1、寫(xiě)了一個(gè)小Demo，實(shí)現(xiàn)上下移動(dòng)的效果圖：
    
    
    
    主要代碼如下：
    - (IBAction)upChange:(id)sender {
    if (typeView == down) {
    [self.downBtn setHidden:NO];
    [self.upBtn setHidden:NO];
    [UIView animateWithDuration:0.5 animations:^{
    self.upView.center = CGPointMake(self.upView.center.x, 0);
    self.downView.center = CGPointMake(self.downView.center.x, (self.upView.frame.size.height+self.downView.frame.size.height)/2);
    }];
    typeView = middle;
    }else if(typeView == middle){
    [self.downBtn setHidden:NO];
    [self.upBtn setHidden:YES];
    [UIView animateWithDuration:0.5 animations:^{
    self.upView.center = CGPointMake(self.upView.center.x, -(self.upView.frame.size.height/2));
    self.downView.center = CGPointMake(self.downView.center.x, self.downView.frame.size.height/2);
    }];
    typeView = up;
    }
    }
    - (IBAction)downChange:(id)sender {
    if (typeView == middle) {
    [self.downBtn setHidden:YES];
    [self.upBtn setHidden:NO];
    [UIView animateWithDuration:0.5 animations:^{
    self.upView.center = CGPointMake(self.upView.center.x, self.upView.frame.size.height/2);
    self.downView.center = CGPointMake(self.downView.center.x, self.upView.frame.size.height+self.downView.frame.size.height/2);
    }];
    typeView = down;
    }else if(typeView == up)
    {
    [self.downBtn setHidden:NO];
    [self.upBtn setHidden:NO];
    [UIView animateWithDuration:0.5 animations:^{
    self.upView.center = CGPointMake(self.upView.center.x, 0);
    self.downView.center = CGPointMake(self.downView.center.x, (self.upView.frame.size.height+self.downView.frame.size.height)/2);
    }];
    typeView = middle;
    }
    }
    這是主要的代碼，另外還有一些需要注意的一些小細(xì)，如你的兩個(gè)view的大小，需要計(jì)算出精確位置。
    下面開(kāi)始學(xué)習(xí)[UIView animateWithDuration]方法的使用：
    函數(shù)原型：
    + (void)animateWithDuration:(NSTimeInterval)duration animations:(void (^)(void))animations __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_4_0); // delay = 0.0, options = 0, completion = NULL
    duration：動(dòng)畫(huà)持續(xù)時(shí)間
    animations：該代碼兒塊中是所有view要完成的動(dòng)畫(huà)的所有屬性的定義;
    還有另外兩個(gè)函數(shù)：
    + (void)animateWithDuration:(NSTimeInterval)duration delay:(NSTimeInterval)delay options:(UIViewAnimationOptions)options animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_4_0);
    + (void)animateWithDuration:(NSTimeInterval)duration animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion__OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_4_0);// delay = 0.0, options = 0
    options:是動(dòng)畫(huà)執(zhí)行的選項(xiàng)
    completion：是動(dòng)畫(huà)完成以后所要執(zhí)行的代碼塊兒。