UILabel(CALayer)正在使用大量虚拟内存 [英] UILabel (CALayer) is using large amounts of virtual memory

问题描述

在Xcode and Instruments中，我看到UILabel (CALayer)使用了大量的虚拟内存(匿名VM).我看到每个UILabel大约235 KB的虚拟内存.

In Xcode and Instruments I see UILabel (CALayer) using large amounts of virtual memory (Anonymous VM). I see about 235 KB of virtual memory per UILabel.

我认为这可能是iOS 7.1或7.1.1的新问题.

I think this perhaps is a new issue with iOS 7.1 or 7.1.1.

这是预期的吗?

我创建了一个简单的程序，该程序可以创建500个UILabels，并且Instruments显示已使用的115MB内存.在大约1500个标签处，应用程序被操作系统终止.

I created a simple program that creates 500 UILabels and Instruments shows 115MB of memory used. At about 1500 labels the application is terminated by the OS.

for (int i = 0; i < 500; i++)
{
    index = (int)[self.items count];
    index++;

    frame = CGRectMake(10.0, 20, 300.0, 50.0);

    UILabel *newLabel = [[UILabel alloc] initWithFrame:frame];
    newLabel.text = [NSString stringWithFormat:@"This is text for label: %d", index];
    newLabel.backgroundColor = [UIColor whiteColor];
    [self.view addSubview:newLabel];

    [self.items setObject:newLabel forKey:[NSNumber numberWithInteger:index]];
}

有想法吗?

推荐答案

UILabel，并且任何使用drawRect的视图(至少在iOS 7+上)都由纹理支持，因此每个UILabel都会使用大量内存，标签越大，使用的内存越多.

UILabel, and any view that uses drawRect (at least on iOS 7+) is backed by a texture, so every UILabel will use a lot of memory, the larger the label, the more memory used.

我发现，在我的照片编辑扩展程序"You Doodle"中，这尤其令人痛苦，该扩展程序允许在照片"应用中添加文本.不幸的是，与常规应用程序崩溃之前，照片扩展名比常规应用程序更受内存使用限制，因此我不得不极大地限制文本的缩放范围.

I've found this especially painful in my photo editing extension for You Doodle which allows adding text in the Photos app. Unfortunately I have to greatly restrict the scale range of the text because photo extensions are much more limited to memory usage than regular apps before they crash.

可以通过运行工具并分配一堆大型UILabel并设置其文本并确保它们均可见来轻松验证这一点，即:

This can easily be verified by running instruments and allocating a bunch of large UILabel's and setting their text and ensuring they are all visible, i.e.:

CGRect f = CGRectMake(0.0.0f, 0.0f, 300.0f, 300.0f);
for (NSInteger i = 0; i < 100; i++)
{
    UILabel* l = [[UILabel alloc] initWithFrame:f];
    l.backgroundColor = UIColor.blueColor;
    l.textColor = UIColor.whiteColor;
    l.text = @"UILabel text for the memory test";
    l.numberOfLines = 0;
    [self.view addSubview:l];
}

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