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Two way binding Android

Maybe I am missing something small here, but I cannot get my binding to work. I set it up as follow:
public class Toolbar extends Fragment {
//Interaction handlers
//interface for interaction with Activity
public interface ToolBarInteraction{
public void Search(String screenName);
}
private ToolbarBind modelData;
private ToolBarInteraction mListener;
public static Toolbar newInstance() {
return new Toolbar();
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
FragmentToolbarBinding binding = DataBindingUtil.setContentView(getActivity(), R.layout.fragment_toolbar);
modelData = ToolbarBind.newInstance();
modelData.searchedText.set("Hello");
binding.setModelData(modelData);
}
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
checkMListener();
View view = inflater.inflate(R.layout.fragment_toolbar, container, false);
//get button to set onClick event
Button button = (Button)view.findViewById(R.id.btnSearch);
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
String hello = modelData.searchedText.get();
}
});
return view;
}
public void OnSearchClicked(View view){
mListener.Search(modelData.searchedText.get());
}
private void checkMListener(){
try{
mListener = (ToolBarInteraction) getActivity();
} catch (ClassCastException ex) {
throw new ClassCastException(getActivity().toString()
+ " must implement the ToolBarInteraction Interface");
}
}
}
Here is the code for ToolbarBind:
public class ToolbarBind extends BaseObservable {
private String _searchText;
public final ObservableField<String> searchedText = new ObservableField<String>();
//factory method
public static ToolbarBind newInstance(){ return new ToolbarBind(); }
}
And in my fragment, I set the binding up as follow, all within the layout tag:
<data>
<variable
name="modelData"
type="Common.CommonObjects.ToolbarBind"/>
</data>
And for binding to property:
<EditText
android:layout_width="match_parent"
android:layout_height="match_parent"
android:hint="Search"
android:text="#={modelData.searchedText}"/>
As can be seen, in the onCreate I set the text to "Hello", but even when the view displays on the phone, the EditText is not populated with this text. When I change the value, and click my button, the value I get back in the event is "Hello", not my new text entered while the app is running.
What am I missing?

The problem with your code is that you set the Activity's content view to something in onCreate(...) but you inflate and use something different in onCreateView(...) as your fragment's view, which gets the model data (not the other one you created in onCreate(...)). I don't know exactly what you try to achieve, but I'm gonna guess that you don't want to change the Activity's content view to something from the fragment, so I'm just gonna show you a variation of what could you use, however, you should change it to whatever pleases you.
Remove onCreate(...) completely then use only onCreateView(...) to inflate the fragment_toolbar layout using data binding:
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
checkMListener();
FragmentToolbarBinding binding = DataBindingUtil.inflate(inflater, R.layout.fragment_toolbar, container, false);
// FIXME you're losing data here; watch out: checking whether savedInstanceState == null is not enough because returning from backstack it will be null
modelData = ToolbarBind.newInstance();
// FIXME modify this so it sets the data from savedInstanceState when configuration changes
modelData.searchedText.set("Hello");
binding.setModelData(modelData);
//get button to set onClick event
binding.btnSearch.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
String hello = modelData.searchedText.get();
}
});
return binding.getRoot();
}
Watch out for the FIXME parts. You could move the modelData init to onCreate(...) which would save it from the backstack-return thing, however, configuration change will still call onCreate(...) unless you call setRetainInstance(true) on the fragment (do not).

Android - where to put onClick on linearlayout of a fragment

Obviously, I am new to Android - XML programming... So I have a navigation drawer, and once item is selected from the drawer, a corresponding fragment on the right side will display. Inside that fragment, I have linear layouts. I'd like to get redirected to another activity once that linear layout has been tapped. I was able to make it work on activities, by using android:onClick on XML file, but can't make it work on fragment. Somebody help me please.
App interface, refer to this image:
http://i.stack.imgur.com/u6dHi.jpg
Code:
fragment_smart.xml - the display once item's selected. I am trying to use the onClick on xml.
<LinearLayout
android:id="#+id/linearLayoutsmart1"
android:layout_width="match_parent"
android:layout_height="30dp"
android:layout_below="#+id/smart_title"
android:layout_marginLeft="15dp"
android:layout_marginTop="15dp"
android:orientation="horizontal"
android:weightSum="1"
android:onClick="smart_recommended_link">
Here's my Java code:
public class FragmentSmart extends Fragment {
public static final String TAG = "stats";
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View myfragment = inflater.inflate(R.layout.fragment_smart, container, false);
return myfragment;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
public void smart_recommended_link(View view) {
Intent smartRecommendedIntent = new Intent(this, SmartRecommended.class);
startActivity(smartRecommendedIntent);
}
}
The app is crashing when I clicked on the linearlayout using this code. What's the best thing to do here? Thank you!

For fragments you need to add the listener programmatically:
public class MyFragment extends Fragment implements View.OnClickListener {
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
view.findViewById(R.id.my_layout).setOnClickListener(this);
}
#Override
public void onClick(View v) {
// Handle click based on v.getId()
}
}

First of all, linear layouts cant trigger onClick events by default.
Check this answer for more information: LinearLayout onClick.
You can get the LinearLayout from the view in your onCreateView() like this:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View myfragment = inflater.inflate(R.layout.fragment_smart, container, false);
LinearLayout layout = (LinearLayout)myFragment.findViewById(R.id.linearLayoutsmart1);
// here you can set a listener of any type you want to the layout
return myfragment;
}

In fragments, you must use getActivity() method instead of this to reference the activity that the fragment is attached to.
public void smart_recommended_link(View view) {
Intent smartRecommendedIntent = new Intent(getActivity(), SmartRecommended.class);
startActivity(smartRecommendedIntent);
}

Nullpointerexception thrown when trying to findViewById

I have the following Activity:
public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new StartFragment())
.commit();
}
Button login = (Button) findViewById(R.id.loginButton);
login.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
Intent intent = new Intent(MainActivity.this,LoginActivity.class);
startActivity(intent);
}
});
}
I get a NPE when I try to invoke findViewByID for R.id.loginButton, and I'm guessing this is because loginButton is within a separate Fragment, which I have as:
public static class StartFragment extends Fragment {
public StartFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_main, container, false);
}
}
However, I am unsure of how to fix this so that I can find the loginButton ID. I haven't worked with fragments before, so I realize I may be using them/implementing them incorrectly. fragment_main contains a few buttons in a LinearLayout, and activity_main has nothing but a single FrameLayout.

Try to implement your onCreateView(...) in Fragment like
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
View something = rootView.findViewById(R.id.something);
something.setOnClickListener(new View.OnClickListener() { ... });
return rootView;
}
The Button is in the fragment layout (fragment_main.xml) and not in the activity layout (activity_main.xml). onCreate() is too early in the lifecycle to find it in the activity view hierarchy, and a null is returned. Invoking a method on null causes the NPE.

Write code to initialize button from fragment becuase your button is into fragment layout not into activity's layout.
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container,
false);
Button login = (Button) rootView.findViewById(R.id.loginButton);
login.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
Intent intent = new Intent(MainActivity.this,
LoginActivity.class);
startActivity(intent);
}
});
return rootView;
}
And remove the login button related code from onCreate of Activity.

findViewById() works with reference to a root view.
Without having a view in the first place will throw a null pointer exception
In any activity you set a view by calling setContentView(someView);.
Thus when you call findViewById() , its with reference to the someView.
Also findViewById() finds the id only if its in that someView. So in you case null pointer exception
For fragments, adapters, activity, .... any view's findViewById() will only find if the id exixts in the view
Alternately if you are inflating a view, then you can also use inflatedView.findViewById() to get a view from that inflatedView
In short make sure you have the id in your layout you are referring to or make findViewById() call in appropriate place(Ex. adapters getView(), activity's onCreate() or onResume() or onPause() , fragments onCreateView(), ....)
Also have an idea about UI & background thread's as you cannot efficiently update UI in bg-threads

SlidingMenu in Child Activities Navigation Android

I am trying to add left side slide menu inside my application but i am facing little trouble getting the slide menu to the following child activities of the fragment.
So far i have tried using this sliding menu example and when i got this image now inside the "Find People" fragment class i have static data.
Find People (Parent Activity) on Button Click go to ---> Friends (Child Activity of Find People) on Button Click go to ----> Names (Child Activity of Friends)
I am trying to get the same sliding menu with the Child Activities also that i failed to achieve so far please can any one help me out
public class FindPeopleFragment extends Fragment {
public FindPeopleFragment(){}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_find_people, container, false);
Button btn = (Button) rootView.findViewById(R.id.butto);
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Intent intent = new Intent(getActivity(), Friends.class);
startActivity(intent);
}
});
return rootView;
}
}
Friends (Child Activity)
public class Friends extends Activity {
Button btnNext;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.friends_xml);
btnNext = (Button)findViewById(R.id.btnNexts);
btnNext.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
// TODO Auto-generated method stub
// Go to Names Child Activity
}
});
}
}
And Similarly Names (Child Activity)
How do i get the same slide menu in both the child activities (Friends & Names). Any idea ??
Plz help me out in this.
Code Snippet will be much helpful.
Thanks

As #Piyush Gupta said you need to call new Fragment instead of calling activities,
In Place of activity you need to use Fragment and move from one Fragment to next used this code
Instead of using Fragment element use Framelayout id of the fragment Xml
Replace ur code with this
public class FindPeopleFragment extends Fragment {
public FindPeopleFragment(){}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_find_people, container, false);
Button btn = (Button) rootView.findViewById(R.id.butto);
btn.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
FragementDemo fd = new FragementDemo();
android.support.v4.app.FragmentTransaction ft =
getFragmentManager().beginTransaction();
ft.replace(R.id.content_frame, fd); // content_frame is your FrameLayout container
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
ft.addToBackStack(null);
ft.commit();
}
});
return rootView;
}
}
And your next child activity will extend Fragment not Activity like this :
public class Friends extends SherlockFragment{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragementdemo, container, false);
// use button click code as used in FindPeopleFragment
return rootView;
}
}
Hope it works fine now for you!!

How to create an interface to get info from a Fragment to an Android Activity?

Over the past days I've desperately been trying to build an android app with a simple fragment (which I use twice). I want to pass the contents of the fragments' EditText-boxes to a new activity. I just can't figure out how to get those contents from the fragments. What I have so far is this:
I've got my edit_text_fragment.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" >
<EditText
android:id="#+id/my_edit_text"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:hint="my hint" />
</LinearLayout>
and the corresponding MyEditTextFragment.java:
public class MyEditTextFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.edit_text_fragment, container, false);
return view;
}
}
I then use this fragment twice in my main.xml like this:
<LinearLayout 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:orientation="vertical">
<fragment
android:id="#+id/detailfragment_placeholder"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
class="com.example.fragmenttester5.MyEditTextFragment" />
<fragment
android:id="#+id/detailfragment_placeholder2"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
class="com.example.fragmenttester5.MyEditTextFragment" />
<Button
android:id="#+id/submit_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Submit all of it" />
</LinearLayout>
and in my MainActivity I hooked up the button to a new activity:
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button submitButton = (Button) findViewById(R.id.submit_button);
submitButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v){
Intent intent = new Intent(MainActivity.this, OtherActivity.class);
intent.putExtra("result1", "the_result_from_the_first_editText");
intent.putExtra("result2", "the_result_from_the_second_editText");
startActivity(intent);
}
});
}
}
I think I now need to define some kind of interface in the Fragment, but I can't find how. I read a couple examples and tutorials (like this one), but they make no sense to me at all. I don't understand the code given and I just don't understand how to adjust it for my use case.
So my question; can anybody help me to get the contents of the fragment from within the activity? Examples would be very very welcome since I'm just banging my head against the wall here..

You are right, that's kind of a standard way to pass data from a Fragment to an activity.
Basically you define a Listener interface which the Activity implements, and the Activity registers itself as a Listener with the Fragment.
Here's a simple example:
Fragment
class MyFragment extends Fragment {
interface Listener {
public void somethingHappenedInFragment(Object... anyDataYouWantToPassToActivity);
}
private Listener mListener;
public void setListener(Listener listener) {
mListener = listener;
}
// ... your code ...
// Now here you pass the data to the activity
mListener.somethingHappenedInFragment(some, data);
// ... more of your code
}
Activity
public MyActivity extends Activity implements MyFragment.Listener {
// ... your code ...
// creating the Fragment
MyFragment f = new MyFragment();
// register activity as listener
f.setListener(this);
// ... more of your code
// implementation of MyFragment.Listener interface
#Override
public void somethingHappenedInFragment(Object... anyDataYouWantToPassToActivity) {
// here you have the data passed from the fragment.
for (Object o : anyDataYouWantToPassToActivity {
System.out.println(o.toString();
}
}
}

On a high level, there are two tasks that you commonly need to solve with Fragments. The first is communicating data from an Activity to a Fragment. The second is communicating data from a Fragment to an Activity.
An Activity knows which Fragments it contains since it creates them, so it's easy to communicate that way - just call methods on the Fragment itself. But the inverse is not true; Fragments might be attached to any number of random Activities, so it doesn't know anything about it's parent.
The solution is to implement an interface that the Activity implements and the Fragment knows how to communicate with. That way, your Fragment has something it knows how to talk with. There are specific code examples for how to do it here: http://developer.android.com/guide/components/fragments.html#CommunicatingWithActivity
(In particular, check out the "Creating event callbacks to the activity" code examples).

So you'd create an Interface to talk with the Activity if the event happened in the Fragment. For situations like this, you can simply make an accessible method in the Fragment that the Activity can call. So
public class MyEditTextFragment extends Fragment {
private EditText mEditText;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.edit_text_fragment, container, false);
return view;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mEditText = (EditText) getView().findViewById(R.id.my_edit_text);
}
public Editable getText() {
return mEditText.getText();
}
}
Then
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final MyEditTextFragment fragment1 = (MyEditTextFragment)
getFragmentManager().findFragmentById(R.id.detailfragment_placeholder);
final MyEditTextFragment fragment2 = (MyEditTextFragment)
getFragmentManager().findFragmentById(R.id.detailfragment_placeholder2);
Button submitButton = (Button) findViewById(R.id.submit_button);
submitButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v){
String firstResult = fragment1.getText().toString();
String secondResult = fragment2.getText().toString();
Intent intent = new Intent(MainActivity.this, OtherActivity.class);
intent.putExtra("result1", firstResult);
intent.putExtra("result2", secondResult);
startActivity(intent);
}
});
}
}
This assumes that you assigned the Fragment tags in your FragmentTransaction. Be sure to check for null Fragments (omitted for brevity)

Activity will be received data from updateDetail() method in Fragment
//// Activity
public class RssfeedActivity extends Activity implements MyListFragment.OnItemSelectedListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_rssfeed);
Button btn = (Button) findViewById(R.id.btn);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.d("Annv - Fragment", "onClick here");
}
});
}
// if the wizard generated an onCreateOptionsMenu you can delete
// it, not needed for this tutorial
#Override
public void onRssItemSelected(String link) {
// DetailFragment fragment = (DetailFragment) getFragmentManager()
// .findFragmentById(R.id.detailFragment);
// if (fragment != null && fragment.isInLayout()) {
// fragment.setText(link);
// }
// Intent start = new Intent(this, RssfeedSecondActivity.class);
// startActivity(start);
DetailFragment fragment = (DetailFragment) getFragmentManager()
.findFragmentById(R.id.detailFragment);
if (fragment != null && fragment.isInLayout()) {
fragment.setText(link);
}
}
}
/// Fragment
public class MyListFragment extends Fragment {
private OnItemSelectedListener listener;
private OnItemStartActivityListener listenerStartAct;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_rsslist_overview,
container, false);
Button button = (Button) view.findViewById(R.id.button1);
Log.d("Annv - Fragment", "run on " + getActivity().toString());
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
updateDetail();
}
});
return view;
}
public interface OnItemSelectedListener {
public void onRssItemSelected(String link);
}
public interface OnItemStartActivityListener {
public void onRssStartActivity(String link);
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
if (activity instanceof OnItemSelectedListener) {
Log.d("Annv - Fragment", "activity " + activity.getLocalClassName());
listener = (OnItemSelectedListener) activity;
} else if (activity instanceof OnItemStartActivityListener) {
Log.d("Annv - Fragment", "activity " + activity.getLocalClassName());
listenerStartAct = (OnItemStartActivityListener) activity;
} else {
throw new ClassCastException(activity.toString()
+ " must implemenet MyListFragment.OnItemSelectedListener");
}
}
// May also be triggered from the Activity
public void updateDetail() {
// create fake data
// String newTime = String.valueOf(System.currentTimeMillis());
// // Send data to Activity
// listenerStartAct.onRssItemSelected(newTime);
if (getActivity() instanceof OnItemSelectedListener) {
listener.onRssItemSelected("start start");
} else {
String newTime = String.valueOf(System.currentTimeMillis());
listenerStartAct.onRssStartActivity(newTime);
}
}
}