UIScrollView滚动问题

Question

我有一个完美的滚动视图，直到我解除键盘。在那之后它滚动但不是一直向下滚动...我有点困惑。

在viewDidLoad中我保存了帧，以便稍后重置

frame = self.scrollView.frame;
NSLog(@"Height beginning: %f",self.scrollView.frame.size.height);
offset = self.scrollView.contentOffset;

为了调试我检查了scrollview的高度629

在我的keyboardDidHide方法中我将旧框架设置回来

self.scrollView.frame = frame;
NSLog(@"Height end: %f",self.scrollView.frame.size.height);

// Reset the scrollview to previous location
self.scrollView.contentOffset = offset;

调试输出也是629，这意味着scrollview的高度已设置为旧值。它确实滚动，但是当我放开它时它会一直反弹到开头......

编辑：

当使用480作为高度时，由于iphone 4

，它不会填满整个屏幕

一些代码

-(void) keyboardDidShow: (NSNotification *)notif 
{
    NSLog(@"Keyboard is visible");
    // If keyboard is visible, return
    if (keyboardVisible) {
        NSLog(@"Keyboard is already visible. Ignore notification.");
        return;
    }

    // Get the size of the keyboard.
    CGRect keyboardEndFrame;
    [[notif.userInfo valueForKey:UIKeyboardFrameEndUserInfoKey] getValue:&keyboardEndFrame];

    // Resize the scroll view to make room for the keyboard
    CGRect viewFrame = frame;
    viewFrame.size.height = 200;
    //viewFrame.size.height -= keyboardEndFrame.size.height;
    self.scrollView.frame = viewFrame;

    offset = self.scrollView.contentOffset;

    CGRect textFieldRect;

    if(!activeField)
        textFieldRect = comment.frame;
    else
        textFieldRect = activeField.frame;

    textFieldRect.origin.y += 10;
    [self.scrollView scrollRectToVisible:textFieldRect animated:YES];

    // Keyboard is now visible
    keyboardVisible = YES;
}

-(void) keyboardDidHide: (NSNotification *)notif 
{
    // Is the keyboard already shown
    if (!keyboardVisible) {
        NSLog(@"Keyboard is already hidden. Ignore notification.");
        return;
    }

    //viewFrame.size.height -= keyboardEndFrame.size.height;
    self.scrollView.frame = frame;
    [self.scrollView setContentSize:CGSizeMake(320, 700)];

    // Reset the scrollview to previous location
    self.scrollView.contentOffset = offset;

    // Keyboard is no longer visible
    keyboardVisible = NO;   
}