UITableViewHeaderFooterView子类，支持自动布局和部分重装不能很好地协同工作 [英] UITableViewHeaderFooterView subclass with auto layout and section reloading won't work well together
问题描述
我试图将汽车布局到我UITableViewHeaderFooterView子类。类是pretty基本，只有两个标签。这是完整的亚类：
I am trying to incorporate auto layout into my UITableViewHeaderFooterView subclass. The class is pretty basic, just two labels. This is the complete subclass:
@implementation MBTableDetailStyleFooterView
static void MBTableDetailStyleFooterViewCommonSetup(MBTableDetailStyleFooterView *_self) {
UILabel *rightLabel = [[UILabel alloc] init];
_self.rightLabel = rightLabel;
rightLabel.translatesAutoresizingMaskIntoConstraints = NO;
[_self.contentView addSubview:rightLabel];
UILabel *leftLabel = [[UILabel alloc] init];
_self.leftLabel = leftLabel;
leftLabel.translatesAutoresizingMaskIntoConstraints = NO;
[_self.contentView addSubview:leftLabel];
NSDictionary *views = NSDictionaryOfVariableBindings(rightLabel, leftLabel);
NSArray *horizontalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"|-10-[leftLabel]-(>=10)-[rightLabel]-10-|" options:0 metrics:nil views:views];
[_self.contentView addConstraints:horizontalConstraints];
// center views vertically in super view
NSLayoutConstraint *leftCenterYConstraint = [NSLayoutConstraint constraintWithItem:leftLabel attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:_self.contentView attribute:NSLayoutAttributeCenterY multiplier:1 constant:0];
[_self.contentView addConstraint:leftCenterYConstraint];
NSLayoutConstraint *rightCenterYConstraint = [NSLayoutConstraint constraintWithItem:rightLabel attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:_self.contentView attribute:NSLayoutAttributeCenterY multiplier:1 constant:0];
[_self.contentView addConstraint:rightCenterYConstraint];
// same height for both labels
NSLayoutConstraint *sameHeightConstraint = [NSLayoutConstraint constraintWithItem:leftLabel attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:rightLabel attribute:NSLayoutAttributeHeight multiplier:1 constant:0];
[_self.contentView addConstraint:sameHeightConstraint];
}
+ (BOOL)requiresConstraintBasedLayout {
return YES;
}
- (id)initWithReuseIdentifier:(NSString *)reuseIdentifier {
self = [super initWithReuseIdentifier:reuseIdentifier];
MBTableDetailStyleFooterViewCommonSetup(self);
return self;
}
@end
本类用作在与的tableView 2段第一部分页脚。第一部分包含动态的项目。所述第二部分具有只有一行，它被用来增加新项目的第一部分。
This class is used as a footer in the first section in a tableView with 2 sections. The first section contains dynamic items. The second section has only one row, which is used to add new items to the first section.
如果有在首节没有任何项目我隐藏footerView。所以，当我加入的第一个新项目我有这么出现footerView重新加载部分。在code，做这一切看起来是这样的：
If there are no items in the first section I hide the footerView. So when I add the first new item I have to reload the section so the footerView appears. The code that does all this looks like this:
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
[tableView deselectRowAtIndexPath:indexPath animated:YES];
if (indexPath.section == 1) {
BOOL sectionNeedsReload = ([self.data count] == 0); // reload section when no data (and therefor no footer) was present before the add
[self.data addObject:[NSDate date]];
NSIndexPath *newIndexPath = [NSIndexPath indexPathForRow:[self.data count]-1 inSection:0];
if (sectionNeedsReload) {
[self.tableView reloadSections:[NSIndexSet indexSetWithIndex:0] withRowAnimation:UITableViewRowAnimationAutomatic];
}
else {
[self.tableView insertRowsAtIndexPaths:@[newIndexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
}
[self configureFooter:(MBTableDetailStyleFooterView *)[tableView footerViewForSection:0] forSection:0];
}
}
- (void)configureFooter:(MBTableDetailStyleFooterView *)footer forSection:(NSInteger)section {
footer.leftLabel.text = @"Total";
footer.rightLabel.text = [NSString stringWithFormat:@"%d", [self.data count]];
}
- (UIView *)tableView:(UITableView *)tableView viewForFooterInSection:(NSInteger)section {
MBTableDetailStyleFooterView *footer = nil;
if (section == 0 && [self.data count]) {
footer = [tableView dequeueReusableHeaderFooterViewWithIdentifier:@"Footer"];
[self configureFooter:footer forSection:section];
}
return footer;
}
- (CGFloat)tableView:(UITableView *)tableView heightForFooterInSection:(NSInteger)section {
CGFloat height = 0;
if (section == 0 && [self.data count]) {
height = 20.0f;
}
return height;
}
没有真正看中的。然而，尽快 reloadSections：withRowAnimations：叫上我的tableView它，因为它是抛出一个异常无法同时满足的约束。
Nothing really fancy. However, as soon as reloadSections:withRowAnimations: is called on my tableView it throws an exception because it is "Unable to simultaneously satisfy constraints.".
某处的tableView增加了自动翻译面具调整大小约束到我的页脚。
Somewhere the tableView added a translated auto resizing mask constraint to my footer.
(
"<NSLayoutConstraint:0x718a1f0 H:[UILabel:0x7189130]-(10)-| (Names: '|':_UITableViewHeaderFooterContentView:0x7188df0 )>",
"<NSLayoutConstraint:0x7189e30 H:[UILabel:0x71892c0]-(>=10)-[UILabel:0x7189130]>",
"<NSLayoutConstraint:0x718a0a0 H:|-(10)-[UILabel:0x71892c0] (Names: '|':_UITableViewHeaderFooterContentView:0x7188df0 )>",
"<NSAutoresizingMaskLayoutConstraint:0x7591ab0 h=--& v=--& H:[_UITableViewHeaderFooterContentView:0x7188df0(0)]>"
)
当我更换 reloadSections：withRowAnimations：一起 reloadData 未添加自动尺寸调整掩码约束，一切正常通话精细。
When I replace reloadSections:withRowAnimations: with a call to reloadData no autoresizing mask constraint is added and everything works fine.
有趣的是，除了告诉我，它试图打破约束＆LT; NSLayoutConstraint：0x7189e30 H：[的UILabel：0x71892c0] - （大于= 10） - 的UILabel：0x7189130] ＆GT;
The interesting thing is that the exception tells me that it tries to break the constraint <NSLayoutConstraint:0x7189e30 H:[UILabel:0x71892c0]-(>=10)-[UILabel:0x7189130]>
但是，当我登录后续调用约束 configureFooter：forSection：此约束依然存在，但自动调整大小面具约束消失了。
But when I log the constraints in subsequent calls to configureFooter:forSection: this constraint still exists, but the auto resizing mask constraint is gone
约束条件是这些人恰恰是我所成立。
The constraints are exactly those that I have set up.
(
"<NSLayoutConstraint:0x718a0a0 H:|-(10)-[UILabel:0x71892c0] (Names: '|':_UITableViewHeaderFooterContentView:0x7188df0 )>",
"<NSLayoutConstraint:0x7189e30 H:[UILabel:0x71892c0]-(>=10)-[UILabel:0x7189130]>",
"<NSLayoutConstraint:0x718a1f0 H:[UILabel:0x7189130]-(10)-| (Names: '|':_UITableViewHeaderFooterContentView:0x7188df0 )>",
"<NSLayoutConstraint:0x718a3f0 UILabel:0x71892c0.centerY == _UITableViewHeaderFooterContentView:0x7188df0.centerY>",
"<NSLayoutConstraint:0x718a430 UILabel:0x7189130.centerY == _UITableViewHeaderFooterContentView:0x7188df0.centerY>",
"<NSLayoutConstraint:0x718a4b0 UILabel:0x71892c0.height == UILabel:0x7189130.height>"
)
在哪里这个自动调整大小面具约束从何而来？它在哪里去了？
Where does this auto resizing mask constraint come from? Where does it go?
我缺少的东西吗？我第一次看着自动布局就像一个星期前，所以这是完全可能的。
Am I missing something? The first time I looked into auto layout was like a week ago, so this is totally possible.
推荐答案
我曾与在内容查看只是一个额外的标签类似的问题。尝试插入
I had a similar problem with just one extra label in the contentView. Try to insert
static void MBTableDetailStyleFooterViewCommonSetup(MBTableDetailStyleFooterView *_self) {
_self.contentView.translatesAutoresizingMaskIntoConstraints = NO
[...]
}
在你的 MBTableDetailStyleFooterViewCommonSetup 函数第一行。对我来说，这个作品结合 reloadSections：withRowAnimations：
at first line in your MBTableDetailStyleFooterViewCommonSetup function. For me, this works in conjunction with reloadSections:withRowAnimations:.
更新：
我还添加了一个新的约束的内容查看使用所有宽度：
I also added a new constraint for the contentView to use all width:
NSArray *horizontalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[contentView]|"
options:0
metrics:nil
views:@{@"contentView" : _self.contentView}];
[_self.contentView.superview addConstraints:horizontalConstraints];
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