We used to think this was just text fields (LPP-2520) but it applies to views as well - it's pretty serious! I'm gonna revive my fix for LPP-2520 and try to get it working for real... Here's a simple test case:

<canvas>
    <view width="60" height="50" bgcolor="black">
        <handler name="onmouseover">
            this.setBGColor(0xcccccc)
        </handler>
        <handler name="onmousedown">
            this.setBGColor(0xeeeeee)
        </handler>
        <handler name="onmouseup">
            this.setBGColor(0xcccccc)
        </handler>
        <handler name="onmouseout">
            this.setBGColor(0x000000)
        </handler>
    </view>

    <view width="30" height="50" opacity=".5" bgcolor="yellow"/>
</canvas>