userInteractionEnabled UIImageView works strangely
<p>I create a UIImageView as below</p>

<pre><code>imageView = [[UIImageView alloc] init];

imageView.image = [UIImage imageNamed:@"military_male_target_001.png"];

imageView.frame = CGRectMake(0, 0, 10, 10);

imageView.alpha = 0.5;
</code></pre>

<p>and I have </p>

<pre><code>   - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {...}
</code></pre>

<p>in my view controller.</p>

<p>so far so good, the image is displayed on screen and respond to touch down event correctly which means touchesEnded method is invoked when I click inside the image.</p>

<p>but if I add</p>

<pre><code>imageView.userInteractionEnabled = YES
</code></pre>

<p>then touchesEnded method won't be invoked when I click inside the image.
but it is still invoked when I click outside the image.</p>

<p>can anyone tell me how userInteractionEnabled works?
thanks in advance.</p>
