点击状态栏回到顶部两种实现
1.局部设置
scrollView有个属性scrollsToTop，默认值为YES. 所以默认情况下点击状态栏就可以回到顶部。但当一个控制器中有多个scrollView或其子类时，因为默认值都是YES,所以系统不知道要让哪个scrollView回到顶部。所以要让需要回到顶部的scrollView.scrollsToTop = YES,而其他的scrollView的设置成NO.
2.全局设置
新建一个window,windowLevel为alert的，背景色为clear,加一个手势，设置点击事件。
注意，iOS9之后，每个window都要设置一个rootViewController
一个范例：
1 @implementation TopWindow 2 3 static UIWindow *window_; 4 5 + (void)initialize 6 { 7 window_ = [[UIWindow alloc] init]; 8 window_.backgroundColor = [UIColor clearColor]; 9 window_.frame = CGRectMake(0, 0, XMGScreenW, 20); 10 window_.windowLevel = UIWindowLevelAlert; 11 [window_ addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(windowClick)]]; 12 UIViewController *vc = [[UIViewController alloc]init]; 13 14 vc.view.backgroundColor = [UIColor clearColor]; 15 window_.rootViewController = vc; 16 } 17 18 + (void)show 19 { 20 window_.hidden = NO; 21 } 22 23 + (void)hide 24 { 25 window_.hidden = YES; 26 } 27 28 /** 29 * 监听窗口点击 30 */ 31 + (void)windowClick 32 { 33 UIWindow *window = [UIApplication sharedApplication].keyWindow; 34 [self searchScrollViewInView:window]; 35 } 36 37 + (void)searchScrollViewInView:(UIView *)superview 38 { 39 for (UIScrollView *subview in superview.subviews) { 40 // 如果是scrollview, 滚动最顶部 41 if ([subview isKindOfClass:[UIScrollView class]] && subview.isShowingOnKeyWindow) { 42 CGPoint offset = subview.contentOffset; 43 offset.y = - subview.contentInset.top; 44 [subview setContentOffset:offset animated:YES]; 45 } 46 47 // 继续查找子控件 48 [self searchScrollViewInView:subview]; 49 } 50 } 51 @end
//UIView的一个分类方法
- (BOOL)isShowingOnKeyWindow
{
// 主窗口
UIWindow *keyWindow = [UIApplication sharedApplication].keyWindow;
// 以主窗口左上角为坐标原点, 计算self的矩形框
CGRect newFrame = [keyWindow convertRect:self.frame fromView:self.superview];
CGRect winBounds = keyWindow.bounds;
// 主窗口的bounds 和 self的矩形框 是否有重叠
BOOL intersects = CGRectIntersectsRect(newFrame, winBounds);
return !self.isHidden && self.alpha > 0.01 && self.window == keyWindow && intersects;
}
