更新到Android 2.2.3后，我得到了一些无法解决方法错误

 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    pref = this.getSharedPreferences(
            getString(R.string.user), Context.MODE_PRIVATE);
    String username = pref.getString(getString(R.string.user), null);
    if (username.length() == 0) {
        Intent intent = new Intent(this, Login.class);
        startActivity(intent);
    }
    setContentView(R.layout.activity_main);
    Toolbar myToolbar = (Toolbar) findViewById(R.id.my_toolbar);
    setSupportActionBar(myToolbar);
    ActionBar ab = getSupportActionBar();
    ab.setDisplayHomeAsUpEnabled(true);
 protected void onCreate(Bundle savedInstanceSt