ios - UILabel 和 UIActivityIndi​​catorView 以 UITableView 的可见区域为中心

Question

我将 UILabel 和 UIActivityIndi​​catorView 作为 subview 添加到 TableView 中作为加载指示器。我希望这些项目位于 TableView 的可见区域的中间，并且如果用户滚动则保留在中心，因此用户将始终看到这些项目。我创建它们的代码是:

if (!spinner) {
        spinner = [[UIActivityIndicatorView alloc]      initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
        [spinner startAnimating];

        loadingLabel = [[UILabel alloc] initWithFrame:CGRectZero];
        loadingLabel.font = [UIFont systemFontOfSize:20];
        loadingLabel.textColor = [UIColor grayColor];
        loadingLabel.text = @"Loading...";
        [loadingLabel sizeToFit];

        static CGFloat bufferWidth = 8.0;

        CGFloat totalWidth = spinner.frame.size.width + bufferWidth + loadingLabel.frame.size.width;

        CGRect spinnerFrame = spinner.frame;
        spinnerFrame.origin.x = (self.tableView.bounds.size.width - totalWidth) / 2.0;
        spinnerFrame.origin.y = (self.tableView.bounds.size.height - spinnerFrame.size.height) / 2.0;
        spinner.frame = spinnerFrame;
        spinner.autoresizingMask = (UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleBottomMargin);
        [self.tableView addSubview:spinner];

        CGRect labelFrame = loadingLabel.frame;
        labelFrame.origin.x = (self.tableView.bounds.size.width - totalWidth) / 2.0 + spinnerFrame.size.width + bufferWidth;
        labelFrame.origin.y = (self.tableView.bounds.size.height - labelFrame.size.height) / 2.0;
        loadingLabel.frame = labelFrame;
        loadingLabel.autoresizingMask = (UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleBottomMargin);
        [self.tableView addSubview:loadingLabel];
    }

table view 滚动时如何让它居中？

编辑

我如何计算将微调器重新定位到中间的尺寸？我要设置什么属性？

Answer 1

1. 将您的 View 添加到 TableView 的 super View (如果可能；UITableViewController使这不可能)

2. 将您的 View 添加到 TableView 并在 -scrollViewDidScroll: 委托(delegate)方法中重新定位它(UITableViewDelegate 是 UIScrollViewDelegate< 的子协议(protocol))

编辑:

为了保持 View 的中心

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{ 

CGSize adSize = [awView actualAdSize]; 

CGRect newFrame = awView.frame; newFrame.origin.x = (self.view.bounds.size.width - adSize.width)/2; 

newFrame.origin.y = (self.tableView.contentOffset.y - adSize.height/2) -21; 

awView.frame = newFrame; 
}