Drawing a round rectange by CADisplayLink

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I am drawing a rectangle with rounded corners which is a frame-by-frame animation by CADisplayLink.

You know, running looks like a snake.

But drawing does not work.

The rectangle's length and width is 50, which's corner radius is 5.

I defined some variables to focus the moving line.

@property (nonatomic, assign) CGPoint linePoint;
@property (nonatomic, assign) CGPoint originPoint;

@property (nonatomic, assign) BOOL isEnd;

Of courese, and some marcos:

#define degreesToRadian(angle) (M_PI * (angle) / 180.0)
#define framePerSecond 60.0f
#define velocity 4.0f

Here is how I implement the Delegate method to draw the shape with deltaTime.

- (void)displayWillUpdateWithDeltaTime:(CFTimeInterval)deltaTime {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
    CGFloat deltaValue = MIN(1.0f, deltaTime / (1.0f / framePerSecond));
    CGFloat tempX = self.linePoint.x;
    CGFloat tempY = self.linePoint.y;
    self.originPoint = CGPointMake(0, 0);
    self.linePoint = self.originPoint;

    switch (self.status) {
        case LineStatusGoStraightRight:
            tempX += velocity * deltaValue;
            if (tempX >= 50 && tempY == 0) {
                self.status = LineStatusTurn;
            }
            break;

        case LineStatusTurn:
            if (tempX > 0 && tempY == 0) {
                tempX = tempX + 5;
                tempY = tempY + 5;
                self.status = LineStatusGoDown;
                break;
            }
            if (tempX >= 55 && tempY > 0) {
                tempX = tempX - 5;
                tempY = tempY + 5;
                self.status = LineStatusGoStraightLeft;
                break;
            }
            if (tempY >= 60 && tempX <= 0) {
                tempX = tempX - 5;
                tempY = tempY - 5;
                self.status = LineStatusGoUp;
                break;
            }
            if (tempY <= 0 && tempX <= -5) {
                tempX = tempX + 5;
                tempY = tempY - 5;
                break;
            }

        case LineStatusGoDown:
            tempY += velocity * deltaValue;
            if (tempY >= 55 && tempX >= 0) {
                self.status = LineStatusTurn;
            }
            break;

        case LineStatusGoStraightLeft:
            tempX -= velocity * deltaValue;
            if (tempX <= 0 && tempY >= 55) {
                self.status = LineStatusTurn;
            }
            break;

        case LineStatusGoUp:
            tempY -= velocity *deltaValue;
            if (tempY <= 5 && tempX < 0) {
                self.status = LineStatusTurn;
            }
            break;

        default:
            break;
    }
    dispatch_async(dispatch_get_main_queue(), ^{

        [self setNeedsDisplay];
    });
});
}

and draw method:

- (UIImage *)preDrawRectImage
{
UIImage *rectImage;
UIGraphicsBeginImageContext(CGSizeMake(self.bounds.size.width, self.bounds.size.height));
CGContextRef context = UIGraphicsGetCurrentContext();

//LineCap
CGContextSetLineCap(context, kCGLineCapRound);

//LineWidth
CGContextSetLineWidth(context, self.hudLineWidth);

//Fill color
CGContextStrokePath(context);

//
CGContextMoveToPoint(context, self.linePoint.x, self.linePoint.y);

rectImage = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();
return rectImage;
}

and also drawInRect method:

- (void)drawRect:(CGRect)rect {
[super drawRect:rect];
[self.rectImage drawInRect:rect];
}

Is the CGContextMoveToPoint method shouldn't be called like this? Or I miss something important maybe?

asked 48 secs ago

Wongzigii

1

Drawing a round rectange by CADisplayLink