title: facebook android sdk 3.0 login another activity crash
body: <p>I use android sdk 3.0 login code Session in the MainActivity can run ..</p>
  
  <p>but I move to new Activtiy FB.JAVA.can't run .click button crash..</p>
  
  <p>plase how to fix:</p>
  
  <p><strong>MAinActivity.JAVA code</strong></p>
  
  <pre><code>public void fbautotest(View v){
  
  fb myffb=new fb();
  myffb.facebookLogin();}
  </code></pre>
  
  <p><strong>FB.JAVA code</strong></p>
  
  <pre><code>public class fb extends Activity{
  
  private static final List&lt;String&gt; PERMISSIONS = Arrays.asList("publish_actions","user_photos");
  private PendingAction pendingAction = PendingAction.NONE;
  private enum PendingAction {
      NONE, POST_PHOTO, POST_STATUS_UPDATE
  }
  
  private StatusCallback callback;
  //private Activity mContext;
  private Activity mContext;
  
  
  public void facebookLogin()
  {
  
  
      Session.openActiveSession(mContext, true, new Session.StatusCallback() {
  
          // callback when session changes state
  
          @Override
          public void call(Session session, SessionState state, Exception exception) {
  
              if (session.isOpened()) {
                  Request.executeMeRequestAsync(session, new Request.GraphUserCallback() {
  
                        // callback after Graph API response with user object
  
  
                      @Override
                      public void onCompleted(GraphUser user,
                              Response response) {
  
  
  
                      }
                      });
  
              }
          }
        });
  
  }
    }
  </code></pre>
  
  <p><strong>Error Code</strong></p>
  
  <pre><code>04-05 06:50:16.246: W/dalvikvm(904): threadid=1: thread exiting with uncaught exception (group=0x40a13300)
  04-05 06:50:16.326: E/AndroidRuntime(904): FATAL EXCEPTION: main
  04-05 06:50:16.326: E/AndroidRuntime(904): java.lang.IllegalStateException: Could not execute method of the activity
  04-05 06:50:16.326: E/AndroidRuntime(904):  at android.view.View$1.onClick(View.java:3591)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at android.view.View.performClick(View.java:4084)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at android.view.View$PerformClick.run(View.java:16966)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at android.os.Handler.handleCallback(Handler.java:615)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at android.os.Handler.dispatchMessage(Handler.java:92)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at android.os.Looper.loop(Looper.java:137)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at android.app.ActivityThread.main(ActivityThread.java:4745)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at java.lang.reflect.Method.invokeNative(Native Method)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at java.lang.reflect.Method.invoke(Method.java:511)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at dalvik.system.NativeStart.main(Native Method)
  04-05 06:50:16.326: E/AndroidRuntime(904): Caused by: java.lang.reflect.InvocationTargetException
  04-05 06:50:16.326: E/AndroidRuntime(904):  at java.lang.reflect.Method.invokeNative(Native Method)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at java.lang.reflect.Method.invoke(Method.java:511)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at android.view.View$1.onClick(View.java:3586)
  04-05 06:50:16.326: E/AndroidRuntime(904):  ... 11 more
  04-05 06:50:16.326: E/AndroidRuntime(904): Caused by: java.lang.NullPointerException: Argument 'applicationId' cannot be null
  04-05 06:50:16.326: E/AndroidRuntime(904):  at com.facebook.internal.Validate.notNull(Validate.java:29)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at com.facebook.Session.&lt;init&gt;(Session.java:224)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at com.facebook.Session.&lt;init&gt;(Session.java:213)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at com.facebook.Session$Builder.build(Session.java:1454)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at com.facebook.Session.openActiveSession(Session.java:863)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at com.facebook.Session.openActiveSession(Session.java:805)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at com.example.mk2weibo.fb.facebookLogin(fb.java:45)
  04-05 06:50:16.326: E/AndroidRuntime(904):  at com.example.mk2weibo.MainActivity.fbautotest(MainActivity.java:410)
  04-05 06:50:16.326: E/AndroidRuntime(904):  ... 14 more
  </code></pre>