Zerstören ein Fragment, als ersetzt

Habe ich ein Fragment (fragment_address), die sich in einem Fragment-container in meine Haupttätigkeit. Meine fragment_address Fragment öffnet eine Liste der gekoppelten Geräte. Bei einem denkmalgeschützten Objekt geklickt wird, das Fragment ersetzt, das ist in meinen wichtigsten Aktivitäten, die von einem anderen fragment.
Dieses Fragment hat Tasten, um andere Fragmente.
Das alles funktioniert gut, bis ich auf eine Schaltfläche klicken, um ein neues Fragment und die fragment_address gezeigt wird, in den hintergrund, als auch mein neues fragment.
Als Adresse fragment ist nur je einmal ist es ein Weg, um sicherzustellen, dass dieses fragment zerstört als ersetzt ?

Meine Haupttätigkeit.

import android.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity implements AddressFragment.OnAddressListener {
    private static final String TAG = "Main Activity";
    //MAC-address of Bluetooth module (you must edit this line)
    private static String address = "No Device Selected";
    private static String deviceName = "No Device Selected";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public void onAddressChanged(String itemAddress, String itemName){
        //Set your address
        address = itemAddress;
        deviceName = itemName;
        MainFragment fragMain = new MainFragment();
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        fragMain.setVariables(address, deviceName);
        ft.replace(R.id.main_frag, fragMain);
        ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
        ft.commit();
    }
}

Xml.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <fragment
        class="com.ming.pondcontroller.AddressFragment"
        android:id="@+id/main_frag"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

Meine Adresse Fragment

import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.Intent;
import android.os.Bundle;
import android.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.Set;

public class AddressFragment extends Fragment {

    private static final String TAG = "Address Activity";
    private BluetoothAdapter BA = null;
    private Set<BluetoothDevice> pairedDevices;
    LayoutInflater inflater2;
    ListView lv;
    String address;
    String itemName;
    String itemString;
    OnAddressListener mListener;

    public AddressFragment() {
        //Required empty public constructor
    }

    //Container Activity must implement this interface
    public interface OnAddressListener {
        public void onAddressChanged(String address, String itemName);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        inflater2 = inflater;
        //Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_address, container, false);
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            mListener = (OnAddressListener ) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement OnAddressListener");
        }
    }

    @Override
    public void onStart(){
        super.onStart();
        lv = (ListView)getView().findViewById(R.id.listView);
        BA = BluetoothAdapter.getDefaultAdapter();
        checkBTState();

        //get paired devices
        pairedDevices = BA.getBondedDevices();
        ArrayList list = new ArrayList();
        //get a list of paired devices
        for(BluetoothDevice bt:pairedDevices){
            list.add(bt.getName()+"\n"+bt.getAddress());
        }
        //display the list in the list view
        final ArrayAdapter adapter = new ArrayAdapter(inflater2.getContext(),android.R.layout.simple_list_item_1,list);
        lv.setAdapter(adapter);

        //onItemClick Listener
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener(){
            @Override
            public void onItemClick(AdapterView<?> adapterView,View view, int position, long l){
                //get the text of the item clicked from position
                itemString = (String)(lv.getItemAtPosition(position));
                //get last 17 characters for MAC address
                address = itemString.substring(itemString.length()-17);
                itemName = itemString.substring(0,itemString.length()-17);
                //send strings back to main Activity
                mListener.onAddressChanged(address,itemName);
            }
        }); //end of onClickListener
    }

    private void checkBTState() {
        //Check for Bluetooth support and then check to make sure it is turned on
        //Emulator doesn't support Bluetooth and will return null
        if(BA==null) {
            Log.d("Fatal Error", "Bluetooth not support");
        } else {
            if (BA.isEnabled()) {
                Log.d(TAG, "...Bluetooth ON...");
            } else {
                //Prompt user to turn on Bluetooth
                Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
                startActivityForResult(enableBtIntent, 1);
            }
        }
    }
}

Meine Adresse Fragment xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorMainBack"
    tools:context="com.ming.pondcontroller.AddressFragment">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:id="@+id/textView"
        android:background="@color/colorPrimary"
        android:textColor="@color/colorWhite"
        android:textSize="20dp"
        android:text="Select Device"/>
    <ListView
        android:id="@+id/listView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/textView"
        android:background="@color/colorTextBack">
    </ListView> />
</RelativeLayout>

Und meine OnStart, dass der Austausch der MainFragment mit der ControlOutputs Fragment, wenn butControlOutputs genannt wird.

@Override
public void onStart() {
    super.onStart();
    TextView tv = (TextView)getView().findViewById(R.id.textIn);
    tv.setText(address);
    TextView tv2 = (TextView)getView().findViewById(R.id.textIn2);
    tv2.setText(deviceName);
    //Get ID's of buttons
    Button butSyncData = (Button)getActivity().findViewById(R.id.butSyncData);
    Button butControlOutputs = (Button)getActivity().findViewById(R.id.butControlOuts);
    Button butDateTime = (Button)getActivity().findViewById(R.id.butDateTime);
    Button butPreferences = (Button)getActivity().findViewById(R.id.butPreferences);
    Button butFullData = (Button)getActivity().findViewById(R.id.butFullData);
    //Create OnClick listener for each button
    butSyncData.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            Log.d(TAG,"Button Get Now data Clicked");
            if(ConStatus == true){
                mConnectedThread.write(MainFragment.getNowData); //Sync Data to start
            }else if(!(address == "No Device Selected")) {
                btAdapter = BluetoothAdapter.getDefaultAdapter();       //get Bluetooth adapter
                BluetoothDevice device = btAdapter.getRemoteDevice(address);

                ConnectThread ct = new ConnectThread(device);
                ct.start();
            }
        }
    });

    butControlOutputs.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            Log.d(TAG,"Control Outputs Clicked");
            //TODO rest of Control Outputs Launch
            OutputsFragment fragOutputs = new OutputsFragment();
            FragmentTransaction ft = getFragmentManager().beginTransaction();
            ft.replace(R.id.main_frag,fragOutputs);
            ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
            ft.commit();
        }
    });

    butDateTime.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            Log.d(TAG,"Date & Time Clicked");
            Toast.makeText(getActivity(),"Date & Time Clicked",Toast.LENGTH_SHORT).show();
            //TODO rest of Date Time Launch
        }
    });

    butPreferences.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            Log.d(TAG,"Preferences Clicked");
            Toast.makeText(getActivity(),"Preferences Clicked",Toast.LENGTH_SHORT).show();
            //TODO rest of Control Outputs Launch
        }
    });

    butFullData.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            Log.d(TAG,"Full Data Clicked");
            Toast.makeText(getActivity(),"Full Data Clicked",Toast.LENGTH_SHORT).show();
            //TODO rest of Control Outputs Launch
        }
    });

    //Start thread to connect to bluetooth
    if(!(address == "No Device Selected")) {
        btAdapter = BluetoothAdapter.getDefaultAdapter();       //get Bluetooth adapter
        BluetoothDevice device = btAdapter.getRemoteDevice(address);

        ConnectThread ct = new ConnectThread(device);
        ct.start();
    }
} //End of on start

Habe ich das addToBackStack und entfernt es wieder. Ich dachte, die ft.ersetzen Sie zerstören würde, die vorherigen Fragment, wenn der Vorherige war nicht mehr auf die zurück-stack ??

Ich habe dies nur Hinzugefügt, um die OnClickListener. Er fügt hinzu, die MainFragment aber immer liefert 'null' für die AddressFragment.

Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.main_frag);
        if(fragment != null) {
            Log.d("In OAC","Fragment Not NULL");
            getSupportFragmentManager().beginTransaction().remove(fragment).commit();
        }else{
            Log.d("In OAC","Fragment NULL");
        }
        MainFragment fragMain = new MainFragment();
        FragmentTransaction ft = getFragmentManager().beginTransaction();
        fragMain.setVariables(address, deviceName);
        ft.add(R.id.main_frag, fragMain);
        ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
        ft.commit();