模拟iOS系统原生导航条隐藏或显示动画

借UIView动画，使更改导航条的hidden属性这一过程动起来。悦德财富：https://yuedecaifu.com

代码     

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[UIView beginAnimations:nil context:nil]; [UIView setAnimationDelegate:self]; [UIView setAnimationDidStopSelector:@selector(didAfterHidden)]; [UIView setAnimationDuration:2.3]; [view setAlpha:0.0f]; [UIView commitAnimations];   [UIView animateWithDuration:0.35                                       delay:0                                     options:(UIViewAnimationCurveEaseOut)                                  animations:^{                                      navigationBar_.alpha = 0.;                                  } completion:^(BOOL finished){                                      navigationBar_.hidden = YES;                                      navigationBar_.alpha = alpha;                                  }];