Question

这是我的代码，我遇到了问题。它可以工作，但加载需要很长时间。我在viewDidLoad中有代码。 self.playedGames和self.messages也是我通过查询另外两个类得到的NSArrays。

newArray = [[NSMutableArray alloc]initWithCapacity:[self.playedGames count]];
messagesArray = [[NSMutableArray alloc]initWithCapacity:[self.messages count]];
ImageArray = [[NSMutableArray alloc]initWithCapacity:[self.playedGames count]];
PFQuery *query = [PFUser query];
[query orderByDescending:@"username"];

NSArray *Userarray1 = [query findObjects];
//NSLog(@"Userarray1 = %@",Userarray1);

PFFile *imageFile = [[PFFile alloc]init];
NSURL *imageFileUrl = [[NSURL alloc]init];
NSData *imageData = [[NSData alloc]init];
for(id i in Userarray1){
    userPerson = [i valueForKey:@"username"];

    for(id object in self.messages){
        if([[object objectForKey:@"senderName"]isEqualToString:userPerson]){
            imageFile = [i objectForKey:@"profilePic"];



            if(imageFile !=nil){
                imageFileUrl = [[NSURL alloc] initWithString:imageFile.url];

                imageData = [NSData dataWithContentsOfURL:imageFileUrl];
                newImageset = [UIImage imageWithData:imageData];
                PFImageView *imgVew = [[PFImageView alloc] initWithFrame:CGRectMake(4, 5, 50, 50)];
                imgVew.image = newImageset;
                imgVew.opaque = YES;
                [messagesArray addObject:imgVew];

            }
            else{
                UIImage *NoPP = [UIImage imageNamed:@"friends_tab.png"];
                NoPP = [self imageScaledToSize:CGSizeMake(50, 50)];
                PFImageView *NoPPView = [[PFImageView alloc]initWithFrame:CGRectMake(4, 5, 50, 50)];
                NoPPView.image = NoPP;
                NoPPView.opaque = YES;
                [messagesArray addObject:NoPPView];

            }
        }
    }

    //step two
    for(id object in self.playedGames){
        if([[object objectForKey:@"yourName"] isEqualToString:userPerson]){
            imageFile = [i objectForKey:@"profilePic"];

            if(imageFile !=nil){
                imageFileUrl = [[NSURL alloc] initWithString:imageFile.url];

                imageData = [NSData dataWithContentsOfURL:imageFileUrl];
                newImageset = [UIImage imageWithData:imageData];
                PFImageView *imgVew = [[PFImageView alloc] initWithFrame:CGRectMake(4, 5, 50, 50)];
                imgVew.image = newImageset;
                imgVew.opaque = YES;
                [ImageArray addObject:imgVew];
                //NSLog(@"ImageArray = %@",ImageArray);


            }
            else{
                UIImage *NoPP = [UIImage imageNamed:@"friends_tab.png"];
                NoPP = [self imageScaledToSize:CGSizeMake(50, 50)];
                PFImageView *NoPPView = [[PFImageView alloc]initWithFrame:CGRectMake(4, 5, 50, 50)];
                NoPPView.image = NoPP;
                NoPPView.opaque = YES;
                [ImageArray addObject:NoPPView];

            }
        }
    }
}

Answer 1

两个非常大的问题。

[query findObjects];是同步的，这意味着它在完成之前不会返回。这需要在后台进行。看一下Parse提供的findInBackground方法之一。
在循环中，您通过调用imageData = [NSData dataWithContentsOfURL:imageFileUrl];从URL加载图像资源。同样，这是同步的，将等到一个图像加载后再继续下一个图像。这些图像加载也需要异步。

Answer 2

解决它并添加了这个

NSURL *imageFileUrl = [[NSURL alloc] initWithString:imageFile.url];
                        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^(void) {
                            NSData *imageData = [NSData dataWithContentsOfURL:imageFileUrl];
                            newImageset = [UIImage imageWithData:imageData];

                            dispatch_sync(dispatch_get_main_queue(), ^(void) {
                                PFImageView *imgVew = [[PFImageView alloc] initWithFrame:CGRectMake(4, 5, 50, 50)];
                                imgVew.image = newImageset;
                                imgVew.opaque = YES;
                                [messagesArray addObject:imgVew];
                            });
                            loadingthesearches1 = YES;
                            [self ReloadTheData];
                        });

它的工作速度提高了90％

缓慢循环，将图像从Parse查询加载到数组中

2 个答案: