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我想子类 UITextView 能够绘制带有自定义边框加上顶部+左内阴影的圆形矩形。

我在为任何（静态边界）视图创建这种效果（通过阅读这篇文章）方面取得了巨大成功，但在滚动视图时遇到了问题。

我在自定义类的 -setFrame 实例方法中做的这个效果：

- (void)setFrame:(CGRect)frame {
[super setFrame:frame];

UIColor *borderColor = [UIColor colorWithRed:BORDER_COLOR_RED green:BORDER_COLOR_GREEN blue:BORDER_COLOR_BLUE alpha:BORDER_COLOR_ALPHA];

// Store index of the shadow sublayer for future use
[self setShadowLayerIndex:[LayerFormatter formatAsRoundRectWithShadowOn:self withBackgroundColor:[UIColor whiteColor] andBorderColor:borderColor]];}

formatAsRoundRectWithShadowOn: 是一个类方法，定义为：

+(NSUInteger)formatAsRoundRectWithShadowOn:(UIView*)view withBackgroundColor:(UIColor *)backgroundColor andBorderColor:(UIColor *)borderColor {
if([view isKindOfClass:[UITextField class]])
    ((UITextField*)view).borderStyle = UITextBorderStyleNone;
view.backgroundColor = backgroundColor;

view.layer.borderWidth = 1.0;
view.layer.borderColor = [borderColor CGColor];
view.layer.cornerRadius = CORNER_RADIUS;
view.layer.masksToBounds = YES;

//Add some insets to the text: https://stackoverflow.com/a/4423805
UIView *paddingView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 5, 20)];

if([view isKindOfClass:[UITextField class]])
{
    ((UITextField*)view).leftView = paddingView;
    ((UITextField*)view).leftViewMode = UITextFieldViewModeAlways;
}

// Create and apply a shadow layer. Help here: https://stackoverflow.com/questions/4431292/inner-shadow-effect-on-uiview-layer
CAShapeLayer* shadowLayer = [CAShapeLayer layer];

[shadowLayer setFrame:view.bounds];
[shadowLayer setShadowColor:[[UIColor blackColor] CGColor]];
[shadowLayer setShadowRadius:3.0f];
[shadowLayer setShadowOpacity:0.35f];
[shadowLayer setShadowOffset:CGSizeMake(2.0f, 2.0f)];

[shadowLayer setFillColor:[backgroundColor CGColor]];

// Causes the inner region in this example to NOT be filled.
[shadowLayer setFillRule:kCAFillRuleEvenOdd];

// Create inner and outer rectangle paths.
CGMutablePathRef path = CGPathCreateMutable();

// Outer path should be bigger than the field
UIBezierPath *bpOuter = [UIBezierPath bezierPathWithRect:CGRectInset(shadowLayer.bounds, -10, -10)];

// Inner path is the visible part of the view
UIBezierPath *bpInner = [UIBezierPath bezierPathWithRoundedRect:shadowLayer.bounds cornerRadius:CORNER_RADIUS];

// Add outer path and then add the inner path so it's subtracted from the outer path.
CGPathAddPath(path, NULL, bpOuter.CGPath);
CGPathAddPath(path, NULL, bpInner.CGPath);

CGPathCloseSubpath(path);

[shadowLayer setPath:path];
CGPathRelease(path);

[[view layer] addSublayer:shadowLayer];

NSUInteger addedAtIndex = [[[view layer] sublayers] indexOfObject:shadowLayer];
return addedAtIndex;}

为了在文本视图滚动时处理正确的阴影+边框显示，我正在使用我的自定义类 -setBounds 方法来更新阴影层框架：

-(void)setBounds:(CGRect)bounds{
[super setBounds:bounds];

// Change the frame of the shadow layer to reflect new bounds
[[[[self layer] sublayers] objectAtIndex:self.shadowLayerIndex] setFrame:bounds];}

我遇到的问题是向下滚动（插入新文本行时）或顶部（向上滚动到文本开头时）底部的阴影+框架绘制不正确。

插入新行或滚动完成（视图再次为静态）后，视图绘制正确。

任何关于这个问题的见解都非常受欢迎。

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1 回答 1

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我有时间深入研究这个问题并找到了我想分享的解决方案。

起初我意识到最好将阴影层设置-awakeFromNib在-setFrame.

为了在文本视图滚动时处理正确的阴影+边框显示，我改变了这样的方法：更新我现在-layoutSubviews在自定义类中使用覆盖的阴影层。在-layoutSubviews覆盖中，我正在重新创建阴影层以尊重新的边界，然后调用[super layoutSubviews].

滚动，改变方向 - 它就像一个魅力！

- (void)layoutSubviews
{
    [self updateShadow];
    [super layoutSubviews];
}

- (void)updateShadow
{
    if (shadowLayer)
        [shadowLayer removeFromSuperlayer];

    shadowLayer = [LayerFormatter addInnerShadowLayerOn:self withShadowColor:[UIColor blackColor]];
}

请注意，+(NSUInteger)formatAsRoundRectWithShadowOn:(UIView*)view withBackgroundColor:(UIColor *)backgroundColor andBorderColor:(UIColor *)borderColor现在将层引用返回到视图层层次结构中已添加的层（返工很简单）：

+(CAShapeLayer *)addInnerShadowLayerOn:(UIView *)view withShadowColor:(UIColor *)shadowColor;

任何证明这种方法是正确的并且不仅仅是有效的证据/评论都将受到高度赞赏。

于 2013-01-29T15:24:36.123 回答