当键盘出现的时候，如何让UITextField自动上移

最新推荐文章于 2024-07-17 08:00:00 发布

最新推荐文章于 2024-07-17 08:00:00 发布 · 131 阅读

本文介绍了一种常见需求的实现方法：当iPhone键盘弹出时，如何通过监听Notification并调整视图的位置和大小来确保输入框不会被遮挡。提供了一个具体的代码示例，演示了如何使用Swift或Objective-C进行实现。

对于iPhone界面控件的操作应该算是开发中必备的能力。键盘出现的时候上移相关的控件算是常见的需求，但是从这么多人问这个问题就可以看出，还是有很多人对这些需求的实现方式有疑问。

对于这个问题，主要是通过增加对键盘出现和消失的相应的Notification，然后在键盘出现和消息的时候，通过设置相关控件的frame来实现。相关代码如下，来源自stackoverflow。

-(void)textFieldDidBeginEditing:(UITextField *)sender
{
    if ([sender isEqual:_textField])
    {
        //move the main view, so that the keyboard does not hide it.
        if  (self.view.frame.origin.y >= 0)
        {
            [self setViewMovedUp:YES];
        }
    }
}

//method to move the view up/down whenever the keyboard is shown/dismissed
-(void)setViewMovedUp:(BOOL)movedUp
{
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.5]; // if you want to slide up the view

    CGRect rect = self.view.frame;
    if (movedUp)
    {
        // 1. move the view's origin up so that the text field that will be hidden come above the keyboard 
        // 2. increase the size of the view so that the area behind the keyboard is covered up.
        rect.origin.y -= kOFFSET_FOR_KEYBOARD;
        rect.size.height += kOFFSET_FOR_KEYBOARD;
    }
    else
    {
        // revert back to the normal state.
        rect.origin.y += kOFFSET_FOR_KEYBOARD;
        rect.size.height -= kOFFSET_FOR_KEYBOARD;
    }
    self.view.frame = rect;

    [UIView commitAnimations];
}


- (void)keyboardWillShow:(NSNotification *)notif
{
    //keyboard will be shown now. depending for which textfield is active, move up or move down the view appropriately

    if ([_textField isFirstResponder] && self.view.frame.origin.y >= 0)
    {
        [self setViewMovedUp:YES];
    }
    else if (![_textField isFirstResponder] && self.view.frame.origin.y < 0)
    {
        [self setViewMovedUp:NO];
    }
}


- (void)viewWillAppear:(BOOL)animated
{
    // register for keyboard notifications
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:)
                                                 name:UIKeyboardWillShowNotification object:self.view.window];
}

- (void)viewWillDisappear:(BOOL)animated
{
     // unregister for keyboard notifications while not visible.
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardWillShowNotification object:nil];
}