iOS判断UIView是否显示在屏幕上

@interface

- (BOOL)isDisplayedInScreen;

@end

@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;

　　}

　　retrun true;

}

@end

//test case

UIView *view = [UIView alloc] initWithFrame:CGRectMake(0,0,40,40)];

//无父视图

BOOL b1 = [view isDisplayedInScreen];

NSLog(@"b1: %d", b1);

[self.view addSubView:view];

BOOL b2 = [view isDisplayedInScreen];

NSLog(@"b2:%d",b2);

v.frame = CGRectZero;

BOOL b3 = [view isDisplayedSceen];

NSLog("b3:%d",b3);

CGRect screenRect = [UIScreen mainScreen].bounds;

CGFloat screenWidth = screenRect.size.width;

CGFloat screenHeight = screenRect.size.height;

view.frame = CGRectMake(-screenWidth, -screenHeight, screenWidth, screenHeight)；

BOOL b4 = [view isDisplayedInscreen];

NSLog(@"b4:%d",b4);