Develop Reference

How to keep fragments state like Instagram in Android?

I need to implement the UI of my app, like the Instagram one. I need to switch from different fragments, with the usage of the bottom navigation view, but I need to keep state of the fragments, like I left them. How Can I achieve this?
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
item.setChecked(true);
switch (item.getItemId()) {
case R.id.action_formation:
if (homeFragment == null) {
homeFragment = new HomeFragment();
}
displayFragment(homeFragment);
break;
case R.id.action_result:
if (introResultFragment == null) {
introResultFragment = new IntroResultFragment();
}
displayFragment(introResultFragment);
break;
case R.id.action_market:
displayFragment(new MarketFragment());
break;
}
return false;
}
public void displayFragment(final Fragment fragment) {
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager
.beginTransaction();
fragmentTransaction.replace(R.id.container, fragment, fragment.getClass().toString());
fragmentTransaction.commit();
}

It's been a long time but I want to offer my open source library in github which implements the same UX of Youtube and Instagram:
https://github.com/ZachBublil/ZNavigator
You got to add this dependency to your gradle:
compile 'com.zach.znavigator:znavigator:1.0.0'
The only thing you have to do is to pass the list of fragments you want to be in the BottomNavigationView:
public class SampleActivity extends NavigationActivity {
private BottomNavigationView navigationView;
#Override
protected void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
navigationView = (BottomNavigationView) findViewById(R.id.navigationView);
LinkedHashMap<Integer, Fragment> rootFragments = new LinkedHashMap<>();
rootFragments.put(R.id.tab1, new FirstTab());
rootFragments.put(R.id.tab2,new SecondTab());
rootFragments.put(R.id.tab3, new ThirdTab());
init(rootFragments, R.id.container);
navigationView.setOnNavigationItemSelectedListener(this);
navigationView.setOnNavigationItemReselectedListener(this);
}
#Override
public void tabChanged(int id) {
navigationView.getMenu().findItem(id).setChecked(true);
}
}
If you want to open a new fragment as inner screen in one of the tabs you can do it by using ZNavigation class in the tab fragment:
ZNavigation.openChildFragment(getFragmentManager(),new ChildFragment());

just remember the active fragment, and use userVisiableHint to get active status in each fragment.
private Fragment currentFragment; // need to be init
private void switch2Fragment(Fragment target){
getFragmentManager().executePendingTransactions();
if(target.isAdded){
getFragmentManager().beginTransaction().hide(currentFragment).show(target).commit();
} else {
getFragmentManager().beginTransaction().hide(currentFragment).add(R.id.xxx, target).commit();
}
currentFragment.setUserVisibleHint(false);
currentFragment = target;
target.setUserVisibleHint(true);
}
private boolean isFragmentActive(Fragment target){
return target.getUserVisibleHint();
}

Back button from activity is removing fragment

I am trying to retain the state of Fragment. I have MotherActivity in which I have FragmentOne,FragmentTwo,FragmentThree and inside from FragmentTwo I am calling another activity ChildActivity. Problem is that When I am pressing back button in ChildActivity it is refreshing MotherActivity and not keeping the state of my FragmentTwo instead it is showing me FragmentOne which come first time.
I only want when I am pressing BackButton from ChildActivity, on container FragmentTwo should be there:
MainAcitivity:
public class MotherActivity extends FragmentActivity {
AHBottomNavigation bottomNavigation;
Fragment selectedFragment = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bottomNavigation = (AHBottomNavigation) findViewById(R.id.navigation);
bottomNavigation.addItem(item1);
bottomNavigation.addItem(item2);
bottomNavigation.addItem(item3);
bottomNavigation.setOnTabSelectedListener(new AHBottomNavigation.OnTabSelectedListener() {
#Override
public boolean onTabSelected(int position, boolean wasSelected) {
if (position == 0) {
selectedFragment = FragmentOne.newInstance(bottomNavigation);
} else if (position == 1) {
selectedFragment = FragmentTwo.newInstance(bottomNavigation);
} else if (position == 2) {
selectedFragment = FragmentThree.newInstance(bottomNavigation);
}
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frame_layout,selectedFragment);
fragmentTransaction.commit();
return true;
}
});
}
#Override
protected void onStart() {
super.onStart();
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.frame_layout, FragmentOne.newInstance(bottomNavigation));
fragmentTransaction.commit();
}
public void setNotification(){
bottomNavigation.setNotification("1", 1);
}
#Override
protected void onSaveInstanceState(Bundle outState) {
//No call for super().
}
#Override
public void onBackPressed() {
Intent intent = new Intent();
setResult(113, intent);
finish();
return;
}
}
FragmentTwo from where I am calling childActivity:
public class FragmentTwo extends Fragment {
public static AHBottomNavigation bottomNavigation1;
Card_detail_Adapter_Footer searchabledapter;
public static boolean showAddress = false;
Fragment selectedFragment;
public static FragmentTwo newInstance(AHBottomNavigation bottomNavigation) {
FragmentTwo fragment = new FragmentTwo();
bottomNavigation1 = bottomNavigation;
showNotificationCounter(3);
return fragment;
}
#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_cart, container, false);
if(showAddress == true){
showAddress = false;
// From here I am calling ChildActivity
Intent intent = new Intent(getActivity(), ChildActivity.class);
startActivity(intent);
}
return view;
}
}
In ChildActivity simply calling onBackPressed()

The problem is with the onStart() method of your MotherActivity.java because when you open another activity from FragmentTwo, your MotherActivity onStop() gets called. When you press back button from ChildActivity onStart() of MotherActivity called which is replacing FragmentTwo from FragmentOne by committing transaction.
Please have a look at https://developer.android.com/guide/components/activities/activity-lifecycle.html

Put code from onStart() method into onCreate() method and check if configuration been changed:
if (savedInstanceState == null) {
android.app.FragmentManager fragmentManager = getFragmentManager();
android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(R.id.frame_layout, FragmentOne.newInstance(bottomNavigation));
fragmentTransaction.commit();
}

problems with Fragment onBackPress

in my navigation drawer there are 5 menu items.one of them is about us item.when I click on this item, I call AboutUsFragment and show it(its content is just a text).but when I click onBackPress, fragment is gone but its texts remains on my activity.how can I solve this problem?what`s it related to?!
select item of navigation drawer in my activity:
public void selectItem(int position) {
Fragment fragment = null;
switch (position) {
case 0:
if (!Constants.login_state) {
fragment = new LoginFragment();
} else {
Logout();
}
break;
case 1:
Constants.filter = false;
Constants.gender = "-1";
fragment = new HomeFragment();
break;
case 2:
Constants.filter = false;
Constants.gender = "2";
StyleFragment.SortingMode = 1;
fragment = new StyleFragment();
break;
case 3:
Constants.filter = false;
Constants.gender = "1";
StyleFragment.SortingMode = 1;
fragment = new StyleFragment();
break;
case 4:
fragment = new AboutUsFragment();
break;
default:
break;
}
if (fragment != null) {
FragmentTransaction fragmentManager = getSupportFragmentManager().beginTransaction();
fragmentManager.replace(R.id.rl_container, fragment);
fragmentManager.addToBackStack(null);
fragmentManager.commit();
mDrawerList.setItemChecked(position, true);
mDrawerList.setSelection(position);
setTitle(mNavigationDrawerItemTitles[position]);
mDrawerLayout.closeDrawer(Gravity.END);
} else {
Log.e("HomeActivity", "Error in creating fragment");
}
}
and AboutUsFragment:
public class AboutUsFragment extends android.support.v4.app.Fragment{
private View view;
private TextView about_us_fragment_text_view;
public static AboutUsFragment newInstance() {
AboutUsFragment fragment = new AboutUsFragment();
Bundle args = new Bundle();
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
view=inflater.inflate(R.layout.fragment_about_us, container, false);
Casting(view);
about_us_fragment_text_view.setText(getResources().getString(R.string.about_us));
ChangeUIFont.ChangeFont((ViewGroup) view, getContext());
return view;
}
//casting parameters
public void Casting(View v){
about_us_fragment_text_view= (TextView) v.findViewById(R.id.about_us_fragment_text_view);
}}
onBackPress in my activity:
#Override
public void onBackPressed() {
if (SearchOpened) {
lv_searchResult.setVisibility(View.GONE);
SearchOpened = false;
} else
super.onBackPressed();
}
---------------------------------------AfterSearching-------------------------------------------
Finally I found the solution!
in my fragment I added below code:
public static final String FRAGMENT_NAME = AboutUsFragment.class.getName();
and in my activity,I set the tag of fragment when I call it,instead of null!
fragmentManager.replace(R.id.rl_container, fragment,fragmentName);

used this method instead of onBackPressed
if you have toolbar then here is my solution,
type under the oncreate method below toolbar,
assert getSupportActionBar() != null;
// getSupportActionBar().setHomeButtonEnabled(true);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
}
and set this code in your manifest file for your fragment
<activity android:name=".yourCurrentFragment">
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value=".whichActivityYouWantToGo" />
</activity>

Try this:
#Override
public void onBackPressed() {
if (getFragmentManager().getBackStackEntryCount() == 0) {
super.onBackPressed();
} else {
getFragmentManager().popBackStack();
}

Fragment is re-created after back from Activity

I have a problem related to fragment life cycle.
Before doing this, I will set DONT KEEP ACTIVITY mode(Setting -> Developer options).
In my project have 2 activity:
Activity 1: keep and control Fragment A and Fragment B
Activity 2: do not have fragment.
Activity 1 will be called first, then Fragment A and Fragment B will be called to visible.
Start Activity 2 from Activity 1, this cause Activity 1 will be destroyed and Fragment A & Fragment B will be destroyed too (Because of dont keep activity mode).
Press back key from Activity 2 to back Activity 1
Problem occurs here: Fragment A and Fragment B will be automatically called onCreateView() after back from activity 2 -> I want to avoid this. Can you give me some tips to resolve it?
Update Code
Activity 1
public class MainActivity extends Activity implements OnClickListener {
private Button mBtnShowFragmentA;
private Button mBtnShowFragmentB;
private Button mBtnGoAcitivity2;
protected String mCurrentFragmentTag;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_activity_1);
mBtnShowFragmentA = (Button) findViewById(R.id.btn_show_fragmentA);
mBtnShowFragmentB = (Button) findViewById(R.id.btn_show_fragmentB);
mBtnGoAcitivity2 = (Button) findViewById(R.id.btn_go_activity2);
mBtnShowFragmentA.setOnClickListener(this);
mBtnShowFragmentB.setOnClickListener(this);
mBtnGoAcitivity2.setOnClickListener(this);
}
#Override
protected void onDestroy() {
super.onDestroy();
}
protected void addFragment(int contentId, Fragment fragment, boolean isAddStack,
String stackName) {
FragmentManager fm = getFragmentManager();
String newFragment = fragment.getClass().getName();
FragmentTransaction ft = fm.beginTransaction();
Fragment currentFragment = fm.findFragmentByTag(mCurrentFragmentTag);
if (currentFragment != null && !TextUtils.equals(currentFragment.getTag(), newFragment)) {
ft.hide(currentFragment);
}
if (fm.findFragmentByTag(newFragment) != null) {
fragment = (Fragment) fm.findFragmentByTag(newFragment);
}
if (!fragment.isAdded()) {
ft.add(contentId, fragment, newFragment);
} else {
ft.show(fragment);
}
if (isAddStack) {
ft.addToBackStack(stackName);
}
try {
ft.commitAllowingStateLoss();
} catch (Exception e) {
}
mCurrentFragmentTag = newFragment;
}
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btn_show_fragmentA:
FragmentA fragmentA = new FragmentA();
addFragment(R.id.activity_main_content, fragmentA, false, null);
break;
case R.id.btn_show_fragmentB:
FragmentB fragmentB = new FragmentB();
addFragment(R.id.activity_main_content, fragmentB, false, null);
break;
case R.id.btn_go_activity2:
Intent intent = new Intent(getApplicationContext(), SettingActivity.class);
startActivity(intent);
break;
default:
break;
}
}
}
Fragment A
public class FragmentA extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.layout_fragment_a, container, false);
return view;
}
}
Fragment B
public class FragmentB extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.layout_fragment_b, container, false);
return view;
}
}
Activity 2
public class SettingActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout_activity_2);
}
#Override
protected void onDestroy() {
super.onDestroy();
}
#Override
public void onBackPressed() {
super.onBackPressed();
}
}
...................

Use below code to remove activity from stack.
FragmentManager fragmentManager = getSupportFragmentManager();
if (fragmentManager .getBackStackEntryCount() > 0) {
fragmentManager .popBackStack();
}

Fragment setRetainInstance(true) not working

I have an Activity that contains a number of Fragments that are swapped based on the selected item in a Navigation Drawer. I am trying to retain the current fragment across an orientation change by calling setRetainInstance(true) on the Fragment and then checking if that fragment exists in onCreate(...). However, the Fragment is always null when I try to get it on onCreate(...). I've been banging my head against my desk for hours over this. Can anyone spot a problem?
Relevant parts of activity
public class StartActivity {
private static final String MAIN_FRAGMENT_TAG = "mainFragment";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
...
if(savedInstanceState != null) {
Fragment f = getSupportFragmentManager().findFragmentByTag(MAIN_FRAGMENT_TAG);
if(f == null) {
// FRAGMENT IS ALWAYS NULL
switchToModeForPosition(...);
} else {
setupActionBarForPosition(...);
}
} else {
// Default to events view
switchToModeForPosition(0);
}
}
private void switchToModeForPosition(int position) {
Fragment fragment;
switch (position) {
default:
case 0: //events
fragment = new EventsByWeekFragment();
setupActionBarForEvents();
break;
case 1: //teams
fragment = new AllTeamsListFragment();
setupActionBarForTeams();
break;
case 2: //insights
fragment = new InsightsFragment();
setupActionBarForInsights();
break;
case 3:
startActivity(new Intent(this, SettingsActivity.class));
mDrawerLayout.closeDrawer(mDrawerList);
return;
}
fragment.setRetainInstance(true);
getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment, MAIN_FRAGMENT_TAG).commit();
}
}

use setRetainInstance(true)it in each Fragment class.
public void onCreated(Bundle savedInstanceState)
{
super.onCreated(savedInstanceState);
setRetainInstance(true);
}
Or
public void onActivityCreated(Bundle savedInstanceState)
{
super.onActivityCreated(savedInstanceState);
setRetainInstance(true);
}