I have a UITableView, and for each cell i add a UITextView to the content view. Then i set the backgroundColor of the UITextView to clearColor in order to make the corner of the table rounded instead of 90 degrees. But then funny things happen. After i scroll up and down the table for a while, the text inside the cell begins overlaying. I can not read the text anymore. I also had this problem when i try to draw the PDF page. The text in the pages begins overlaying after a while. But after i use CGContextSetGrayFillColor, everything works perfect. Actually i dont know why, i just Google. Any idea would be appreciated. Thanks.