在循环 iphone 中创建多个标签的内存管理

Question

我在一个循环中创建多个标签，我对内存管理感到困惑，因为标签的每个实例都具有相同的名称，因为它们都是在循环中创建的，所以这意味着每次在循环，最后分配的标签将被覆盖，不再占用内存，或者它仍然存储在内存中。很困惑，请帮忙，提前谢谢。

- (void)fetchEntrys
{

JournalrAppDelegate *appDelegate =
[[UIApplication sharedApplication] delegate];

NSManagedObjectContext *context =
[appDelegate managedObjectContext];

NSEntityDescription *entityDesc =
[NSEntityDescription entityForName:@"Entrys"
            inManagedObjectContext:context];

NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entityDesc];


NSManagedObject *matches = nil;

NSError *error;
NSArray *objects = [context executeFetchRequest:request
                                          error:&error];

if ([objects count] == 0) {
    NSLog(@"No matches");
} else {


    NSLog(@"Matches found");



    matches = objects[1];

    NSString *firstEntry = [matches valueForKey:@"entry"];
    NSLog(@"First Entry: %@", firstEntry);
    self.totlal = [objects count];
     int i = [objects count] - 1;
    NSLog(@"%i", i);
    while ( i >  -1) {
        matches = objects[i];
        NSString *entry = [matches valueForKey:@"entry"];
        NSDate *date = [matches valueForKey:@"date"];
        NSDateFormatter *formatDate = [[NSDateFormatter alloc]init];
        [formatDate setDateFormat:@"MM/dd/YY"];
        NSString *dateString = [formatDate stringFromDate:date];


        NSLog(@"Date: %@", dateString);
         NSLog(@"Entry: %@", entry);

        UILabel *dateLabel = [[UILabel alloc] init];
        dateLabel.text = dateString;
        dateLabel.frame = CGRectMake(20, cY, 100, 30);
        dateLabel.numberOfLines = 3;
        dateLabel.font = [UIFont boldSystemFontOfSize:24.0];
        [dateLabel setTag:i];

        UIButton *deleteButton  = [[UIButton alloc]initWithFrame:CGRectMake(230, dateLabel.frame.origin.y, 70, 27)];
        [deleteButton addTarget:self action:@selector(deleteButtonPressed) forControlEvents:UIControlEventTouchDown];
        [deleteButton setBackgroundImage:[UIImage imageNamed:@"delete.jpg"] forState:UIControlStateNormal];
        [deleteButton setTag:i];


        cY += 35;

        UILabel *labelEntry = [[UILabel alloc]init];
        labelEntry.numberOfLines = 0;
        labelEntry.text = entry;
        CGRect lblFrame =  CGRectMake(20, cY, 280, 1000);
        labelEntry.frame = lblFrame;
        labelEntry.textAlignment = NSTextAlignmentLeft;
        labelEntry.backgroundColor = [UIColor clearColor];
        [labelEntry sizeToFit];
        [labelEntry setTag:i];





        UILabel *outerLabel = [[UILabel alloc]initWithFrame:CGRectMake(10, cY - 50, 300, labelEntry.frame.size.height + 80)];
        [scrollView addSubview:outerLabel];

        outerLabel.layer.borderColor = [UIColor grayColor].CGColor;
        outerLabel.layer.borderWidth = 1.0;
        outerLabel.tag = i;

        if(i ==[objects count] - 1){
            self.firstY = outerLabel.frame.origin.y;
        }

        //UIImageView *backgroundImage = [[UIImageView alloc]initWithFrame:CGRectMake(10, cY, 312, labelEntry.frame.size.height)];
        //backgroundImage.contentMode = UIViewContentModeScaleToFill;
        //backgroundImage.image = [UIImage imageNamed:@"post.jpg"];
        //NSLog(@"Image Height :%f", backgroundImage.frame.size.height);

        //[scrollView addSubview:backgroundImage];






        cY += labelEntry.frame.size.height;
        NSLog(@"Label Height: %f", labelEntry.frame.size.height);
        NSLog(@"currenty: %f", cY);
        cY += 100.f;

        scrollView.scrollEnabled = YES;
        scrollView.showsVerticalScrollIndicator = YES;
        [scrollView addSubview: labelEntry];
        [scrollView addSubview:dateLabel];
        [scrollView addSubview:deleteButton];

        NSLog(@"%i", i);

                    i--;
    }

    scrollView.contentSize = CGSizeMake(320, cY);
    NSLog(@"cY: %f", cY);
    self.currentI = i;

Answer 1

只要还有一些对标签的引用，它的内存就会被保留。例如，如果您使用[self.view addSubview:label]，那么标签将与self.view 一样保留在内存中。

同样，如果将标签添加到数组中，标签的内存将被保留，直到数组被释放。

创建具有相同实例名称的新标签后，您将无法再通过它访问旧标签。如果您的标签是视图的子视图，则可以使用[view subviews] 返回子视图数组并使用该数组查找标签。