iOS 解决表单被键盘遮住的问题

问题

处理表单的时候,一定会碰到的就是输入控件被键盘遮住的问题,如图:

实例

左边是普通表单,中间是2B表单,右边是文艺表单.

分析

处理这种问题无非就是2个步骤:

1. 键盘弹出时,缩小UITableView的frame
2. 滚动UITableView,让当前输入的控件可见

代码写出来就是这几步

1. 捕获键盘事件
2. 计算键盘高度并调整UITableView的frame
3. 获取当前正在输入的控件
4. 计算其在UITableView中的位置,并滚动到其位置让其可见

那么如何一步一步的来实现这些步骤呢?

捕获键盘事件

捕获键盘事件

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[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(actionKeyboardShow:) name:UIKeyboardDidShowNotification object:nil]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(actionKeyboardHide:) name:UIKeyboardWillHideNotification object:nil]; - (void)actionKeyboardShow:(NSNotification *)notification { [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidShowNotification object:nil]; [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidChangeFrameNotification object:nil]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(actionKeyboardShow:) name:UIKeyboardDidChangeFrameNotification object:nil]; } - (void)actionKeyboardHide:(NSNotification *)notification { [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidChangeFrameNotification object:nil]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(actionKeyboardShow:) name:UIKeyboardDidShowNotification object:nil]; }

计算键盘高度并调整UITableView的frame

计算键盘高度并调整UITableView的frame

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- (void)actionKeyboardShow:(NSNotification *)notification { CGSize keyboardSize = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size self.tableView.frame = CGRectMake(0, 0, 320, self.view.h-keyboardSize.height); [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidShowNotification object:nil]; [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidChangeFrameNotification object:nil]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(actionKeyboardShow:) name:UIKeyboardDidChangeFrameNotification object:nil]; }

获取当前正在输入的控件

这里得说一句,普通程序员一般是这样来获取的

UIView的Category

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- (UIView *) getFirstResponder { if (self.isFirstResponder) { return self; } for (UIView *subView in self.subviews) { UIView *firstResponder = [subView getFirstResponder]; if (firstResponder != nil) { return firstResponder; } } return nil; }

虽然没错,但是文艺程序员应该这样来获取

UIResponder的Category

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static __weak id currentFirstResponder; +(id)currentFirstResponder { currentFirstResponder = nil; [[UIApplication sharedApplication] sendAction:@selector(findFirstResponder:) to:nil from:nil forEvent:nil]; return currentFirstResponder; } -(void)findFirstResponder:(id)sender { currentFirstResponder = self; }

同理,有时候我们需要让键盘消失,那么也有三种做法可以选择

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[someView resignFirstResponder]; [self.view endEditing:YES]; [[UIApplication sharedApplication] sendAction:@selector(resignFirstResponder) to:nil from:nil forEvent:nil];

如何选择呢? It’s up to U.

计算其在UITableView中的位置,并滚动到其位置让其可见

计算其在UITableView中的位置,并滚动到其位置让其可见

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- (void)actionKeyboardShow:(NSNotification *)notification { CGSize keyboardSize = [[[notification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue].size; self.tableView.frame = CGRectMake(0, 0, 320, self.view.h-keyboardSize.height); UIView *v = [UIResponder currentFirstResponder]; if ( v ) { while ( ![v isKindOfClass:[UITableViewCell class]]) { v = v.superview; } UITableViewCell *cell = (UITableViewCell*)v; [self.tableView scrollToRowAtIndexPath:[self.tableView indexPathForRowAtPoint:cell.center] atScrollPosition:UITableViewScrollPositionBottom animated:YES]; } [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidShowNotification object:nil]; [[NSNotificationCenter defaultCenter] removeObserver:self name:UIKeyboardDidChangeFrameNotification object:nil]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(actionKeyboardShow:) name:UIKeyboardDidChangeFrameNotification object:nil]; }