我阅读了文档Synchronizing Scroll Views，并且完全按照文档进行操作，但是存在一个问题。
我想同步一个 NSTableView 和一个 NSTextView。先让NSTableView监控NSTextView，当我滚动TextView的时候一切正常，但是当我尝试滚动TableView的时候，我发现TableView一开始会跳转到另一个地方（可能向后几行），然后从那个地方继续滚动.
即使在我让 TextView 监控 TableView 之后，这个问题仍然存在。
有谁知道有什么问题？我不能同步 TableView 和 TextView 吗？
编辑： 好的，现在我发现 TableView 会回到上次滚动后的位置。比如TableView的顶行是第10行，然后我滚动TextView，现在TableView的顶行是第20行，如果我再次滚动TableView，TableView会先回到第10行，然后开始滚动。
我在对非常相似的情况（在 Lion 上）进行故障排除时遇到了这个确切的问题。我注意到这只发生在滚动条被隐藏时——但我证实它们仍然存在于笔尖中，并且仍然被正确实例化。
我什至确保打电话给-[NSScrollView reflectScrolledClipView:]，但这并没有什么不同。看起来这确实是 NSScrollView 中的一个错误。
无论如何，我能够通过创建自定义滚动类来解决这个问题。我所要做的就是重写以下类方法：
+ (BOOL)isCompatibleWithOverlayScrollers
{
// Let this scroller sit on top of the content view, rather than next to it.
return YES;
}
- (void)setHidden:(BOOL)flag
{
// Ugly hack: make sure we are always hidden.
[super setHidden:YES];
}
然后，我允许滚动条在 Interface Builder 中“可见”。但是，由于它们隐藏自己，它们不会出现在屏幕上，并且用户无法单击它们。令人惊讶的是 IB 设置和hidden属性不等价，但从行为中可以清楚地看出它们不等价。
这不是最好的解决方案，但它是我想出的最简单的解决方法（到目前为止）。
我有一个非常相似的问题。我有 3 个滚动视图要同步。一个只水平滚动的标题。一个是仅垂直滚动的侧栏。一个是标题下方和侧栏右侧的内容区域。页眉和侧边栏应随内容区域移动。如果滚动，内容区域应与标题或侧栏一起移动。
水平滚动从来都不是问题。垂直滚动总是导致两个视图滚动相反的方向。
我想到的奇怪的解决方案是创建一个 clipView 子类（我已经这样做了，如果你想要任何开箱即用的好东西，你几乎总是需要这样做。）在 clipView 子类中，我添加了一个属性BOOL isInverted 并且在 isFlipped 的覆盖中我返回 self.isInverted。
奇怪的是，这些用于翻转的 BOOL 值从一开始就在所有 3 个视图中设置并匹配。滚动机器似乎确实有问题。我偶然发现的解决方法是将滚动同步代码夹在调用之间，以将侧栏和内容视图都设置为未翻转，然后更新任何垂直滚动，然后再次将两者设置为翻转。一定是滚动机器中的一些老化代码试图支持反向滚动......
这些是 NSNotificationCenter addObserver 方法调用的方法，用于观察 clipViews 的 NSViewBoundsDidChangeNotification。
- (void)synchWithVerticalControlClipView:(NSNotification *)aNotification
{
NSPoint mouseInWindow = self.view.window.currentEvent.locationInWindow;
NSPoint converted = [self.verticalControl.enclosingScrollView convertPoint:mouseInWindow fromView:nil];
if (!NSPointInRect(converted, self.verticalControl.enclosingScrollView.bounds)) {
return;
}
[self.contentGridClipView setIsInverted:NO];
[self.verticalControlClipView setIsInverted:NO];
// ONLY update the contentGrid view.
NSLog(@"%@", NSStringFromSelector(_cmd));
NSPoint changedBoundsOrigin = self.verticalControlClipView.documentVisibleRect.origin;
NSPoint currentOffset = self.contentGridClipView.bounds.origin;
NSPoint newOffset = currentOffset;
newOffset.y = changedBoundsOrigin.y;
NSLog(@"\n changedBoundsOrigin=%@\n currentOffset=%@\n newOffset=%@", NSStringFromPoint(changedBoundsOrigin), NSStringFromPoint(currentOffset), NSStringFromPoint(newOffset));
[self.contentGridClipView scrollToPoint:newOffset];
[self.contentGridClipView.enclosingScrollView reflectScrolledClipView:self.contentGridClipView];
[self.contentGridClipView setIsInverted:YES];
[self.verticalControlClipView setIsInverted:YES];
}
- (void)synchWithContentGridClipView:(NSNotification *)aNotification
{
NSPoint mouseInWindow = self.view.window.currentEvent.locationInWindow;
NSPoint converted = [self.contentGridView.enclosingScrollView convertPoint:mouseInWindow fromView:nil];
if (!NSPointInRect(converted, self.contentGridView.enclosingScrollView.bounds)) {
return;
}
[self.contentGridClipView setIsInverted:NO];
[self.verticalControlClipView setIsInverted:NO];
// Update BOTH the control views.
NSLog(@"%@", NSStringFromSelector(_cmd));
NSPoint changedBoundsOrigin = self.contentGridClipView.documentVisibleRect.origin;
NSPoint currentHOffset = self.horizontalControlClipView.documentVisibleRect.origin;
NSPoint currentVOffset = self.verticalControlClipView.documentVisibleRect.origin;
NSPoint newHOffset, newVOffset;
newHOffset = currentHOffset;
newVOffset = currentVOffset;
newHOffset.x = changedBoundsOrigin.x;
newVOffset.y = changedBoundsOrigin.y;
[self.horizontalControlClipView scrollToPoint:newHOffset];
[self.verticalControlClipView scrollToPoint:newVOffset];
[self.horizontalControlClipView.enclosingScrollView reflectScrolledClipView:self.horizontalControlClipView];
[self.verticalControlClipView.enclosingScrollView reflectScrolledClipView:self.verticalControlClipView];
[self.contentGridClipView setIsInverted:YES];
[self.verticalControlClipView setIsInverted:YES];
}
这在 99% 的时间里都有效，只有偶尔的抖动。水平滚动同步没有问题。
在自动布局环境中使用文档视图的 Swift 4 版本。基于 Apple 文章Synchronizing Scroll Views与NSView.boundsDidChangeNotification同步到其他滚动视图时在剪辑视图上临时忽略的区别。为了隐藏垂直滚动条，使用了可重用类型InvisibleScroller。
文件SynchronedScrollViewController.swift – 带有两个滚动视图的视图控制器。
class SynchronedScrollViewController: ViewController {
private lazy var leftView = TestView().autolayoutView()
private lazy var rightView = TestView().autolayoutView()
private lazy var leftScrollView = ScrollView(horizontallyScrolledDocumentView: leftView).autolayoutView()
private lazy var rightScrollView = ScrollView(horizontallyScrolledDocumentView: rightView).autolayoutView()
override func setupUI() {
view.addSubviews(leftScrollView, rightScrollView)
leftView.backgroundColor = .red
rightView.backgroundColor = .blue
contentView.backgroundColor = .green
leftScrollView.verticalScroller = InvisibleScroller()
leftView.setIntrinsicContentSize(CGSize(intrinsicHeight: 720)) // Some fake height
rightView.setIntrinsicContentSize(CGSize(intrinsicHeight: 720)) // Some fake height
}
override func setupHandlers() {
(leftScrollView.contentView as? ClipView)?.onBoundsDidChange = { [weak self] in
print("\(Date().timeIntervalSinceReferenceDate) : Left scroll view changed")
self?.syncScrollViews(origin: $0)
}
(rightScrollView.contentView as? ClipView)?.onBoundsDidChange = { [weak self] in
print("\(Date().timeIntervalSinceReferenceDate) : Right scroll view changed.")
self?.syncScrollViews(origin: $0)
}
}
override func setupLayout() {
LayoutConstraint.pin(to: .vertically, leftScrollView, rightScrollView).activate()
LayoutConstraint.withFormat("|[*(==40)]-[*]|", leftScrollView, rightScrollView).activate()
}
private func syncScrollViews(origin: NSClipView) {
// See also:
// https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/NSScrollViewGuide/Articles/SynchroScroll.html
let changedBoundsOrigin = origin.documentVisibleRect.origin
let targetScrollView = leftScrollView.contentView == origin ? rightScrollView : leftScrollView
let curOffset = targetScrollView.contentView.bounds.origin
var newOffset = curOffset
newOffset.y = changedBoundsOrigin.y
if curOffset != changedBoundsOrigin {
(targetScrollView.contentView as? ClipView)?.scroll(newOffset, shouldNotifyBoundsChange: false)
targetScrollView.reflectScrolledClipView(targetScrollView.contentView)
}
}
}
文件：TestView.swift – 测试视图。每 20 个点画一条线。
class TestView: View {
override init() {
super.init()
setIsFlipped(true)
}
override func setupLayout() {
needsDisplay = true
}
required init?(coder decoder: NSCoder) {
fatalError()
}
override func draw(_ dirtyRect: NSRect) {
super.draw(dirtyRect)
guard let context = NSGraphicsContext.current else {
return
}
context.saveGraphicsState()
let cgContext = context.cgContext
cgContext.setStrokeColor(NSColor.white.cgColor)
for x in stride(from: CGFloat(20), through: bounds.height, by: 20) {
cgContext.addLines(between: [CGPoint(x: 0, y: x), CGPoint(x: bounds.width, y: x)])
NSString(string: "\(Int(x))").draw(at: CGPoint(x: 0, y: x), withAttributes: nil)
}
cgContext.strokePath()
context.restoreGraphicsState()
}
}
文件：NSScrollView.swift - 可重用扩展。
extension NSScrollView {
public convenience init(documentView view: NSView) {
let frame = CGRect(dimension: 10) // Some dummy non zero value
self.init(frame: frame)
let clipView = ClipView(frame: frame)
clipView.documentView = view
clipView.autoresizingMask = [.height, .width]
contentView = clipView
view.frame = frame
view.translatesAutoresizingMaskIntoConstraints = true
view.autoresizingMask = [.width, .height]
}
public convenience init(horizontallyScrolledDocumentView view: NSView) {
self.init(documentView: view)
contentView.setIsFlipped(true)
view.translatesAutoresizingMaskIntoConstraints = false
LayoutConstraint.pin(in: contentView, to: .horizontally, view).activate()
view.topAnchor.constraint(equalTo: contentView.topAnchor).activate()
hasVerticalScroller = true // Without this scroll might not work properly. Seems Apple bug.
}
}
文件：InvisibleScroller.swift - 可重复使用的隐形滚动条。
// Disabling scroll view indicators.
// See: https://stackoverflow.com/questions/9364953/hide-scrollers-while-leaving-scrolling-itself-enabled-in-nsscrollview
public class InvisibleScroller: Scroller {
public override class var isCompatibleWithOverlayScrollers: Bool {
return true
}
public override class func scrollerWidth(for controlSize: NSControl.ControlSize, scrollerStyle: NSScroller.Style) -> CGFloat {
return CGFloat.leastNormalMagnitude // Dimension of scroller is equal to `FLT_MIN`
}
public override func setupUI() {
// Below assignments not really needed, but why not.
scrollerStyle = .overlay
alphaValue = 0
}
}
文件：ClipView.swift - NSClipView 的自定义子类。
open class ClipView: NSClipView {
public var onBoundsDidChange: ((NSClipView) -> Void)? {
didSet {
setupBoundsChangeObserver()
}
}
private var boundsChangeObserver: NotificationObserver?
private var mIsFlipped: Bool?
open override var isFlipped: Bool {
return mIsFlipped ?? super.isFlipped
}
// MARK: -
public func setIsFlipped(_ value: Bool?) {
mIsFlipped = value
}
open func scroll(_ point: NSPoint, shouldNotifyBoundsChange: Bool) {
if shouldNotifyBoundsChange {
scroll(to: point)
} else {
boundsChangeObserver?.isActive = false
scroll(to: point)
boundsChangeObserver?.isActive = true
}
}
// MARK: - Private
private func setupBoundsChangeObserver() {
postsBoundsChangedNotifications = onBoundsDidChange != nil
boundsChangeObserver = nil
if postsBoundsChangedNotifications {
boundsChangeObserver = NotificationObserver(name: NSView.boundsDidChangeNotification, object: self) { [weak self] _ in
guard let this = self else { return }
self?.onBoundsDidChange?(this)
}
}
}
}
文件：NotificationObserver.swift – 可重用的通知观察者。
public class NotificationObserver: NSObject {
public typealias Handler = ((Foundation.Notification) -> Void)
private var notificationObserver: NSObjectProtocol!
private let notificationObject: Any?
public var handler: Handler?
public var isActive: Bool = true
public private(set) var notificationName: NSNotification.Name
public init(name: NSNotification.Name, object: Any? = nil, queue: OperationQueue = .main, handler: Handler? = nil) {
notificationName = name
notificationObject = object
self.handler = handler
super.init()
notificationObserver = NotificationCenter.default.addObserver(forName: name, object: object, queue: queue) { [weak self] in
guard let this = self else { return }
if this.isActive {
self?.handler?($0)
}
}
}
deinit {
NotificationCenter.default.removeObserver(notificationObserver, name: notificationName, object: notificationObject)
}
}
结果：
