将子视图添加到屏幕问题

Posted 2023-02-27

【中文标题】将子视图添加到屏幕问题

【英文标题】：Adding subviews to screen issue

【发布时间】：2013-09-16 17:03:10

【问题描述】：

我在 iPhone 应用程序的屏幕上添加了大量图像按钮。我的代码一切正常。

问题是在每个子视图都准备好显示之前，子视图不会显示。例如，我有 48 个子视图，我不想等到每个子视图都准备好后，我希望在加载时能够明显地看到每个子视图出现在屏幕上。

我希望这是有道理的。随着我向集合中添加更多图像，问题变得越来越大。

这是我的代码给你看：

for (int i = 0; i < imgNumbers.count; i++) 
    myButton = [UIButton buttonWithType:UIButtonTypeCustom];
    CGRect buttonValue = [[btn9Locations objectAtIndex:location] CGRectValue];
    myButton.frame = buttonValue;
    NSString *imagePart1 = [[NSString alloc] initWithFormat:@"%@", imgNumbers[i]];

    [myButton addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchDownRepeat];

    NSURL *tmpDirURL = [NSURL fileURLWithPath:NSTemporaryDirectory() isDirectory:YES];
    NSURL *fileURL = [tmpDirURL URLByAppendingPathComponent:imagePart1];

    NSString *imageLocation = [[NSString alloc]initWithFormat:@"%@", [fileURL path]];
    UIImage * image = [UIImage imageWithContentsOfFile:imageLocation];

    [myButton setBackgroundColor:[UIColor colorWithRed:0.94 green:0.39 blue:0.13 alpha:0.0]];
    [myButton setBackgroundImage:image forState:UIControlStateNormal];
    [myButton setTitle:[imageNames[i] uppercaseString] forState:UIControlStateNormal];
    [myButton.titleLabel setFont:[UIFont fontWithName:@"Helvetica-Light" size:20]];
    [myButton setContentHorizontalAlignment:UIControlContentHorizontalAlignmentRight];
    [myButton setContentVerticalAlignment:UIControlContentVerticalAlignmentBottom];
    [myButton setTitleColor:[UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:0.5] forState:UIControlStateNormal];
    myButton.imageView.layer.cornerRadius = 7.0f;
    myButton.layer.shadowRadius = 3.0f;
    myButton.layer.shadowColor = [UIColor blackColor].CGColor;
    myButton.layer.shadowOffset = CGSizeMake(0.0f, 1.0f);
    myButton.layer.shadowOpacity = 0.5f;
    myButton.layer.masksToBounds = NO;
    [buttons addObject:myButton];
    [scrollview addSubview:myButton];  

希望这是有道理的，我见过一些应用程序，当您向下滚动时，每个项目都会淡入屏幕，但我似乎无法先对这部分进行排序！

谢谢

【参考方案1】：

尝试将初始化代码移动到后台队列中，并且只在主队列上调用addSubview。

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^
        for (int i = 0; i < imgNumbers.count; i++) 
            myButton = [UIButton buttonWithType:UIButtonTypeCustom];
            CGRect buttonValue = [[btn9Locations objectAtIndex:location] CGRectValue];
            myButton.frame = buttonValue;
            NSString *imagePart1 = [[NSString alloc] initWithFormat:@"%@", imgNumbers[i]];

            [myButton addTarget:self action:@selector(buttonClick:) forControlEvents:UIControlEventTouchDownRepeat];

            NSURL *tmpDirURL = [NSURL fileURLWithPath:NSTemporaryDirectory() isDirectory:YES];
            NSURL *fileURL = [tmpDirURL URLByAppendingPathComponent:imagePart1];

            NSString *imageLocation = [[NSString alloc]initWithFormat:@"%@", [fileURL path]];
            UIImage * image = [UIImage imageWithContentsOfFile:imageLocation];

            [myButton setBackgroundColor:[UIColor colorWithRed:0.94 green:0.39 blue:0.13 alpha:0.0]];
            [myButton setBackgroundImage:image forState:UIControlStateNormal];
            [myButton setTitle:[imageNames[i] uppercaseString] forState:UIControlStateNormal];
            [myButton.titleLabel setFont:[UIFont fontWithName:@"Helvetica-Light" size:20]];
            [myButton setContentHorizontalAlignment:UIControlContentHorizontalAlignmentRight];
            [myButton setContentVerticalAlignment:UIControlContentVerticalAlignmentBottom];
            [myButton setTitleColor:[UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:0.5] forState:UIControlStateNormal];
            myButton.imageView.layer.cornerRadius = 7.0f;
            myButton.layer.shadowRadius = 3.0f;
            myButton.layer.shadowColor = [UIColor blackColor].CGColor;
            myButton.layer.shadowOffset = CGSizeMake(0.0f, 1.0f);
            myButton.layer.shadowOpacity = 0.5f;
            myButton.layer.masksToBounds = NO;
            [buttons addObject:myButton];
            dispatch_async(dispatch_get_main_queue(), ^
               [scrollview addSubview:myButton]; 
            );
        
    );

【讨论】：

感谢您的回复。但这使得屏幕时间增加了 5 倍，并且仍然同时出现。任何其他想法:)

我一直在玩这个想法，我在每个按钮下都有标签，奇怪的是，如果我移动 dispatch_async(dispatch_get_main_queue(), ^ 标签几乎立即出现但带有图像的按钮仍然比以前花费更长的时间。希望有人能帮助我......！！