General :: Drawing Buttons At Different Times?

I am writing a calculator app as my first android app.

I have a mode button on the calculator that changes the buttons to make new functions available.

When mode switches, certain buttons get changed to a different drawable with different colors, and all the text gets updated on all the buttons.

Each mode has a new string array corresponding to the text for that mode.What I am currently trying to achieve is having a delay between the time that each button is updated, a sort of cascade effect. I have not successfully implemented this.

In the following code I have a toggleLabels method which attempts to do this. It has three if blocks corresponding to the three modes, which each gets a new set of text and buttons. There are two nested for loops in each running i=width and j=height.

To create the cascade effect I grabbed system time, and then subtracted from current time to see that 100ms had passed.No cascade effect takes place, and when I hit the mode button, there is a long delay then all of the buttons switch at once. The delay seems to be exactly 2 seconds, which corresponds to the cumulative delay of 100ms per button X 20 buttons.

I also tried an alternate method of Thread.Sleep() which yielded the same result, and which I read was bad practice to implement in your UI thread.Basically I am doing..

loop through each button
{
Change button drawable[code]......