我已经构建了一个滑动导航控制器，它允许 UIViewController 以快速流畅的方式（Facebook 风格）滑动。我已经添加了一个 UIViewController 和一个子视图控制器，它有自己的子视图控制器，以及一个表格视图。最低的子视图控制器也有一个视图子视图。此 UIViewController 具有在顶视图滑开时可见的视图。
我已经测试了有无这个视图控制器的平滑度。没有它，幻灯片以每秒 60 帧的速度运行，但有了它，我的设备只能以 20 到 30 fps 的速度运行。
我也尝试过删除似乎略有改善的子视图，但没有我预期的那么多。即使使用另一个相当复杂的视图控制器（虽然没有子视图控件）切换出来，我也会获得更好的性能。
我在整个应用程序中使用自动布局，并且开始相信这是问题所在。在发生这种糟糕的滑动时，我的任何代码都没有被执行，所以我相信它与正在计算的约束有关，因为正在显示更多视图，但不能确定。
为了避免包含整个类，这里是视图控制器和子视图中的 updateViewConstraint 方法：
顶视图控制器
/**
* Called when the view controller’s view needs to update its constraints.
*/
- (void)updateViewConstraints
{
[super updateViewConstraints];
// remove all constraints
[self.view removeConstraints:self.view.constraints];
NSArray *constraints;
// add the table view to the top of the view and the parameters view to the bottom
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(Panel)-[tableView]|"
options:kNilOptions
metrics:@{@"Panel": @(kPanelWidth)}
views:self.viewsDictionary];
[self.view addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[tableView]-|"
options:kNilOptions
metrics:nil
views:self.viewsDictionary];
[self.view addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-(PanelPlus)-[recipeParameters]-|"
options:kNilOptions
metrics:@{@"PanelPlus": @(kPanelWidth + 20)}
views:self.viewsDictionary];
[self.view addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[recipeParameters(==Height)]|"
options:kNilOptions
metrics:@{ @"Height" : @(kParametersControllerHeight)}
views:self.viewsDictionary];
[self.view addConstraints:constraints];
}
第一儿童视图控制器
/**
* Called when the view controller’s view needs to update its constraints.
*/
- (void)updateViewConstraints
{
[super updateViewConstraints];
// remove all constraints
[self.view removeConstraints:self.view.constraints];
NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[pageView]|" options:kNilOptions
metrics:nil views:self.viewsDictionary];
[self.view addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[pageView]|" options:kNilOptions
metrics:nil views:self.viewsDictionary];
[self.view addConstraints:constraints];
}
第二个孩子视图控制器
- (void)updateViewConstraints
{
[super updateViewConstraints];
NSArray *constraints;
// remove all constraints
[self.view removeConstraints:self.view.constraints];
if (self.interfaceOrientation == UIInterfaceOrientationPortrait || self.interfaceOrientation == UIInterfaceOrientationPortraitUpsideDown)
{
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-(8)-[optionLabel]-[selectionWheel]-[includeExclude(==32)]-|"
options:NSLayoutFormatAlignAllCenterX
metrics:nil
views:self.viewsDictionary];
[self.view addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[selectionWheel]-|"
options:kNilOptions
metrics:nil
views:self.viewsDictionary];
[self.view addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[includeExclude]-|"
options:kNilOptions
metrics:nil
views:self.viewsDictionary];
[self.view addConstraints:constraints];
}
else
{
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-[selectionWheel]-|" options:kNilOptions
metrics:nil views:self.viewsDictionary];
[self.view addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[optionLabel]-[selectionWheel]-(Balance)-|"
options:NSLayoutFormatAlignAllCenterY
metrics:@{@"Balance": @(self.optionLabel.bounds.size.width + 40)}
views:self.viewsDictionary];
[self.view addConstraints:constraints];
}
}
自定义 UICONTROL（第二个子视图控制器的子视图）
/**
* Update constraints for the view.
*/
- (void)updateConstraints
{
[super updateConstraints];
[self removeConstraints:self.constraints];
[self.excludeButton removeConstraints:self.excludeButton.constraints];
[self.includeButton removeConstraints:self.includeButton.constraints];
NSArray *constraints;
NSLayoutConstraint *constraint;
// add everything to fill the bounds
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|-(==6)-[excludeButton]-(==6)-|"
options:kNilOptions
metrics:nil
views:self.viewsDictionary];
[self addConstraints:constraints];
constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:|[excludeButton][optionLabel][includeButton]|"
options:NSLayoutFormatAlignAllTop | NSLayoutFormatAlignAllBottom
metrics:nil
views:self.viewsDictionary];
[self addConstraints:constraints];
// make the exclude and include buttons square
constraint = [NSLayoutConstraint constraintWithItem:self.excludeButton attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.excludeButton attribute:NSLayoutAttributeHeight multiplier:1.0f constant:0.0f];
[self.excludeButton addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:self.includeButton attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self.includeButton attribute:NSLayoutAttributeHeight multiplier:1.0f constant:0.0f];
[self.includeButton addConstraint:constraint];
}