UITextField的一些操作

一.判断正在编辑的UITextField或UITextView的内容是否为空，以此来控制button的点亮状态

#pragma mark- UITextFieldDelegate

- (BOOL)textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)rangereplacementString:(NSString*)string

{

    

   NSMutableString* changedString=[[NSMutableStringalloc]initWithString:textField.text];

    [changedStringreplaceCharactersInRange:rangewithString:string];

    

   if(changedString.length!=0){

      self.navigationItem.rightBarButtonItem.enabled=YES;

    }else{

      self.navigationItem.rightBarButtonItem.enabled=NO;

    }

   return YES;

}

#pragma mark- UITextViewDelegate

- (BOOL)textView:(UITextView*)textView shouldChangeTextInRange:(NSRange)rangereplacementText:(NSString*)text

{

   NSMutableString* changedString=[[NSMutableStringalloc]initWithString:textView.text];

   [changedStringreplaceCharactersInRange:rangewithString:text];

    

   if(changedString.length!=0){

      self.navigationItem.rightBarButtonItem.enabled=YES;

    }else{

      self.navigationItem.rightBarButtonItem.enabled=NO;

    }

    

   return YES;

}

二.解决退格键一次清处所有的问题

#pragma mark- UITextFieldDelegate
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    if (range.location > 0 && range.length == 1 && string.length == 0)
    {
        //存储光标位置
        UITextPosition *beginning = textField.beginningOfDocument;
        UITextPosition *start = [textField positionFromPosition:beginning offset:range.location];
        NSInteger cursorOffset = [textField offsetFromPosition:beginning toPosition:start] + string.length;
        //保存当前文本,以防iOS删除整个文本
        NSString *text = textField.text;
        //触发删除
        [textField deleteBackward];
        //iOS删除整个字符串
        if (textField.text.length != text.length - 1)
        {
            textField.text = [text stringByReplacingCharactersInRange:range withString:string];
            //更新光标位置
            UITextPosition *newCursorPosition = [textField positionFromPosition:textField.beginningOfDocument offset:cursorOffset];
            UITextRange *newSelectedRange = [textField textRangeFromPosition:newCursorPosition toPosition:newCursorPosition];
            [textField setSelectedTextRange:newSelectedRange];
        }
        return NO;
    }
    return YES;
}