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[操作系统]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UITableViewframe
  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UITableViewframe
  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UITableViewframe

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];

}