title: android setText crashes my app
body: <p>I've got problem with using <code>setText()</code> method on Android 16 (4.1) app. I'm trying to put programatically anything into <code>TextView tvopis</code> (here's just some test string, later I plan on putting there string from intent).
  When I open activity opis, the app crashes. If I comment <code>setText()</code> part, everything works fine.</p>
  
  <p>Here's java code</p>
  
  <pre><code>package com.example.pierwszyandroid;
  
  import android.app.Activity;
  import android.app.ActionBar;
  import android.app.Fragment;
  import android.os.Bundle;
  import android.view.LayoutInflater;
  import android.view.Menu;
  import android.view.MenuItem;
  import android.view.View;
  import android.view.ViewGroup;
  import android.widget.TextView;
  import android.os.Build;
  
  public class OpisActivity extends Activity {
  
      public TextView tvopis;
      String txt;
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_opis);
           tvopis = (TextView) findViewById(R.id.tvotest);
  
           tvopis.setText("txt test");
  
  
          if (savedInstanceState == null) {
              getFragmentManager().beginTransaction().add(R.id.container, new PlaceholderFragment()).commit();
          }
      }
  </code></pre>
  
  <p>Here's fragment_opis.xml for this activity:</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:paddingBottom="@dimen/activity_vertical_margin"
      android:paddingLeft="@dimen/activity_horizontal_margin"
      android:paddingRight="@dimen/activity_horizontal_margin"
      android:paddingTop="@dimen/activity_vertical_margin"
      tools:context="com.example.pierwszyandroid.OpisActivity$PlaceholderFragment" &gt;
  
      &lt;TextView
          android:id="@+id/tvotest"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_centerVertical="true"
          android:text="@string/hello_world" /&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>and this is activity_opis.xml</p>
  
  <pre><code>&lt;FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      android:id="@+id/container"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      tools:context="com.example.pierwszyandroid.OpisActivity"
      tools:ignore="MergeRootFrame" /&gt;
  </code></pre>
  
  <p>and here's logcat with error message:</p>
  
  <pre><code>04-18 10:44:59.665: I/Choreographer(723): Skipped 206 frames!  The application may be doing too much work on its main thread.
  04-18 10:46:34.016: I/Choreographer(723): Skipped 41 frames!  The application may be doing too much work on its main thread.
  04-18 10:46:34.135: D/AndroidRuntime(723): Shutting down VM
  04-18 10:46:34.135: W/dalvikvm(723): threadid=1: thread exiting with uncaught exception (group=0x2bc9a300)
  04-18 10:46:34.155: E/AndroidRuntime(723): FATAL EXCEPTION: main
  04-18 10:46:34.155: E/AndroidRuntime(723): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.pierwszyandroid/com.example.pierwszyandroid.OpisActivity}: java.lang.NullPointerException
  04-18 10:46:34.155: E/AndroidRuntime(723):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at android.app.ActivityThread.access$600(ActivityThread.java:130)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at android.os.Handler.dispatchMessage(Handler.java:99)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at android.os.Looper.loop(Looper.java:137)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at android.app.ActivityThread.main(ActivityThread.java:4745)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at java.lang.reflect.Method.invokeNative(Native Method)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at java.lang.reflect.Method.invoke(Method.java:511)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at dalvik.system.NativeStart.main(Native Method)
  04-18 10:46:34.155: E/AndroidRuntime(723): Caused by: java.lang.NullPointerException
  04-18 10:46:34.155: E/AndroidRuntime(723):  at com.example.pierwszyandroid.OpisActivity.onCreate(OpisActivity.java:25)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at android.app.Activity.performCreate(Activity.java:5008)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
  04-18 10:46:34.155: E/AndroidRuntime(723):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
  04-18 10:46:34.155: E/AndroidRuntime(723):  ... 11 more
  </code></pre>
  
  <p>Any help would be really appreciated, because I couldn't find any answer on already posted similar problems.</p>