I'm trying to get the filenames in a folder inside a listview(that listview is inside a layout of a ViewPager) but i'm getting a NullPointerException and i can't figure what's wrong.

 public void citire() {
    ListView lv1 = (ListView) findViewById(R.id.lv1);
    myList = new ArrayList<String>();

    File directory = Environment.getExternalStorageDirectory();
    file = new File(directory + "/InterSRL");
    File list[] = file.listFiles();

    for (int i = 0; i < list.length; i++) {
        myList.add(list[i].getName());
    }
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, android.R.id.text1, myList);
    lv1.setAdapter(adapter);
}

I'm getting the error at lv1.setAdapter(adapter);

 06-28 13:10:57.987: E/AndroidRuntime(30450): Caused by: java.lang.NullPointerException
 06-28 13:10:57.987: E/AndroidRuntime(30450):   at        com.example.testlayout.Gestionare.citire(Gestionare.java:169)
 06-28 13:10:57.987: E/AndroidRuntime(30450):   at com.example.testlayout.Gestionare.onCreate(Gestionare.java:33)
 06-28 13:10:57.987: E/AndroidRuntime(30450):   at android.app.Activity.performCreate(Activity.java:5104)
 06-28 13:10:57.987: E/AndroidRuntime(30450):   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
 06-28 13:10:57.987: E/AndroidRuntime(30450):   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)