崩溃原因
-[UIView setImage:]: unrecognized selector sent to instance 0x11be32340
崩溃堆栈：
0 CoreFoundation ___exceptionPreprocess + 124
1 libobjc.A.dylib objc_exception_throw + 56
2 CoreFoundation +[NSException raise:format:]
3 Foundation -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 112
6 CoreFoundation ____forwarding___ + 624
7 CoreFoundation _CF_forwarding_prep_0 + 92
8 UIKit -[UIPageControl _transitionIndicator:toEnabled:index:legible:] + 168
9 UIKit -[UIPageControl _transitionIndicator:toEnabled:index:] + 96
10 UIKit -[UIPageControl _setDisplayedPage:] + 132
原因是 产品需求 要改 UIPageControl 的样式，但是系统没有给方法，所以参照网上的方法，调用私有 api，设置_pageImage 和 _currentPageImage，
[pageControl setValue:[UIImage imageNamed:@"currentPageImage"] forKeyPath:@"_currentPageImage"];
[pageControl setValue:[UIImage imageNamed:@"pageImage"] forKeyPath:@"_pageImage"];
完了之后一切都很正常，样式也修改了，但是莫名其妙总是偶尔会有崩溃。查看日志是发现 在 pageControl.currentPage = index; 时，pageControl 的 subview 还是 UIView，并不是 UIImageView。
打印日志发现 UIPageControl 的 subView，在初始化的时候是 UIView，但是到了显示的时候就变成了 UIImageView，这里崩溃的时候是不知为何没有变成 UIImageView。
知道了问题。那么解决方案就是换一种实现自己建立 UIImageView 覆盖在 UIPageControl 上面：
//overide the setCurrentPage
-(void) setCurrentPage:(NSInteger)page
{
[super setCurrentPage:page];
[self updateDots];
}
- (void)updateDots
{
for (int i = 0; i < [self.subviews count]; i++)
{
UIImageView * dot = [self imageViewForSubview: [self.subviews objectAtIndex: i]];
if (i == self.currentPage) dot.image = self.activeImage;
else dot.image = self.inactiveImage;
}
}
- (UIImageView *)imageViewForSubview: (UIView *) view
{
UIImageView * dot = nil;
if ([view isKindOfClass: [UIView class]])
{
for (UIView* subview in view.subviews)
{
if ([subview isKindOfClass:[UIImageView class]])
{
dot = (UIImageView *)subview;
break;
}
}
if (dot == nil)
{
dot = [[UIImageView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, view.frame.size.width, view.frame.size.height)];
[view addSubview:dot];
}
}
else
{
dot = (UIImageView *) view;
}
return dot;
}
参考：
