计算uitableview的滚动指示器大小

Question

I am displaying the custom scroll bar in my uitableview. So I want to calculate the size/height of scroll indicator. So please suggest me how should I calculate this.

thanks

Answer 1

Update

My apologies, my formula is incomplete.

I got confused between my percentage and frame height.

So the proper formula is like this:

scrollBar percentage height = table view height / table view contentSize

scrollBar height = scrollBar percentage height * table view height

Translating this into code again:

CGSize scrollBarSize;

scrollBarSize.width = 10.0;

CGFloat percentageHeight = self.tableView.bounds.size.height / self.tableView.contentSize.height;

scrollBarSize.height = percentageHeight * self.tableView.bounds.size.height;

NSLog(@"scrollBar height = %lf", scrollBarSize.height);

Here's a photoshop screenshot example, try using the rectangle selection marquee to measure the scrollBar height in my screenshot, it should come out about 166.644 px:

Original Answer

I think the scroll indicator height is a visual representation of the visible percentage of entire tableView content size.

So maybe you can calculate it by taking the height of the device screen, divide by the tableView's content size height:

scroll bar height = table view height / table view contentSize

Translating this into code might be something like:

CGSize scrollBarSize;

scrollBarSize.width = 10.0;

scrollBarSize.height = self.tableView.bounds.size.height / self.tableView.contentSize.height;

NSLog(@"scrollBar height = %lf", scrollBarSize.height);

Does this work for you?

Answer 2

CGRect scrollFrame = CGRectMake(self.view.frame.size.with - (SCROLLBAR_WIDTH + PADDING),
                                (self.scrollView.contentOffset * self.scrollView.frame.size.height) / self.contentSize.height,
                                SCROLLBAR_WIDHT, 
                                SCROLLBAR_HEIGHT);

Try this by replacing some variables with the ones in your context.

Set this in - (void)scrollViewDidScroll:(UIScrollView *)scrollView delegate method so the scrollBar stays updated with correct position.