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无论用户如何绘制它，如何在 iOS 中绘制一条直线。

我希望这条线是用户拖动手指的像素数的长度。

但它需要是垂直的还是水平的，这取决于用户是从屏幕的左到右还是从屏幕的上到下滑动手指。

线条不应倾斜或任何其他形状。它需要是直的。

我浏览过文章说“Open GL”是唯一的方法。

我自己尝试过编码，但是当我将方向从垂直更改为水平或反之亦然时，我会在水平线的结束位置和垂直线的开始位置之间出现一些额外的线条或间隙：

在头文件中：

@interface ViewController : UIViewController
{
    BOOL mouseSwiped;
    CGPoint lastPoint;
    CGPoint previousPoint;
    UIBezierPath *currentPath;
    CGFloat lastPointY;
    CGFloat lastPointX;
    BOOL xchanging;
    BOOL ychanging;
    NSMutableArray *arrayTouch;
}
@property (weak, nonatomic) IBOutlet UIImageView *drawImage;
@property UIBezierPath *currentPath;
@end

在实现文件中：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {


    mouseSwiped = NO;
    UITouch *touch = [touches anyObject];

    if ([touch tapCount] == 2) {
        drawImage.image = nil;
        [arrayTouch removeAllObjects];
        return;
    }

    lastPoint = [touch locationInView:self.view];
    [arrayTouch addObject:touch];
    lastPointY  = lastPoint.y;
    lastPointX = lastPoint.x;
    lastPoint.y -= 1;
} 


- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    mouseSwiped = YES;

    UITouch *touch = [touches anyObject];
    CGPoint currentPoint = [touch locationInView:self.view];
    currentPoint.y -= 1;
    int currentPointXVal = currentPoint.x;
    int currentPointYVal = currentPoint.y;

    int lastPointXVal = lastPoint.x;
    int lastPointYVal = lastPoint.y;

    int diffX = abs(currentPointXVal - lastPointXVal);
    int diffY = abs(currentPointYVal - lastPointYVal);

    if(currentPoint.x > lastPoint.x && diffX > diffY)
    {
        if(ychanging == YES)
        {
            lastPointY  = currentPoint.y;
            lastPointX = currentPoint.x;
            ychanging = NO;
        }
        xchanging = YES;
        NSLog(@"x increasing");
        NSLog(@"currentPoint: %@",NSStringFromCGPoint(currentPoint));
        NSLog(@"lastPoint: %@",NSStringFromCGPoint(lastPoint));

        UIGraphicsBeginImageContext(self.view.frame.size);
        [drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
        CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0);
        CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);
        CGContextBeginPath(UIGraphicsGetCurrentContext());
        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPointY);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, lastPointY);
        CGContextStrokePath(UIGraphicsGetCurrentContext());
        drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }

    if(currentPoint.y > lastPoint.y && diffY > diffX)
    {
        if(xchanging == YES)
        {
            lastPointY  = currentPoint.y;
            lastPointX = currentPoint.x;
            xchanging = NO;
        }
        ychanging = YES;
        NSLog(@"y increasing");
        NSLog(@"currentPoint: %@",NSStringFromCGPoint(currentPoint));
        NSLog(@"lastPoint: %@",NSStringFromCGPoint(lastPoint));

        UIGraphicsBeginImageContext(self.view.frame.size);
        [drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
        CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0);
        CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);
        CGContextBeginPath(UIGraphicsGetCurrentContext());
        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPointX, lastPoint.y);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPointX, currentPoint.y);
        CGContextStrokePath(UIGraphicsGetCurrentContext());
        drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }

    if(currentPoint.x < lastPoint.x && diffX > diffY)
    {
        if(ychanging == YES)
        {
            lastPointY  = currentPoint.y;
            lastPointX = currentPoint.x;
            ychanging = NO;
        }
        xchanging = YES;
        NSLog(@"x decreasing");
        NSLog(@"currentPoint: %@",NSStringFromCGPoint(currentPoint));
        NSLog(@"lastPoint: %@",NSStringFromCGPoint(lastPoint));

        UIGraphicsBeginImageContext(self.view.frame.size);
        [drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
        CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0);
        CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);
        CGContextBeginPath(UIGraphicsGetCurrentContext());
        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPointY);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, lastPointY);
        CGContextStrokePath(UIGraphicsGetCurrentContext());
        drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }

    if(currentPoint.y < lastPoint.y && diffY > diffX)
    {
        if(xchanging == YES)
        {
            lastPointY  = currentPoint.y;
            lastPointX = currentPoint.x;
            xchanging = NO;
        }

        ychanging = YES;
        NSLog(@"y decreasing");
        NSLog(@"currentPoint: %@",NSStringFromCGPoint(currentPoint));
        NSLog(@"lastPoint: %@",NSStringFromCGPoint(lastPoint));

        UIGraphicsBeginImageContext(self.view.frame.size);
        [drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
        CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
        CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0);
        CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);
        CGContextBeginPath(UIGraphicsGetCurrentContext());
        CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPointX, lastPoint.y);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPointX, currentPoint.y);
        CGContextStrokePath(UIGraphicsGetCurrentContext());
        drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();

    }





    lastPoint = currentPoint;

}

如果没有 Open GL，我有什么办法可以做到吗？

4

1 回答 1

3

当然-您可以这样做，只需从直线上移开坡度即可：

@implementation LineDrawingView
{
    CGPoint touchStart;
    CGPoint touchCurrent;
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
        touchStart   = (CGPoint) { -1, -1 };
        touchCurrent = (CGPoint) { -1, -1 };
    }
    return self;
}

- (void)drawRect:(CGRect)rect
{
    if (touchStart.x != -1)
    {
        // calculate the line rotation
        enum { horizontal, vertical } lineRot = horizontal;

        if (touchStart.y == touchCurrent.y)
        {
            // straight line
            lineRot = horizontal;
        }
        else
        {
            // calculate the slope
            double slope = fabs((touchCurrent.y - touchStart.y) / (touchCurrent.x - touchStart.x));

            if (slope > 1)
                lineRot = vertical;
        }

        // draw the actual line
        CGPoint lineEndPoint = { };

        if (lineRot == horizontal)
            lineEndPoint = (CGPoint) { touchCurrent.x, touchStart.y }; // horizontal line
        else
            lineEndPoint = (CGPoint) { touchStart.x, touchCurrent.y }; // vertical line

        // actually draw the line
        [[UIColor redColor] setStroke];

        UIBezierPath *path = [UIBezierPath bezierPath];
        [path moveToPoint:touchStart];
        [path addLineToPoint:lineEndPoint];

        [path stroke];
    }
}

-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    touchStart = [[touches anyObject] locationInView:self];
    touchCurrent = touchStart;
    [self setNeedsDisplay];
}

-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    touchCurrent = [[touches anyObject] locationInView:self];
    [self setNeedsDisplay];
}

-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    touchStart = touchCurrent = (CGPoint) { -1, -1 };
    [self setNeedsDisplay];
}

@end

如果您愿意，您可以将其扩展为使用行数组，这只是一个简单的解释。

于 2012-08-21T12:53:30.797 回答