IOS数字键盘左下角添加完成按钮的实现方法

实现代码：

- (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(inti = 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(inti = 0; i < [needWindow.subviews count]; i++) {
      keyboard = [needWindow.subviews objectAtIndex:i];
      if(([[keyboard description] hasPrefix:@"