DrawerActions.java

package com.google.android.apps.common.testing.ui.espresso.contrib;
import static com.google.android.apps.common.testing.ui.espresso.Espresso.onView;
import static com.google.android.apps.common.testing.ui.espresso.contrib.DrawerMatchers.isClosed;
import static com.google.android.apps.common.testing.ui.espresso.contrib.DrawerMatchers.isOpen;
import static com.google.android.apps.common.testing.ui.espresso.matcher.ViewMatchers.isAssignableFrom;
import static com.google.android.apps.common.testing.ui.espresso.matcher.ViewMatchers.withId;

import com.google.android.apps.common.testing.ui.espresso.Espresso;
import com.google.android.apps.common.testing.ui.espresso.IdlingResource;
import com.google.android.apps.common.testing.ui.espresso.PerformException;
import com.google.android.apps.common.testing.ui.espresso.UiController;
import com.google.android.apps.common.testing.ui.espresso.ViewAction;

import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v4.widget.DrawerLayout.DrawerListener;
import android.view.View;

import org.hamcrest.Matcher;

import java.lang.reflect.Field;
import java.util.concurrent.atomic.AtomicBoolean;

import javax.annotation.Nullable;

/**
 * Espresso actions for using a {@link DrawerLayout}.
 *
 * @see <a href="http://developer.android.com/design/patterns/navigation-drawer.html">Navigation
 *      drawer design guide</a>
 */
public final class DrawerActions {

  private DrawerActions() {
    // forbid instantiation
  }

  private static Field listenerField;

  /**
   * Opens the {@link DrawerLayout} with the given id. This method blocks until the drawer is fully
   * open. No operation if the drawer is already open.
   */
  public static void openDrawer(int drawerLayoutId) {
    //if the drawer is already open, return.
    if (checkDrawer(drawerLayoutId, isOpen())) {
      return;
    }
    onView(withId(drawerLayoutId)).perform(registerListener());
    onView(withId(drawerLayoutId)).perform(actionOpenDrawer());
  }

  /**
   * Closes the {@link DrawerLayout} with the given id. This method blocks until the drawer is fully
   * closed. No operation if the drawer is already closed.
   */
  public static void closeDrawer(int drawerLayoutId) {
    //if the drawer is already closed, return.
    if (checkDrawer(drawerLayoutId, isClosed())) {
      return;
    }
    onView(withId(drawerLayoutId)).perform(registerListener());
    onView(withId(drawerLayoutId)).perform(actionCloseDrawer());
  }

  /**
   * Returns true if the given matcher matches the drawer.
   */
  private static boolean checkDrawer(int drawerLayoutId, final Matcher<View> matcher) {
    final AtomicBoolean matches = new AtomicBoolean(false);
    onView(withId(drawerLayoutId)).perform(new ViewAction() {

      @Override
      public Matcher<View> getConstraints() {
        return isAssignableFrom(DrawerLayout.class);
      }

      @Override
      public String getDescription() {
        return "check drawer";
      }

      @Override
      public void perform(UiController uiController, View view) {
        matches.set(matcher.matches(view));
      }
    });
    return matches.get();
  }

  private static ViewAction actionOpenDrawer() {
    return new ViewAction() {
      @Override
      public Matcher<View> getConstraints() {
        return isAssignableFrom(DrawerLayout.class);
      }

      @Override
      public String getDescription() {
        return "open drawer";
      }

      @Override
      public void perform(UiController uiController, View view) {
        ((DrawerLayout) view).openDrawer(GravityCompat.START);
      }
    };
  }

  private static ViewAction actionCloseDrawer() {
    return new ViewAction() {
      @Override
      public Matcher<View> getConstraints() {
        return isAssignableFrom(DrawerLayout.class);
      }

      @Override
      public String getDescription() {
        return "close drawer";
      }

      @Override
      public void perform(UiController uiController, View view) {
        ((DrawerLayout) view).closeDrawer(GravityCompat.START);
      }
    };
  }

  /**
   * Returns a {@link ViewAction} that adds an {@link IdlingDrawerListener} as a drawer listener to
   * the {@link DrawerLayout}. The idling drawer listener wraps any listener that already exists.
   */
  private static ViewAction registerListener() {
    return new ViewAction() {
      @Override
      public Matcher<View> getConstraints() {
        return isAssignableFrom(DrawerLayout.class);
      }

      @Override
      public String getDescription() {
        return "register idling drawer listener";
      }

      @Override
      public void perform(UiController uiController, View view) {
        DrawerLayout drawer = (DrawerLayout) view;
        DrawerListener existingListener = getDrawerListener(drawer);
        if (existingListener instanceof IdlingDrawerListener) {
          // listener is already registered. No need to assign.
          return;
        }
        drawer.setDrawerListener(IdlingDrawerListener.getInstance(existingListener));
      }
    };
  }

  /**
   * Pries the current {@link DrawerListener} loose from the cold dead hands of the given
   * {@link DrawerLayout}. Uses reflection.
   */
  @Nullable
  private static DrawerListener getDrawerListener(DrawerLayout drawer) {
    try {
      if (listenerField == null) {
        // lazy initialization of reflected field.
        listenerField = DrawerLayout.class.getDeclaredField("mListener");
        listenerField.setAccessible(true);
      }
      return (DrawerListener) listenerField.get(drawer);
    } catch (IllegalArgumentException ex) {
      // Pity we can't use Java 7 multi-catch for all of these.
      throw new PerformException.Builder().withCause(ex).build();
    } catch (IllegalAccessException ex) {
      throw new PerformException.Builder().withCause(ex).build();
    } catch (NoSuchFieldException ex) {
      throw new PerformException.Builder().withCause(ex).build();
    } catch (SecurityException ex) {
      throw new PerformException.Builder().withCause(ex).build();
    }
  }

  /**
   * Drawer listener that wraps an existing {@link DrawerListener}, and functions as an
   * {@link IdlingResource} for Espresso.
   */
  private static class IdlingDrawerListener implements DrawerListener, IdlingResource {

    private static IdlingDrawerListener instance;
    private static IdlingDrawerListener getInstance(DrawerListener parentListener) {
      if (instance == null) {
        instance = new IdlingDrawerListener();
        Espresso.registerIdlingResources(instance);
      }
      instance.setParentListener(parentListener);
      return instance;
    }

    @Nullable private DrawerListener parentListener;
    private ResourceCallback callback;
    // Idle state is only accessible from main thread.
    private boolean idle = true;

    public void setParentListener(@Nullable DrawerListener parentListener) {
      this.parentListener = parentListener;
    }

    @Override
    public void onDrawerClosed(View drawer) {
      if (parentListener != null) {
        parentListener.onDrawerClosed(drawer);
      }
    }

    @Override
    public void onDrawerOpened(View drawer) {
      if (parentListener != null) {
        parentListener.onDrawerOpened(drawer);
      }
    }

    @Override
    public void onDrawerSlide(View drawer, float slideOffset) {
      if (parentListener != null) {
        parentListener.onDrawerSlide(drawer, slideOffset);
      }
    }

    @Override
    public void onDrawerStateChanged(int newState) {
      if (newState == DrawerLayout.STATE_IDLE) {
        idle = true;
        if (callback != null) {
          callback.onTransitionToIdle();
        }
      } else {
        idle = false;
      }
      if (parentListener != null) {
        parentListener.onDrawerStateChanged(newState);
      }
    }

    @Override
    public String getName() {
      return "IdlingDrawerListener";
    }

    @Override
    public boolean isIdleNow() {
      return idle;
    }

    @Override
    public void registerIdleTransitionCallback(ResourceCallback callback) {
      this.callback = callback;
    }
  }
}