Android Junit4 tests UI thread

Question

I am writing unit tests for Android using the Junit4 syntax through the Android Testing Support Library ( here ). I want to check my custom view. The test involves clicking on the check box and verifying that the value elsewhere gets the update properly, but I get this error when I try to run the test:

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) 

I don't define any custom animations, and I really don't care about them for this test, but I assume that the Android 5.0 theme creates a checkbox animation.

I assume the exception is thrown because the test does not run in the user interface thread and the animator cannot animate. So how do I run a test on a UI thread?

Answer 1

Use 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 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, 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()); } } 

(from this sample project )