objective-c - 滚动 UIScrollView 以显示几个文本字段中的最低部分

Question

我有一个 UIScrollView，里面有几个动态 View ，每个 View 都有一个文本字段。当我开始在其中一个框中键入内容时，我希望 ScrollView 滚动，以便该字段位于屏幕顶部(在键盘上方可见)。效果很好；这是代码:

(void)didStartTyping:(id)sender {
    [scrollView setContentOffset:CGPointMake(0, subView.frame.origin.y) animated:YES];
    scrollView.scrollEnabled = NO;
}

(void)didFinishTyping:(id)sender {
    scrollView.scrollEnabled = YES;
}

但是，每当 ScrollView 向上滚动到最顶部并且我开始在最低的可见文本字段中键入内容时，它就不会向下滚动足够远(短约 40 像素)。令人费解的是，如果我从 ScrollView 的顶部向下滚动一个像素，它就可以工作，但是当我向上滚动到顶部时，它的行为却大不相同。

Answer 1

我设法做到这一点的最好方法是捕获键盘框架，然后在 TextView 调用 textViewDidBeginEditing: 时更新我的​​ ScrollView 插入。我在这里使用的是 tableview，但相同的逻辑应该适用于 scrollview，主要区别在于滚动方式。我使用 scrollToRowAtIndexPath，你会想要使用 scrollRectToVisible

//setup keyboard callbacks
- (void)viewDidLoad
{
    [super viewDidLoad];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:) 
                                                 name:UIKeyboardWillShowNotification 
                                               object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyboardWillShow:) 
                                                 name:UIKeyboardWillHideNotification 
                                               object:nil];
}

- (void)keyboardWillShow:(NSNotification*)aNotification
{
    NSDictionary* info = [aNotification userInfo];
    kbFrame = [[info objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
}

//this is called from your UITextViewDelegate when textViewDidBeginEditing: is called
- (void)updateActiveTextScroll:(UITextView*)textView
{
    activeTextView = textView;
    UIEdgeInsets inset;
    UIInterfaceOrientation orient = [[UIApplication sharedApplication] statusBarOrientation];
    if( UIInterfaceOrientationIsLandscape(orient) )
    {
        inset = UIEdgeInsetsMake(0.0, 0.0, kbFrame.size.width, 0.0);
    }
    else
    {
        inset = UIEdgeInsetsMake(0.0, 0.0, kbFrame.size.height, 0.0);
    }
    myTableView.contentInset = inset;
    myTableView.scrollIndicatorInsets = inset;

    [myTableView scrollToRowAtIndexPath:activeNSIndexPath
                       atScrollPosition:UITableViewScrollPositionBottom
                               animated:YES];
}

//dont forget to reset when the keyboard goes away
- (void)keyboardWillBeHidden:(NSNotification*)aNotification
{
    UIEdgeInsets inset = UIEdgeInsetsZero;
    myTableView.contentInset = inset;
    myTableView.scrollIndicatorInsets = inset;
}