我试图了解 UIScrollView 在自动布局环境中是如何工作的。到目前为止，我已经尝试阅读 Apple 文档、Stack Overflow 研究、Google 研究以及研究 Matt Neuberg 的工作示例。

Apple 6.1 文档说:

The central notion of a UIScrollView object (or, simply, a scroll view) is that it is a view whose origin is adjustable over the content view. It clips the content to its frame, which generally (but not necessarily) coincides with that of the application’s main window. A scroll view tracks the movements of fingers and adjusts the origin accordingly. The view that is showing its content “through” the scroll view draws that portion of itself based on the new origin, which is pinned to an offset in the content view. The scroll view itself does no drawing except for displaying vertical and horizontal scroll indicators. The scroll view must know the size of the content view so it knows when to stop scrolling; by default, it “bounces” back when scrolling exceeds the bounds of the content.

最佳答案

工作示例

你好。首先，这是几天前编写的工作代码 ScrollView 示例。

[self addSubview:scrollView];

id views = NSDictionaryOfVariableBindings(scrollView);
[self addConstraints:PVVFL(@"H:|[scrollView]|").withViews(views).asArray];
[self addConstraints:PVVFL(@"V:|[scrollView]|").withViews(views).asArray];

id views = NSDictionaryOfVariableBindings(photoView, storeNameLabel, selectStoreButton, tagsLabel, tagsContainer, editTagsButton, commentView, sendButton, cancelButton);
[scrollView addConstraints:PVVFL(@"V:|-15-[photoView(150)]").withViews(views).asArray];
[scrollView addConstraints:PVVFL(@"|-15-[photoView]-15-|").withViews(views).asArray];
[scrollView addConstraint:PVCenterXOf(photoView).equalTo.centerXOf(scrollView).asConstraint];

[scrollView addConstraint:PVTopOf(storeNameLabel).equalTo.bottomOf(photoView).plus(20).asConstraint];
[scrollView addConstraints:
 PVVFL(@"|-15-[storeNameLabel]-(>=15)-[selectStoreButton]-15-|")
 .alignAllBaseline.withViews(views).asArray];
[selectStoreButton setContentCompressionResistancePriority:UILayoutPriorityRequired
                                                   forAxis:UILayoutConstraintAxisHorizontal];

[scrollView addConstraints:
 PVVFL(@"V:[storeNameLabel]-15-[tagsLabel][tagsContainer]").alignAllLeft.withViews(views).asArray];
[scrollView addConstraint:PVRightOf(tagsContainer).equalTo.rightOf(selectStoreButton).asConstraint];
[scrollView addConstraint:PVTopOf(editTagsButton).equalTo.bottomOf(tagsContainer).plus(10).asConstraint];
[scrollView addConstraint:PVWidthOf(editTagsButton).equalTo.widthOf(tagsContainer).asConstraint];
[scrollView addConstraint:PVLeftOf(editTagsButton).equalTo.leftOf(tagsContainer).asConstraint];

[scrollView addConstraint:PVTopOf(commentView).equalTo.bottomOf(editTagsButton).plus(10).asConstraint];
[scrollView addConstraint:PVWidthOf(commentView).equalTo.widthOf(editTagsButton).asConstraint];
[scrollView addConstraint:PVLeftOf(commentView).equalTo.leftOf(editTagsButton).asConstraint];
[scrollView addConstraint:PVHeightOf(commentView).moreThan.constant(100).asConstraint];
[scrollView addConstraint:PVLeftOf(cancelButton).equalTo.leftOf(commentView).asConstraint];
[scrollView addConstraints:PVVFL(@"[cancelButton]-(>=15)-[sendButton(==cancelButton)]").alignAllBaseline.withViews(views).asArray];
[scrollView addConstraint:PVRightOf(sendButton).equalTo.rightOf(commentView).asConstraint];
[scrollView addConstraints:PVVFL(@"V:[commentView]-10-[cancelButton]-10-|").withViews(views).asArray];

To make this work with Auto Layout, the top, left, bottom, and right edges within a scroll view now mean the edges of its content view.

Question 1 - Why is this?

Question 2 - why is this?

Question 3 - Can someone please explain what's happening when a scrollview scrolls, which object's frame origin is actually changing, and why is it done this way?

Question 4 - Can anyone explain how the constraints should be set between (A), (B), and (C) in plain English?

关于ios - Scrollview 如何与 Autolayout 一起工作，为什么设置底部垂直空间约束使其工作？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/15583077/