How to Set Opacity (Alpha) for View in Android

I'm amazed by everyone else's MUCH more complicated answers.

XML

You can very simply define the alpha in the color definition of the button (or any other view) in your xml:

android:color="#66FF0000"    // Partially transparent red

In the above example, the color would be a partially transparent red.

When defining the color of a view, the format can be either #RRGGBB or #AARRGGBB, where AA is the hex alpha value. FF would be fully opaque and 00 would be full transparent.

Dynamically

If you need to dynamically alter the opacity in your code, use

myButton.getBackground().setAlpha(128);  // 50% transparent

Where the INT ranges from 0 (fully transparent) to 255 (fully opaque).

I guess you may have already found the answer, but if not (and for other developers), you can do it like this:

btnMybutton.getBackground().setAlpha(45);

Here I have set the opacity to 45. You can basically set it from anything between 0(fully transparent) to 255 (completely opaque)

Much more easier from the above. Default alpha attribute is there for button

android:alpha="0.5"

The range is between 0 for complete transparent and 1 for complete opacity.