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Editorial Team
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Asked: 2026-05-24T17:02:08+00:00

I have the following setup: LibProjectWithActivity – an android library project which contains PreviewActivity

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I have the following setup:

  • LibProjectWithActivity – an android library project which contains PreviewActivity
  • AppProject – usual Android Project which uses LibProjectWithActivity
  • AppProjectTest – an Android JUnit Test Project which is an ActivityInstumentationTestCase2

First of all: all basic dependencies are set up correctly, because I can perfectly launch my app in emulator, it shows PreviewActivity just ok, things work – no problems here.

But I fail to launch the test… Here’s the setup:

public class PreviewActivityTest 
      extends ActivityInstrumentationTestCase2<PreviewActivity> {
    public PreviewActivityTest() {
        // note: if i put "com.the7art.libprojectwithactivity" instead it wont find it
        // and will fail with "activity not found"
        super("com.the7art.appproject", PreviewActivity.class);
    }

    public void testDummy() {
        getActivity();
    }
}

This throws a NullPointerException like this:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.the7art.appproject/com.the7art.libprojectwithactivity.PreviewActivity}: java.lang.NullPointerException
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2401)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417)
    .......
Caused by: java.lang.NullPointerException
    at com.the7art.libprojectwithactivity.PreviewActivity.onCreate(PreviewActivity.java:37)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364)
    ... 11 more

Here are lines PreviewActivity.java:36,37:

mButtonAdd = (Button) findViewById(R.id.button_add);
mButtonAdd.setOnClickListener(this);

So what this exception means is that R.id.button_add (which is in a libproject) is perfectly found, but the view by this id can’t be found. If I comment out this code, it’ll crash similarly when trying to obtain another resource.

Looks like test uses right R.java, but wrong Context object. Or something like this.

Again, the app code is ok, because it works in emulator, something is wrong with test setup…

Any hints on what is wrong and how to fix this?

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1 Answer

  1. Editorial Team

    Yes the test can be only use the Activity project as a target, look at the projectTarget in your Test manifest file.
    This means that your test can use the same context as your application does. Accessing only the application’s project resources. However, you can’t access Library’s project resources, you can use the R.string.XX from the library’s project because this was first built it, and it’s only a generated identifier that will be used in the application’s context to find the resource. So the result will be an mistake in the resource found or a resource not found exception.
    There are 2 ways to test a library project, here they are

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