如何使CALayer可访问?具体来说,我希望图层能够动态更改其标签,因为它可以随时更改。官方文档的sample code并不真正允许这样做。
答案 0 :(得分:3)
以下假设你有一个超级视图,其图层都是类AccessableLayer
,但是如果你有一个更复杂的布局,可以修改这个方案来处理它。
为了使CALayer
可访问,您需要一个实现UIAccessibilityContainer
方法的父视图。以下是一种建议的方法。
首先,让每个图层拥有其UIAccessibilityElement
@interface AccessableLayer : CALayer
@property (nonatomic) UIAccessibilityElement *accessibilityElement;
@end
现在在其实现中,您可以在元素发生更改时修改它:
@implementation AccessableLayer
... self.accessibilityElement.accessibilityLabel = text;
@end
AccessableLayer永远不会创建UIAccessibilityElement
,因为构造函数需要UIAccessibilityContainer。因此,超级视图创建并分配它:
#pragma mark - accessibility
// The container itself is not accessible, so return NO
- (BOOL)isAccessibilityElement
{
return NO;
}
// The following methods are implementations of UIAccessibilityContainer protocol methods.
- (NSInteger)accessibilityElementCount
{
return [self.layer.sublayers count];
}
- (id)accessibilityElementAtIndex:(NSInteger)index
{
AccessableLayer *panel = [self.layer.sublayers objectAtIndex:index];
UIAccessibilityElement *element = panel.accessibilityElement;
if (element == nil) {
element = [[UIAccessibilityElement alloc] initWithAccessibilityContainer:self];
element.accessibilityFrame = [self convertRect:panel.frame toView:[UIApplication sharedApplication].keyWindow];
element.accessibilityTraits = UIAccessibilityTraitButton;
element.accessibilityHint = @"some hint";
element.accessibilityLabel = @"some text";
panel.accessibilityElement = element;
}
return element;
}
- (NSInteger)indexOfAccessibilityElement:(id)element
{
int numElements = [self accessibilityElementCount];
for (int i = 0; i < numElements; i++) {
if (element == [self accessibilityElementAtIndex:i]) {
return i;
}
}
return NSNotFound;
}