Read android assets files throw NullPointerException

Question

I am working on android automation test, I create a test project in eclipse. (In automation, it will be packed as apk and deploy onto emulator) And In my project, I want to read a xml file in assets folder. I put my xml file "mytest.xml" directly in the folder assets . And I want to load it and parse. But it seems I will always get NullPointerException. Below is my code

1.the function is defined in a class OSNCommonLib.

public class OSNCommonLib extends Activity {
    public  String readTranslationFile(String fileName,String transunitId) 
    {
        if(doc == null)
            {
                try
                    {
                    InputStream in = getAssets().open(fileName);
                    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); 
                    DocumentBuilder builder = factory.newDocumentBuilder(); 
                    doc = builder.parse(in);

                    }

                    catch ( Exception e )
                    {
                        System.out.println("mytest catch" + e.toString() );
                        e.printStackTrace();
                    }
                }


                org.w3c.dom.Element root = doc.getDocumentElement();
                NodeList nodes = root.getElementsByTagName( "trans-unit" );
            .......
                }
                ....
    }  

And the function above will be called in another java class

public class TC01_OSNdemo extends ActivityInstrumentationTestCase2 {
OSNCommonLib ocl = new OSNCommonLib();
...
public void testSortByButton(){

    ....
        String getstr = ocl.readTranslationFile("mytest","osn_menu_sortby");
        Assert.assertTrue(solo.searchText(getstr));
    ...
}

And in the catch, I will always get java.lang.NullPointerException. Does it means it can't load my file? I tried many times and still the same errors.

Can anyone give some suggestions about this issue?

Besides: here is the full log

java.lang.NullPointerException
at com.stg.osn.lib.OSNCommonLib.readTranslationFile(OSNCommonLib.java:107) --> **point to org.w3c.dom.Element root = doc.getDocumentElement();**

at com.sgt.osn.junit.test.TC01_OSNdemo.testSortByButton(TC01_OSNdemo.java:142)
at java.lang.reflect.Method.invokeNative(Native Method)
at android.test.InstrumentationTestCase.runMethod(InstrumentationTestCase.java:214)
at android.test.InstrumentationTestCase.runTest(InstrumentationTestCase.java:199)
at android.test.ActivityInstrumentationTestCase2.runTest(ActivityInstrumentationTestCase2.java:192)
at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:190)
at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:175)
at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:555)
at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1661)

At last, the problem is sovled. As I extend my test case on Instruments, I should use the below method to call: InputStream in = getInstrumentation().getContext().getAssets().open("mytest.xml"); The useful link http://developer.android.com/reference/android/test/InstrumentationTestCase.html http://www.mail-archive.com/android-developers@googlegroups.com/msg62671.html

Thanks to all!!!

Answer 1

You can try this..

public String readDataFromAssets(String file) {
    try {
      InputStream is = getAssets().open(file);
      BufferedReader reader = new BufferedReader(new InputStreamReader(is));
      StringBuilder builder = new StringBuilder();

      String line = null;
      try {
        while ((line = reader.readLine()) != null) {
          builder.append(line);
          // builder.append("\n"); // append a new line
        }
      } catch (IOException e) {

        e.printStackTrace();
      } finally {
        try {
          is.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }

      return builder.toString();      

    } catch (IOException e) {

      e.printStackTrace();
    }
    return null;
  }

Answer 2

You should be able to access the file using the R -object. This would mean that you put your XML-file in the RAW-folder. Then you can access the file by simply writing

InputStream inputStream = activity.getResources().openRawResource(R.raw.mytest);