objective-c - UIImage调整大小drawRect用黑色填充背景

我有一个名为MNTRectangle的类，它是UIImage的子类。我已经重写了此类的drawRect方法以在图像上绘制边框(使用其框架)。我有它，所以当用户在名为DocumentView(UIView的子类)的类上开始平移/拖动手势时，它将MNTRectangle的实例作为子视图添加到DocumentView的实例。随着用户继续拖动，MNTRectangle会调整大小。问题是MNTRectangle最终显示为纯黑色，我尝试清除图形上下文以及在绘制边框之前保存上下文，并在绘制边框之后还原上下文。无论我如何尝试，我都无法清除MNTRectangle并仅显示调整大小的边框。

这是我的MNTRectangle类的代码:

@implementation MNTRectangle

- (id)init
{
    self = [super init];

    if (self)
    {
        [self setup];
    }

    return self;
}

- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super initWithCoder:aDecoder];

    if (self)
    {
        [self setup];
    }

    return self;
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];

    if (self)
    {
        [self setup];
    }

    return self;
}

- (void)setup
{
    [self setBackgroundColor:[UIColor clearColor]];
}

- (void)drawRect:(CGRect)rect
{
    // Get graphics context
    CGContextRef context = UIGraphicsGetCurrentContext();

//    CGContextSaveGState(context);

//    CGContextClearRect(context, rect);

    // Draw border
    CGContextSetLineWidth(context, 4.0);
    [[UIColor blackColor] setStroke];
    CGContextStrokeRect(context, rect);

//    CGContextRestoreGState(context);
}

这是DocumentView中用于UIView上的平移/拖动处理的代码:

-(id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];

    if (self)
    {
         _panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    }

    return self;
}

- (void)handlePan:(UIPanGestureRecognizer *)sender
{
    if ([sender state] == UIGestureRecognizerStateBegan)
    {
        _startPanPoint = [sender locationInView:self];

        MNTRectangle *rectangle = [[MNTRectangle alloc] initWithFrame:CGRectMake(_startPanPoint.x, _startPanPoint.y, 1, 1)];
        [_objects addObject:rectangle];
        _currentPanObject = rectangle;
        [self addSubview:rectangle];
    }
    else if ([sender state] == UIGestureRecognizerStateChanged)
    {
        CGPoint endPanPoint = [sender locationInView:self];

        float height = fabsf(endPanPoint.y - _startPanPoint.y);
        float width = fabsf(endPanPoint.x - _startPanPoint.x);
        float x = MIN(_startPanPoint.x, endPanPoint.x);
        float y = MIN(_startPanPoint.y, endPanPoint.y);

        MNTRectangle *rectangle = (MNTRectangle *)_currentPanObject;
        [rectangle setFrame:CGRectMake(x, y, width, height)];
    }
    else if ([sender state] == UIGestureRecognizerStateEnded)
    {
        CGPoint endPanPoint = [sender locationInView:self];

        float height = fabsf(endPanPoint.y - _startPanPoint.y);
        float width = fabsf(endPanPoint.x - _startPanPoint.x);
        float x = MIN(_startPanPoint.x, endPanPoint.x);
        float y = MIN(_startPanPoint.y, endPanPoint.y);

        MNTRectangle *rectangle = (MNTRectangle *)_currentPanObject;
        [rectangle setFrame:CGRectMake(x, y, width, height)];
    }
}

任何帮助，将不胜感激。

最佳答案

我终于弄明白了。设置矩形的框架后，在handlePan:方法中，我缺少[rectangle setNeedsDisplay];。

现在我的DocumentView代码如下所示:

-(id)initWithFrame:(CGRect)frame
{
   self = [super initWithFrame:frame];

    if (self)
    {
         _panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    }

    return self;
}

- (void)handlePan:(UIPanGestureRecognizer *)sender
{
   if ([sender state] == UIGestureRecognizerStateBegan)
   {
        _startPanPoint = [sender locationInView:self];

        MNTRectangle *rectangle = [[MNTRectangle alloc] initWithFrame:CGRectMake(_startPanPoint.x, _startPanPoint.y, 1, 1)];
        [_objects addObject:rectangle];
        _currentPanObject = rectangle;
        [self addSubview:rectangle];
    }
    else if ([sender state] == UIGestureRecognizerStateChanged)
    {
        CGPoint endPanPoint = [sender locationInView:self];

        float height = fabsf(endPanPoint.y - _startPanPoint.y);
        float width = fabsf(endPanPoint.x - _startPanPoint.x);
        float x = MIN(_startPanPoint.x, endPanPoint.x);
        float y = MIN(_startPanPoint.y, endPanPoint.y);

        MNTRectangle *rectangle = (MNTRectangle *)_currentPanObject;
        [rectangle setFrame:CGRectMake(x, y, width, height)];
        [rectangle setNeedsDisplay];
    }
    else if ([sender state] == UIGestureRecognizerStateEnded)
    {
        CGPoint endPanPoint = [sender locationInView:self];

        float height = fabsf(endPanPoint.y - _startPanPoint.y);
        float width = fabsf(endPanPoint.x - _startPanPoint.x);
        float x = MIN(_startPanPoint.x, endPanPoint.x);
        float y = MIN(_startPanPoint.y, endPanPoint.y);

        MNTRectangle *rectangle = (MNTRectangle *)_currentPanObject;
        [rectangle setFrame:CGRectMake(x, y, width, height)];
        [rectangle setNeedsDisplay];
    }
}

关于objective-c - UIImage调整大小drawRect用黑色填充背景，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/13772073/