iOS 判斷view是否在屏幕上

- (BOOL)isDisplayedInScreen:(UIView *)view{
    // view不存在 或未添加到superview
    if (view == nil || view.superview == nil) {
        return FALSE;
    }
    
    // view 隱藏
    if (view.hidden) {
        return FALSE;
    }
    
    // 轉換view對應window的Rect
    CGRect rect = [view convertRect:view.frame toView:nil];
    
    //若是能夠滾動，清除偏移量
    if ([[view class] isSubclassOfClass:[UIScrollView class]]) {
        UIScrollView * scorll = (UIScrollView *)view;
        rect.origin.x += scorll.contentOffset.x;
        rect.origin.y += scorll.contentOffset.y;
    }
    
    // 若size爲CGrectZero
    if (CGRectIsEmpty(rect) ||
        CGRectIsNull(rect)  ||
        CGSizeEqualToSize(rect.size, CGSizeZero)) {
        return FALSE;
    }
    
    // 獲取 該view與window 交叉的 Rect
    CGRect screenRect = [UIScreen mainScreen].bounds;
    CGRect intersectionRect = CGRectIntersection(rect, screenRect);
    if (CGRectIsEmpty(intersectionRect) || CGRectIsNull(intersectionRect)) {
        return FALSE;
    }
    
    return TRUE;
}
複製代碼