当内存消耗攀升但 Leaks 未检测到泄漏时，如何处理 iOS 中的泄漏？ [关闭]

Question

我正在开发一个 iOS ARC 应用程序（可根据要求提供更多代码），之前我正在制作和丢弃大量图像。我认为我在某个地方仍然有对图像的引用，即使我调用 removeFromSuperview 并尝试删除对不再使用的图像的所有引用。我尝试了 Leaks，Leaks 报告内存使用量随着时间的推移大致呈线性增长，从 17M 左右开始。

我检查并将所有对图像的引用替换为实例变量，因此它们将占用少量、有限且固定数量的内存，并转换而不是摆脱用于时钟指针的图像。不幸的是，这导致内存使用量随着时间的推移缓慢增加，从 5M 而不是 17M 开始，但除此之外，同样的问题，只是转换为更好的起点。

我的代码的精简版本如下。您能否告诉我什么是泄漏（或“伪泄漏”，因为泄漏并未表示泄漏）以及如何保持接近代码启动时使用的内存边界？

谢谢，

- (void) renderScreen
{
int height = floor([[UIScreen mainScreen] bounds].size.height + .4);
int width = floor([[UIScreen mainScreen] bounds].size.width + .4);

if (height == 2048 || height == 2008 || height == 1024 || height == 1004 || height == 984)
{
    if (UIInterfaceOrientationIsPortrait([UIApplication sharedApplication].statusBarOrientation))
    {
        _backgroundImage = [UIImage imageNamed:@"Background-Default-Portrait.png"];
    }
    else
    {
        _backgroundImage = [UIImage imageNamed:@"Background-Default-Landscape.png"];
    }
}
else if (height == 1536 || height == 768 || height == 748 || height == 728)
{
    _backgroundImage = [UIImage imageNamed:@"Background-Default-Landscape.png"];
}
else if (height == 1136 || height == 1116 || height == 1096)
{
    if (UIInterfaceOrientationIsPortrait([UIApplication sharedApplication].statusBarOrientation))
    {
        _backgroundImage = [UIImage imageNamed:@"Background-Default-568.png"];
    }
    else
    {
        _backgroundImage = [UIImage imageNamed:@"Background-Default-Rotated-568.png"];
    }
}
else if (height == 960 || height == 940 || height == 920 || height == 480 || height == 460 || height == 440)
{
    if (UIInterfaceOrientationIsPortrait([UIApplication sharedApplication].statusBarOrientation))
    {
        _backgroundImage = [UIImage imageNamed:@"Background-Default.png"];
    }
    else
    {
        _backgroundImage = [UIImage imageNamed:@"Background-Default-Rotated.png"];
    }
}
else if ((height == 640 || height == 620 || height == 600) && (width == 1136 || width == 1116 || width == 1096))
{
    _backgroundImage = [UIImage imageNamed:@"Background-Rotated-568.png"];
}
else if ((height == 640 || height == 620 || height == 600 || height == 320 || height == 300 || height == 280) && (width == 960 || width == 940 || width == 920 || width == 480 || width == 470 || width == 410))
{
    if (UIInterfaceOrientationIsPortrait([UIApplication sharedApplication].statusBarOrientation))
    {
        _backgroundImage = [UIImage imageNamed:@"Background-Default-Portrait.png"];
    }
    else
    {
        _backgroundImage = [UIImage imageNamed:@"Background-Default-Rotated.png"];
    }
}
else
{
    _backgroundImage = [UIImage imageNamed:@"Background-Default-Portrait.png"];

}
if (!UIInterfaceOrientationIsPortrait([UIApplication sharedApplication].statusBarOrientation))
{
    int juggle = height;
    height = width;
    width = juggle;
}
NSUInteger centerX = width * .5;
NSUInteger centerY = height * .5;

_containerRect = CGRectZero;
_containerRect.size = [[UIScreen mainScreen] bounds].size;

self.view.backgroundColor = [UIColor colorWithPatternImage:_backgroundImage];
_backgroundView = [[UIImageView alloc] initWithImage:_backgroundImage];
[self.view addSubview:_backgroundView];
if (_changed)
{
    _containerView = [[UIView alloc] initWithFrame:_containerRect];
}

double timeStampSeconds = [[NSDate date] timeIntervalSince1970];
double hours   = fmod(timeStampSeconds / 86400, 24);
double minutes = fmod(timeStampSeconds /  3600, 60);
double seconds = fmod(timeStampSeconds,     60);
NSLog(@"Milliseconds: %lf, Hours: %.0f, minutes: %.0f, seconds: %.0f", timeStampSeconds * 1000.0, hours, minutes, seconds);
[_containerView removeFromSuperview];
_containerView = [[UIView alloc] initWithFrame:_containerRect];
_hourHandImage = [UIImage imageNamed:@"hour-hand.png"];
_hourHandView = [[UIImageView alloc] initWithImage:_hourHandImage];
_hourHandImage = [UIImage imageNamed:@"hour-hand.png"];
_hourHandView = [[UIImageView alloc] initWithImage:_hourHandImage];
[self.view addSubview:_hourHandView];

_hourHandView.layer.anchorPoint = CGPointMake(0.5f, 0.5f);
_hourTransform = CGAffineTransformMakeTranslation(centerX, centerY);
_hourTransform = CGAffineTransformTranslate(_hourTransform, -17, -127);
_hourTransform = CGAffineTransformRotate(_hourTransform, hours / 12.0 * M_PI * 2.0);
_minuteTransform = CGAffineTransformMakeTranslation(centerX, centerY);
_minuteTransform = CGAffineTransformTranslate(_minuteTransform, -10, -182);
_minuteTransform = CGAffineTransformRotate(_minuteTransform, minutes / 60.0 * M_PI * 2.0);
_hourHandView.transform = _hourTransform;
_minuteHandImage = [UIImage imageNamed:@"minute-hand.png"];
_minuteHandView = [[UIImageView alloc] initWithImage:_minuteHandImage];
_minuteHandView.transform = _minuteTransform;
[self.view addSubview:_minuteHandView];
_minuteTransform = CGAffineTransformRotate(_minuteTransform, minutes / 60.0 * M_PI * 2.0);
_secondHandImage = [UIImage imageNamed:@"second-hand.png"];
_secondTransform = CGAffineTransformMakeTranslation(centerX, centerY);
_secondTransform = CGAffineTransformTranslate(_secondTransform, -10, -189);
_secondTransform = CGAffineTransformRotate(_secondTransform, seconds / 60.0 * M_PI * 2.0);
_secondHandView = [[UIImageView alloc] initWithImage:_secondHandImage];
_secondHandView.transform = _secondTransform;
[self.view addSubview:_secondHandView];
}

--编辑--

我将一种方法重构为两种方法，一种用于初始显示，一种用于增量更新。增量更新方法似乎只调用了一次，因为时钟被冻结并且签名日志语句只调用了一次。

我现在有，对于更新部分：

- (void)render
{
    [self renderScreenInitial];
    [NSTimer scheduledTimerWithTimeInterval:0.002
                                     target:self
                                   selector:@selector(renderingTimer:)
                                   userInfo:nil
                                    repeats:YES];
}

- (void) renderScreenIncremental
{
    int height = floor([[UIScreen mainScreen] bounds].size.height + .4);
    int width = floor([[UIScreen mainScreen] bounds].size.width + .4);
    if (!UIInterfaceOrientationIsPortrait([UIApplication sharedApplication].statusBarOrientation))
    {
        int juggle = height;
        height = width;
        width = juggle;
    }
    double decibelAngle = M_PI / 4 + (_decibel / 60) * M_PI / 2;
    double decibelAngleDifference = decibelAngle - _previousDecibelAngle;
    _previousDecibelAngle = decibelAngle;
    NSLog(@"%lf %lf", _decibel, decibelAngle);
    _decibelNeedleView = [[UIImageView alloc] initWithImage:_decibelNeedle];
    // CGAffineTransform decibelTransform = CGAffineTransformMakeTranslation(centerX, centerY);
    CGAffineTransform decibelTransform = CGAffineTransformMakeRotation(decibelAngleDifference);
    decibelTransform = CGAffineTransformTranslate(decibelTransform, sin(decibelAngle - .06) * -298, -cos(decibelAngle - .06) * 298);
    _decibelNeedleView.transform = decibelTransform;
    [self.view addSubview:_decibelNeedleView];
    double timestampSeconds = [[NSDate date] timeIntervalSince1970];
    double timestampSecondsDifference = timestampSeconds - _previousTimestampSeconds;
    _previousTimestampSeconds = timestampSeconds;
    double hoursDifference   = fmod(timestampSecondsDifference / 86400, 24);
    double minutesDifference = fmod(timestampSecondsDifference /  3600, 60);
    double secondsDifference = fmod(timestampSecondsDifference,     60);
    NSLog(@"Milliseconds: %lf, Hours: %.0f, minutes: %.0f, seconds: %.0f", timestampSecondsDifference * 1000.0, hoursDifference, minutesDifference, secondsDifference);
    _hourHandView.transform = CGAffineTransformMakeRotation(hoursDifference);
    _minuteHandView.transform = CGAffineTransformMakeRotation(minutesDifference);
    _secondHandView.transform = CGAffineTransformMakeRotation(secondsDifference);
}

-(void)renderingTimer:(NSTimer *)timer {
    [self renderScreenIncremental];
}

感谢您的帮助。你明白为什么它应该更新一次显示然后不继续保持更新了吗？

谢谢，

Answer 1

首先，您应该使用 Instruments 中的分配工具来识别正在分配和未释放的内容。我建议你想要 WWDC 2012 视频iOS App Performance: Memory，它演示了这一点，除其他外。

使用 Instrument 的 Allocations 工具，您不会猜测正在分配和未释放的内容，而是可以使用 heapshots/generations 来识别在您选择的某个时间范围内正在分配和未释放的实际对象.您甚至可以深入查看最初分配有问题的对象的位置。

除此之外，看看您的代码，您似乎正在删除并重新添加容器，但没有任何东西进入容器。而且您正在添加时针/分针/秒针，但从不删除它们。也许您打算将它们添加到容器中？

另外，您的代码没有描述 _changed 所做的事情，但如果那是 YES，那么您实际上是在创建一个 _containerView，将其从其父视图中删除（即使它从未添加到父视图中） )，然后丢弃它并创建另一个_containerView。很奇怪。

我还从这段代码推断出您将多次调用renderScreen。如果这是真的，那么我可能建议将视图内容的“创建”（添加背景、各种图像等）与视图的“更改”（transform 值的调整）分开。如果可能，您应该添加一次视图，然后在更新时执行最低限度的操作（更改转换）。

Answer 2

使用您正在使用的 API 逐渐增加内存是预期行为。 [UIImage imageNamed:]will cache the image。如果您想测试这些是否在刷新缓存时被释放，请导致发生内存警告。您可以在模拟器中通过转到Hardware 菜单并选择Simulate Memory Warning 来执行此操作。

您也可以使用以下代码在设备上以编程方式执行此操作：

[[NSNotificationCenter defaultCenter] postNotificationName:UIApplicationDidReceiveMemoryWarningNotification 
                                                    object:[UIApplication sharedApplication]];

您不应使用此代码发布生产应用程序