所以我得到了这个 UITableView，它从内存中获取数据（已经预加载，滚动时没有请求，所有内容都在布局视图之前加载）。每个单元格的高度根据 UITextView 和自动布局中的文本量动态计算。单元格是从笔尖加载的，并且重复使用单元格工作正常（至少我希望如此）。我在计算行高时使用 UITableViewAutomaticDimension，因此我不会像 iOS 8 之前那样强制单元格布局两次。
以下是我填充单元格并计算高度的相关方法：
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *cellType = [self reuseIdentifierForIndexPath:indexPath];
if ([cellType isEqualToString:kLoadingCell])
return kLoadingCellHeight;
else if ([cellType isEqualToString:kOfflineCell])
return kOfflineCellHeight;
else if ([cellType isEqualToString:kFootprintListHeaderCell])
return kHeaderCellHeight;
else if ([cellType isEqualToString:kFootprintCellUnsynced])
return kUnsyncedCellHeight;
else if ([cellType isEqualToString:kShowFullTripCell])
return kShowFullTripCellHeight;
else if ([cellType isEqualToString:kFootprintOnMapCell])
return kFootprintOnMapCellHeight;
else
{
return UITableViewAutomaticDimension;
}
}
- (CGFloat)tableView:(UITableView *)tableView estimatedHeightForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *cellType = [self reuseIdentifierForIndexPath:indexPath];
if ([cellType isEqualToString:kLoadingCell])
return kLoadingCellHeight;
else if ([cellType isEqualToString:kOfflineCell])
return kOfflineCellHeight;
else if ([cellType isEqualToString:kFootprintListHeaderCell])
return kHeaderCellHeight;
else if ([cellType isEqualToString:kFootprintCellUnsynced])
return kUnsyncedCellHeight;
else if ([cellType isEqualToString:kShowFullTripCell])
return kShowFullTripCellHeight;
else if ([cellType isEqualToString:kFootprintOnMapCell])
return kFootprintOnMapCellHeight;
else
{
return UITableViewAutomaticDimension;
}
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *cellType = [self reuseIdentifierForIndexPath:indexPath];
if ([cellType isEqualToString:kLoadingCell])
{
UITableViewCell *loadingCell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:nil];
loadingCell.tag = kLoadingCellTag;
loadingCell.selectionStyle = UITableViewCellSelectionStyleNone;
loadingCell.backgroundColor = loadingCell.contentView.backgroundColor = [UIColor clearColor];
UIActivityIndicatorView *activityIndicatorView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
activityIndicatorView.center = CGPointMake(tableView.frame.size.width / 2, 20);
[loadingCell.contentView addSubview:activityIndicatorView];
[activityIndicatorView startAnimating];
return loadingCell;
}
else if ([cellType isEqualToString:kOfflineCell])
{
FPOfflineCell *offlineCell = [tableView dequeueReusableCellWithIdentifier:kOfflineCell];
return offlineCell;
}
else if ([cellType isEqualToString:kFootprintListHeaderCell])
{
FPFootprintListHeaderCell *headerCell = [tableView dequeueReusableCellWithIdentifier:kFootprintListHeaderCell];
[headerCell.syncButton addTarget:self action:@selector(syncButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
return headerCell;
}
else if ([cellType isEqualToString:kFootprintCellUnsynced])
{
FPFootprintCellUnsynced *unsyncedCell = [tableView dequeueReusableCellWithIdentifier:kFootprintCellUnsynced];
unsyncedCell.footprint = self.map.footprintsNonSynced[[self unsyncedFootprintIndexForIndexPath:indexPath]];
return unsyncedCell;
}
else if ([cellType isEqualToString:kShowFullTripCell])
{
FPShowFullTripCell *showFullTripCell = [tableView dequeueReusableCellWithIdentifier:kShowFullTripCell];
return showFullTripCell;
}
else if ([cellType isEqualToString:kFootprintOnMapCell])
{
FPFootprintOnMapCell *footprintOnMapCell = [tableView dequeueReusableCellWithIdentifier:kFootprintOnMapCell];
footprintOnMapCell.footprint = self.map.footprints[0];
return footprintOnMapCell;
}
else
{
FPFootprint *footprint = self.map.footprints[[self footprintIndexForIndexPath:indexPath]];
FootprintCell *cell = [tableView dequeueReusableCellWithIdentifier:kFootprintCell];
cell.titleLabel.text = footprint.name;
cell.dateLabel.text = footprint.displayDate;
cell.textView.text = nil;
if (footprint.text && footprint.text.length > 0) {
if ([self.readmoreCache[@(footprint.hash)] boolValue]) {
cell.textView.text = footprint.text;
} else {
cell.textView.text = [footprint.text stringByAppendingReadMoreAndLimitingToCharacterCount:300 screenWidth:tableView.frame.size.width];
}
} else {
cell.hasText = NO;
}
cell.textView.markdownLinkTextViewDelegate = self;
[cell.textView setNeedsDisplay];
cell.isPrivate = footprint.isPrivate;
[cell.likesAndCommentsView setLikesCount:footprint.likes andCommentsCount:footprint.comments];
[cell.likesAndCommentsView setLiked:footprint.liked];
[cell.likesAndCommentsView.likeButton addTarget:self action:@selector(likeButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
[cell.likesAndCommentsView.likesTextButton addTarget:self action:@selector(likesTextButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
[cell.likesAndCommentsView.commentButton addTarget:self action:@selector(commentButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
[cell.likesAndCommentsView.commentsTextButton addTarget:self action:@selector(commentsTextButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
[cell.detailButton addTarget:self action:@selector(detailButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
[cell.translateButton addTarget:self action:@selector(translateButtonPressed:) forControlEvents:UIControlEventTouchUpInside];
if (footprint.canBeTranslated) {
cell.translationStatus = footprint.translationState;
if (footprint.translationState == FPFootprintTranslationStateTranslated) {
cell.translatedTextView.text = footprint.translatedText;
}
} else {
cell.translationStatus = FPFootprintTranslationStateNotAvailible;
}
cell.numberOfImages = 2;
return cell;
}
}
这是我的手机：
import UIKit
@objc class FootprintCell: UITableViewCell {
var translationStatus: FPFootprintTranslationState = .NotTranslated {
didSet {
translateButton.hidden = true
translateLoader.stopAnimating()
translatedTextView.hidden = true
translatedTextView.text = nil
translatedTextView.addConstraint(translatedTextViewHeightConstraint)
translationButtonHeightConstraint.constant = 0
loaderHeightConstraint.constant = 0
switch translationStatus {
case .NotAvailible:
break
case .NotTranslated:
translateButton.hidden = false
translationButtonHeightConstraint.constant = translationButtonHeightConstraintConstant
case .Translating:
translateLoader.startAnimating()
loaderHeightConstraint.constant = loaderHeightConstraintConstant
translatedTextView.text = nil
case .Translated:
translatedTextView.hidden = false
translatedTextView.removeConstraint(translatedTextViewHeightConstraint)
}
}
}
var isPrivate: Bool = false {
didSet {
privacyBar.hidden = !isPrivate
privacyIcon.image = UIImage(named: isPrivate ? "ic_lock" : "ic_globe")
}
}
var hasText: Bool = true {
didSet {
if hasText {
textView.removeConstraint(textViewHeightConstraint)
} else {
textView.addConstraint(textViewHeightConstraint)
}
}
}
var numberOfImages: Int = 0 {
didSet {
if numberOfImages == 0 {
imagesContainer.subviews.map { $0.removeFromSuperview() }
} else if numberOfImages == 2 {
twoImagesContainer = NSBundle.mainBundle().loadNibNamed("FootprintCellTwoImagesContainer", owner: nil, options: nil)[0] as? FootprintCellTwoImagesContainer
twoImagesContainer?.setTranslatesAutoresizingMaskIntoConstraints(false)
imagesContainer.addSubview(twoImagesContainer!)
let views = ["foo" : twoImagesContainer!] as [NSString : AnyObject]
imagesContainer.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|[foo]|", options: .allZeros, metrics: nil, views: views))
imagesContainer.addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[foo]|", options: .allZeros, metrics: nil, views: views))
}
}
}
@IBOutlet private(set) weak var titleLabel: UILabel!
@IBOutlet private(set) weak var dateLabel: UILabel!
@IBOutlet private(set) weak var textView: FPForwardingTextView!
@IBOutlet private(set) weak var likesAndCommentsView: FPLikesAndCommentsView!
@IBOutlet private weak var privacyBar: UIView!
@IBOutlet private weak var privacyIcon: UIImageView!
@IBOutlet private(set) weak var detailButton: UIButton!
@IBOutlet private(set) weak var translateButton: UIButton!
@IBOutlet private weak var translateLoader: UIActivityIndicatorView!
@IBOutlet private(set) weak var translatedTextView: FPForwardingTextView!
@IBOutlet private(set) weak var imagesContainer: UIView!
private(set) var twoImagesContainer: FootprintCellTwoImagesContainer?
@IBOutlet private weak var translationButtonHeightConstraint: NSLayoutConstraint!
@IBOutlet private weak var loaderHeightConstraint: NSLayoutConstraint!
@IBOutlet private var translatedTextViewHeightConstraint: NSLayoutConstraint!
@IBOutlet private var textViewHeightConstraint: NSLayoutConstraint!
private var translationButtonHeightConstraintConstant: CGFloat!
private var loaderHeightConstraintConstant: CGFloat!
override func awakeFromNib() {
super.awakeFromNib()
textView.contentInset = UIEdgeInsets(top: -10, left: -5, bottom: 0, right: 0)
textView.linkColor = UIColor(fromHexString: "0088CC")
translatedTextView.contentInset = UIEdgeInsets(top: -10, left: -5, bottom: 0, right: 0)
translatedTextView.linkColor = UIColor(fromHexString: "0088CC")
privacyBar.backgroundColor = UIColor(patternImage: UIImage(named: "ic_privacy_bar"))
translatedTextView.text = nil
translatedTextView.hidden = true
translateButton.hidden = true
translationButtonHeightConstraintConstant = translationButtonHeightConstraint.constant
loaderHeightConstraintConstant = loaderHeightConstraint.constant
hasText = true
}
func layoutMargins() -> UIEdgeInsets {
return UIEdgeInsetsZero
}
override func prepareForReuse() {
super.prepareForReuse()
numberOfImages = 0
translationStatus = .NotAvailible
hasText = true
}
}
FootprintCellTwoImagesContainer and FPLikesAndCommentsView从 Nib 加载，当前不包含任何图像或加载任何内容，只是一些自动布局。
所以主要问题是，即使整个 tableView 被加载并且每个单元格至少显示一次（所以应该有足够的单元格可以重用），在缓慢地向上或向下滚动单元格边框后，我会得到一个小跳跃（比如 5像素向上和向下）。这种情况发生在每台设备上，甚至是 6 Plus 上。
有什么想法可能是问题出在哪里吗？我希望这不是我在 xibs 中的限制，至少 Interface Builder 不会在那里抛出警告......
