Answers for "why action bar color doesn't change in mobile device but works in emulator"

status bar color android kotlin

Window window = activity.getWindow();

// clear FLAG_TRANSLUCENT_STATUS flag:
window.clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS);

// add FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS flag to the window
window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);

// finally change the color
window.setStatusBarColor(ContextCompat.getColor(activity,R.color.my_statusbar_color));