iphone - 在 UITextView 上滚动内部阴影

Question

我想子类化 UITextView 以便能够绘制带有自定义边框和顶部+左侧内部阴影的圆形矩形。

我在为任何(静态边界) View 创建这种效果(通过阅读 this 帖子)方面取得了巨大成功，但在 ScrollView 方面遇到了问题。

我在我的自定义类的 -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 TextView 滚动时处理正确的阴影+边框显示，我使用我的自定义类 -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后( View 再次是静态的) View 绘制正确。

欢迎就此问题提出任何见解。

Answer 1

我花了一些时间来深入研究这个问题并找到了一个我想分享的解决方案。

起初我意识到最好在 -awakeFromNib 中而不是在 -setFrame 中设置阴影层。

为了在 TextView 滚动时处理正确的阴影+边框显示，我改变了这样的方法:更新阴影层我现在在我的自定义类中使用 -layoutSubviews 覆盖。在 -layoutSubviews 重写中，我重新创建阴影层以遵守新边界，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 现在返回对 View 中已添加图层的图层引用层次结构(返工很简单):

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

任何证明此方法正确且不仅有效的证据/评论都将受到高度赞赏。