Fragment kann nicht umgewandelt werden, ein android.app.Aktivität

Erstellte ich eine sehr fragment zum testen meiner app und ich bekam die folgende Fehlermeldung:

03-28 11:11:58.079: E/AndroidRuntime(11760):
java.lang.RuntimeException: Unable to instantiate activity
ComponentInfo{com.android.demoresponsevision/com.android.demoresponsevision.fragment.BarcodeScreen}:
java.lang.Classcastexception-Fehler:
com.android.demoresponsevision.fragment.BarcodeScreen nicht gegossen werden
zu android.app.Aktivität

Fragment-Code:-

public class BarcodeScreen extends Fragment {
    TextView tvStatus;
    TextView tvResult;

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {

        super.onActivityCreated(savedInstanceState);

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.barcode, container, false);
        tvStatus = (TextView) view.findViewById(R.id.tvStatus);
        tvResult = (TextView) view.findViewById(R.id.tvResult);

        Button scanBtn = (Button) view.findViewById(R.id.btnScan);
        //in some trigger function e.g. button press within your code you
        //should add:
        scanBtn.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {

                try {
                    Utilites.showToast(getActivity(), "Try");
                    Intent intent = new Intent(
                            "com.google.zxing.client.android.SCAN");
                    intent.putExtra("SCAN_MODE", "QR_CODE_MODE,PRODUCT_MODE");
                    startActivityForResult(intent, 0);

                } catch (Exception e) {
                    e.printStackTrace();
                    Toast.makeText(getActivity(), "ERROR:" + e, 1).show();

                }
            }
        });
        return view;

    }

    //In the same activity you’ll need the following to retrieve the results:
    public void onActivityResult(int requestCode, int resultCode, Intent intent) {
        Toast.makeText(getActivity(), "result ", 1000).show();
        if (requestCode == 0) {

            if (resultCode == getActivity().RESULT_OK) {
                tvStatus.setText(intent.getStringExtra("SCAN_RESULT_FORMAT"));
                tvResult.setText(intent.getStringExtra("SCAN_RESULT"));
            }

            else if (resultCode == getActivity().RESULT_CANCELED) {
                tvStatus.setText("Press a button to start a scan.");
                tvResult.setText("Scan cancelled.");
            }
        }
    }

}

Dies ist mein Fragment-Aktivität

public class TabActivity extends FragmentActivity implements
        OnTabChangeListener {
    TextView txt;
    private TabHost mTabHost;
    private HashMap mapTabInfo = new HashMap();
    private TabInfo mLastTab = null;

    private class TabInfo {
        private String tag;
        private Class clss;
        private Bundle args;
        private Fragment fragment;

        TabInfo(String tag, Class clazz, Bundle args) {
            this.tag = tag;
            this.clss = clazz;
            this.args = args;
        }
    }

    class TabFactory implements TabContentFactory {
        private final Context mContext;

        /** * @param context */
        public TabFactory(Context context) {
            mContext = context;
        }

        public View createTabContent(String tag) {
            View v = new View(mContext);
            v.setMinimumWidth(0);
            v.setMinimumHeight(0);
            return v;
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.tabs);
        //Step 2: Setup TabHost

        initialiseTabHost(savedInstanceState);
        if (savedInstanceState != null) {
            mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab"));
        }
    }

    protected void onSaveInstanceState(Bundle outState) {
        outState.putString("tab", mTabHost.getCurrentTabTag()); //save the tab
                                                                //selected
        super.onSaveInstanceState(outState);
    }

    /**
     * Step 2: Setup TabHost
     */
    private void initialiseTabHost(Bundle args) {
        mTabHost = (TabHost) findViewById(android.R.id.tabhost);
        mTabHost.setup();
        TabInfo tabInfo = null;
        TabActivity.addTab(this, this.mTabHost, this.mTabHost
                .newTabSpec("Tab1").setIndicator("HomeScreen"),
                (tabInfo = new TabInfo("Tab1", HomeScreen.class, args)));
        this.mapTabInfo.put(tabInfo.tag, tabInfo);

        TabActivity.addTab(this, this.mTabHost, this.mTabHost
                .newTabSpec("Tab2").setIndicator("SecondScreen"),
                (tabInfo = new TabInfo("Tab2", SecondHomeScreen.class, args)));
        this.mapTabInfo.put(tabInfo.tag, tabInfo);

        //Default to first tab
        this.onTabChanged("Tab1");
        //
        mTabHost.setOnTabChangedListener((OnTabChangeListener) this);
    }

    private static void addTab(TabActivity activity, TabHost tabHost,
            TabHost.TabSpec tabSpec, TabInfo tabInfo) { //Attach a Tab view
                                                        //factory to the spec
        tabSpec.setContent(activity.new TabFactory(activity));
        String tag = tabSpec.getTag();
        //Check to see if we already have a fragment for this tab, probably
        //from a previously saved state. If so, deactivate it, because our
        //initial state is that a tab isn't shown.

        tabInfo.fragment = activity.getSupportFragmentManager()
                .findFragmentByTag(tag);
        if (tabInfo.fragment != null && !tabInfo.fragment.isDetached()) {
            FragmentTransaction ft = activity.getSupportFragmentManager()
                    .beginTransaction();
            ft.detach(tabInfo.fragment);
            ft.commit();
            activity.getSupportFragmentManager().executePendingTransactions();
        }
        tabHost.addTab(tabSpec);
    }

    /**
     * (non-Javadoc) * @see
     * android.widget.TabHost.OnTabChangeListener#onTabChanged(java.lang.String)
     */
    public void onTabChanged(String tag) {
        TabInfo newTab = (TabInfo) this.mapTabInfo.get(tag);
        if (mLastTab != newTab) {
            FragmentTransaction ft = this.getSupportFragmentManager()
                    .beginTransaction();
            if (mLastTab != null) {
                if (mLastTab.fragment != null) {
                    ft.detach(mLastTab.fragment);
                }
            }
            if (newTab != null) {
                if (newTab.fragment == null) {
                    newTab.fragment = Fragment.instantiate(this,
                            newTab.clss.getName(), newTab.args);
                    ft.add(R.id.realtabcontent, newTab.fragment, newTab.tag);
                } else {
                    ft.attach(newTab.fragment);

                }
            }
            mLastTab = newTab;
            ft.commit();
            this.getSupportFragmentManager().executePendingTransactions();

        }
    }

}

HomeScreen :-

public class HomeScreen extends Fragment implements OnItemClickListener {
    ListView list;

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {

        super.onActivityCreated(savedInstanceState);

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.home, container, false);

        list = (ListView) view.findViewById(R.id.list);
        String[] values = new String[] { "Barcode scanner", "Photos ", "Map",
                "Signature" };

        ArrayAdapter<String> files = new ArrayAdapter<String>(getActivity(),
                android.R.layout.simple_list_item_1, values);

        list.setAdapter(files);
        list.setOnItemClickListener(this);
        return view;

    }

    @Override
    public void onItemClick(AdapterView<?> parent, View v, int position, long id) {

        if (position == 0) {
            Utilites.showToast(getActivity(), "Barcode");
            Intent i_barcode = new Intent(getActivity(), BarcodeScreen.class);
            startActivity(i_barcode);
        }

        if (position == 1) {
            Utilites.showToast(getActivity(), "Photos");
            Intent i_photo = new Intent(getActivity(), PhotoScreen.class);
            startActivity(i_photo);
        }
        if (position == 2) {
            Utilites.showToast(getActivity(), "Map");
            Intent i_map = new Intent(getActivity(), MapScreen.class);
            startActivity(i_map);
        }
        if (position == 3) {
            Utilites.showToast(getActivity(), "Signature");
            Intent i_signature = new Intent(getActivity(), BarcodeScreen.class);
            startActivity(i_signature);
        }

    }

}