键盘上移

//在UITextField 编辑之前调用方法
- (void)textFieldDidBeginEditing:(UITextField *)textField
{
    [self animateTextField: textField up: YES];   
}
//在UITextField 编辑完成调用方法
- (void)textFieldDidEndEditing:(UITextField *)textField
{
    [self animateTextField: textField up: NO];
}
//视图上移的方法
- (void) animateTextField: (UITextField *) textField up: (BOOL) up
{
    //设置视图上移的距离，单位像素
    const int movementDistance = 100; // tweak as needed
    //三目运算，判定是否需要上移视图或者不变
    int movement = (up ? -movementDistance : movementDistance);
    //设置动画的名字
    [UIView beginAnimations: @"Animation" context: nil];
    //设置动画的开始移动位置
    [UIView setAnimationBeginsFromCurrentState: YES];
    //设置动画的间隔时间
    [UIView setAnimationDuration: 0.20];
    //设置视图移动的位移
    self.view.frame = CGRectOffset(self.view.frame, 0, movement);
    //设置动画结束
    [UIView commitAnimations];   
}