UITableView 的 contentSize 何时设置?

2022-01-12 00:00:00 ios uiscrollview uitableview

我在 UIScrollView 中有一个非滚动 UITableView.我将 UITableView 的帧大小设置为其内容大小.

I have a non scrolling UITableView in a UIScrollView. I set the frame size of the UITableView to its content size.

当我向 UITableView 添加一行时，我在 UITableView 上调用 insertRowsAtIndexPaths:withRowAnimation:.然后我调用一个方法来调整 UITableView 的框架:

When I add a row to the UITableView, I call insertRowsAtIndexPaths:withRowAnimation: on the UITableView. Then I call a method to resize the frame of the UITableView:

- (void)resizeTableViewFrameHeight
{
    // Table view does not scroll, so its frame height should be equal to its contentSize height
    CGRect frame = self.tableView.frame;
    frame.size = self.tableView.contentSize;
    self.tableView.frame = frame;
}

目前看来，contentSize 尚未更新.如果我在上述方法中根据行数和节数手动计算框架，则该方法可以正常工作.

It seems though that the contentSize hasn't been updated at this point. If I manually calculate the frame in the above method based on the number of rows and sections, then the method works properly.

我的问题是，如何让 UITableView 更新其 contentSize?我想我可以调用 reloadData 并且可能会这样做，但是当我只插入一个单元格时重新加载整个表格似乎效率低下.

My question is, how can I get the UITableView to update its contentSize? I suppose I could call reloadData and that would probably do it, but it seems inefficient to reload the entire table when I'm just inserting one cell.

推荐答案

在UITableView上调用layoutIfNeeded可以让UITableView立即计算出内容的大小.这将运行所有必要的计算来布局 UITableView.

You can make the UITableView calculate the size of the content immediately by calling layoutIfNeeded on the UITableView. This will run all the necessary calculations to layout the UITableView.

UITableViewController 子类示例，您希望将其放入可变大小的容器视图中:

Example for a UITableViewController subclass that you want to put in a container view with variable size:

Objective-C

- (CGSize)preferredContentSize
{
    // Force the table view to calculate its height
    [self.tableView layoutIfNeeded];
    return self.tableView.contentSize;
}

斯威夫特

override var preferredContentSize: CGSize {
    get {
        // Force the table view to calculate its height
        self.tableView.layoutIfNeeded()
        return self.tableView.contentSize
    }
    set {}
}

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