title: NullPointerException in Android when trying to use Getter or Setter at EditText
body: <p>The following code throws a NullPointerException and I do not know why. The problem seems that I am not referencing the EditText objects correctly. But I don't know how to make it correct.</p>
  
  <p>Here the interesting part of my code:</p>
  
  <pre><code>private static ArrayList&lt;String&gt; roomList = new ArrayList&lt;String&gt;();
      private static ArrayList&lt;String&gt; deviceList = new ArrayList&lt;String&gt;();
  
      private static String project_name;
      private static String router_ip;
      private static String port;
      private static String device_name;
      private static String room_name;
      private static String datatype;
      private static String grpaddr;
      private static boolean status;
  
      private EditText et_project_name;
      private EditText et_router_ip;
      private EditText et_port;
  
      private Spinner spinner_dpt; 
      private CheckBox cb_checkStatus;
      private EditText et_device_name;
      private EditText et_groupaddress;
      private View textEntryView;
  
      private static final String[] items={"1.001 (Lichtschalter)", "5.001 (Dimmer/Jalousien)",
            "9.001 (Temperaturanzeige)", "1.008 (Jalousien)"};
  
      private SectionsPagerAdapter mSectionsPagerAdapter;
      private ViewPager mViewPager;
  
      private static ManualConfigDBAdapter dbHelper;
  
      /**
       * OnCreate
       * */ 
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_create_project_manually);
  
          setup();
      }
  
      /**
       * Setup
       * */ 
      public void setup(){
  
          //DATABASE
          // Add project to Database
          dbHelper = new ManualConfigDBAdapter(this);
          dbHelper.open();
  
          // Create the adapter that will return a fragment for each of the three primary sections
          // of the app.
          mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
  
          // Set up the action bar.
          final ActionBar actionBar = getActionBar();
          // set the app icon as an action to go home
          actionBar.setDisplayHomeAsUpEnabled(true); 
          //enable tabs in actionbar
          actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
  
          // Set up the ViewPager with the sections adapter.
          mViewPager = (ViewPager) findViewById(R.id.pager);
          mViewPager.setAdapter(mSectionsPagerAdapter);
  
          // When swiping between different sections, select the corresponding tab.
          // We can also use ActionBar.Tab#select() to do this if we have a reference to the
          // Tab.
          mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
              @Override
              public void onPageSelected(int position) {
                  actionBar.setSelectedNavigationItem(position);
              }
          });
  
          // For each of the sections in the app, add a tab to the action bar.
          for (int i = 0; i &lt; mSectionsPagerAdapter.getCount(); i++) {
              // Create a tab with text corresponding to the page title defined by the adapter.
              // Also specify this Activity object, which implements the TabListener interface, as the
              // listener for when this tab is selected.
              actionBar.addTab(
                      actionBar.newTab()
                              .setText(mSectionsPagerAdapter.getPageTitle(i))
                              .setTabListener(this));
          }
  
  
          //get the controls from the layout
          et_project_name = (EditText) mViewPager.findViewById(R.id.project_name);
          et_router_ip = (EditText) mViewPager.findViewById(R.id.router_ip);
          et_port = (EditText) mViewPager.findViewById(R.id.port);
  
          //Use a input filter for the input of the IP adress
          InputFilter[] filters = new InputFilter[1];
          filters[0] = new InputFilter() {
              public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
                  if (end &gt; start) {
                      String destTxt = dest.toString();
                      String resultingTxt = destTxt.substring(0, dstart) + source.subSequence(start, end) + destTxt.substring(dend);
                      if (!resultingTxt.matches ("^\\d{1,3}(\\.(\\d{1,3}(\\.(\\d{1,3}(\\.(\\d{1,3})?)?)?)?)?)?")) { 
                          return "";
                      } else {
                          String[] splits = resultingTxt.split("\\.");
                          for (int i=0; i&lt;splits.length; i++) {
                              if (Integer.valueOf(splits[i]) &gt; 255) {
                                  return "";
                              }
                          }
                      }
                  }
              return null;
              }
          };
  
          et_router_ip.setFilters(filters);
  
      }
  </code></pre>
  
  <p>And LogCat:</p>
  
  <pre><code>02-16 20:09:25.755: E/AndroidRuntime(26658): FATAL EXCEPTION: main
  02-16 20:09:25.755: E/AndroidRuntime(26658): java.lang.RuntimeException: Unable to start activity ComponentInfo{de.bertrandt.bertrandtknx/de.bertrandt.bertrandtknx.CreateProjectManually}: java.lang.NullPointerException
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1970)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1995)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at android.app.ActivityThread.access$600(ActivityThread.java:128)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1161)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at android.os.Handler.dispatchMessage(Handler.java:99)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at android.os.Looper.loop(Looper.java:137)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at android.app.ActivityThread.main(ActivityThread.java:4514)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at java.lang.reflect.Method.invokeNative(Native Method)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at java.lang.reflect.Method.invoke(Method.java:511)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at dalvik.system.NativeStart.main(Native Method)
  02-16 20:09:25.755: E/AndroidRuntime(26658): Caused by: java.lang.NullPointerException
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at de.bertrandt.bertrandtknx.CreateProjectManually.setup(CreateProjectManually.java:152)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at de.bertrandt.bertrandtknx.CreateProjectManually.onCreate(CreateProjectManually.java:75)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at android.app.Activity.performCreate(Activity.java:4562)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1053)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1934)
  02-16 20:09:25.755: E/AndroidRuntime(26658):    ... 11 more
  02-16 20:09:25.770: D/dalvikvm(26658): GC_CONCURRENT freed 396K, 4% free 14704K/15303K, paused 2ms+3ms
  </code></pre>
  
  <p>The used xml-file:</p>
  
  <pre><code>&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:background="@color/black" &gt;
  
  
  
  
      &lt;RelativeLayout
          android:id="@+id/project_save_text"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:layout_alignParentLeft="true"
          android:layout_alignParentTop="true"
          android:background="@color/black"
          android:orientation="vertical" &gt;
  
          &lt;TextView
              android:id="@+id/textView2"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_alignParentLeft="true"
              android:layout_alignParentTop="true"
              android:layout_marginTop="10dp"
              android:text="@string/project_name"
              android:textAppearance="?android:attr/textAppearanceMedium" /&gt;
  
          &lt;EditText
              android:id="@+id/project_name"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_alignParentLeft="true"
              android:layout_below="@+id/textView2"
              android:ems="10"
              android:hint="@string/project_name_hint" &gt;
          &lt;/EditText&gt;
  
          &lt;TextView
              android:id="@+id/textView4"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_alignParentLeft="true"
              android:layout_below="@+id/project_name"
              android:layout_marginTop="10dp"
              android:text="@string/router_ip"
              android:textAppearance="?android:attr/textAppearanceMedium" /&gt;
  
          &lt;EditText
              android:id="@+id/router_ip"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_alignParentLeft="true"
              android:layout_below="@+id/textView4"
              android:digits="0123456789."
              android:ems="10"
              android:hint="@string/router_adress_info"
              android:inputType="numberDecimal|phone" /&gt;
  
          &lt;ImageView
              android:id="@+id/imageView1"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_alignParentBottom="true"
              android:layout_alignParentLeft="true"
              android:contentDescription="@string/placeholder"
              android:src="@drawable/bertrandtlogoinv" /&gt;
  
          &lt;TextView
              android:id="@+id/info_text"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_above="@+id/imageView1"
              android:layout_alignParentLeft="true"
              android:gravity="center"
              android:text="@string/info_settings"
              android:textAppearance="?android:attr/textAppearanceSmall"
              android:textSize="16dp" /&gt;
  
          &lt;ImageView
              xmlns:android="http://schemas.android.com/apk/res/android"
              android:id="@+id/ImageView1"
              android:layout_width="fill_parent"
              android:layout_height="wrap_content"
              android:layout_above="@+id/info_text"
              android:layout_alignParentLeft="true"
              android:contentDescription="@string/placeholder"
              android:paddingBottom="2dp"
              android:paddingLeft="5dp"
              android:paddingRight="5dp"
              android:paddingTop="2dp"
              android:scaleType="fitXY"
              android:src="@color/ics_blue" /&gt;
  
          &lt;ImageView
              xmlns:android="http://schemas.android.com/apk/res/android"
              android:id="@+id/ImageView01"
              android:layout_width="fill_parent"
              android:layout_height="wrap_content"
              android:layout_alignParentLeft="true"
              android:layout_alignTop="@+id/imageView1"
              android:contentDescription="@string/placeholder"
              android:paddingBottom="2dp"
              android:paddingLeft="5dp"
              android:paddingRight="5dp"
              android:paddingTop="2dp"
              android:scaleType="fitXY"
              android:src="@color/ics_blue" /&gt;
  
  
          &lt;TextView
              android:id="@+id/textView3"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_alignParentLeft="true"
              android:layout_below="@+id/router_ip"
              android:layout_marginTop="10dp"
              android:text="@string/Port"
              android:textAppearance="?android:attr/textAppearanceMedium" /&gt;
  
          &lt;EditText
              android:id="@+id/port"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_alignParentLeft="true"
              android:layout_below="@+id/textView3"
              android:digits="0123456789"
              android:ems="10"
              android:hint="@string/port_hint"
              android:inputType="number"
              android:maxLength="5" /&gt;
  
      &lt;/RelativeLayout&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>The following line throws the error:</p>
  
  <pre><code>et_router_ip.setFilters(filters);
  </code></pre>
  
  <p><strong>SOLUTION</strong></p>
  
  <p>To create a 3 different fragments with view pager you should:</p>
  
  <p>1)Create FragmentActivity with view pager and view pager adapter.</p>
  
  <p>2)Create 3 Fragments with static instance </p>
  
  <pre><code>public final class Fragment1 extends Fragment
  {   
      public static Fragment1 newInstance() {
          return new Fragment1();
      }
  
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
      }
  
      @Override
      public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
          LinearLayout layout = new LinearLayout(getActivity());
  // your fragment xml view
          return view;
      }
  }
  </code></pre>
  
  <p>3)Fill view pager adapter with it;</p>
  
  <pre><code>public class FragmentAdapter extends FragmentPagerAdapter
  
  {    
      public InstallFragmentAdapter(FragmentManager fm) {
          super(fm);
      }
      @Override
      public Fragment getItem(int position) {     
          switch (position) {
              case 0:
                  return Fragment1.newInstance();
              case 1:
                  return Fragment2.newInstance();
              case 2:
                  return Fragment3.newInstance();
          }
          return null;
      }
  }
  </code></pre>