1、问题描述：通过手写键盘操作的时候，键盘下面会出现灰色的条块，然后点击屏幕的任何位置应用直接崩溃。
2、问题截图：

崩溃截图.jpg

3、问题分析：
有一个用scrollview做的一个编号输入页面，只要在填写时，切换到手写输入法，手写之后就会crash，然后错误提示：[UIKBBlurredKeyView candidateList]: unrecognized selector sent to instance，之前从来没遇到过这种错误，一直不知所措。
由于之前开发的时候，为了让填写表单是弹出的键盘能点击空白处收回键盘，就给scrollview写了一个分类，重写了三个方法。

• (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
  [[self nextResponder] touchesBegan:touches withEvent:event];
  [super touchesBegan:touches withEvent:event];
  }

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [[self nextResponder] touchesBegan:touches withEvent:event];
    [super touchesBegan:touches withEvent:event];
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    [[self nextResponder] touchesMoved:touches withEvent:event];
    [super touchesMoved:touches withEvent:event];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    [[self nextResponder] touchesEnded:touches withEvent:event];
    [super touchesEnded:touches withEvent:event];
}

手写输入法和这个分类处理手势冲突导致app crash了。调试了很久，我发现手写键盘在调用UIScrollView的这个分类的方法时，self的类型是UIKBCandidateCollectionView，一种系统没有暴露出来的类型，应该是UIScrollView的一个子类，所以解决办法就呼之欲出了，直接上代码。

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    if (![self isMemberOfClass:[UIScrollView class]]) {

    } else {
        [[self nextResponder] touchesBegan:touches withEvent:event];
        if ([super respondsToSelector:@selector(touchesBegan:withEvent:)]) {
            [super touchesBegan:touches withEvent:event];
        }
    }
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    if (![self isMemberOfClass:[UIScrollView class]]) {

    } else {
        [[self nextResponder] touchesMoved:touches withEvent:event];
        if ([super respondsToSelector:@selector(touchesBegan:withEvent:)]) {
            [super touchesMoved:touches withEvent:event];
        }
    }
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    if (![self isMemberOfClass:[UIScrollView class]]) {

    } else {
        [[self nextResponder] touchesEnded:touches withEvent:event];
        if ([super respondsToSelector:@selector(touchesBegan:withEvent:)]) {
            [super touchesEnded:touches withEvent:event];
        }
    }
}