iOS SIGSEGV SEGV_ACCERR在layoutSubviews中崩潰

Question

我的應用有時會在layoutSubview方法中崩潰。 當應用計算UITableViewCell的高度時會發生這種情況。 應用有時會崩潰，但並非總是如此。 這里的功能代碼：

+ (CGFloat)heightForEditorialCommentData:(EditorialCommentVMData *)editorialData
{
    EditorialCommentCell * cell = [EditorialCommentCell instanceCell];
    [cell applyViewModelData:editorialData];
    [cell layoutSubviews];
    return cell.commentTextLabel.frameBottom + kTextInsets.bottom;
}

+ (EditorialCommentCell *)instanceCell {
    static EditorialCommentCell *instance = nil;

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        NSArray *views = [[NSBundle mainBundle] loadNibNamed: @"EditorialCommentCell" owner:0 options:0];
        instance = views[0];
        instance.frame = CGRectMake(instance.contentView.frame.origin.x,
                                        instance.contentView.frame.origin.y,
                                        [[UIScreen mainScreen] bounds].size.width,
                                        instance.contentView.frame.size.height);
    });

    return instance;
}

這是堆棧跟蹤：

Thread : Crashed: com.apple.root.default-qos
 0  UIKit                          0x2ff92b3a -[_UIViewAdditiveAnimationAction runActionForKey:object:arguments:] + 569
 1  UIKit                          0x2ff92cf5 __67-[_UIViewAdditiveAnimationAction runActionForKey:object:arguments:]_block_invoke + 408
 2  QuartzCore                     0x2f71e4c5 CA::Layer::end_change(CA::Transaction*, unsigned int, objc_object*) + 96
 3  QuartzCore                     0x2f71f06b CA::Layer::set_bounds(CA::Rect const&, bool) + 530
 4  QuartzCore                     0x2f71ed87 -[CALayer setBounds:] + 110
 5  UIKit                          0x3017f84f -[_UILabelLayer setBounds:] + 58
 6  QuartzCore                     0x2f71fe01 -[CALayer setFrame:] + 600
 7  UIKit                          0x3017f7eb -[_UILabelLayer setFrame:] + 58
 8  UIKit                          0x2fcfc4d7 -[UIView(Geometry) setFrame:] + 254
 9  UIKit                          0x2fd09f53 -[UILabel setFrame:] + 138
 CRASH->10 MYAPP                     0x000fb611 -[UIView(Frame) setFrameWidth:] (UIView+Frame.m:103)
 11 MYAPP                     0x00130c75 -[EditorialCommentCell layoutSubviews] (EditorialCommentCell.m:139)
 12 MYAPP                     0x001324ed +[EditorialCommentCell heightForEditorialCommentData:] (EditorialCommentCell.m:351)
 13 MYAPP                     0x00115733 -[EditorialCommentsViewModel applyDataFromItem:toVMItem:] (EditorialCommentsViewModel.m:298)
 14 MYAPP                     0x00114e73 -[EditorialCommentsViewModel vmDataFromItem:] (EditorialCommentsViewModel.m:222)
 15 MYAPP                     0x000fac29 -[FatherViewModel insertItemsUpdatingExisting:intoVMItems:] (FatherViewModel.m:418)
 16 MYAPP                     0x000f9cfd __39-[FatherViewModel updateItems:failure:]_block_invoke_3 (FatherViewModel.m:281)
 17 libdispatch.dylib              0x3a4718cb _dispatch_call_block_and_release + 10
 18 libdispatch.dylib              0x3a47ada3 _dispatch_root_queue_drain + 834
 19 libdispatch.dylib              0x3a47bcd7 _dispatch_worker_thread3 + 94
 20 libsystem_pthread.dylib        0x3a5d2e31 _pthread_wqthread + 668

這里是我的layoutSubview代碼：

- (void)layoutSubviews {
    [super layoutSubviews]; // Sometimes crashed here

    CGFloat contentLeft = kTextInsets.left;

    BOOL isReply = self.editorialCommentData.inReplyToCommentId != 0;

    if (isReply) {
        contentLeft += kAuthorLeftInset + self.authorImageView.frameWidth;
    }

    self.authorImageView.frameOrigin = CGPointMake(contentLeft, kContentInsets.top);

    self.votesLabel.frameWidth = 200; // Sometimes crashed here
    [self.votesLabel sizeToFit];

    self.votesLabel.frameTop = self.authorImageView.frameTop - 1.5f;
    self.votesLabel.frameRight = self.contentView.bounds.size.width - kContentInsets.right;

    <.....more code here.....>
}

我認為這是內存管理問題。

Answer 1

好！ 我修好了它。 在Marco關於layoutSubviews方法的評論中：“您不應該直接調用此方法。如果要強制更新布局，請在下次下一次圖形更新之前調用setNeedsLayout方法。” 我只是將layoutSubviews更改為layoutIfNeeded方法：

+ (CGFloat)heightForEditorialCommentData:(EditorialCommentVMData *)editorialData
{
    EditorialCommentCell * cell = [EditorialCommentCell instanceCell];
    [cell applyViewModelData:editorialData];
    [cell layoutIfNeeded];
    return cell.commentTextLabel.frameBottom + kTextInsets.bottom;
}

從Apple有關layoutIfNeeded的文檔中：

使用此方法可以在繪制之前強制子視圖的布局。 使用接收消息的視圖作為根視圖，此方法從根開始布置視圖子樹。