Lines drawn using drawRect method not getting scrolled - ios

Question

I am creating an app where I want to draw lines on scrollView. I am able to draw lines.
Here is my code
#interface GraphOnScrollView : UIScrollView
#property(strong,nonatomic)NSMutableArray *intensityArray;
#end
import "GraphOnScrollView.h"
#implementation GraphOnScrollView
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
// Initialization code
self.userInteractionEnabled=YES;
self.scrollEnabled=YES;
UIButton *DirectMsgBtn1 =[UIButton buttonWithType:UIButtonTypeCustom];
DirectMsgBtn1.titleLabel.font =[UIFont systemFontOfSize:12.0];
[DirectMsgBtn1 setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[DirectMsgBtn1 setTitle:#"direct message" forState:UIControlStateNormal];
[DirectMsgBtn1 setBackgroundColor:[UIColor clearColor]];
[DirectMsgBtn1 addTarget:self
action:#selector(DirectMessageViewPopUp:)
forControlEvents:UIControlEventTouchDown];
DirectMsgBtn1.frame = CGRectMake(0.0, 0, 100, 30);
[self addSubview:DirectMsgBtn1];
DirectMsgBtn1 = nil;
}
return self; }
// Only override drawRect: if you perform custom drawing. // An
empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
// Drawing code
CGFloat y_Axix =20.0;
CGFloat lineWidth=1.0;
for (int i=0; i<[self.intensityArray count]; i++)
{
CGContextRef c = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(c, 2.0);
lineWidth+=1;
CGFloat red[4] = {1.0f, 0.5f, 0.0f, 1.0f};
CGContextSetStrokeColor(c, red);
CGContextBeginPath(c);
CGFloat width=[[self.intensityArray objectAtIndex:i] floatValue];
CGContextMoveToPoint(c, 5.0f, y_Axix);
CGContextAddLineToPoint(c, width, y_Axix);
CGContextStrokePath(c);
CGContextAddArc(c,width,y_Axix,1.0f,0,2*3.1415926535898,1);
CGContextDrawPath(c,kCGPathStroke);
y_Axix=y_Axix+50;
}
NSLog(#"intensity array %#", self.intensityArray);
self.contentSize = CGSizeMake(self.frame.size.width, 1000);
}
This is code I am using for adding scrollview on my view
GraphOnScrollView *GraphView =[[GraphOnScrollView
alloc]initWithFrame:CGRectMake(0.0, 150.0, 320.0, 280.0)];
GraphView.backgroundColor =[UIColor whiteColor];
GraphView.intensityArray =[NSMutableArray arrayWithObjects:#"60",#"100",#"40",#"10",#"20",#"40",#"40",#"100",
nil];
[self.view addSubview:GraphView];
Using this code the lines which i have drawn is not getting scrolled but the scrollview is scrolled. I don't know what is the problem.
Thanks

Answer 1

While drawing on any view it draws everything on the canvas of that view.
In the case of your, you are drawing on UIScrollView so all drawing performs on the canvas of the UIScrollView, so it is not scrollable.
To solve that problem you can create on separate UIView with the size you want, perform any drawing on it and add that view in scrollview. I think this will be the best solution.
You can also refer to this link for some more help.

Answer 2

Alternate Approach (i actually used uiview for drawing and made it look like scroll)
save the touch location in
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
}
record the touch point in touches moved.
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
}
now you can translate coordinate of your points as
newX=x+(touchstart.x-touchMoved.x);//do this for x of every point
newy=y+(touchstart.y-touchMoved.y);// do this for y of every point
put the above lines in a function and call them from touches moved you can do it in touches ended method as well if lag is ok with you.
Point is translate the point and calculate the degree of translation from user touch began and moved or swipe