFrame.size.width = 252;
        postTextView.frame = newFrame;


        [[cell description] sizeToFit];

        [[cell viewForBackground] sizeToFit];
        [cell setNeedsDisplay];


    }// Ok, all done for filling the normal cells, next we probaply reach the +1 index, which doesn’t contain anything yet

    if ( [jsonArray count] == 9 ) { // Only call this if the array count is 25
        if(indexPath.row == [localJsonArray count] ) { // Here we check if we reached the end of the index, so the +1 row 
            if (cell == nil) {
                cell = [[[PostTableCustomCellController alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];
            }
            // Reset previous content of the cell, I have these defined in a UITableCell subclass, change them where needed
            cell.authorName.text = nil;
            cell.deadline.text = nil;
            cell.budget.text = nil;
            cell.description.text = nil;

            // Here we create the ‘Load more’ cell
            UILabel *loadMore =[[UILabel alloc]initWithFrame: CGRectMake(20,0,362,100)];
            loadMore.textColor = [UIColor blackColor];
            loadMore.highlightedTextColor = [UIColor darkGrayColor];
            loadMore.backgroundColor = [UIColor clearColor];
            loadMore.font=[UIFont fontWithName:@"Verdana" size:20];
            loadMore.textAlignment=UITextAlignmentCenter;
            loadMore.font=[UIFont boldSystemFontOfSize:20];
            loadMore.text=@"Load More..";
            [cell addSubview:loadMore];
        }
    }

    return cell;
}

 (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath;
{
    if (indexPath.row != [localJsonArray count] ) {
        Post *myPost = [localJsonArray objectAtIndex:[indexPath row]];
        NSString *text = myPost.description;

        CGSize constraint = CGSizeMake(CELL_CONTENT_WIDTH  (CELL_CONTENT_MARGIN * 2), 88.0f);

        CGSize size = [text sizeWithFont:[UIFont systemFontOfSize:FONT_SIZE] constrainedToSize:constraint lineBreakMode:UILineBreakModeWordWrap];

        CGFloat height = MAX(size.height, 35.0f);

        return height + (CELL_CONTENT_MARGIN * 2) + 28.0f; 
    }else{
        return 100.0f;
    }

}

(IBAction)nextTwentyFivePlease:(NSString *)thePostID{
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    self.jsonArray = [Post findNextTwentyFiveRemote:thePostID];
    if (self.localJsonArray == nil) {
        self.localJsonArray = [[NSMutableArray alloc]init]; // init the local array if it’s empty
    }
    [self.localJsonArray addObjectsFromArray:self.jsonArray];
    [self.tableView reloadData];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}


 (IBAction)refresh {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    self.jsonArray = [Post findAllRemote];
    if (self.localJsonArray == nil) {
        self.localJsonArray = [[NSMutableArray alloc]init]; // init the local array if it’s empty
    }
    [self.localJsonArray addObjectsFromArray:self.jsonArray];


    //self.localJsonArray = [Post findAllRemote];
    [self.tableView reloadData];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}


pragma mark 
pragma mark Table view delegate

 (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {

    if ( [jsonArray count] == 9 ) {  // only check for the load more function if we have 25 results in the dynamic array
        if (indexPath.row == [localJsonArray count] ) { // See if we reached the +1 in the results
            Post *tempPost = [jsonArray objectAtIndex:indexPath.row];
            NSLog('What is at tempPost');
            [self nextTwentyFivePlease:tempPost.postID]; // function to load more results
        }
    } else {
        NSInteger row = [indexPath row];
        if (self.postDetailViewController == nil) {
            PostDetailViewController *aPostDetail = [[PostDetailViewController alloc] initWithNibName:@"PostDetailView" bundle:nil];
            self.postDetailViewController = aPostDetail;
            postDetailViewController.post = [localJsonArray objectAtIndex:row];
            [aPostDetail release];
        }
        postDetailViewController.title = [NSString stringWithFormat:@"Details"];

        MackdabMobileAppDelegate *delegate = [[UIApplication sharedApplication] delegate]; 
        [delegate.allMacksNavController pushViewController:postDetailViewController animated:YES];
        [tableView deselectRowAtIndexPath:indexPath animated:YES];
    }
}


pragma mark 
pragma mark Timer set accessor methods

 (void)setMinuteTimer:(NSTimer *)newTimer {

    if (minuteTimer != newTimer) {
        [minuteTimer invalidate];
        minuteTimer = newTimer;
    }
}


 (void)setRegionsTimer:(NSTimer *)newTimer {

    if (regionsTimer != newTimer) {
        [regionsTimer invalidate];
        regionsTimer = newTimer;
    }
}


pragma mark 
pragma mark Memory management

 (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Relinquish ownership any cached data, images, etc that aren't in use.
}

 (void)viewDidUnload {
    // Relinquish ownership of anything that can be recreated in viewDidLoad or on demand.
    // For example: self.myOutlet = nil;
}


 (void)dealloc {
    [allPostsTableView release];
    [postDetailViewController release];
    [localJsonArray release]; // may need to remove this
    [super dealloc];
}


@end

Answer 1

在viewDidLoad中调用的刷新方法中，似乎它正在进行大量网络访问以下载某些信息。这可以解释为什么显示你的初始标签需要很长时间。

您希望在后台线程中进行该网络访问，以便您的UI不会阻止。然后，一旦得到结果，您就可以从主线程更新UI。类似的东西：

- (IBAction) refresh {
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
    [self performSelectorInBackground:@selector(refreshInBackground) withObject:nil];
}

- (void) refreshInBackground {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    self.jsonArray = [Post findAllRemote];
    if (self.localJsonArray == nil) {
        self.localJsonArray = [[NSMutableArray alloc]init]; // init the local array if it’s empty
    }
    [self.localJsonArray addObjectsFromArray:self.jsonArray];

    [self performSelectorOnMainThread:@selector(refreshComplete) withObject:nil waitUntilDone:NO];

}

- (void) refreshComplete {
    [self.tableView reloadData];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}

编辑：正如Rob在下面的评论中指出的那样，你需要添加某种标志（或信号量）以避免同时触发多次刷新调用。线程和竞争条件总是很棘手，但我上面的目标只是让你朝着正确的方向前进，以便你可以使用后台线程进行网络呼叫。

数组越界和缓慢的应用程序

1 个答案: