iOS判断UIView是否显示在屏幕上

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头文件：

/***************************************************** *  MIT Licence *   *  Author: __承_影__ * *  Date:   2015.2.10 * ****************************************************/@interface UIView (UIScreenDisplaying)// 判断View是否显示在屏幕上- (BOOL)isDisplayedInScreen;@end

实现文件

/***************************************************** *  MIT Licence *   *  Author: __承_影__ * *  Date:   2015.2.10 * ****************************************************/@implementation UIView (UIScreenDisplaying)// 判断View是否显示在屏幕上- (BOOL)isDisplayedInScreen{    if (self == nil) {        return FALSE;    }        CGRect screenRect = [UIScreen mainScreen].bounds;        // 转换view对应window的Rect    CGRect rect = [self convertRect:self.frame fromView:nil];    if (CGRectIsEmpty(rect) || CGRectIsNull(rect)) {        return FALSE;    }        // 若view 隐藏    if (self.hidden) {        return FALSE;    }        // 若没有superview    if (self.superview == nil) {        return FALSE;    }        // 若size为CGrectZero    if (CGSizeEqualToSize(rect.size, CGSizeZero)) {        return  FALSE;    }        // 获取 该view与window 交叉的 Rect    CGRect intersectionRect = CGRectIntersection(rect, screenRect);    if (CGRectIsEmpty(intersectionRect) || CGRectIsNull(intersectionRect)) {        return FALSE;    }        return TRUE;}

测试用例：

    UIView *v = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 40, 40)];        // 无父视图    BOOL b1 = [v isDisplayedInScreen];    NSLog(@"b1: %d", b1);            //    [self.view addSubview:v];        BOOL b2 = [v isDisplayedInScreen];    NSLog(@"b2: %d", b2);            v.frame = CGRectZero;    BOOL b3 = [v isDisplayedInScreen];    NSLog(@"b3: %d", b3);            CGRect screenRect = [UIScreen mainScreen].bounds;    CGFloat screenWidth = screenRect.size.width;    CGFloat screenHeight = screenRect.size.height;        v.frame = CGRectMake(-screenWidth, -screenHeight, screenWidth, screenHeight);    BOOL b4 = [v isDisplayedInScreen];    NSLog(@"b4: %d", b4);

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