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I want to draw a simple line on the iPhone by touching and dragging across the screen. I managed to do that by subclassing UIView and change the default drawRect: method. At the same time in my viewcontroller I detect the touch event and call the [myView setNeedsDisplay] when necessary. The problem is that when I try to draw the second line the previous line disappears. Is there a way to keep the previous line on the screen?
Any input will be very much appreciated.
If you use drawRect: to draw, then you need to draw the whole area. So you need to store not only the data for the latest part but everything.
As an alternative, you might draw directly into a bitmap, or generate dynamically subviews for your lines (makes only sense for very limited drawing (i.e. some few vector-based stuff).