Dim the background using PopupWindow in Android

It seems that I figured out how to get rid of API version checks. Using container = popupWindow.getContentView().getRootView() solves the problem, however I haven't tested it for old APIs yet. Adapting Junyue Cao's solution:

public static void dimBehind(PopupWindow popupWindow) {
    View container = popupWindow.getContentView().getRootView();
    Context context = popupWindow.getContentView().getContext();
    WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
    WindowManager.LayoutParams p = (WindowManager.LayoutParams) container.getLayoutParams();
    p.flags |= WindowManager.LayoutParams.FLAG_DIM_BEHIND;
    p.dimAmount = 0.3f;
    wm.updateViewLayout(container, p);
}

I use the following code, and it works well for me.

public static void dimBehind(PopupWindow popupWindow) {
    View container;
    if (popupWindow.getBackground() == null) {
        if (VERSION.SDK_INT >= VERSION_CODES.M){
            container = (View) popupWindow.getContentView().getParent();
        } else {
            container = popupWindow.getContentView();
        }
    } else {
        if (VERSION.SDK_INT >= VERSION_CODES.M) {
            container = (View) popupWindow.getContentView().getParent().getParent();
        } else {
            container = (View) popupWindow.getContentView().getParent();
        }
    }
    Context context = popupWindow.getContentView().getContext();
    WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
    WindowManager.LayoutParams p = (WindowManager.LayoutParams) container.getLayoutParams();
    p.flags = WindowManager.LayoutParams.FLAG_DIM_BEHIND;
    p.dimAmount = 0.3f;
    wm.updateViewLayout(container, p);
}

From this answer.

Update：

The fdermishin's answer below is better. I have tested it backwards to API level 19 and it works well.

If you are using Kotlin, it is better to use it as Kotlin extension:

//Just new a kotlin file(e.g. ComponmentExts),
//copy the following function declaration into it
/**
 * Dim the background when PopupWindow shows
 */
fun PopupWindow.dimBehind() {
    val container = contentView.rootView
    val context = contentView.context
    val wm = context.getSystemService(Context.WINDOW_SERVICE) as WindowManager
    val p = container.layoutParams as WindowManager.LayoutParams
    p.flags = p.flags or WindowManager.LayoutParams.FLAG_DIM_BEHIND
    p.dimAmount = 0.3f
    wm.updateViewLayout(container, p)
}

//then use it in other place like this：
popupWindow.dimBehind()