How to set background color of a View

Question

You made your button transparent. The first byte is the alpha.

Try v.setBackgroundColor(0xFF00FF00);

When you call setBackgoundColor it overwrites/removes any existing background resource, including any borders, corners, padding, etc. What you want to do is change the color of the existing background resource...

View v;
v.getBackground().setColorFilter(Color.parseColor("#00ff00"), PorterDuff.Mode.DARKEN);

Experiment with PorterDuff.Mode.* for different effects.

Several choices to do this...

Set background to green:

v.setBackgroundColor(0x00FF00);

Set background to green with Alpha:

v.setBackgroundColor(0xFF00FF00);

Set background to green with Color.GREEN constant:

v.setBackgroundColor(Color.GREEN);

Set background to green defining in Colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>     
    <color name="myGreen">#00FF00</color> 
    <color name="myGreenWithAlpha">#FF00FF00</color> 
</resources>

and using:

v.setBackgroundResource(R.color.myGreen);

and:

v.setBackgroundResource(R.color.myGreenWithAlpha);

or the longer winded:

v.setBackgroundColor(ContextCompat.getColor(getContext(), R.color.myGreen));

and:

v.setBackgroundColor(ContextCompat.getColor(getContext(), R.color.myGreenWithAlpha));

You can set the hex-color to any resource with:

View.setBackgroundColor(Color.parseColor("#e7eecc"));