ViewContainer.java

package com.jakewharton.u2020.ui;

import android.app.Activity;
import android.view.ViewGroup;

import static butterknife.ButterKnife.findById;

/** An indirection which allows controlling the root container used for each activity. */
public interface ViewContainer {
  /** The root {@link android.view.ViewGroup} into which the activity should place its contents. */
  ViewGroup forActivity(Activity activity);

  /** An {@link ViewContainer} which returns the normal activity content view. */
  ViewContainer DEFAULT = activity -> findById(activity, android.R.id.content);
}