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How to make changes in widget in parent activity based on the logic written in fragment

As an exercise i am writing a simple Ebook reader app. This has only 1 Main Activity with 3 widgets on it, 2 buttons (Previous, Next) and one Fragment container(I have used Frame Layout). All pages are different fragments that I have created that will go inside the container, and these fragments have only 1 scrollable text view that will only display text. when "next" button is pressed it should go to page2(fragment2) and when previous is pressed it should go back(previous fragment).
My problem is I don't want the "previous" button to show up on the initial screen (page1) and similarly the "next" button should not be observed on the last page.
The approach i tried was, in my fragment1(page1) class, i wrote an if condition like,
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup
container, #Nullable Bundle savedInstanceState) {
View view=inflater.inflate(R.layout.fragmentpage1,container,false);
textView1=(TextView)view.findViewById(R.id.tview);
**View listView = getActivity().findViewById(R.id.previous);**
textView1.setText(R.string.page1);
if (textView1.isEnabled()){
listView.setVisibility(View.INVISIBLE);
}
return view;
}
I am checking if textview1(the first fragment) is present or not , if yes then hide the previous button on the Main Activity. This works but it completely hides the previous button even when i go to page2. I tried all possible "is" options but none of them are giving me the results I want.
One workaround that i found was to add "setvisibility" of previous button to all fragments, so on fragment1 it is invisible and then on fragment2 i changed that to visible. But that becomes lengthy if there are 100s of fragments(pages).
Please provide me with a simple solution, I am new to Android.
Below is my Main Activity code:(Do let me know if any changes needs to be done to make code more clean)
public class MainActivity extends FragmentActivity {
Fragment fragment;
FragmentManager fm=getSupportFragmentManager();
FragmentTransaction ft;
private static Button next;
private static Button previous;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
next=(Button)findViewById(R.id.next);
previous=(Button)findViewById(R.id.previous);
create();
}
public void create(){
fragment= new FragmentPage1();
ft= fm.beginTransaction();
ft.add(container,fragment);
ft.commit();
}
public void next(View view){
fragment= new FragmentPage2();
ft= fm.beginTransaction();
ft.replace(container,fragment);
ft.commit();
}
}

Maybe you can try to use the getItem() method in FragmentPagerAdapter class.
Try to disable or enable your buttons using the switch case. Hope this can help =)

Android - Blank fragment when returning from backstack

I have a view that shows a List of Properties, at the bottom of the screen there's a button that opens a fragment containing a MapView.
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.find_property_btn_map:
PropertyMapFragment fragment = PropertyMapFragment.newInstance(false, null);
getActivity().getSupportFragmentManager().beginTransaction()
.addToBackStack(null)
.replace(((ViewGroup) getView().getParent()).getId(), fragment, PropertyMapFragment.class.getSimpleName())
.commit();
break;
}
}
The onCreateView method for my Properties fragments is as follows
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
mRootView = inflater.inflate(R.layout.fragment_properties_list, container, false);
getmBtnMap().setOnClickListener(this);
getmBtnSaveSearch().setOnClickListener(this);
getmBtnSort().setOnClickListener(this);
getmListView().setAdapter(getPropertyAdapter());
getmListView().setOnItemClickListener(this);
getmListView().setOnScrollListener(this);
getmListView().setScrollingCacheEnabled(false);
searchProperties();
return mRootView;
}
searchProperties(); takes care of calling a Web Service and filling the ArrayAdapter.
The thing is that, when I open the MapFragment and then press the back button, my Property fragment is blank and the buttons do not respond to onClick events.
I tried debugging and saw that onCreateView() is being called when coming back to Property fragment, but the buttons are no longer working and the listview is nowhere to be seen.
What am I doing wrong?

If you are trying to launch that web view from a fragment, then try to use add fragment instead of replace.
For example :
getActivity().getSupportFragmentManager().beginTransaction()
.addToBackStack(null)
.replace(YOUR_CONTAINER_ID, fragment, PropertyMapFragment.class.getSimpleName())
.commit();
The code above is replace that fragment container with the new one and not adding that fragment on top of that. So when you do a replace fragment with that ID, it just replaces that view with new one.
Now,
Same code but with add:
getActivity().getSupportFragmentManager().beginTransaction()
.addToBackStack(null)
.add(YOUR_CONTAINER_ID, fragment, PropertyMapFragment.class.getSimpleName())
.commit();
Now, that web view fragment that you have will be added to the view/fragment and now when you press back from that web view, you previous fragment will be visible.
Just make sure that that the ID you are replacing is the same as the one in which you have all the other properties.
Maybe i misinterpreted the question so please correct me in that context.
Hope this helps.

addToBackStack() <--dont include this for your first fragment.-->
if(getSupportFragmentManager().getBackStackEntryCount() !=1){
fragmentTransaction.addToBackStack(null);
}

How can I maintain a child view's state when switching fragments?

I am having a hard time understanding how the fragment lifecycle relates to switching between fragments in the back stack. Please bear with me if my question exposes more than one misconception.
Here is my code:
public class SomeFragment extends Fragment {
private SomeCustomView customView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.some_fragment, container, false);
return view;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
// Create the child view
customView = (SomeCustomView) getView().findViewById(R.id.some_fragment_child_view);
customView.initializeMyCustomView();
}
}
As you can see, my fragment has a child view. The child view is a custom one. Here's code:
public class SomeCustomView extends SurfaceView implements SurfaceHolder.Callback {
private boolean aVariableWhichMustPersistForLifetimeOfApplication;
}
Whenever this fragment is added to the back stack and then later restored, the variable customView is recreated, and so I loose the value of aVariableWhichMustPersistForLifetimeOfApplication. This is creating all sorts of problems for me.
The application started out using an Activity that only displayed SomeCustomView and there were no fragments. Now I have to add functionality and so I have turned the custom view into a fragment, and thus I arrive at this problem.

I found an answer which works for me. The FragmentTransaction class has a number of methods which allow you to switch fragments in/out. (Android documentation for FragmentTransaction is here and a great StackOverflow explanation is here.)
In my case, I wanted SomeFragment to never loose the data contained in its view. To do this, use this code:
SomeFragment fragment = new SomeFragment();
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.add(R.id.activity_fragment_placeholder, fragment, "some_fragment");
transaction.commit();
and then later:
getFragmentManager().beginTransaction().hide(fragment).commit();
You can now add/attach a different fragment to R.id.activity_fragment_placeholder. Notice that I'm using hide() rather than replace(), that's the key difference that keeps the view from being destroyed. When you want the fragment back, you can use show() or Android will do this automatically when the user clicks "Back" if you use addToBackStack() when adding/attaching your other fragment.

How to replace a Fragment on button click of that fragment?

I have an activity containing multiple fragments. Activity initially have fragment and in it have two buttons. Upon clicking this button I have to replace the fragment by new fragment. Each fragment has various widgets and replace the current fragment as various events.
This is my problem. How can I achieve this?
Suggest me ideas.

you can replace fragment by FragmentTransaction.
Here you go.
Make an interface.
public interface FragmentChangeListener
{
public void replaceFragment(Fragment fragment);
}
implements your Fragment holding activity with this interface.
public class HomeScreen extends FragmentActivity implements
FragmentChangeListener {
#Override
public void replaceFragment(Fragment fragment) {
FragmentManager fragmentManager = getSupportFragmentManager();;
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(mContainerId, fragment, fragment.toString());
fragmentTransaction.addToBackStack(fragment.toString());
fragmentTransaction.commit();
}
}
Call this method from Fragments like this.
//In your fragment.
public void showOtherFragment()
{
Fragment fr=new NewDisplayingFragment();
FragmentChangeListener fc=(FragmentChangeListener)getActivity();
fc.replaceFragment(fr);
}
Hope this will work!
NOTE: mContainerId is id of the view who is holding the fragments inside.
You should override Fragment's onString() method as well.

Well even I am learning android...
I solved same problem recently, "How to Change Fragment On button's click event".
buttonName.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
FragmentTransaction fragmentTransaction = getActivity()
.getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.frame1, new Homefragment());
fragmentTransaction.commit();
}
});
Here frame1 is id of FrameLayout which have define in my DrawerLayer's XML.
So now whenever I want fragment transaction I use this code. Each time it will replace frame1 instated of your last fragment.
FragmentTransaction fragmentTransaction = getActivity()
.getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.frame1, new newfragment());
fragmentTransaction.commit()
Hope this will help..

You can use the following to replace a fragment on button click of that fragment:
getFragmentManager().beginTransaction().replace(R.id.main_content, new insertFragmentNameHere()).addToBackStack(null).commit();

Define an interface and call it IChangeListener (or something like that) and define a method inside which will do the work (ex, changeFragment()) (or call another method which will do the work) for changing the fragment).
Make your activity implement the interface, or make an anonymous class within the activity implement it.
Make a paramerized constructor of your fragment, which accepts a IChangeListener parameter.
When initializing the fragment, pass your IChangeListener implementation (the anonymous class or the activity, implementing it)
Make the onClick listener of the button call the changing method of the IChangeListener.

From the future 2017 and after, there exists different libraries that triggers Events using Bus and now you can use it to tell the activity when an event is trigger in a fragment that it owns.
Refer to:
RxBus with RxJava
You can check new architectures suggested by Google
ViewModel
Don't use the approach in the accepted answer, get really ugly with more than 3 different events from fragments

you can try this code it's work fine with me , inflate the layout to view , Define the buton and on click ,
Button btn_unstable;
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_home,container,false);
btn_unstable = (Button)view.findViewById(R.id.btn_unstable);
btn_unstable.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.fragment_replace, new UnstableFragment()).commit();
}
});
return view;
}

New layouts in TabHost

I'm using tabHost in my application but in one of the views (corresponding to one of the tabs) I have a button that have to take me to another activity and then another layout. The question is: how do I get this new layout can continue to have access to the tabs? or better say, How do I load this new layout inside the FrameLayout ?.
Here I have uploaded what I'm trying to do: http://imageshack.us/photo/my-images/541/exampleu.png/
Thanks in advance.!
Pd: I'm new in Android, maybe is there a better way to achieve my purpouse without using TabActivity. I'm open to any suggestion.
EDITED: so I decided to use Fragments as I was suggested. And now I have the following:
AplicationActivity extends FragmentActivity
ClientActivity extends Fragment
SettingsActivity extends Fragment
DataClientActivity extends Fragment
and the following layouts:
activity_aplicacion
activity_client
activity_settings
activity_data_client
The activity_aplicacion.xml has TabHost, FrameLayout and TabWidget and from these I can go to ClientActivity and SettingsActivity using tabs.
In ClientActivity I have a button called "new" and when I press this button I want to go to
DataClientActivity. So, in ClientActivity I have te following:
public void onClickNew(View view){
DataClientActivity fragmentDataClient = new DataClientActivity ();
final FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(android.R.id.tabcontent,fragmentDataClient , "fragmentDataClient ");
ft.addToBackStack(null);
ft.commit();
}
But when I run my app, I got the folling error:
05-04 21:55:04.780: E/AndroidRuntime(7515): java.lang.IllegalStateException: Could not find a method onClickNew(View) in the activity class com.n.r.AplicationActivity for onClick handler on view class android.widget.Button with id 'buttonNew'
So I'm a little confuse rigth now. Why should I have the onClickNew method in AplicationActivity and not in ClientActivity where I have the button?
EDITED 2: I found the solution for this:
public class ClientActivity extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
View view = inflater.inflate(R.layout.activity_clientes, container, false);
**// Register for the Button.OnClick event
Button b = (Button)view.findViewById(R.id.buttonNew);
b.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// Toast.makeText(Tab1Fragment.this.getActivity(), "OnClickMe button clicked", Toast.LENGTH_LONG).show();
Log.e("onClickNuevo2 ", "inicio");
DataClientActivity fragmentDataClient= new DataClientActivity();
final FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(android.R.id.tabcontent,fragmentDataClient, "fragmentDataClient");
ft.addToBackStack(null);
ft.commit();
}
});**
return view;
}
}
I just needed to register the onClick listener to my button inside my ClientActivity. Now every works perfectly!. Thanks so much Divya Motiwala :) and thanks to this link: http://thepseudocoder.wordpress.com/2011/10/04/android-tabs-the-fragment-way/#comment-410

You can use Fragments instead of activites inside Tab. And on click of button, you can replace existing fragment with a new one like this :
final FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.realtabcontent,newFrag, "New Fragment");
ft.addToBackStack(null);
ft.commit();
In ft.replace 1st parameter is the frameLayout to which fragment is to be attached, second is the fragment class object to be instatiated and third is the tag name.