在iPhone上绘制图像滞后

Question

我想在视图上画线，这是我的代码。

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

- (void)drawNewLine {
    UIGraphicsBeginImageContext(self.bounds.size);
    [self.image drawInRect:self.bounds];

    CGContextRef ctx = UIGraphicsGetCurrentContext();

    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetRGBStrokeColor(ctx, 0.51, 0.85, 0.81, 1);
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 4.0);
    CGContextBeginPath(ctx);

    CGPoint mid1 = midPoint(previousPoint1, previousPoint2);
    CGPoint mid2 = midPoint(currentPoint, previousPoint1);

    CGContextMoveToPoint(ctx, mid1.x, mid1.y);
    CGContextAddQuadCurveToPoint(ctx, previousPoint1.x, previousPoint1.y, mid2.x, mid2.y);

    CGContextStrokePath(UIGraphicsGetCurrentContext());
    self.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    [self setNeedsDisplay];
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [recognizer resetTouches];
    [recognizer addTouches:touches fromView:self];
    self.image = nil;
    previousPoint1 = previousPoint2 = currentPoint = [[touches anyObject] locationInView:self];
    [self setNeedsDisplay];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    previousPoint2 = previousPoint1;
    previousPoint1 = currentPoint;
    currentPoint = [[touches anyObject] locationInView:self];
    [self drawNewLine];
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    [self drawNewLine];
    [self processGestureData];
}

除了iPhone +之外，它在其他设备上运行良好，在6 / 6s / 7 plus上，你可以看到明显的延迟。有人可以告诉我我做错了什么。非常感谢。

这是我的应用。 CallHoney