ViewAnimator helper which allows setting the selected child by ID rather than index

SquareViewAnimator.java

package com.squareup.widgets;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ViewAnimator;

/** ViewAnimator helper which allows setting the selected child by ID rather than index. */
public class SquareViewAnimator extends ViewAnimator {
  public SquareViewAnimator(Context context) {
    super(context);
  }

  public SquareViewAnimator(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  /**
   * Set the currently displayed child by its ID.
   *
   * @param id ID of child.
   * @throws IllegalArgumentException If child with specified ID does not exist.
   */
  public void setDisplayedChildById(int id) {
    for (int i = getChildCount() - 1; i >= 0; i--) {
      View child = getChildAt(i);
      if (child.getId() == id) {
        if (i != getDisplayedChild()) {
          setDisplayedChild(i);
        }
        return;
      }
    }
    throw new IllegalArgumentException("View with ID " + id + " not found.");
  }

  /** Get the view ID of the currently displayed child. */
  public int getDisplayedChildId() {
    return getChildAt(getDisplayedChild()).getId();
  }
}