title: Null object reference on setText in Android app
body: <p>My app crashes on this <code>setText</code> here. I think probably because it cannot find the id so I looked into to R.java  and found the id there. I'm confused why it still crashes.</p>
  
  <pre><code>TextView city = (TextView)findViewById(R.id.city_result);
  city.setText(msg[0]);
  </code></pre>
  
  <p>R.java</p>
  
  <pre><code>public static final int city_result=0x7f080041;
  </code></pre>
  
  <p>and this code is in the <code>public static final class id</code> method.</p>
  
  <p>Any help will be appreciated! Thanks!!</p>
  
  <p>================
  More Code:</p>
  
  <pre><code> protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_weather_report);
      if (savedInstanceState == null) {
          getSupportFragmentManager().beginTransaction()
                  .add(R.id.container, new PlaceholderFragment())
                  .commit();
      }
  
      //get message from intent
      Intent intent = getIntent();
      String[] message = intent.getStringArrayExtra(MainActivity.EXTRA_MESSAGE);
      setResult(message);
  }
  public void setResult(String[] msg)
      {
          //test
          TextView city = (TextView)findViewById(R.id.city_result);
          city.setText(msg[0]);
      }
  </code></pre>
  
  <p>This file I just started, elsewhere is just system generated new file code, I didn't edit yet.
  Here's logcat:</p>
  
  <pre><code>    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.chen.weather/com.example.chen.weather.WeatherReport}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
              at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
              at android.app.ActivityThread.access$800(ActivityThread.java:144)
              at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
              at android.os.Handler.dispatchMessage(Handler.java:102)
              at android.os.Looper.loop(Looper.java:135)
              at android.app.ActivityThread.main(ActivityThread.java:5221)
              at java.lang.reflect.Method.invoke(Native Method)
              at java.lang.reflect.Method.invoke(Method.java:372)
              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
       Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
              at com.example.chen.weather.WeatherReport.setResult(WeatherReport.java:78)
              at com.example.chen.weather.WeatherReport.onCreate(WeatherReport.java:32)
              at android.app.Activity.performCreate(Activity.java:5933)
              at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
              at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
                  at android.app.ActivityThread.access$800(ActivityThread.java:144)
                  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:135)
                  at android.app.ActivityThread.main(ActivityThread.java:5221)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at java.lang.reflect.Method.invoke(Method.java:372)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
  </code></pre>