ActivityRule.java

/*
 * Copyright (C) 2015 Jake Wharton
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.jakewharton.test;

import android.app.Activity;
import android.app.Instrumentation;
import android.content.Intent;
import android.support.test.InstrumentationRegistry;
import org.junit.Before;
import org.junit.Rule;
import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;

/**
 * A JUnit {@link Rule @Rule} which launches an activity when your test starts. Stop extending
 * gross {@code ActivityInstrumentationBarfCase2}!
 * <p>
 * Usage:
 * <pre>{@code
 * &#064;Rule
 * public final ActivityRule<ExampleActivity> example =
 *     new ActivityRule<>(ExampleActivity.class);
 * }</pre>
 *
 * This will automatically launch the activity for each test method. The instance will also be
 * created sooner should you need to use it in a {@link Before @Before} method.
 * <p>
 * You can also customize the way in which the activity is launched by overriding
 * {@link #getLaunchIntent(String, Class)} and customizing or replacing the {@link Intent}.
 * <pre>{@code
 * &#064;Rule
 * public final ActivityRule<ExampleActivity> example =
 *     new ActivityRule<ExampleActivity>(ExampleActivity.class) {
 *       &#064;Override
 *       protected Intent getLaunchIntent(String packageName, Class<ExampleActivity> activityClass) {
 *         Intent intent = super.getLaunchIntent(packageName, activityClass);
 *         intent.putExtra("Hello", "World!");
 *         return intent;
 *       }
 *     };
 * }</pre>
 */
public class ActivityRule<T extends Activity> implements TestRule {
  private final Class<T> activityClass;

  private T activity;
  private Instrumentation instrumentation;

  public ActivityRule(Class<T> activityClass) {
    this.activityClass = activityClass;
  }

  protected Intent getLaunchIntent(String targetPackage, Class<T> activityClass) {
    Intent intent = new Intent(Intent.ACTION_MAIN);
    intent.setClassName(targetPackage, activityClass.getName());
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    return intent;
  }

  /**
   * Get the running instance of the specified activity. This will launch it if it is not already
   * running.
   */
  public final T get() {
    launchActivity();
    return activity;
  }

  /** Get the {@link Instrumentation} instance for this test. */
  public final Instrumentation instrumentation() {
    launchActivity();
    return instrumentation;
  }

  @Override public final Statement apply(final Statement base, Description description) {
    return new Statement() {
      @Override public void evaluate() throws Throwable {
        launchActivity();

        base.evaluate();

        if (!activity.isFinishing()) {
          activity.finish();
        }
        activity = null; // Eager reference kill in case someone leaked our reference.
      }
    };
  }

  private Instrumentation fetchInstrumentation() {
    Instrumentation result = instrumentation;
    return result != null ? result
        : (instrumentation = InstrumentationRegistry.getInstrumentation());
  }

  @SuppressWarnings("unchecked") // Guarded by generics at the constructor.
  private void launchActivity() {
    if (activity != null) return;

    Instrumentation instrumentation = fetchInstrumentation();

    String targetPackage = instrumentation.getTargetContext().getPackageName();
    Intent intent = getLaunchIntent(targetPackage, activityClass);

    activity = (T) instrumentation.startActivitySync(intent);
    instrumentation.waitForIdleSync();
  }
}