Draw line in UIView

问题:

I need to draw a horizontal line in a UIView. What is the easiest way to do it. For example, I want to draw a black horizontal line at y-coord=200.

I am NOT using Interface Builder.

回答1:

The easiest way in your case (horizontal line) is to add a subview with black background color and frame [0, 200, 320, 1].

Code sample (I hope there are no errors - I wrote it without Xcode):

UIView *lineView = [[UIView alloc] initWithFrame:CGRectMake(0, 200, self.view.bounds.size.width, 1)];
lineView.backgroundColor = [UIColor blackColor];
[self.view addSubview:lineView];
[lineView release];
// You might also keep a reference to this view 
// if you are about to change its coordinates.
// Just create a member and a property for this...

Another way is to create a class that will draw a line in its drawRect method (you can see my code sample for this here).

回答2:

Maybe this is a bit late, but I want to add that there is a better way. Using UIView is simple, but relatively slow. This method overrides how the view draws itself and is faster:

- (void)drawRect:(CGRect)rect {
    [super drawRect:rect];

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);

    // Draw them with a 2.0 stroke width so they are a bit more visible.
    CGContextSetLineWidth(context, 2.0f);

    CGContextMoveToPoint(context, 0.0f, 0.0f); //start at this point

    CGContextAddLineToPoint(context, 20.0f, 20.0f); //draw to this point

    // and now draw the Path!
    CGContextStrokePath(context);
}

回答3:

Swift 3 and Swift 4

This is how you can draw a gray line at the end of your view (same idea as b123400's answer)

class CustomView: UIView {

    override func draw(_ rect: CGRect) {
        super.draw(rect)

        if let context = UIGraphicsGetCurrentContext() {
            context.setStrokeColor(UIColor.gray.cgColor)
            context.setLineWidth(1)
            context.move(to: CGPoint(x: 0, y: bounds.height))
            context.addLine(to: CGPoint(x: bounds.width, y: bounds.height))
            context.strokePath()
        }
    }
}

回答4:

Just add a Label without text and with background color. Set the Coordinates of your choice and also height and width. You can do it manually or with Interface Builder.

回答5:

You can user UIBezierPath Class for this:

And can draw as many lines as you want:

I have subclassed UIView :

    @interface MyLineDrawingView()
    {
       NSMutableArray *pathArray;
       NSMutableDictionary *dict_path;
       CGPoint startPoint, endPoint;
    }

       @property (nonatomic,retain)   UIBezierPath *myPath;
    @end

And initialized the pathArray and dictPAth objects which will be used for line drawing. I am writing the main portion of the code from my own project:

- (void)drawRect:(CGRect)rect
{

    for(NSDictionary *_pathDict in pathArray)
    {
        [((UIColor *)[_pathDict valueForKey:@"color"]) setStroke]; // this method will choose the color from the receiver color object (in this case this object is :strokeColor)
        [[_pathDict valueForKey:@"path"] strokeWithBlendMode:kCGBlendModeNormal alpha:1.0];
    }

    [[dict_path objectForKey:@"color"] setStroke]; // this method will choose the color from the receiver color object (in this case this object is :strokeColor)
    [[dict_path objectForKey:@"path"] strokeWithBlendMode:kCGBlendModeNormal alpha:1.0];

}

touchesBegin method :

UITouch *touch = [touches anyObject];
startPoint = [touch locationInView:self];
myPath=[[UIBezierPath alloc]init];
myPath.lineWidth = currentSliderValue*2;
dict_path = [[NSMutableDictionary alloc] init];

touchesMoved Method:

UITouch *touch = [touches anyObject];
endPoint = [touch locationInView:self];

 [myPath removeAllPoints];
        [dict_path removeAllObjects];// remove prev object in dict (this dict is used for current drawing, All past drawings are managed by pathArry)

    // actual drawing
    [myPath moveToPoint:startPoint];
    [myPath addLineToPoint:endPoint];

    [dict_path setValue:myPath forKey:@"path"];
    [dict_path setValue:strokeColor forKey:@"color"];

    //                NSDictionary *tempDict = [NSDictionary dictionaryWithDictionary:dict_path];
    //                [pathArray addObject:tempDict];
    //                [dict_path removeAllObjects];
    [self setNeedsDisplay];

touchesEnded Method:

        NSDictionary *tempDict = [NSDictionary dictionaryWithDictionary:dict_path];
        [pathArray addObject:tempDict];
        [dict_path removeAllObjects];
        [self setNeedsDisplay];

回答6:

One other (and an even shorter) possibility. If you're inside drawRect, something like the following:

[[UIColor blackColor] setFill];
UIRectFill((CGRect){0,200,rect.size.width,1});

回答7:

Based on Guy Daher's answer.

I try to avoid using ? because it can cause an application crash if the GetCurrentContext() returns nil.

I would do nil check if statement:

class CustomView: UIView 
{    
    override func draw(_ rect: CGRect) 
    {
        super.draw(rect)
        if let context = UIGraphicsGetCurrentContext()
        {
            context.setStrokeColor(UIColor.gray.cgColor)
            context.setLineWidth(1)
            context.move(to: CGPoint(x: 0, y: bounds.height))
            context.addLine(to: CGPoint(x: bounds.width, y: bounds.height))
            context.strokePath()
        }
    }
}

回答8:

Add label without text and with background color corresponding frame size(ex:height=1). Do it through code or in interface builder.