我有一个活动，从内拉从应用程序扩展类（应用程序上下文）的对象的OnCreate（）方法。

I have an Activity that pulls an object from an Application extended class (application context) from within the OnCreate() method.

在单元测试这个活动，所需要的对象是不存在的，因为它是从previous活动人口，并存储在上述应用程序上下文。

When unit testing this activity, the object needed isn't there because it is populated from a previous Activity and stored in the above mentioned application context.

不用说，当我打电话 getActivity（）从我的 ActivityInstrumentationTestCase2 扩展的测试情况下，我得到一个空指针异常。

Needless to say, when I call getActivity() from within my ActivityInstrumentationTestCase2 extended test case I get a null pointer exception.

我如何填充一个活动开始前的背景和有它可用于该活动？

How can I populate the context before an activity is started and have it available to that Activity?

更新： 经过一番挖掘我的发现： this.getInstrumentation（）getTargetContext（），然后将其转换为我的应用程序类型扩展的类。但我得到一个类转换异常和跟踪点，以这样的：

Updated: After a bit of digging I found: this.getInstrumentation().getTargetContext() and then cast it to the type of my Application extended class. But I get a class cast exception and the trace points to this:

04-04 21:02:27.036: INFO/TestRunner(431): started: testIt(edu.rockies.rockies.activity.courses.test.TopicTest)
04-04 21:02:27.126: INFO/TestRunner(431): failed: testIt(edu.rockies.rockies.activity.courses.test.TopicTest)
04-04 21:02:27.126: INFO/TestRunner(431): ----- begin exception -----
04-04 21:02:27.136: INFO/TestRunner(431): java.lang.ClassCastException: android.app.ApplicationContext
04-04 21:02:27.136: INFO/TestRunner(431):     at edu.rockies.rockies.activity.courses.test.TopicTest.setUp(TopicTest.java:27)
04-04 21:02:27.136: INFO/TestRunner(431):     at junit.framework.TestCase.runBare(TestCase.java:125)
04-04 21:02:27.136: INFO/TestRunner(431):     at junit.framework.TestResult$1.protect(TestResult.java:106)
04-04 21:02:27.136: INFO/TestRunner(431):     at junit.framework.TestResult.runProtected(TestResult.java:124)
04-04 21:02:27.136: INFO/TestRunner(431):     at junit.framework.TestResult.run(TestResult.java:109)
04-04 21:02:27.136: INFO/TestRunner(431):     at junit.framework.TestCase.run(TestCase.java:118)
04-04 21:02:27.136: INFO/TestRunner(431):     at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:169)
04-04 21:02:27.136: INFO/TestRunner(431):     at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:154)
04-04 21:02:27.136: INFO/TestRunner(431):     at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:430)
04-04 21:02:27.136: INFO/TestRunner(431):     at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1447)
04-04 21:02:27.136: INFO/TestRunner(431): ----- end exception -----
04-04 21:02:27.156: INFO/TestRunner(431): finished: testIt(edu.rockies.rockies.activity.courses.test.TopicTest)

this.getInstrumentation（）。getTargetContext（）应该返回类型的上下文对象。但我得到的 android.app.ApplicationContext 类转换exeption这没有任何意义。

this.getInstrumentation().getTargetContext() is supposed to return an object of type context. But I get the android.app.ApplicationContext class cast exeption which doesn't make sense.

更新2：

我做了一些调查研究，发现本作android.app.Application

I did some more research and discovered this for android.app.Application

java.lang.Object
    android.content.Context
        android.app.ApplicationContext
            android.app.Application

不过，谷歌的自己的Andr​​oid的Javadoc指这个：

java.lang.Object
    android.content.Context
        android.content.ContextWrapper
            android.app.Application

这是怎么回事？不对了。

What's going on? Something's not right.

更新3：

我已经更换了code以下行：

I have replaced the following line of code:

this.getInstrumentation().getTargetContext();

这一行的code。

with this line of code.

this.getInstrumentation().getTargetContext().getApplicationContext();

虽然背景下解决得当，它似乎并不相同上下文中的活动的。

Although the context resolves properly, it doesn't seem to be the same context as the activity's.

推荐答案

好吧，这个问题解决了。要访问之前getActivity（）被调用，你需要调用这个函数的上下文：

Ok, this issue is resolved. To get access to the context before getActivity() has been called you need to call this function:

Context context = this.getInstrumentation().getTargetContext().getApplicationContext();