1、修改某个UITextField的键盘的返回键类型：

[_bottomTextView setReturnKeyType:UIReturnKeyDone];

1.1、textFied点击return键之后有处理方法：

UITextViewDelegate里面有这样一个代理函数：
- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)tex

 1.2、textView点击return键之后的处理：

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{

if ([text isEqualToString:@"\n"]){ //判断输入的字是否是回车，即按下return

//在这里做你响应return键的代码

[self.rejectReasonTextView resignFirstResponder];

return NO; //这里返回NO，就代表return键值失效，即页面上按下return，不会出现换行，如果为yes，则输入页面会换行

}

return YES;

}

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以及监听键盘的高度变化，一起随着键盘顶出来或者压下去：

[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardHeightChange:) name:UIKeyboardWillChangeFrameNotification object:nil];

keyboardHeightChange：

-(void)keyboardHeightChange:(NSNotification *)notifi

{

self.dropButton.hidden = YES;

NSDictionary *dict=[notifi userInfo];

CGRect keyBoardRect=[[dict objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];

CGFloat keyBoardHeight=keyBoardRect.size.height;

CGFloat keyBoardY=keyBoardRect.origin.y;

float animationDuration = [[dict objectForKey:UIKeyboardAnimationDurationUserInfoKey] floatValue];//取到键盘动画退出弹出的时间，好处，不同的键盘时间可能不一样

[UIView animateWithDuration:animationDuration animations:^{

CGRect bottomNewFrame=CGRectMake(_bottomView.frame.origin.x, keyBoardY+_bottomView.frame.size.height, _bottomView.frame.size.width, _bottomView.frame.size.height);

_bottomView.frame=bottomNewFrame;

}];