ClassCastException（片段不能轉換爲android.app.Activity）

Question

Unable to instantiate activity Component, ClassCastExceptio我是新來的android，所以我跟着不同的教程來完成我的任務。我有一個錯誤，儘管所有的努力仍然無法解決。我有一個主要活動，我稱之爲積極主動（如果用戶在提醒時選擇「是」）。積極的活動基本上包含三個項目的列表視圖，我想顯示用戶點擊第一個項目時的移動聯繫人。 我把聯繫人的代碼檢索到的片段類，但它給出了即使在我沒有使用簡單的意圖調用片段的鑄造錯誤。 爲主要活動的代碼如下：

public class activity_home extends ActionBarActivity { 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_home); 
    Context context = this; 
    new AlertDialog.Builder(context) 
      .setTitle("Alert") 
      .setMessage("Do you want to enable the app right now?") 
      .setPositiveButton("Yes", new DialogInterface.OnClickListener() 
{ 
       public void onClick(DialogInterface dialog,int id) { 
        // go to a new activity of the app 

        Intent positiveActivity = new 
Intent(getApplicationContext(), 

          PositiveActivity.class); 

        startActivity(positiveActivity); 

       } 

      }) 

    .setNegativeButton("No", new DialogInterface.OnClickListener() { 
     public void onClick(DialogInterface dialog, int which) { 
      // do nothing 
     } 
    }) 


      .setNeutralButton("Remind Me later", new 
DialogInterface.OnClickListener() { 
         public void onClick(DialogInterface dialog, int 
which) { 
          // do nothing 
         } 
        } 

      ) 


      . 

        setIcon(android.R.drawable.ic_dialog_alert) 


      .show(); 
}} 
PositiveActivity.java: 
public class PositiveActivity extends FragmentActivity { 
ListView listView; 
ArrayList<String> listname; 
ArrayList<String> list_no; 
Context context; 
LayoutInflater inflater; 


@Override 
protected void onCreate(Bundle savedInstanceState) { 





    super.onCreate(savedInstanceState); 
    setContentView(R.layout.positive_view); 
    Context context = this; 
    listView = (ListView) findViewById(R.id.mobile_list); 
    TextView textView = new TextView(context); 
    textView.setTypeface(null, Typeface.BOLD); 
    textView.setHeight(100); 
    textView.setText("Define Specifications for Enabling Auto Pickup!"); 

    listView.addHeaderView(textView); 


    // Array of strings... 
    String[] mobileArray = new String[] {"Add Numbers to the list","Select 
Timer","Pick Selection Mode"}; 


    final ArrayAdapter <String> adapter = new ArrayAdapter<String>(this, 
      android.R.layout.simple_list_item_1, android.R.id.text1, 
mobileArray); 


    listView.setAdapter(adapter); 

    // ListView Item Click Listener 
    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 

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

      // ListView Clicked item index 
      int itemPosition = position; 

      // ListView Clicked item value 
      String itemValue = (String) 
listView.getItemAtPosition(position); 
      if (itemPosition == 1) { 


       ContactListFragment fragmentS1 = new ContactListFragment(); 

getSupportFragmentManager().beginTransaction().replace 
(R.id.headlines_fragment, 
fragmentS1).commit(); 


      }}});}} 

And the code of Fragment: 

import android.support.v4.widget.SimpleCursorAdapter; 

public class ContactListFragment extends ListFragment implements 
LoaderCallbacks<Cursor> { 

private CursorAdapter mAdapter; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    // create adapter once 
    Context context = getActivity(); 
    int layout = android.R.layout.simple_list_item_1; 
    Cursor c = null; // there is no cursor yet 
    int flags = 0; // no auto-requery! Loader requeries. 
    mAdapter = new SimpleCursorAdapter(context, layout, c, FROM, TO, flags); 
} 

@Override 
public void onActivityCreated(Bundle savedInstanceState) { 
    super.onActivityCreated(savedInstanceState); 

    // each time we are started use our listadapter 
    setListAdapter(mAdapter); 
    // and tell loader manager to start loading 
    getLoaderManager().initLoader(0, null, this); 
} 

// columns requested from the database 
private static final String[] PROJECTION = { 
     Contacts._ID, // _ID is always required 
     Contacts.DISPLAY_NAME_PRIMARY // that's what we want to display 
}; 

// and name should be displayed in the text1 textview in item layout 
private static final String[] FROM = { Contacts.DISPLAY_NAME_PRIMARY }; 
private static final int[] TO = { android.R.id.text1 }; 

@Override 
public Loader<Cursor> onCreateLoader(int id, Bundle args) { 

    // load from the "Contacts table" 
    Uri contentUri = Contacts.CONTENT_URI; 

    // no sub-selection, no sort order, simply every row 
    // projection says we want just the _id and the name column 
    return new CursorLoader(getActivity(), 
      contentUri, 
      PROJECTION, 
      null, 
      null, 
      null); 
} 

@Override 
public void onLoadFinished(Loader<Cursor> loader, Cursor data) { 
    // Once cursor is loaded, give it to adapter 
    mAdapter.swapCursor(data); 
} 

@Override 
public void onLoaderReset(Loader<Cursor> loader) { 
    // on reset take any old cursor away 
    mAdapter.swapCursor(null); 
} 
} 

如果有人指出，在代碼中的錯誤，我會感激

Answer 1

嘗試使用補充，而不是替代

getSupportFragmentManager().beginTransaction().add 
(R.id.headlines_fragment, fragmentS1).commit();