Develop Reference

How to disable the transition of fragments?

I am building a quiz app with three questions and therefore I have 6 Fragments but I would like to disable the default transition from one fragment to another, how can I achieve this? I already disabled that you can swipe between the fragments, you have to click a button to get to the next fragment, but there is still somehow a swiping transition after clicking the button. I searched for this but there was never an answer that would fit my problem. Here is one fragment example:
public class FragmentQuestion1 extends Fragment {
private Button btnNavFrag1;
private EditText editText;
private ProgressBar m_bar;
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_question_1, container, false);
btnNavFrag1 = view.findViewById(R.id.btn_question1);
editText = view.findViewById(R.id.edit_text_question_1);
editText.addTextChangedListener(new NumberTextWatcher(editText));
m_bar = view.findViewById(R.id.progress_bar_question_1);
btnNavFrag1.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
((GameActivity)getActivity()).setViewPager(2);
}
});
return view;
}
// Method that is used so the countdown starts when the user gets to this fragment
#Override
public void setMenuVisibility(final boolean visible) {
super.setMenuVisibility(visible);
if (visible) {
startCountdownTimer();
}
}
// Countdown 17 seconds
int i = 0;
private void startCountdownTimer() {
m_bar.setProgress(i);
final int totalMsecs = 17 * 1000; // 17 seconds in milli seconds
int callInterval = 100;
/** CountDownTimer */
new CountDownTimer(totalMsecs, callInterval) {
public void onTick(long millisUntilFinished) {
int secondsRemaining = (int) millisUntilFinished / 1000;
float fraction = millisUntilFinished / (float) totalMsecs;
// progress bar is based on scale of 1 to 100;
m_bar.setProgress((int) (fraction * 100));
}
public void onFinish() {
}
}.start();
}

Because you are using a viewPager, you could use a library like this which lets you add a transformer (some sort of effect) to the viewPager when going to the next fragment. I'd recommend the ZoomOutTranformer for your use-case. If the transition is not what you expect you can always extend from that class and override the transition so it's more to your liking.
ViewPagerTransformers are native, so you don't need to use a library. Just create a class, implement the PageTransformer interface and override the method transformPage.

In your layout xml define a tablayout and a FrameLayout like this:
..................your xml code...............
.............................................................
<com.google.android.material.tabs.TabLayout
android:id="#+id/simpleTabLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:tabBackground="#color/colorPrimary"
app:tabIndicatorColor="#0080FF"
app:tabSelectedTextColor="#050505"
app:tabTextColor="#color/colorAccent">
<com.google.android.material.tabs.TabItem
android:id="#+id/abcd"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Item 1" />
<com.google.android.material.tabs.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="item 2" />
<com.google.android.material.tabs.TabItem
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="item 3" />
</com.google.android.material.tabs.TabLayout>
<FrameLayout
android:id="#+id/simpleFrameLayout"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
This layout is defined for three tabs. You can make it for more tabs by adding more tabs if you like.
Then define the fragments for each tab. In this case:
item_one_fragment:
<?xml version="1.0" encoding="utf-8"?>
<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"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context="your.activity.context">
......................................
............................................
fragments xml
.............................
,.....................................
</RelativeLayout>
Similarly item 2 and item 3 fragment layouts.
Then define the fragments in java:
public class FirstItemFragment extends Fragment {
public ListView CallListView;
public FirstFragment() {
// Required empty public constructor
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View view = inflater.inflate(R.layout.item_one_fragment, container, false);
// Inflate the layout for this fragment
return view;
}
}
Simiarly second and third fragment.
Then in your Main Activity:
FrameLayout simpleFrameLayout = (FrameLayout) findViewById(R.id.simpleFrameLayout);
TabLayout tabLayout = (TabLayout) findViewById(R.id.simpleTabLayout);
FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.simpleFrameLayout, new FirstItemFragment());
ft.commit();
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
#Override
public void onTabSelected(TabLayout.Tab tab) {
// get the current selected tab's position and replace the fragment accordingly
Fragment fragment = null;
switch (tab.getPosition()) {
case 0:
fragment = new FirstItemFragment();
break;
case 1:
fragment = new SecondItemFragment();
break;
case 2:
fragment = new ThirdItemFragment();
break;
}
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.simpleFrameLayout, fragment)
.addToBackStack(null)
//Commit the transaction.
.commit();
}
#Override
public void onTabUnselected(TabLayout.Tab tab) {
}
#Override
public void onTabReselected(TabLayout.Tab tab) {
}
});
Now when you run your activity you will have three tabs and when you click on any one you will go to the respective fragment without any swipe

I have a checkbox inside a fragment and i want to it respond on click of a button this button is inside my main activity?

i am just working with fragments for the 1st time, i have a checkbox inside a fragment and a submit button inside my main activity. what i want to do is when i press submit button i want to toast a message whether the checkbox item is checked or not?
MainActivity.java
public class MainActivity extends AppCompatActivity {
private Spinner Dspinner;
private Button Subbtn;
ArrayAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Subbtn = (Button)findViewById(R.id.button);
adapter = ArrayAdapter.createFromResource(this, R.array.spinner_options, android.R.layout.simple_spinner_item);
spinnerListner();
}
public void spinnerListner(){
Dspinner = (Spinner)findViewById(R.id.spinner);
Dspinner.setAdapter(adapter);
Dspinner.setOnItemSelectedListener(
new AdapterView.OnItemSelectedListener() {
#Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
switch (position){
case 0:
getSupportFragmentManager().beginTransaction().replace(R.id.frag, BlankFragment.newInstance()).addToBackStack(null).commit();
break;
case 1:
getSupportFragmentManager().beginTransaction().replace(R.id.frag, BlankFragment2.newInstance()).addToBackStack(null).commit();
break;
}
}
#Override
public void onNothingSelected(AdapterView<?> parent) {
}
}
);
}
}
BlankFragment.java
public class BlankFragment extends Fragment {
public BlankFragment(){
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_blank, container, false);
}
public static Fragment newInstance() {
BlankFragment fragment = new BlankFragment();
return fragment;
}
}
BlankFragment2.java
public class BlankFragment2 extends Fragment {
public BlankFragment2(){
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_blank_2, container, false);
}
public static Fragment newInstance() {
BlankFragment2 fragment = new BlankFragment2();
return fragment;
}
}

You can use interface to communicate back to MainActivity.
Create a interface and implement it on MainActivity.
Pass the implemented interface to fragment and store it in the fragment
Then When your checkbox state change check that the stored interface is null or not if not null then call the implemented method
of the interface, which is actually implemented in MainActivity.
This way you can communicate back to MainActivity. In MainActivity store your checkbox state and do what you want to do in button press.
Interface
public interface OnStateChanged {
public void onChange(int state);
}
Implement it on MainActivity like
MainActivity implements OnStateChanged {
#Override
public void onChange(int state){
// store your data here
}
Create a variable for OnStateChanged interface and function in Fragment that will pass the interface
In Fragment:
OnStateChanged mListener;
public void setOnStateChangeListener(OnStateChanged listener){
mLinstener = listener;
}
When checkbox state change call the interface function
In Fragment:
//...if state change...
if(mListener!= null) {
mListener.onChange(/*your value*/);
}
Pass the implemented interface instance in MainActivity to fragment
In MainActivity:
fragment.setOnStateChangeListener(this);

There are several ways to realize this function. The easiest way is Defining an interface in your Activity, and let the Fragment implements it.(Or you can define a interface individually and let the Activity implements it, it's the similar solution)
For more solutions you can Google "Fragment and Activity Interaction".
I just can offer you some fragmentary code since I cannot find specific variable names.
First, defining a Interface in your Activity like this:
public static class MainActivity extends AppCompatActivity{
...
//Container Activity must implement this interface
public interface CheckBoxStateCallback{
public Boolean getTheState();
}
...
Second, let your fragments implements it:
public class BlankFragment extends Fragment implements CheckBoxStateCallback{
public BlankFragment(){
}
#Override
public Boolean getTheState(){
//return your checkbox state
}
...
Last, you need to add a click listener onto your Button in Activity:
...
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
Boolean b = BlankFragment.newInstance().getTheState();
//then you can make a toast
}
});
...

In MainActivity you would implement an interface CheckboxStatusObserver which we define with a method checkBoxChanged.
public class MainActivity extends AppCompatActivity implements CheckboxStatusObserver{
// other methods
void checkBoxChanged(boolean checkedStatus){
Toast.makeText(getContext(), "status " + checkedStatus, Toast.LENGTH_LONG).show();
}
public interface CheckboxStatusObserver{
void checkBoxChanged(boolean checkedStatus);
}
}
In the Fragment, we would get a reference to the CheckboxStatusObserver as the parent Activity. Then while inflating the contents of the Fragment, we can set up a listener to detect the on change of the checkbox(s). Then we would call the observer.checkBoxChanged(checkedStatus); and pass it the checked status of the checkbox.
public class BlankFragment extends Fragment {
private CheckboxStatusObserver observer;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
observer = (CheckboxStatusObserver) getActivity();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_blank, container, false);
// Find the checkbox instace using view.findViewById();
// Setup change listener on checkbox instance and notify the observer
{
observer.checkBoxChanged(checkedStatus);
}
return view;
}
}
Whenever the checkbox status changes, the method in the MainActivity will get invoked.
See below links for more information:
https://stackoverflow.com/a/25392549/592025
https://developer.android.com/training/basics/fragments/communicating.html
To allow a Fragment to communicate up to its Activity, you can define an interface in the Fragment class and implement it within the Activity. The Fragment captures the interface implementation during its onAttach() lifecycle method and can then call the Interface methods in order to communicate with the Activity.

Create an Interface in Your MainActivity and click listeners as below
try {
((OnClick) this).onSubmitClicked();
} catch (ClassCastException cce) {
cce.printStackTrace();
}
public interface OnClick {
public void onSubmitClicked();
}
Now implement listeners in your Fragment thus you will get onSubmitClicked implemented method as below Enjoy!
public class BlankFragment extends Fragment implements MainActivity.OnClick{
#Override
public void onSubmitClicked() {
//do something here
}
}

This is yet another way different from what i commented that day this might meet your need
In Main Activty
Blank1Fragment fragment1 = new Blank1Fragment();
Blank2Fragment fragment2 = new Blank2Fragment();
Subbtn..setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if(position==0)
fragment1.function();
else if(position==1)
fragment2.function();
}
);
in OnitemClick of spinner
switch (position){
case 0:
position=0;
getSupportFragmentManager().beginTransaction().replace(R.id.frag, fragment1).addToBackStack(null).commit();
break;
case 1:
position=1;
getSupportFragmentManager().beginTransaction().replace(R.id.frag, fragment2).addToBackStack(null).commit();
break;
}
}
Each fragment will have
public class Blank1Fragment extends Fragment {
....
public void function(){
//check which checkbox selected and toast;
}
}
public class Blank2Fragment extends Fragment {
....
public void function(){
//check which checkbox selected and toast;
}
}

Does FragmentStatePagerAdapter save fragment state on orientation change?

I have 3 fragments that need to be in a ViewPager. These fragment will hold dynamic information retrieved from a database. I understand that on an orientation change, the activity and fragments are destroyed and recreated. But I was under the impression by its name, that the FragmentStatePagerAdapter will save the state of the fragment. Apparently, I was wrong because every time I did something to the fragment, then change orientation, the fragment is reverted back to how it was laid out in the layout xml file.
As I was debugging, I noticed that on orientation change, the Adapter's getItem() method was never invoked - meaning that it wasn't recreated. So then how come the fragment state reverted back to its original state?
How do I save the fragment state using the FragmentStatePagerAdapter?
Please note that I have been following this tutorial and used their version of the SmartFragmentStatePagerAdapter.java class to manage the fragment dynamically.
And the following are my sample codes.
PageLoader.java - This interface allows MainActivity to manage the loading of the fragment pages dynamically at run time.
public interface PageLoader {
void loadPage(int from, int target);
}
MainActivity.java
public class MainActivity extends AppCompatActivity implements PageLoader {
MyPagerAdapter adapter;
DirectionalViewPager pager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Get the ViewPager and set it's PagerAdapter so that it can display items
pager = (DirectionalViewPager) findViewById(R.id.vpPager);
adapter = new MyPagerAdapter(getSupportFragmentManager());
pager.setOffscreenPageLimit(5);
pager.setAdapter(adapter);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
int position = pager.getCurrentItem();
if (position > 0) pager.setCurrentItem(position - 1);
return true;
}
#Override
public void loadPage(int from, int target) {
PageLoader fragment = (PageLoader) adapter.getRegisteredFragment(target);
fragment.loadPage(from, target);
}
}
MyPagerAdapter.java
public class MyPagerAdapter extends SmartFragmentStatePagerAdapter {
private static final int NUM_ITEMS = 4;
public MyPagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
// Returns total number of pages
#Override
public int getCount() {
return NUM_ITEMS;
}
// Returns the fragment to display for that page
#Override
public Fragment getItem(int position) {
switch (position) {
case 0: // Fragment # 0 - This will show Frag1
return Frag1.newInstance(position, Frag1.class.getSimpleName());
case 1: // Fragment # 0 - This will show Frag1 different title
return Frag1.newInstance(position, Frag1.class.getSimpleName());
case 2: // Fragment # 1 - This will show Frag2
return Frag2.newInstance(position, Frag2.class.getSimpleName());
default:
return Frag3.newInstance(position, Frag3.class.getSimpleName());
}
}
// Returns the page title for the top indicator
#Override
public CharSequence getPageTitle(int position) {
return "Page " + position;
}
}
Frag1.java Frag2.java Frag3.java - these are all the same, except for the numbering.
public class Frag1 extends Fragment implements PageLoader {
// Store instance variables
private String title;
private int page;
private TextView txtView;
// newInstance constructor for creating fragment with arguments
public static Frag1 newInstance(int page, String title) {
Frag1 fragmentFirst = new Frag1();
Bundle args = new Bundle();
args.putInt("someInt", page);
args.putString("someTitle", title);
fragmentFirst.setArguments(args);
return fragmentFirst;
}
// Store instance variables based on arguments passed
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
page = getArguments().getInt("someInt", 0);
title = getArguments().getString("someTitle");
}
// Inflate the view for the fragment based on layout XML
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.frag1, container, false);
txtView = (TextView) view.findViewById(R.id.txt_frag1);
txtView.setText(page + " - " + title);
Button btn = (Button) view.findViewById(R.id.btn_frag1);
btn.setOnClickListener( new View.OnClickListener() {
#Override
public void onClick(View v) {
PageLoader activity = (PageLoader) getActivity();
activity.loadPage(page, page+1);
}
});
return view;
}
#Override
public void loadPage(int from, int target) {
txtView.setText(txtView.getText() + "\nThis message was created from" + from + " to " + target);
}
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<com.example.someone.smartfragmentstatepageradapter.custom.DirectionalViewPager
android:id="#+id/vpPager"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</com.example.someone.smartfragmentstatepageradapter.custom.DirectionalViewPager>
</LinearLayout>
frag1.xml frag2.xml frag3.xml - again these are all the same except for the numbering
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="#cc2">
<TextView
android:id="#+id/txt_frag1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="txt_frag1"
/>
<Button
android:id="#+id/btn_frag1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="btn_frag1"
android:textSize="26dp" />
</LinearLayout>
PLEASE tell me how I can use the FragmentStatePagerAdapter to save the "State" of my fragments. I've been scouring the internet from 9am to 9pm today... 12 hours... I really need some help figuring this out. Thanks in advance!

EDIT Try this:
Add another instance variable to your fragment:
private String text; // this is part of saved state
Set this variable in loadPage:
#Override
public void loadPage(int from, int target) {
text = txtView.getText().toString() + "\nThis message was created from" + from + " to " + target;
txtView.setText(text);
}
Override onSaveInstanceState to save this variable:
#Override
public void onSaveInstanceState(Bundle outState);
outState.putString("text", text);
super.onSaveInstanceState(outState);
}
Then restore the the TextView state using this variable:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (savedInstanceState != null) {
// not null means we are restoring the fragment
text = savedInstanceState.getString("text");
} else {
text = "" + page + " - " + title;
}
View view = inflater.inflate(R.layout.frag1, container, false);
txtView = (TextView) view.findViewById(R.id.txt_frag1);
txtView.setText(text);
Button btn = (Button) view.findViewById(R.id.btn_frag1);
btn.setOnClickListener( new View.OnClickListener() {
#Override
public void onClick(View v) {
PageLoader activity = (PageLoader) getActivity();
activity.loadPage(page, page+1);
}
});
return view;
}
Any time you want something in your fragment to stay the same when things like configuration changes occur, this is how you would track the state, then save and restore it.
This is where you would use onSaveInstanceState for fragments and activities.
This is the method you would override to save any necessary state. Anything you change in your fragment that you want to have recreated on configuration change must be saved and then restored during onCreate or onCreateView.
So if you're trying to restore the text created in loadPage, you would create a class-level String for the text, set it in loadPage, save that in the onSaveInstanceState override, and then restore in in onCreateView from the savedInstanceState parameter.
Now here's the kicker: You are noticing that getItem on your adapter isn't called after a config change. But did you notice that your fragment is still there (even though it wasn't how you left it)? Keep in mind that the activity has a FragmentManager that is managing the fragments and their transactions. When the activity goes to config change, it saves its state. The FragmentManager and all of the active fragments are part of that state. Then the fragments are restored in such a way that adapter.getItem isn't called.
Turns out, that SmartFragmentPagerAdapter isn't so smart. It can't recreate its registeredFragments array after a configuration change, so it's really not very useful. I would discourage you from using it.
So how do you send events to off-page fragments when the ViewPager has appropriated the fragment's tag for its own use?
The technique I use is to define event listener interfaces, and have the fragments register as listeners with the activity. When I fire an event, it's by calling a method on the activity that notifies its active listeners. I give a pretty complete example of this in this answer.

Keep fragments info between activities

I have my main activity actionbaractivity One where you can screenslide through some fragmets, on each fragment you have an imageView and a ListView where you can click any item and the image will change. Also in the menu options you have a button where you change to an almost exact activity: actiobbaractivity Two which also have this button to change to activity One
What I'm able to do is to keep the image when sliding the fragments, but unable to keep the fragments state's through the change of activities.
For example
I'm in activity One on fragment 3 with the image: "something". I click on the button to change to activity Two, I do things here and then, I click on the button to change to activity One and I want to see my fragment 3 with the image: "something" and not the default fragment 1 and default image
Im using ActionBarActivity, FragmentStatePagerAdapter and Fragment for each activity
Thanks for the help

According to the Activity and Fragment lifecycles (http://developer.android.com/reference/android/app/Activity.html#ActivityLifecycle and http://developer.android.com/guide/components/fragments.html#Lifecycle), the most reliable way of persisting states between activity/fragment changes is to use the default API for saving and restoring states:
When the activity/fragment is being dismissed (either because of a configuration change such as screen rotation or because the user requested to go to another activity/fragment), you can save its state in a Bundle object. When it is being created, you can restore its saved state, thus recreating a new instance exactly like the one the user left - so the user feels nothing has changed. This does not depend on the specific subclass of activity/fragment you are using.
I have implemented something like what you want: in my case, a fragment containing a menu with buttons that would each lead the user to another fragment containing a submenu with a "back" button. So if the user went from menu to submenu 1, then back to menu, then to submenu 2, then back to menu and finally again to submenu 1, I wanted that submenu 1 to appear just like the user has left it in the first time.
For that I have created:
1) an interface defining my submenu types, implemented by my activities so they could change between my submenus
2) a master generic class, which all my submenus would extend, that had a Bundle object to store their state
3) in my activities, I had an array of Bundle capable of storing one instance of each of my submenus (because I am only interested in restoring the last state, so I don't need more than one)
The interface (item 1):
public interface SubmenusManager {
public static enum Submenus {
ROOTMENU,
SUBMENU1,
SUBMENU2;
private static final int size = Submenus.values().length;
public static int size() {
return size;
}
public static int getId(Submenus test) {
switch(test) {
case SUBMENU1:
return 1;
case SUBMENU2:
return 2;
case ROOTMENU:
default:
return 0;
}
}
}
public void cloneCurrentSubmenuState(Parcelable toOverwrite);
public Bundle getLastStoredSubmenuState(Submenus submenu);
public void setCurrentSubmenuTo(Submenus submenu);
}
The generic class (item 2):
public class MenuFragment extends Fragment {
private Bundle menuData = new Bundle();
public static String RESTORE_MAIN_OBJECT = "restore_main";
public Bundle getMenuData() {
return menuData;
}
public Bundle cloneMenuData() {
return new Bundle(menuData);
}
public void setMenuData(Bundle menuData) {
this.menuData = menuData;
}
}
One of the activities (item 3):
public class ExampleAct extends FragmentActivity implements SubmenusManager {
/**
* instance variables
*/
private MenuFragment mMenu;
private Bundle [] menuData; // the Array of Bundles!
private static final String CONTAINER = "parcelable_container";
private static final String SUBMENU = "saved_submenu";
private Submenus curSubmenu = Submenus.ROOTMENU; // the default state is the ROOTMENU
private boolean restoreLastSavedState = false;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null) { // first time creating this activity
menuData = new Bundle[Submenus.size()];
} else { // this activity has a saved state from before
// restore all the data from all the submenus
menuData = (Bundle[]) savedInstanceState.getParcelableArray(CONTAINER);
// restore the info about which is the current active submenu
curSubmenu = (Submenus) savedInstanceState.getSerializable(SUBMENU);
}
buildMenuFragment(true);
//(...) stuff
}
private void buildMenuFragment(boolean restoreState) {
// (re)builds fragment inside menu.
// restoreState flags whether activity should look for
// saved state data and restore it
restoreLastSavedState = restoreState;
switch(curSubmenu) {
// Eclipse warns you about which are the constants in your enum
case ROOTMENU:
mMenu = new FragmentRootMenu();
break;
case SUBMENU1:
mMenu = new FragmentSubmenu1();
break;
case SUBMENU2:
mMenu = new FragmentSubmenu2();
break;
}
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.menu_frame, mMenu)
.commit();
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putSerializable(SUBMENU, curSubmenu);
cloneCurrentSubmenuState(mMenu.getMenuData().
getParcelable(MenuFragment.RESTORE_MAIN_OBJECT));
outState.putParcelableArray(CONTAINER, menuData);
// (...) stuff
}
#Override
public void cloneCurrentSubmenuState(Parcelable toOverwrite) {
if (menuData == null) menuData = new Bundle[Submenus.size()];
if (toOverwrite != null)
mMenu.getMenuData().putParcelable(MenuFragment.RESTORE_MAIN_OBJECT, toOverwrite);
menuData[Submenus.getId(curSubmenu)] = mMenu.cloneMenuData();
}
#Override
public Bundle getLastStoredSubmenuState(Submenus forThisSubmenu) {
return
(menuData == null || !restoreLastSavedState) ? new Bundle() : menuData[Submenus.getId(forThisSubmenu)];
}
#Override
public void setCurrentSubmenuTo(Submenus toThisSubmenu) {
if (mMenu != null) {
cloneCurrentSubmenuState(mMenu.getMenuData().
getParcelable(MenuFragment.RESTORE_MAIN_OBJECT));
}
curSubmenu = toThisSubmenu;
buildMenuFragment(true);
}
One of the submenus (extension of item 2):
public class FragmentSubmenu1 extends MenuFragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_submenu1, null);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
init();
}
public void init() {
// (...) stuff
MyParcelableObject tmp = null; // MyParcelableObject is a class
// that implements Parcelable and stores
// relevant info to rebuild this menu
// from a saved state
SubmenusManager m = (SubmenusManager) getActivity(); // remember activity implements SubmenusManager
Bundle bnd = m.getLastStoredSubmenuState(SubmenusManager.Submenus.SUBMENU1);
if (bnd != null) tmp = bnd.getParcelable(MenuFragment.RESTORE_MAIN_OBJECT);
if (tmp == null) {
tmp = new MyParcelableObject();
tmp.buildFromScratch(); // initializes with default data
}
// back button
Button backToMainMenu = (Button) getView().findViewById(R.id.submenu1_back);
backToMainMenu.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
((SubmenusManager) getActivity()).
setCurrentSubmenuTo(SubmenusManager.Submenus.ROOTMENU);
}
});
// (...) stuff
}
}
The Root menu (extension of item 2):
public class FragmentRootMenu extends MenuFragment {
View myView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
myView = inflater.inflate(R.layout.fragment_rootmenu, null);
return myView;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
init();
}
public void init() {
Button btnSubmenu1 = (Button) myView.findViewById(R.id.btn_call_submenu1);
btnSubmenu1.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
((SubmenusManager) getActivity()).
setCurrentSubmenuTo(SubmenusManager.Submenus.SUBMENU1);
}
});
Button btnSubmenu2 = (Button) myView.findViewById(R.id.btn_call_submenu2);
btnSubmenu2.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
((SubmenusManager) getActivity()).
setCurrentSubmenuTo(SubmenusManager.Submenus.SUBMENU2);
}
});
}
}
For that to work between activities, all you need to do is pass that object that stores the last state of all fragments (in my case, that would be Bundle [] menuData) to the activity that is being called through its Intent; you would recover it the same way as my ExampleAct did in its onCreate(). You could also wrap that Bundle [] inside a custom Parcelable object (very similar to my example MyParcelableObject; inside that one I had stuff like HashMap) if using an array is a problem.
Here how to pass a Parcelable between activities:
How to send an object from one Android Activity to another using Intents?

Fragment getView().findViewById(R.id.box1) Returning null

So here's the problem. I'm coding an app with two EditText views inside a fragment and a button. When the button is clicked, it changes the text of the EditText. In the onViewCreated() method I use this code to get the EditText instance and store it to a variable.
EditText box1 = (EditText)(getView.findViewById(R.id.box1));
This works fine. However, when I try to access variable box1 when the button is clicked, the EditText has become null and throws a NullPointerException. Does anyone know why this would happen?
Here is the fragment code:
public class MyFragment extends Fragment {
EditText box1, box2;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_text_coder_free,
container, false);
//Works here.
box1 = (EditText)(rootView.findViewById(R.id.box1));
box2 = (EditText)(rootView.findViewById(R.id.box2));
//Same thing. Sets the text correctly
box1.setText("hey look at me!");
return rootView;
}
//Called when the button is clicked.
public void setBox1Text(String text) {
//It's null here so it skips to the else
if(box1 != null) {
box1.setText(text);
}
else {
//This doesn't work. Throws the exception here.
box1 = (EditText)(getView().findViewById(R.id.box1));
}
}
public void setBox2Text(String text) {
if(box2 != null) {
box2.setText(text);
}
else {
//This doesn't work. Throws the exception here.
box2 = (EditText)(getView().findViewById(R.id.box2));
}
}
public String getBox1Text() {
if(box1 == null) {
return "Nice try.";
}
return box1.getText().toString();
}
public String getBox2Text() {
if(box2 == null) {
return "Nice try.";
}
return box2.getText().toString();
}
}
Here is the activity which houses the fragment:
public class MyActivity extends Activity {
MyFragment myFragment
EditText box1, box2;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_text_coder);
if (savedInstanceState == null) {
myFragment = new MyFragment();
getFragmentManager().beginTransaction()
.add(R.id.container, myFragment.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.my_app, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
public void box1Click(View v) {
myFragment.setBox2Text("Some text");
}
public void box2Click(View v) {
myFragment.setBox2Text("Some text");
}
}
And here is the XML from the fragment:
<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:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.mycode.MyFragment" >
<EditText
android:id="#+id/box1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:inputType="textMultiLine" />
<EditText
android:id="#+id/box2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="#id/box1"
android:inputType="textMultiLine|none"
android:focusable="false" />
<Button
android:id="#+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#id/box2"
android:layout_alignParentRight="true"
android:onClick="box2Click" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/encrypt_button_text"
android:layout_below="#id/box2"
android:layout_toLeftOf="#id/button2"
android:onClick="box1Click" />
</RelativeLayout>

Exemple of use:
public class main extends Fragment{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.core_info_tab, container, false);
ImageButton ib = (ImageButton) view.findViewById(R.id.imageButton1);
return view;
}
}

Make sure the fragment is attached to the activity before calling setBox1Text(String text) else the view is not initialized and getView returns null.
There is no need to initialize the edittext again.
You can just have
public void setBox1Text(String text) {
box1.setText(text); // box1 is already initialized in onCreate no need to initialize again
}
If you want use getView use it in onActivtiyCreated
box1 = (EditText)getView().findViewById(R.id.box1));

That's because you're trying to execute setBoxXText(...) before having created the fragment, onCreateView is not yet executed. Be sure that your fragment is loaded before access it's views.
If you check your code, the only way to box1 & box2 to be null is that onCreateView is not yet called, so when you do
if(box1 != null) {
box1.setText(text);
}
else {
and it goes through the else statement, it's because you didn't initialize the fragment.
You have several ways to fix this, for example you can set this values in the fragment initialization (1) or use a listener to notify when the fragment is loaded (2).
1-
Use a factory to initialize your fragment, fragments in android need empty constructors, so in this way you will use an empty constructor and also ensure yourself that in onCreateView you will have setted the box1 and box2 strings
public class YourFragment extends Fragment{
//Empty and private constructor
private YourFragment(){
}
private String box1Text;
private String box2Text;
public void setBox1Text(String box1Text){
this.box1Text = box1Text;
}
public void setBox2Text(String box2Text){
this.box2Text = box2Text;
}
public static YourFragment YourFragmentFactory(String box1Text, String box2Text){
YourFragment result = new YourFragment();
result.setBox1Text(box1Text);
result.setBox2Text(box2Text);
return result;
}
}
and 2:
use a listener to notify your activity when you can start to set the texts:
public interface YourFragmentListener{
public void onViewCreated();
}
private YourFragmentListener listener;
public void setListener(YourFragmentListener listener){
this.listener = listener;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onViewCreated(view, savedInstanceState);
if(this.listener != null){
this.listener.onViewCreated(); 
}
}

To use findViewById you have to execute it on Context (eg. an Activity).
Use: View.getContext().getViewById...
You can also try cleaning the project