android - 使用 ActivityUnitTestCase 测试对 Android ListView 的点击

Question

我实现了一个 ListView，它在单击列表项时启动一个新的 Activity。当我手动测试它时，它工作得很好。但是，当我尝试使用 ActivityUnitTestCase 进行自动化测试时，我得到了一个 NullPointerException，就好像 ListView 是空的一样。

MainActivity(部分):

public class MainActivity extends ListActivity {

  @Override
  protected void onResume() {
    super.onResume();

    String[] items = new String[] {"item 1", "item 2"};
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, items);
    setListAdapter(adapter);

    getListView().setOnItemClickListener(new OnItemClickListener () {

      @Override
      public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        TextView clickedItem = (TextView) view;
        CharSequence clickedItemText = clickedItem.getText(); // throws a NullPointerException when running testWithPerformItemClick()!
        Intent intent = new Intent(MainActivity.this, ItemDisplayActivity.class);
        intent.putExtra("parameter", clickedItemText);
        startActivity(intent);
      }
    });
  }
}

失败的测试代码:

public class MainActivityTest extends ActivityUnitTestCase<MainActivity> {

  ListView listView;
  View child0;

  public MainActivityTest() {
    super(MainActivity.class);
  }

  private void setUpTest() {
    MainActivity activity = startActivity(new Intent(), null, null);
    getInstrumentation().callActivityOnStart(activity);
    getInstrumentation().callActivityOnResume(activity);
    listView = (ListView) activity.findViewById(android.R.id.list);
    child0 = listView.getChildAt(0); // returns null!
  }

  public void testWithPerformClick() {
    setUpTest();

    child0.performClick(); // throws a NullPointerException!

    Intent startedIntent = getStartedActivityIntent();
    assertEquals("item 1", startedIntent.getStringExtra("parameter"));
  }

  public void testWithPerformItemClick() {
    setUpTest();
    long itemId = listView.getAdapter().getItemId(0);

    listView.performItemClick(child0, 0, itemId); // throws a NullPointerException!

    Intent startedIntent = getStartedActivityIntent();
    assertEquals("item 1", startedIntent.getStringExtra("parameter"));
  }

两种测试方法均失败，因为 listView.getChildAt(0) 返回 null。为什么 ListView 是空的？我怎样才能强制它用正确的 child 更新自己？

Answer 1

根据documentation ，如果您更喜欢功能测试，您应该使用 ActivityInstrumentationTestCase2。要执行单击，效果会更好。 @fewe 的回答是正确的，你必须等待列表被绘制，等待 fragment 被加载你可以使用 getInstrumentation().waitForIdleSync();

尝试这样的事情。

public class ActivityTests extends
    ActivityInstrumentationTestCase2<Activity>

final ListView list = (ListView) mActivity.findViewById(R.id.listId);
         assertNotNull("The list was not loaded", list);
         getInstrumentation().runOnMainSync(new Runnable() {
             @Override
             public void run() {

                 list.performItemClick(list.getAdapter().getView(position, null, null),
                         position, list.getAdapter().getItemId(position));
             }

         });

 getInstrumentation().waitForIdleSync();

那么你就不能测试，例如，如果一个 fragment 被加载了。

  mFragment frag = mActivity.getFragment();
  assertNotNull("Fragment was not loaded", frag);