iOS判断UIView是否显示在屏幕上

转载 请注明出处：ALDRIDGE1的专栏

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);