附代码：
- (void)applicationWillResignActive:(UIApplication *)application
{
//盖上view
UIView* view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 568)];
view.backgroundColor = [UIColor redColor];
view.alpha = 0.5;
view.tag = 1111;
[[[UIApplication sharedApplication] keyWindow] addSubview:view];
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
//移除
NSArray* array = [[UIApplication sharedApplication] keyWindow].subviews;
for(id view in array)
{
if ([view isKindOfClass:[UIView class]])
{
UIView* myView = view;
if (myView.tag == 1111)
{
[myView removeFromSuperview];
}
}
}
}
