DuoDrawerToggle.java 文件源码

void setActionBarUpIndicator(Drawable upDrawable, int contentDescRes) {
    if (!mWarnedForDisplayHomeAsUp && !mActivityImpl.isNavigationVisible()) {
        Log.w("DuoDrawerToggle", "DrawerToggle may not show up because NavigationIcon"
                + " is not visible. You may need to call "
                + "actionbar.setDisplayHomeAsUpEnabled(true);");
        mWarnedForDisplayHomeAsUp = true;
    }
    mActivityImpl.setActionBarUpIndicator(upDrawable, contentDescRes);
}