Develop Reference

Go back from a fragment to main fragment

This is my main activity where I am calling my fragments:
public class what extends AppCompatActivity {
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mToggle;
private ListView mDrawerList;
private ArrayAdapter<String> mAdapter;
private FragmentTransaction fragmentTransaction;
NavigationView navigationView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_what);
mDrawerLayout=(DrawerLayout)findViewById(R.id.drawer_layout);
mToggle=new ActionBarDrawerToggle(this, mDrawerLayout, R.string.open, R.string.close);
mDrawerLayout.addDrawerListener(mToggle);
mToggle.syncState();
fragmentTransaction= getSupportFragmentManager().beginTransaction();
fragmentTransaction.add(R.id.main_content,new mainfrag());
fragmentTransaction.commit();
ActionBar actionBar= getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
navigationView=(NavigationView)findViewById(R.id.nav_view);
navigationView.getMenu().getItem(1).setChecked(false);
navigationView.getMenu().getItem(0).setChecked(true);
navigationView.getMenu().getItem(2).setChecked(false);
navigationView.getMenu().getItem(3).setChecked(false);
navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.nav_main:
navigationView.getMenu().getItem(1).setChecked(false);
navigationView.getMenu().getItem(2).setChecked(false);
navigationView.getMenu().getItem(3).setChecked(false);
navigationView.setCheckedItem(R.id.nav_main);
mDrawerLayout.closeDrawers();
fragmentTransaction=getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_content, new mainfrag());
fragmentTransaction.commit();
getSupportActionBar().setTitle(("SGPA and CGPA Calculator"));
item.setChecked(true);
break;
case R.id.nav_savedcal:
navigationView.getMenu().getItem(0).setChecked(false);
navigationView.getMenu().getItem(2).setChecked(false);
navigationView.getMenu().getItem(3).setChecked(false);
navigationView.setCheckedItem(R.id.nav_savedcal);
mDrawerLayout.closeDrawers();
fragmentTransaction=getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_content, new savedFragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle(("Saved Calculations"));
item.setChecked(true);
break;
case R.id.nav_upldoc:
navigationView.getMenu().getItem(0).setChecked(false);
navigationView.getMenu().getItem(1).setChecked(false);
navigationView.getMenu().getItem(3).setChecked(false);
navigationView.setCheckedItem(R.id.nav_upldoc);
mDrawerLayout.closeDrawers();
fragmentTransaction=getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_content, new uploadedfragment());
fragmentTransaction.commit();
getSupportActionBar().setTitle(("Uploaded documents"));
item.setChecked(true);
break;
case R.id.nav_site:
navigationView.getMenu().getItem(0).setChecked(false);
navigationView.getMenu().getItem(1).setChecked(false);
navigationView.getMenu().getItem(2).setChecked(false);
navigationView.setCheckedItem(R.id.nav_site);
mDrawerLayout.closeDrawers();
fragmentTransaction=getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.main_content, new resultsite());
fragmentTransaction.commit();
getSupportActionBar().setTitle(("VTU Results"));
item.setChecked(true);
break;
}
return false;
}
});
}
public boolean onOptionsItemSelected(MenuItem item ){
if(mToggle.onOptionsItemSelected(item)){
return true;
}
return super.onOptionsItemSelected(item);
}
#Override
public void onBackPressed() {
DialogInterface.OnClickListener dialogClickListener = new DialogInterface.OnClickListener() {
#Override
public void onClick(DialogInterface dialog, int which) {
switch (which) {
case DialogInterface.BUTTON_POSITIVE: {
finish();
}
break;
case DialogInterface.BUTTON_NEGATIVE:
break;
}
}
};
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit?").setPositiveButton("Yes", dialogClickListener)
.setNegativeButton("No", dialogClickListener).show();
return;
}
}
This is my default fragment :
public class mainfrag extends Fragment {
private View view;
private AdView adView;
private Button button10;
private Button button11;
public mainfrag() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
view = inflater.inflate(R.layout.fragment_mainfrag, container, false);
adView = view.findViewById(R.id.adView);
button10 = (Button) view.findViewById(R.id.button10);
button10.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
openmainactivity();
}
});
button11 = (Button) view.findViewById(R.id.button11);
button11.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
openscheme();
}
});
return view;
}
public void openmainactivity() {
Intent intent = new Intent(getContext(), MainActivity.class);
startActivity(intent);
}
public void openscheme(){
Intent intent=new Intent(getContext(), scheme.class);
startActivity(intent);
}
}
This is one of the other fragments:
public class savedFragment extends Fragment {
RecyclerView recyclerview;
adapter_sgpa recyclerAdapter;
ArrayList<POJO> sgpaArrayList;
public savedFragment() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FragmentTransaction tx = getChildFragmentManager().beginTransaction();
tx.replace(R.id.container, new sgpa_frag());
tx.commit();
}
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
int id = item.getItemId();
Fragment fragment = null;
switch (id) {
case R.id.navigation_sgpa:
sgpa_frag sf = new sgpa_frag();
FragmentManager fragmentManager = getChildFragmentManager();
fragmentManager.beginTransaction().replace(R.id.container, sf).commit();
return true;
case R.id.navigation_cgpa:
cgpa_frag cf = new cgpa_frag();
fragmentManager = getChildFragmentManager();
fragmentManager.beginTransaction().replace(R.id.container, cf).commit();
return true;
}
return false;
}
};
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View v = inflater.inflate(R.layout.fragment_saved, container, false);
BottomNavigationView nav = (BottomNavigationView) v.findViewById(R.id.bottom_navigation);
nav.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
return v;
}
}
What changes should I make in this code so that I am able to move back from the other fragments to the main fragment on pressing back button ?

Maintain one boolean variable to check current fragment is MainFragment or not.
if its not MainFragment -> replace MainFragment
Else -> super.onBackPressed()
ex:
private boolean isMainFragment=true; //make it false when move to other fragment
#Override
public void onBackPressed() {
if(!isMainFragment){
isMainFragment=true;
//replace your MainFragment
}
else{
//your logic show dialog or super.onBackPressed()
}
}

Ithink I know what you need. have a look at the last part of this documentation
"You can add a fragment transaction to the back stack. The back stack keeps track of actions in your app which can be backtracked when the user clicks Android's standard "back" button on the device. If you add a fragment transaction to the back stack then the transaction can be backtracked (reversed) with a click on the back button on the device" quotet from Jenkov
simply do fragmentTransaction.addToBackStack(null) on your main activity before you do the commit this will allow you to travel back using the back button
if you always want to travel back to the main fragment then you want to only add the main fragment to the backstack that way on pressing the back button you will always land there
in this part of your oncreate:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_what);
mDrawerLayout=(DrawerLayout)findViewById(R.id.drawer_layout);
mToggle=new ActionBarDrawerToggle(this, mDrawerLayout, R.string.open, R.string.close);
mDrawerLayout.addDrawerListener(mToggle);
mToggle.syncState();
fragmentTransaction= getSupportFragmentManager().beginTransaction();
fragmentTransaction.add(R.id.main_content,new mainfrag());
//HERE YOU PUT THE CODE V
fragmentTransaction.addToBackStack(null);
//HERE YOU PUT THE CODE ^
fragmentTransaction.commit();
ActionBar actionBar= getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
// ALL THE OTHER STUFF COMMING AFTER

Android home button with drawer navigation stops to work with rotation screen

I have a main activity with navigation drawer and a button to load fragment.
When the main ativity is launched I load the MainFragment.
In this moment all works well. The hamburger icon is showing and my Main fragment was loaded.
Next, I click a button and load a secondFragment. After I load the second fragment, I can use the backbutton and homebutton to come back to main activity without problems.
When I am with second fragment loaded and I make a rotation screen, the back button continues to work well, but the home button disappears and hamburger icon appears.
What am i doing wrong?
public class MainActivity extends AppCompatActivity {
private ActionBarDrawerToggle actionBarDrawerToggle;
private DrawerLayout drawerLayout;
private Toolbar toolbar;
private CharSequence mDrawerTitle;
private CharSequence mTitle;
private String mSubTitle;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
initNavigationDrawer();
if (savedInstanceState != null) {
return;
}
MainActivityFragment mainFragment = new MainActivityFragment();
firstFragment.setArguments(getIntent().getExtras());
// Add the fragment to the 'fragment_container' FrameLayout
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
//transaction.replace(R.id.fragment_container, firstFragment);
transaction.replace(R.id.fragment_container, mainFragment, "princ");
transaction.commit();
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Only handle with DrawerToggle if the drawer indicator is enabled.
if (actionBarDrawerToggle.isDrawerIndicatorEnabled() &&
actionBarDrawerToggle.onOptionsItemSelected(item)) {
return true;
}
// Handle your other action bar items...
return super.onOptionsItemSelected(item);
}
}
public Fragment getCurrentFragment(){
FragmentManager frgmgr = getSupportFragmentManager();
return frgmgr.findFragmentById(R.id.fragment_container);
}
#Override
public void onBackPressed() {
if (drawerLayout != null) {
if (drawerLayout.isDrawerOpen(GravityCompat.START)) {
drawerLayout.closeDrawer(GravityCompat.START);
return;
}
}
if ((getCurrentFragment() instanceof MainFragment)) {
finish();
} else if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
getSupportFragmentManager().popBackStack();
} else super.onBackPressed();
}
public void initNavigationDrawer() {
NavigationView navigationView = (NavigationView) findViewById(R.id.navigation_view);
navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
FragmentManager frgmgr = getSupportFragmentManager();
FragmentTransaction transaction = frgmgr.beginTransaction();
Fragment cur_frag;
// Handle navigation view item clicks here.
int id = menuItem.getItemId();
switch (id) {
case R.id.home:
cur_frag = frgmgr.findFragmentById(R.id.fragment_container);
if (!(cur_frag instanceof MainActivityFragment)) {
MainActivityFragment frag = new MainActivityFragment();
transaction.setCustomAnimations(R.anim.enter_from_left, R.anim.exit_to_right, R.anim.enter_from_right, R.anim.exit_to_left);
transaction.replace(R.id.fragment_container, frag);
transaction.commit();
break;
}
drawerLayout.closeDrawers();
break;
case R.id.logout_drw:
finish();
}
drawerLayout.closeDrawer(GravityCompat.START);
return true;
}
});
View header = navigationView.getHeaderView(0);
TextView tv_email = (TextView) header.findViewById(R.id.tv_email);
tv_email.setText("Agendamento");
drawerLayout = (DrawerLayout) findViewById(R.id.drawer);
mTitle = mDrawerTitle = getTitle();
actionBarDrawerToggle = new ActionBarDrawerToggle(this, drawerLayout, toolbar, R.string.drawer_open, R.string.drawer_close) {
#Override
public void onDrawerClosed(View v) {
super.onDrawerClosed(v);
}
#Override
public void onDrawerOpened(View v) {
super.onDrawerOpened(v);
}
};
drawerLayout.addDrawerListener(actionBarDrawerToggle);
actionBarDrawerToggle.syncState();
if (toolbar != null) {
getSupportFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
#Override
public void onBackStackChanged() {
int i=getSupportFragmentManager().getBackStackEntryCount();
if ((i > 0) || (!(getCurrentFragment() instanceof MainActivityFragment))) {
getSupportActionBar().setDisplayHomeAsUpEnabled(true); // show back button
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
onBackPressed();
}
});
} else {
getSupportActionBar().setDisplayHomeAsUpEnabled(false);
actionBarDrawerToggle.syncState();
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
drawerLayout.openDrawer(GravityCompat.START);
}
});
}
}
});
}
}
}
Main Fragment:
public class MainFragment extends Fragment {
public MainFragment() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment_main, container, false);
Button butCons= (Button) view.findViewById(R.id.butcons);
butCons.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
SecundaryFrag frag = new SecundaryFragFrag();
// Add the fragment to the 'fragment_container' FrameLayout
FragmentTransaction transaction=getFragmentManager().beginTransaction();
transaction.setCustomAnimations(R.anim.enter_from_left, R.anim.exit_to_right, R.anim.enter_from_right, R.anim.exit_to_left);
transaction.replace(R.id.fragment_container, frag);
transaction.addToBackStack(null);
transaction.commit();
}
});
return view;
}
}
Secondary Fragment:
public class SecundaryFrag extends Fragment{
public SecundaryFrag() {
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragment_consulta_ag, container, false);
return view;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
((MainActivity)getActivity()).onBackPressed();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
}
After Rotation:
Main activty with main fragment:
Before Rotation:

I believe it is related to the fact that the view is recreated after the orientation change. I would take a closer look to the onCreate() from the MainActivity in particular when the
if (savedInstanceState != null) {
return;
}
is triggered.
One option is to retain the fragments and restoring them onCreate. Also you could turn off the recreation by catching the orientation and handle it yourself in the application, you can see here both options explained developer.android.com/guide/topics/resources/

How to show a text from one fragment in another fragment?

I WAS WORKING BY THE EXAMPLE YOU JUST GAVE ME AS DUPLICATE, READ THE ENTIRE POST, TY
I'm making a simple app with sliding menu by using the template provided by android studio. And I have to use fragments to switch between items of the sliding menu.
What I wanna do? (check app design at the bottom)
When I click on button pass data it should set the text in the Fragment B to the text that I entered in a Fragment A but without going directly to the Fragment B. So when I press the button pass data then I wanna go to the sliding menu and select item that containts fragment B and then I wanna see the text from Fragment A. Thanks in advance.
public class MainActivity extends AppCompatActivity implements FragmentA.DataPassListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.nav_camera) {
// Handle the camera action
displayFragmentA();
} else if (id == R.id.nav_gallery) {
displayFragmentB();
} else if (id == R.id.nav_slideshow) {
} else if (id == R.id.nav_manage) {
} else if (id == R.id.nav_share) {
} else if (id == R.id.nav_send) {
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
});
}
#Override
public void onBackPressed() {
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
if (drawer.isDrawerOpen(GravityCompat.START)) {
drawer.closeDrawer(GravityCompat.START);
} else {
super.onBackPressed();
}
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
#Override
public void passData(String data) {
FragmentB fragmentB = new FragmentB();
Bundle args = new Bundle();
args.putString("data", data);
fragmentB.setArguments(args);
//getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, fragmentB).commit();
//it works with the commented part but I dont wanna go directly to the fragment when I press pass data button
}
public void displayFragmentA() {
FragmentA frag = new FragmentA();
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, frag);
fragmentTransaction.commit();
}
public void displayFragmentB() {
FragmentB frag = new FragmentB();
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, frag);
fragmentTransaction.commit();
}
}
Fragment A code:
public class FragmentA extends Fragment {
DataPassListener mCallback;
public interface DataPassListener {
public void passData(String data);
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// Make sure that container activity implement the callback interface
try {
mCallback = (DataPassListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement DataPassListener");
}
}
public FragmentA() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_a, container, false);
final EditText input = (EditText) view.findViewById(R.id.etInputID);
Button passDataButton = (Button) view.findViewById(R.id.bPassDataID);
passDataButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
mCallback.passData(input.getText().toString());
}
});
return view;
}
}
Fragment B code:
public class FragmentB extends Fragment {
TextView showReceivedData;
public FragmentB() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_fragment_b, container, false);
showReceivedData = (TextView) view.findViewById(R.id.showReceivedData);
Bundle args = getArguments();
if (args != null) {
showReceivedData.setText(args.getString("data"));
} else {
Toast.makeText(getActivity(), "didnt get the bundle from mainactivity", Toast.LENGTH_LONG).show();
}
return view;
}
}
Design of the app:

If these two fragments use same activity,
to set value to fragment :
getActivity().getIntent().putExtra("key", "value");
To get value from fragment :
getActivity().getIntent().getExtras().getString("key");

MainActivity to fragment and back to MainActivity on pressing back button

I have a Mainactivity which contains a Layout which is parent of 4 sub layout. on clicking on sub layout i am going to a new fragment replacing main layout. But i cant go back to MainActivity after pressing Back button
MainActivity.java
public class MainActivity extends AppCompatActivity {
RelativeLayout aboutUs;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
aboutUs = (RelativeLayout) findViewById(R.id.aboutUs);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
//click methods goes here
public void clickAboutUs(View view){
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
FragmentAboutUs fragmentAboutUs = new FragmentAboutUs();
fragmentTransaction.replace(R.id.fragment_container,fragmentAboutUs);
fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
FragmentAboutUs.java
public class FragmentAboutUs extends Fragment
{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.about_us, container,false);
return view;
}
}
How to go back to main page again after pressing back button from fragment.

Try Like this
public boolean popFragment() {
boolean isPop = false;
Fragment currentFragment = getSupportFragmentManager()
.findFragmentById(R.id.flContent);
if (getSupportFragmentManager().getBackStackEntryCount() > 0) {
isPop = true;
getSupportFragmentManager().popBackStackImmediate();
}
return isPop;
}
#Override
public void onBackPressed() {
if (!popFragment()) {
finish();
}
}
public void replaceFragment(Fragment fragment, boolean addToBackStack) {
FragmentTransaction transaction = getSupportFragmentManager()
.beginTransaction();
if (addToBackStack) {
transaction.addToBackStack(null);
} else {
getSupportFragmentManager().popBackStack(null,
FragmentManager.POP_BACK_STACK_INCLUSIVE);
}
transaction.replace(R.id.fragment_container, fragment);
transaction.commit();
getSupportFragmentManager().executePendingTransactions();
}
add above method is in your parent Activity
And Use like
FragmentAboutUs fragmentAboutUs = new FragmentAboutUs();
replaceFragment(fragmentAboutUs , true);

If you have one Activity and four fragments then set onBackPressed() as below in your MainActivity.
#Override
public void onBackPressed()
{
super.onBackPressed();
finish();
}
And in fragments:
#Override
public void onResume() {
super.onResume();
new PlayListFragment();
getView().setFocusableInTouchMode(true);
getView().requestFocus();
getView().setOnKeyListener(new View.OnKeyListener() {
#Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK){
if(getFragmentManager().getBackStackEntryCount() > 0) {
getFragmentManager().popBackStack();
}
return true;
}
return false;
}
});
}

You can Override the onBackPressed of MainActivity
#Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() > 1) {
getFragmentManager().popBackStack();
} else {
super.onBackPressed();
}
}

Here is how it can be done in Xamarin:
Load fragment (I wrote helper method for that, but it's not necessary):
public void LoadFragment(Activity activity, Fragment fragment)
{
var backStateName = fragment.GetType().Name;
var fm = activity.FragmentManager;
var ft = fm.BeginTransaction();
ft.Replace(Resource.Id.mainContainer, fragment);
ft.AddToBackStack(backStateName);
ft.Commit();
}
Back button (in MainActivity):
public override void OnBackPressed()
{
if (isNavDrawerOpen()) drawerLayout.CloseDrawers();
else
{
var backStackEntryCount = FragmentManager.BackStackEntryCount;
if (backStackEntryCount == 1) Finish();
else if (backStackEntryCount > 1) FragmentManager.PopBackStack();
else base.OnBackPressed();
}
}
isNavDrawerOpen method:
bool isNavDrawerOpen()
{
return drawerLayout != null && drawerLayout.IsDrawerOpen(Android.Support.V4.View.GravityCompat.Start);
}

Implement back navigation with DrawerLayout and AppCompatActivity without DrawerToggle

I've been searching and thinking how to implement the desire behaviour that I want when switching back and forth between fragments when using a Navigation Drawer. Actually the documentation says:
When using fragments in your app, individual FragmentTransaction objects may represent context changes that should be added to the back stack. For example, if you are implementing a master/detail flow on a handset by swapping out fragments, you should ensure that pressing the Back button on a detail screen returns the user to the master screen
So in my app I have a MainActivity that controls everything and a navigation layout within you can change between predefined options. This is the view when you launch the app
When you click on an item in the navigation drawer it opens a new fragment that replaces the main_content as follows:
At this point the behaviour is the correct one, so if you want to change the options you need to open the navigation drawer again to toggle between the menu options.
This is the Main Activity (notice that there is no Drawer Toggle)
MainActivity.java
public class MainActivity extends AppCompatActivity {
ActionBarDrawerToggle mDrawerToggle;
private DrawerLayout drawerLayout;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mSnackBarView = findViewById(R.id.myCoordinatorLayout);
setToolbar(); // Set Toolbar como action bar
if (savedInstanceState != null) {
mCurrentSelectedPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION);
mFromSavedInstanceState = true;
}
drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
if (navigationView != null) {
setupDrawerContent(navigationView);
}
drawerTitle = getResources().getString(R.string.app_name);
if (savedInstanceState == null) {
selectItem(drawerTitle, mCurrentSelectedPosition);
}
}
private void setToolbar() {
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
final ActionBar ab = getSupportActionBar();
if (ab != null) {
// Poner ícono del drawer toggle
ab.setHomeAsUpIndicator(R.drawable.ic_menu);
ab.setDisplayHomeAsUpEnabled(true);
}
}
private void setupDrawerContent(final NavigationView navigationView) {
navigationView.setNavigationItemSelectedListener(
new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
// Marcar item presionado
menuItem.setChecked(true);
// Crear nuevo fragmento
String title = menuItem.getTitle().toString();
int id = menuItem.getItemId();
selectItem(title, id);
return true;
}
}
);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
if (!drawerLayout.isDrawerOpen(GravityCompat.START)) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
return super.onCreateOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
drawerLayout.openDrawer(GravityCompat.START);
return true;
}
return super.onOptionsItemSelected(item);
}
private void selectItem(String title, int id) {
Bundle args = new Bundle();
args.putString(PlaceholderFragment.ARG_SECTION_TITLE, title);
Fragment fragment = PlaceholderFragment.newInstance(title);
fragment.setArguments(args);
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager
.beginTransaction()
.replace(R.id.main_content, fragment)
.commit();
switch (id) {
case R.id.nav_localizacion:
//Snackbar.make(mSnackBarView, R.string.menu_localization, Snackbar.LENGTH_SHORT).show();
mCurrentSelectedPosition = 0;
LocalizacionFragment fragment_localizacion = new LocalizacionFragment();
// fragmentManager = getSupportFragmentManager();
Snackbar.make(mSnackBarView, R.string.menu_localization, Snackbar.LENGTH_SHORT).show();
fragmentManager
.beginTransaction()
.replace(R.id.main_content, fragment_localizacion)
.commit();
break;
case R.id.nav_productos:
Snackbar.make(mSnackBarView, R.string.menu_productos, Snackbar.LENGTH_SHORT).show();
mCurrentSelectedPosition = 1;
fragmentManager
.beginTransaction()
.replace(R.id.main_content, fragment)
.commit();
break;
case R.id.nav_consejos:
Snackbar.make(mSnackBarView, R.string.menu_consejos, Snackbar.LENGTH_SHORT).show();
mCurrentSelectedPosition = 3;
ConsejosFragment fragment_consejo = new ConsejosFragment();
fragmentManager
.beginTransaction()
.replace(R.id.main_content, fragment_consejo)
.commit();
break;
default:
break;
}
drawerLayout.closeDrawers(); // Cerrar drawer
setTitle(title); // título actual
}
}
I don't use the hamburger icon because it hides under the Navigation Layout, but here is the thing. When you click on "Recetas" in the recycle view it open a new fragment (replace) but now I want to show the up caret icon and give proper back navigation to my app.
Here is the code of the "Consejos" fragment class
Consejos.java
public class ConsejosFragment extends Fragment {
RecyclerView mRecycler;
ConsejosAdapter mAdapter;
FragmentActivity mActivity;
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
this.mActivity = (FragmentActivity) activity;
setRetainInstance(true);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setHasOptionsMenu(true);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
List items = new ArrayList();
items.add(new ConsejosInfo("Recetas", R.drawable.icon_recetas));
/* Inflamos el layout */
View v = inflater.inflate(R.layout.consejos_layout_recycler, container, false);
/* Obtenemos el Recycle */
mRecycler = (RecyclerView) v.findViewById(R.id.recycler_consejos);
/* Creamos el adaptador */
mAdapter = new ConsejosAdapter(mActivity, items);
/* Set click en adapter */
return v;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
mRecycler.setHasFixedSize(true);
mRecycler.setLayoutManager(new LinearLayoutManager(getActivity()));
mRecycler.setAdapter(mAdapter);
}
}
And this is the adapter that the Recyclerview use and handles the click on the item inside:
Adapter.java
public class ConsejosAdapter extends RecyclerView.Adapter<ConsejosAdapter.ConsejosViewHolder> {
private List<ConsejosInfo> _items = new ArrayList<ConsejosInfo>();
private final FragmentActivity mActivity;
private Context context;
public ConsejosAdapter(FragmentActivity mActivity, List<ConsejosInfo> items) {
this._items = items;
this.mActivity = mActivity;
}
#Override
public int getItemCount() {
return _items.size();
}
#Override
public ConsejosViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
View v = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.cardview_consejos, viewGroup, false);
return new ConsejosViewHolder(v);
}
#Override
public void onBindViewHolder(ConsejosViewHolder viewHolder, int position) {
viewHolder.imagen.setImageResource(_items.get(position).get_imagen());
viewHolder.nombre.setText(_items.get(position).get_nombre());
}
public class ConsejosViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public ImageView imagen;
public TextView nombre;
public ConsejosViewHolder(final View itemView) {
super(itemView);
imagen = (ImageView) itemView.findViewById(R.id.consejos_imagen);
nombre = (TextView) itemView.findViewById(R.id.consejos_nombre);
itemView.setOnClickListener(this);
}
#Override
public void onClick(View v) {
RecetasFragment recetasFragment = new RecetasFragment();
FragmentManager fragmentManager = mActivity.getSupportFragmentManager();
fragmentManager
.beginTransaction()
.replace(R.id.main_content, recetasFragment)
.addToBackStack(null)
.commit();
}
}
}
In the Consejos Adapter I added to backstack the fragment before calling the new fragment (inside fragment) and that changes the behaviour of the back button, so before this if you press the back button is closes the app but now it takes you to the Consejos fragment, but now I want to add the up caret and make the exactly same operation as when you click the back button but I don't know how to achieve it.
Please feel free to ask for more code
Thank you very much

I will give you the full answer:
We will use the interfaces to communicate with the MainActivity from RecetasFragment so we can enable and disable navigation back button.
RecetasFragment class:
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
/**
* Created by hema on 8/19/2015.
*/
public class RecetasFragment extends Fragment {
private CommunicateWithActivity mWithActivity;
public RecetasFragment() {
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mWithActivity = (CommunicateWithActivity) activity; // MainActivity must implement CommunicateWithActivity interface.
mWithActivity.enableNavigationBack(true); // We enable navigation back here.
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement CommunicateWithActivity");
}
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_recetas, container, false);
}
#Override
public void onDestroy() {
super.onDestroy();
mWithActivity.enableNavigationBack(false); // We disable navigation back here, restore menu icon.
}
public interface CommunicateWithActivity {
void enableNavigationBack(boolean enable);// we will implement this method in MainActivity class.
}
}
And in MainActivity class we will implement CommunicateWithActivity interface, Modify your MainActivity class (only required modifications):
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
public class MainActivity extends AppCompatActivity implements RecetasFragment.CommunicateWithActivity {
private Toolbar mToolbar;
private DrawerLayout drawerLayout;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mToolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(mToolbar);
mToolbar.setNavigationIcon(R.drawable.ic_menu);
mSnackBarView = findViewById(R.id.myCoordinatorLayout);
if (savedInstanceState != null) {
mCurrentSelectedPosition = savedInstanceState.getInt(STATE_SELECTED_POSITION);
mFromSavedInstanceState = true;
}
drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
if (navigationView != null) {
setupDrawerContent(navigationView);
}
drawerTitle = getResources().getString(R.string.app_name);
if (savedInstanceState == null) {
selectItem(drawerTitle, mCurrentSelectedPosition);
}
}
private void setupDrawerContent(final NavigationView navigationView) {
navigationView.setNavigationItemSelectedListener(
new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
// Marcar item presionado
menuItem.setChecked(true);
// Crear nuevo fragmento
String title = menuItem.getTitle().toString();
int id = menuItem.getItemId();
selectItem(title, id);
return true;
}
}
);
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
if (!drawerLayout.isDrawerOpen(GravityCompat.START)) {
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
return super.onCreateOptionsMenu(menu);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
drawerLayout.openDrawer(GravityCompat.START);
return true;
}
return super.onOptionsItemSelected(item);
}
private void selectItem(String title, int id) {
Bundle args = new Bundle();
args.putString(PlaceholderFragment.ARG_SECTION_TITLE, title);
Fragment fragment = PlaceholderFragment.newInstance(title);
fragment.setArguments(args);
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager
.beginTransaction()
.replace(R.id.main_content, fragment)
.commit();
switch (id) {
case R.id.nav_localizacion:
//Snackbar.make(mSnackBarView, R.string.menu_localization, Snackbar.LENGTH_SHORT).show();
mCurrentSelectedPosition = 0;
LocalizacionFragment fragment_localizacion = new LocalizacionFragment();
// fragmentManager = getSupportFragmentManager();
Snackbar.make(mSnackBarView, R.string.menu_localization, Snackbar.LENGTH_SHORT).show();
fragmentManager
.beginTransaction()
.replace(R.id.main_content, fragment_localizacion)
.commit();
break;
case R.id.nav_productos:
Snackbar.make(mSnackBarView, R.string.menu_productos, Snackbar.LENGTH_SHORT).show();
mCurrentSelectedPosition = 1;
fragmentManager
.beginTransaction()
.replace(R.id.main_content, fragment)
.commit();
break;
case R.id.nav_consejos:
Snackbar.make(mSnackBarView, R.string.menu_consejos, Snackbar.LENGTH_SHORT).show();
mCurrentSelectedPosition = 3;
ConsejosFragment fragment_consejo = new ConsejosFragment();
fragmentManager
.beginTransaction()
.replace(R.id.main_content, fragment_consejo)
.commit();
break;
default:
break;
}
drawerLayout.closeDrawers(); // Cerrar drawer
setTitle(title); // título actual
}
#Override
public void enableNavigationBack(boolean enable) {
if(enable) {
// We enable the navigation back button here
mToolbar.setNavigationIcon(R.drawable.abc_ic_ab_back_mtrl_am_alpha);
mToolbar.setNavigationOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// On navigation back button clicked.
if(getSupportFragmentManager().getBackStackEntryCount() > 0) { // Check if there is fragments in BackStack.
getSupportFragmentManager().popBackStack(); // PopBackStack.
} else {
// You can implement this part as you want.
return;
}
}
});
} else {
mToolbar.setNavigationIcon(R.drawable.ic_menu);
mToolbar.setNavigationOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
if(drawerLayout != null) {
drawerLayout.openDrawer(Gravity.LEFT);
}
}
});
}
}
}
Please let me know if there is something you don't understand.