Programmatically change the value of a color resource obtained from API response

You can create a class which extends Resources and override the methods getColor(int) and getColor(int, Theme).

Example:

colors.xml

xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="your_special_color">#FF0099CC</color>
</resources>

Res.java

java

public class Res extends Resources {

    public Res(Resources original) {
        super(original.getAssets(), original.getDisplayMetrics(), original.getConfiguration());
    }

    @Override public int getColor(int id) throws NotFoundException {
        return getColor(id, null);
    }

    @Override public int getColor(int id, Theme theme) throws NotFoundException {
        switch (getResourceEntryName(id)) {
            case "your_special_color":
                // You can change the return value to an instance field that loads from SharedPreferences.
                return Color.RED; // used as an example. Change as needed.
            default:
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    return super.getColor(id, theme);
                }
                return super.getColor(id);
        }
    }
}

BaseActivity.java

java

public class BaseActivity extends AppCompatActivity {

    ...

    private Res res;

    @Override public Resources getResources() {
        if (res == null) {
            res = new Res(super.getResources());
        }
        return res;
    }

    ...

}

This is the approach I have used in one of my apps, Root Check. If you override getResources in your activities and main application class you can change the theme programmatically (even though themes are immutable). If you want, download the app and see how you can set the primary, accent, and background colors from preferences.