ios进入后台的模糊效果

@property (strong, nonatomic)UIVisualEffectView *visualEffectView;

- (UIVisualEffectView *)visualEffectView{
    if (!_visualEffectView) {
        UIBlurEffect *blurEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleLight];
        _visualEffectView = [[UIVisualEffectView alloc] initWithEffect:blurEffect];
        _visualEffectView.frame = [UIScreen mainScreen].bounds;
    }
    return _visualEffectView;
}

- (void)applicationWillResignActive:(UIApplication *)application {
    [[UIApplication sharedApplication].keyWindow addSubview:self.visualEffectView];
}

- (void)applicationDidBecomeActive:(UIApplication *)application {
    if (_visualEffectView) {
        [self.visualEffectView removeFromSuperview];
    }
}