在UI线程上测试Android Junit4

我正在使用Junit4语法,通过 android测试支持库( here)为Android编写单元测试.我想测试我的自定义视图.测试包括单击复选框并确保其他位置的值得到正确更新,但是当我尝试运行测试时出现此错误：

android.util.AndroidRuntimeException: Animators may only be run on Looper threads
at android.animation.ValueAnimator.start(ValueAnimator.java:1002)
at android.animation.ValueAnimator.start(ValueAnimator.java:1050)
at android.animation.ObjectAnimator.start(ObjectAnimator.java:829)
at android.graphics.drawable.AnimatedStateListDrawable$AnimationDrawableTransition.start(AnimatedStateListDrawable.java:294)
at android.graphics.drawable.AnimatedStateListDrawable.selectTransition(AnimatedStateListDrawable.java:226)
at android.graphics.drawable.AnimatedStateListDrawable.onStateChange(AnimatedStateListDrawable.java:145)
at android.graphics.drawable.Drawable.setState(Drawable.java:599)
at android.widget.CompoundButton.drawableStateChanged(CompoundButton.java:438)
at android.view.View.refreshDrawableState(View.java:16032)
at android.widget.CompoundButton.setChecked(CompoundButton.java:143)
at android.widget.CompoundButton.toggle(CompoundButton.java:113)

我没有定义任何自定义动画,我并不真正关心它们进行此测试,但我认为它是Android 5.0材质主题,可以创建一个复选框动画.

我假设抛出异常是因为测试不在UI线程上运行而且动画师无法动画.那么如何在UI线程上运行测试呢？

解决方法

使用InstrumentationRegistry.getInstrumentation().runOnMainSync()：

/***
    copyright (c) 2008-2015 CommonsWare,LLC
    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.

    From _The Busy Coder's Guide to Android Development_
        http://commonsware.com/Android
 */

package com.commonsware.android.abf.test;

import android.support.test.InstrumentationRegistry;
import android.support.test.runner.AndroidJUnit4;
import android.test.AndroidTestCase;
import android.test.UiThreadTest;
import android.view.LayoutInflater;
import android.view.View;
import com.commonsware.android.abf.R;
import junit.framework.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;

@RunWith(AndroidJUnit4.class)
public class DemoContextTest {
  private View field=null;
  private View root=null;

  @Before
  public void init() {
    InstrumentationRegistry.getInstrumentation().runOnMainSync(new Runnable() {
      @Override
      public void run() {
        LayoutInflater inflater=LayoutInflater
            .from(InstrumentationRegistry.getTargetContext());

        root=inflater.inflate(R.layout.add,null);
      }
    });

    root.measure(800,480);
    root.layout(0,800,480);

    field=root.findViewById(R.id.title);
  }

  @Test
  public void exists() {
    init();
    Assert.assertNotNull(field);
  }

  @Test
  public void position() {
    init();
    Assert.assertEquals(0,field.getTop());
    Assert.assertEquals(0,field.getLeft());
  }
}

(自this sample project起)