iOS判断UIView是否显示在屏幕上

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头文件：

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@interfaceUIView (UIScreenDisplaying)
 
// 判断View是否显示在屏幕上
- (BOOL)isDisplayedInScreen;
 
@end

实现文件

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/*****************************************************
 *  MIT Licence
 *  
 *  Author: __承_影__
 *
 *  Date:   2015.2.10
 *
 ****************************************************/
 
@implementationUIView (UIScreenDisplaying)
 
// 判断View是否显示在屏幕上
- (BOOL)isDisplayedInScreen
{
    if(self == nil) {
        returnFALSE;
    }
     
    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)) {
        returnFALSE;
    }
     
    // 若view 隐藏
    if(self.hidden) {
        returnFALSE;
    }
     
    // 若没有superview
    if(self.superview == nil) {
        returnFALSE;
    }
     
    // 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)) {
        returnFALSE;
    }
     
    returnTRUE;
}

测试用例：

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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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