单击返回按钮后如何从片段返回主布局

Question

I am trying to create an app. I want to go back to my main layout from a fragment when click on back button in the fragment Using the following code-

 public class MainActivity extends FragmentActivity implements OnMapReadyCallback, ConnectionCallbacks, OnConnectionFailedListener,LocationListener{
 DrawerLayout mDrawerLayout;
 ListView mDrawerList;
 @SuppressWarnings("deprecation")
ActionBarDrawerToggle mDrawerToggle;
 String mTitle="";
 private final String  TAG = this.getClass().getSimpleName();

    LocationRequest mLocationRequest;
    GoogleApiClient mGoogleApiClient;

    LatLng latLng;
    GoogleMap mMap;
    SupportMapFragment mFragment;
    Marker CurrentMarker,NearbyPlace,FindMarker;
    EditText editplace = null;
    Button findbtn = null;
    boolean firstRun = true;
    private Boolean exit = false;


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

    //for connectivity service
    ConnectivityManager cManager = (ConnectivityManager) getSystemService(this.CONNECTIVITY_SERVICE);
    NetworkInfo nInfo = cManager.getActiveNetworkInfo();
    if (nInfo != null && nInfo.isConnected()) {
        Toast.makeText(this, "Network is available ", Toast.LENGTH_SHORT).show();

        AdView adView = (AdView)findViewById(R.id.adView);
        AdRequest adRequest = new AdRequest.Builder()
        //.addTestDevice("abc")
        .build();
        adView.loadAd(adRequest);
    mFragment=(SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);
    mFragment.getMapAsync(this);

    }


    else{
        Toast.makeText(this, "Network is not available ", Toast.LENGTH_SHORT).show();
        Fragment newFragment;
        FragmentTransaction transaction = getFragmentManager().beginTransaction();
        newFragment = new NetworkCheck();
        transaction.replace(R.id.content_frame, newFragment);
        transaction.addToBackStack(null);
        transaction.commit();
    }

    editplace = (EditText) findViewById(R.id.editplace);
    findbtn = (Button) findViewById(R.id.findbtn);

    setListnerOnWidget();

    mTitle = (String) getTitle();
    // Getting reference to the DrawerLayout
    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    mDrawerList = (ListView) findViewById(R.id.drawer_list);

    // Getting reference to the ActionBarDrawerToggle
    mDrawerToggle = new ActionBarDrawerToggle( this,
        mDrawerLayout,
        R.drawable.ic_drawer,
        R.string.drawer_open,
        R.string.drawer_close){

            /** Called when drawer is closed */
            public void onDrawerClosed(View view) {
                getActionBar().setTitle(mTitle);
                invalidateOptionsMenu();
            }

            /** Called when a drawer is opened */
            public void onDrawerOpened(View drawerView) {
                getActionBar().setTitle("Select a menu");
                invalidateOptionsMenu();
            }
    };

    // Setting DrawerToggle on DrawerLayout
    mDrawerLayout.setDrawerListener(mDrawerToggle);
    mDrawerToggle.setDrawerIndicatorEnabled(true);

    // Creating an ArrayAdapter to add items to the listview mDrawerList
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(
        getBaseContext(),
        R.layout.drawer_list_item ,
        getResources().getStringArray(R.array.menu)
    );

    mDrawerList.setAdapter(adapter);

    getActionBar().setHomeButtonEnabled(true);
    getActionBar().setDisplayHomeAsUpEnabled(true);


    // Setting item click listener for the listview mDrawerList
    mDrawerList.setOnItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent,
            View view,
            int position,
            long id) {
            displayView(position);
            // Updating the action bar title
            String[] menu = getResources().getStringArray(R.array.menu);
            mTitle = menu[position];

            mDrawerLayout.closeDrawer(mDrawerList);

        }

        private void displayView(int position) {
            // TODO Auto-generated method stub
            Fragment newFragment;
            FragmentTransaction transaction = getFragmentManager().beginTransaction();
            switch (position) {
            case 0:

                newFragment = new Help();
                transaction.replace(R.id.content_frame, newFragment);
                transaction.addToBackStack(null);
                transaction.commit();
                Log.e(TAG, "help button is clicked");
                break;

            case 1:

                newFragment = new ContactUs();
                transaction.replace(R.id.content_frame, newFragment);
                transaction.addToBackStack(null);
                transaction.commit();
                Log.e(TAG, "ContactUs button is clicked");
                break;

              case 2:
                  transaction.addToBackStack(null);
                try
                { Intent i = new Intent(Intent.ACTION_SEND);  
                  i.setType("text/plain");
                  i.putExtra(Intent.EXTRA_SUBJECT, "My application name");
                  String sAux = "\nLet me recommend you this application\n\n";
                  sAux = sAux + "https://play.google.com/store/apps/details?id=com.iqwiner\n\n";
                  i.putExtra(Intent.EXTRA_TEXT, sAux);  
                  startActivity(Intent.createChooser(i, "Choose an action"));

                }
                catch(Exception e)
                { //e.toString();
                }   
                Log.e(TAG, "share button is clicked");
                break;

              case 3:
                newFragment = new Suggestion_Address();
                transaction.replace(R.id.content_frame, newFragment);
                transaction.addToBackStack(null);
                transaction.commit();
                Log.e(TAG, "Suggestion Address button is clicked");
                break;

            }

        }

    });



}

Please tell me how to go back to my main layout from a fragment layout when click on back button..

Thanks

Answer 1

Try this in your activity

@Override
public void onBackPressed() {
  if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
    getSupportFragmentManager().popBackStackImmediate();
  } else {
    super.onBackPressed();
  }
}

Answer 2

Here is a code which navigates from activity to fragment and on pressing back button it navigates back to activity.

MainActivity to fragment and back to MainActivity on pressing back button