How to set opacity/alpha in SpannableString Android

Issue

How to actually set the alpha/opacity for spanned text using SpannableStringBuilder in Android? I want to achieve this design in one TextView:

The main text Current location have full opacity/alpha (1.0) and the sub text Kungstan 43 have opacity of 84%.

I have set the SpannableStringBuilder as follows:

SpannableStringBuilder OriginText = new SpannableStringBuilder();
OriginText.Append(OriginMainText + ", ");
int SubTextIndex = OriginText.Length();
OriginText.Append(OriginSubText);
OriginText.SetSpan(<what need to set here??>, SubTextIndex, OriginText.Length(), 0)

What object should I put in <what need to set here??>? The closest approach is to set the foreground color but I prefer if it has way to set the alpha/opacity.

Solution

You can use the TextAppearanceSpan.

OriginText.setSpan(new TextAppearanceSpan(...), SubTextIndex, OriginText.Length(), 0);

The syntax is:

TextAppearanceSpan(String family, 
                   int style, 
                   int size, 
                   ColorStateList color, 
                   ColorStateList linkColor)

The important parameter for you here is the ColorStateList color, which is defined like this:

<selector xmlns:android="http://schemas.android.com/apk/res/android">
   <item android:state_focused="true"
         android:color="@color/sample_focused" />
   <item android:state_pressed="true"
         android:state_enabled="false"
         android:color="@color/sample_disabled_pressed" />
   <item android:state_enabled="false"
         android:color="@color/sample_disabled_not_pressed" />
   <item android:color="@color/sample_default" />
</selector>

Starting with API 23, items may optionally define an android:alpha attribute to modify the base color's opacity, which is what you want. For example, the following item has 84% opacity as you wanted:

<item android:state_enabled="false"
      android:color="?android:attr/colorAccent"
      android:alpha="0.84" />

To get the color definition from resource, you can use:

ContextCompat.getColor(context, R.color.your_color);

Answered By - Racil Hilan