Autolayout，编程与界面构建器

Question

只是添加一个与其他两个相关视图位于同一父视图中的视图。

self.vDist = [[UILabel alloc] initWithFrame:CGRectMake(20, 20, 42, 21)];
[self.vDist setTranslatesAutoresizingMaskIntoConstraints:NO];
[self.view addSubview:self.vDist];
NSLayoutConstraint *lc;
lc = [NSLayoutConstraint constraintWithItem:self.vDist attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1.0 constant:20.0];
[self.view addConstraint:lc];
lc = [NSLayoutConstraint constraintWithItem:self.vDist attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeft multiplier:1.0 constant:20.0];
[self.view addConstraint:lc];

然后，我在顶部

创建小方形视图

/*********************** video view */
self.videoView = [[UIView alloc] initWithFrame:CGRectMake(90, 20, 140, 140)];
[self.videoView setBackgroundColor:[UIColor greenColor]];
[self.videoView setTranslatesAutoresizingMaskIntoConstraints:NO];
[self.view addSubview:self.videoView];

// width & height constraints, as UIViews don't have intrinsic constraints

lc = [NSLayoutConstraint constraintWithItem:self.videoView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:140.0];
[self.videoView addConstraint:lc];
lc = [NSLayoutConstraint constraintWithItem:self.videoView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:140.0];
[self.videoView addConstraint:lc];

// center constraint

lc = [NSLayoutConstraint constraintWithItem:self.videoView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0.0];
[self.view addConstraint:lc];

// top constraint with its parent view

lc = [NSLayoutConstraint constraintWithItem:self.videoView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1.0 constant:20.0];
[self.view addConstraint:lc];

这个平方视图在任何设备方向都显示正常

现在我在屏幕下方创建第二个视图。当我为每个尺寸属性

创建约束时，它的尺寸无关紧要

/*********************** listado view */
self.listadoView = [[UIView alloc] initWithFrame:CGRectMake(5, 248, 310, 100)];
[self.listadoView setTranslatesAutoresizingMaskIntoConstraints:NO];
[self.listadoView setBackgroundColor:[UIColor whiteColor]];
[self.view addSubview:self.listadoView];

// height and width constraints as UIView don't have intrinsic constraints

lc = [NSLayoutConstraint constraintWithItem:self.listadoView attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:310];
[self.listadoView addConstraint:lc];
lc = [NSLayoutConstraint constraintWithItem:self.listadoView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1.0 constant:300];

// make it weak to be able to squeeze contents

lc.priority = 250;
[self.listadoView addConstraint:lc];

// top with videoView's bottom

lc = [NSLayoutConstraint constraintWithItem:self.listadoView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationLessThanOrEqual toItem:self.videoView attribute:NSLayoutAttributeBottom multiplier:1.0 constant:88.0];
[self.view addConstraint:lc];

// top with parent's view top

lc = [NSLayoutConstraint constraintWithItem:self.listadoView attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeBottom multiplier:1.0 constant:248.0];
[self.view addConstraint:lc];

// center constraint

lc = [NSLayoutConstraint constraintWithItem:self.listadoView attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:0.0];
[self.view addConstraint:lc];

试图在这里复制IB对其他视图中的约束所做的事情

lc = [NSLayoutConstraint constraintWithItem:self.listadoView attribute:NSLayoutAttributeLeft relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeLeft multiplier:1.0 constant:5];
[self.view addConstraint:lc];
lc = [NSLayoutConstraint constraintWithItem:self.listadoView attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeBottom multiplier:1.0 constant:10];
[self.view addConstraint:lc];

结果屏幕在下方，绿色正方形。垂直绿色屏幕显示了我的期望（见下面的黄色图像），但在绿色水平，正如您所看到的，listadoView的下边缘位于屏幕边缘下方，即使我正在设置所有约束IB为黄色设置，那些连同我在黄色设置的那些。

关于如何设置约束的任何建议？...也许它们的创建顺序与它有关？，因为有时候我删除了一个约束并且它有效，然后我重新添加了约束，仍然有效！再次使用所有约束，然后停止工作（什么？！）。为了提交错误，很难成功地重现它，但它确实发生了。

我已经在iOS5.1和6.x下的XCode 4.6和iOS6.1下的xCode 5中测试了这段代码。

Answer 1

发现我的错误。我设置了listadoView的底部约束，其父视图为10，即+10，它应该是-10。这样，界面显示与另一个.xib（黄色方块）一样。