- (void)addDoneButtonToNumPadKeyboard 
{ 
  UIButton *doneButton = [UIButton buttonWithType:UIButtonTypeCustom]; 
  if (systemVersion < 8.0){ 
    doneButton.frame = CGRectMake(0, 163, 106, 53); 
  }else{ 
    doneButton.frame = CGRectMake(0, SCREEN_SIZE.height-53, 106, 53); 
  } 
  doneButton.tag = NUM_PAD_DONE_BUTTON_TAG; 
  doneButton.adjustsImageWhenHighlighted = NO; 
  [doneButton setTitle:@"完成" forState:UIControlStateNormal]; 
  [doneButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal]; 
  [doneButton addTarget:self action:@selector(doneButton:) forControlEvents:UIControlEventTouchUpInside]; 
   
  NSArray *windowArr = [[UIApplication sharedApplication] windows]; 
  if (windowArr != nil && windowArr.count > 1){ 
    UIWindow *needWindow = [windowArr objectAtIndex:1]; 
    UIView *keyboard; 
    for(int i = 0; i < [needWindow.subviews count]; i++) { 
      keyboard = [needWindow.subviews objectAtIndex:i]; 
      NSLog(@"%@", [keyboard description]); 
      if(([[keyboard description] hasPrefix:@" 1){ 
    UIWindow *needWindow = [windowArr objectAtIndex:1]; 
    UIView *keyboard; 
    for(int i = 0; i < [needWindow.subviews count]; i++) { 
      keyboard = [needWindow.subviews objectAtIndex:i]; 
      if(([[keyboard description] hasPrefix:@"