Modifying TextView's MaxLines property with animation?

I have a TextView, with a MaxLine property set to X. When the user pushes a button, I'd like to increase this X value to a greater Y. This works, but the extra lines appear suddenly, without animation. Also, 开发者_运维问答this TextView is in a ListView-row (in case that matters, tho I doubt it).

In the new Android Market app., when you open the detailed view of an application, the details of the app. is presented exactly the way I'd like to achive. Initially, only 3 lines of text is shown, then when the user taps on the 'more' buttons, the rest of the lines animate in.

Could somebody explain to me how to achieve this effect?

Thanks

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Merge two layouts on top of each other, layout B on top of layout A.

When the user clicks a button, apply an animation to layout B so that the y-position of the layout changes by increasing y value.