IncompatibleClassChangeError: interface not implemented
<p>From android market i got the following crash report. which i haven't found while testing my app. The crash occur in PasswordActivity class. I am sending the stack trace and the code. Can anyone suggest me where the crash occur and why this occur.</p>

<p><strong>Stack Trace</strong></p>

<pre><code>java.lang.IncompatibleClassChangeError: interface not implemented
at in.plackal.lovecyclesfree.PasswordActivity.onCreate(PasswordActivity.java)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
at android.app.ActivityThread.access$2300(ActivityThread.java:125)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:4627)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:521)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:878)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636)
at dalvik.system.NativeStart.main(Native Method)
</code></pre>

<p><strong>My Code</strong></p>

<pre><code>public class PasswordActivity extends Activity implements Utilities
{
//Private Variables
private EditText m_passwrdEditText;

private TextView m_passwrdErrorText;

private Resources m_res;

@Override
public void onCreate(Bundle savedInstanceState) 
{
    //Setup the activity
    super.onCreate(savedInstanceState);
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);
    setRequestedOrientation (ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);     
    DisplayMetrics dm = new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(dm);


    if(dm.widthPixels == 320 &amp;&amp; dm.heightPixels == 480)
    {
        setContentView(R.layout.password_activity_hvga);
    }
    else
    {
        setContentView(R.layout.password_activity);
    }

    GoogleAnalyticsTracker tracker = GoogleAnalyticsTracker.getInstance();;
    tracker.startNewSession("UA-xxxxxxx-1", this);
    tracker.trackPageView("Password");
    tracker.dispatch();

    m_res = getResources();

    final Typeface face = Typeface.createFromAsset(getAssets(), "fonts/Cicle Semi.otf");     

    m_passwrdErrorText  = (TextView) findViewById(R.id.txt_error_message);
    m_passwrdErrorText.setTypeface(face);

    m_passwrdEditText  = (EditText) findViewById(R.id.txt_edit_passwrd);
    m_passwrdEditText.setOnClickListener(new OnClickListener() 
    {           
        @Override
        public void onClick(View v) 
        {
            m_passwrdEditText.setHint("");
            m_passwrdEditText.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);
            m_passwrdEditText.setTypeface(face);
        }
    });

    m_passwrdEditText.setTypeface(face);

    m_passwrdEditText.setOnKeyListener(new OnKeyListener() 
    {
        public boolean onKey(View v, int keyCode, KeyEvent event) 
        {           
            if ((event.getAction() == KeyEvent.ACTION_DOWN) &amp;&amp; (keyCode == KeyEvent.KEYCODE_ENTER))
            {                             
                String strPassEntered = m_passwrdEditText.getText().toString();
                String strPassSaved = CycleManager.getSingletonObject().getPassWord();
                m_passwrdEditText.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);
                if (strPassSaved.equals(strPassEntered) || strPassEntered.equals(DEFAULT_PASSWORD))
                {
                    Intent intent = new Intent(PasswordActivity.this, ActivityManager.class);
                    startActivity(intent);  
                    PasswordActivity.this.finish();
                }
                else
                {
                    m_passwrdErrorText.setText(m_res.getString(R.string.passwrd_error_text));
                    m_passwrdEditText.setFocusable(true);                                           
                }
            }

            else if(keyCode == KeyEvent.KEYCODE_DEL)
            {
                m_passwrdEditText.setHint(m_res.getString(R.string.passwrd_hint_text));
                m_passwrdErrorText.setText("");
            }

            m_passwrdEditText.setTypeface(face);
            return false;
        }
  });
}
}
</code></pre>
