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1、寫了一個小Demo，實現上下移動的效果圖：

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，如你的兩個view的大小，需要計算出精確位置。

下面開始學習[UIView animateWithDuration]方法的使用：

函數原型：

+ (void)animateWithDuration:(NSTimeInterval)duration animations:(void (^)(void))animations __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_4_0); // delay = 0.0, options = 0, completion = NULL

duration：動畫持續時間

animations：該代碼兒塊中是所有view要完成的動畫的所有屬性的定義;

還有另外兩個函數：

+ (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:是動畫執行的選項

completion：是動畫完成以后所要執行的代碼塊兒。

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