title: change the background image of button in objective-c?
body: <p>I've a <code>UIButton</code> on cell of <code>UITableView</code> in my VC like this</p>
  
  <pre><code>arrowBtnUp = [UIButton buttonWithType:UIButtonTypeCustom];
  arrowBtnUp.frame = CGRectMake(50,(65-19)/2,31, 31);
  [arrowBtnUp setBackgroundImage:[UIImage imageNamed:@"arrow_up.png"] forState:UIControlStateNormal];
  [arrowBtnUp addTarget:self action:@selector(slideAction) forControlEvents:UIControlEventTouchUpInside];
  [cell.contentView addSubview:arrowBtnUp];
  </code></pre>
  
  <p>and this my <code>slideAction</code></p>
  
  <pre><code>-(void) slideAction
  {
      [arrowBtnUp setBackgroundImage:[UIImage imageNamed:@"arrow_down.png"] forState:UIControlStateNormal];
      // also tried  with UIControlStateSelected/Highlighted
  }
  </code></pre>
  
  <p>But it didn't work.I found <a href="https://stackoverflow.com/questions/6479301/change-background-image-of-a-button-without-extra-buttons">this</a> link but didn't help.
  Any suggestion or sample would be appreciated. </p>