点击底部textView，tableView当前界面最后一个ce

[[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];

-(void)keyboardWillShow:(NSNotification*)note{
    NSArray *cellArray =  self.tableView.visibleCells;
    if (cellArray.count==0) {
        return;
    }
    
    CGRect keyboardFrame = [note.userInfo[UIKeyboardFrameEndUserInfoKey]CGRectValue];
    
    UITableViewCell *cell  = cellArray[cellArray.count-1];
    CGFloat y = cell.frame.size.height + cell.frame.origin.y;
    NSLog(@"%@",NSStringFromCGRect(keyboardFrame));

//20为导航栏，49为包裹textView的toolBarView
    CGFloat newY = (y+20)-(kScreenHeight - (49+keyboardFrame.size.height));
    
    if (newY>0) {
            [self.tableView setContentOffset:CGPointMake(0, newY) animated:YES];
        }
    
}