Develop Reference

How can i call a method in my fragment from my activity?

Theoretically, lets say i have two classes with corresponding XML files - Activity and Frag
Activity.java
public class Activity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Fragment fragment = new Frag();
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.fragmentArea, fragment);
ft.commit();
}
}
Frag.java
public class Frag extends Fragment {
private TextView txtView;
public Frag() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_, container, false);
txtView = view.findViewById(R.id.textView);
return view;
}
public void setTextView(String str) {
txtView.setText(str);
}
}
activity xml
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.eksamen.chris.eksempelfragment.Activity">
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:id="#+id/fragmentArea">
</LinearLayout>
</android.support.constraint.ConstraintLayout>
Fragment xml
<FrameLayout 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"
tools:context="com.eksamen.chris.eksempelfragment.Frag">
<!-- TODO: Update blank fragment layout -->
<TextView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="Fragment"
android:id="#+id/textView"/>
</FrameLayout>
As you can see, i have the method setTextView() in my Frag class. Obviously enough, what i would like to do is to call that method from my Activity class.
I have tried grasping this for some hours now, and i really cannot figure out a way to do this. Every example/tutorial out there makes my app crash.
Could someone explain to me how this works, taken the example we have in hand into consideration? Or maybe there is a better way to provide the fragment with data from my activity?
I'd be grateful!
Edit: awful indentation, had some issues, trying to fix.

In order to pass data from Activity to Fragment , you have to use :
Bundle
which is a KEY VALUE data structure for passing values between fragments and activity so at your onCreate() in Activity class will be
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String str = "your_string_here";
// 1 -
Bundle bundle = new Bundle();
// 2 -
bundle.putString("KEY", str);
Fragment fragment = new Frag();
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
// 3 -
fragment.setArguments(bundle);
ft.replace(R.id.fragmentArea, fragment);
ft.commit(); }
and at your fragment
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_, container, false);
txtView = view.findViewById(R.id.textView);
// 4 - NOTE : Should hould the same key at the Activity class :
String str = getArguments().getString("KEY");
setTextView(str);
return view;
}

Implement Bottom Navigation View into a fragment

In my Android Studio project I want to implement into the MainActivity a NavigationDrawer with fragments and on every fragments a bottom navigation view.
This is the code of one fragment:
public class U16 extends Fragment{
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
getActivity().setTitle("TITOLO U16");
}
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
switch (item.getItemId()) {
case R.id.navigation_home:
fragmentTransaction.replace(R.id.content, new Calendario()).commit();
return true;
case R.id.navigation_dashboard:
fragmentTransaction.replace(R.id.content, new Palestre()).commit();
return true;
case R.id.navigation_notifications:
fragmentTransaction.replace(R.id.content, new Squadra()).commit();
return true;
}
return false;
}
};
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
BottomNavigationView navigation = (BottomNavigationView) getActivity().findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.content, new Calendario()).commit();
return inflater.inflate(R.layout.u16_layout, container, false);
}
}
I get this error:
FATAL EXCEPTION: main
Process: app.navigationdrawerfragment, PID: 21499
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.design.widget.BottomNavigationView.setOnNavigationItemSelectedListener(android.support.design.widget.BottomNavigationView$OnNavigationItemSelectedListener)' on a null object reference at app.navigationdrawerfragment.U16.onCreateView(U16.java:52)
I know that this error in into the procedure "OnCreateView" doing " navigation.setOnNavigationItemSelectedListener..."
This is the u16_layout.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="simone.biliato.navigationdrawerfragment.MainActivity">
<FrameLayout
android:id="#+id/content"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1">
</FrameLayout>
<android.support.design.widget.BottomNavigationView
android:id="#+id/navigation"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:background="?android:attr/windowBackground"
app:menu="#menu/navigation" />
</LinearLayout>
So, anyone tried to do the same?

You are trying do set someone that is isn't already created.
So move the code into the event onViewCreated, like this:
#Override
public void onViewCreated(View view, #Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
getActivity().setTitle("Titolo");
BottomNavigationView navigation = (BottomNavigationView) getActivity().findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.content, new Calendario()).commit();
return inflater.inflate(R.layout.u16_layout, container, false);
}
This will work :)

How to add Fragment into Activity in Android

I want add 2 fragment into activity, and when click on button switch between this fragments!
I want show Fragment_1 for by default in activity (my mean is : when running activity, show fragment_1) and when click on button switch between fragment_2 and fragment_1 !
I write below codes, and when running activity show fragment_1 but when click on button for switch between fragments, show me Force Close error.
FC error :
08-27 14:15:41.363 14224-14224/com.mohammad.nouri.diaryday E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.mohammad.nouri.diaryday, PID: 14224
java.lang.IllegalStateException: commit already called
at android.support.v4.app.BackStackRecord.commitInternal(BackStackRecord.java:641)
at android.support.v4.app.BackStackRecord.commit(BackStackRecord.java:621)
at com.mohammad.nouri.diaryday.Activities.LoginActivity$1.onClick(LoginActivity.java:58)
at android.view.View.performClick(View.java:4764)
at android.view.View$PerformClick.run(View.java:19844)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5349)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:908)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:703)
Activity codes:
public class LoginActivity extends AppCompatActivity {
private Context context;
private boolean status = false;
FragmentTransaction fT;
FragmentManager fM;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
context = this;
Glide.with(this).load(R.drawable.login_header_image)
.bitmapTransform(new BlurTransformation(context, 20))
.into((ImageView) findViewById(R.id.login_background));
fM = getSupportFragmentManager();
fT = fM.beginTransaction();
if (!status) {
LoginFragment f1 = new LoginFragment();
fT.add(R.id.login_cardView, f1);
fT.commit();
status = true;
}
FloatingActionButton f = (FloatingActionButton) findViewById(R.id.login_registerButton);
f.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if (!status) {
RegisterFragment f1 = new RegisterFragment();
fT.add(R.id.login_cardView, f1);
fT.commit();
status = true;
}else {
LoginFragment f2 = new LoginFragment();
fT.add(R.id.login_cardView, f2);
fT.commit();
status = false;
}
}
});
}
}
How can I fix it ? Thanks all <3

You only call commit() once in a FragmentTransaction which you already do in the onCreate(). So, just create a new FragmentTransaction within your fab:
FloatingActionButton f = (FloatingActionButton) findViewById(R.id.login_registerButton);
f.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if (!status) {
RegisterFragment f1 = new RegisterFragment();
fM.beginTransaction().add(R.id.login_cardView, f1)
.commit();
status = true;
}else {
LoginFragment f2 = new LoginFragment();
fM.beginTransaction().add(R.id.login_cardView, f2)
.commit();
status = false;
}
}
});

Instead of adding the fragments try replacing because you have already added once above.
MainActivity.java
public class MainActivity extends AppCompatActivity {
Button btnFragment;
LinearLayout fragmentContainer;
boolean toggleFlag = false;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
fragmentContainer = (LinearLayout) findViewById(R.id.fragment_container);
FragmentA fragmentA = new FragmentA();
final FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragmentA);
fragmentTransaction.commit();
btnFragment = (Button) findViewById(R.id.btn_fragment);
btnFragment.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
if(toggleFlag) {
FragmentA fragmentA = new FragmentA();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragmentA);
fragmentTransaction.commit();
} else {
FragmentB fragmentB = new FragmentB();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, fragmentB);
fragmentTransaction.commit();
}
toggleFlag = !toggleFlag;
}
});
}
}
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">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal">
<Button
android:id="#+id/btn_fragment"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Toggle Fragment" />
</LinearLayout>
<LinearLayout
android:id="#+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
</LinearLayout>
</LinearLayout>
FragmentA.java
public class FragmentA extends Fragment {
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootview = inflater.inflate(R.layout.layout_fragment_a, null);
return rootview;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
}
}
layout_fragment_a.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">
<ImageView
android:id="#+id/picture"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="#mipmap/ic_launcher"/>
<TextView
android:id="#+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Demo Fragment A"
android:textColor="#android:color/black"/>
</LinearLayout>
FragmentB.java
public class FragmentB extends Fragment {
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootview = inflater.inflate(R.layout.layout_fragment_b, null);
return rootview;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
}
}
layout_fragment_b.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">
<ImageView
android:id="#+id/picture"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="#mipmap/ic_launcher"/>
<TextView
android:id="#+id/text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Demo Fragment B"
android:textColor="#android:color/black"/>
</LinearLayout>

use this method to call fragment
rplaceFragment(Fragment fragment , int id){
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(id, fragment);
fragmentTransaction.commit();
}

Fragment's onDestroyView called but view is not being destroyed

The Android fragment lifecycle shows that when a fragment is added to the backstack and then removed/replaced, onDestroyView() is called, and later on, when the fragment returns to the layout from the backstack, onCreateView() is called.
From my understanding it means that the fragment's view is being destroyed and recreated. If the user has input text in an EditText in fragment A and goes to fragment B and then back to A, when the fragment comes back the EditText's contents will have been erased.
However, this is not happening in the following code; can anybody explain why? I have already verified that FragmentA's onDestroyView() is being called.
MainActivity.java
public class MainActivity extends FragmentActivity {
private Fragment currentFragment = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
addFragment(new FragmentA());
}
}
public void setCurrentFragment(Fragment fragment) {
this.currentFragment = fragment;
}
#Override
public void onBackPressed() {
if (currentFragment instanceof FragmentB) {
getSupportFragmentManager().popBackStackImmediate();
} else {
super.onBackPressed();
}
}
public void addFragment(Fragment fragment) {
getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment).addToBackStack(null).commit();
setCurrentFragment(fragment);
}
}
FragmentA.java
public class FragmentA extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_a, container, false);
final EditText editText = (EditText)view.findViewById(R.id.editText);
Button button = (Button)view.findViewById(R.id.button);
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
FragmentB fragmentB = new FragmentB();
Bundle arguments = new Bundle();
arguments.putString("text", editText.getText().toString());
fragmentB.setArguments(arguments);
((MainActivity)getActivity()).addFragment(fragmentB);
}
});
return view;
}
#Override
public void onDestroyView() {
super.onDestroyView();
Log.d("Tag", "FragmentA.onDestroyView() has been called.");
}
}
FragmentB.java
public class FragmentB extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_b, container, false);
TextView textView = (TextView)view.findViewById(R.id.textView);
textView.setText(getArguments().getString("text"));
return view;
}
}
activity_main.xml
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.fragmenttest.MainActivity"
tools:ignore="MergeRootFrame" />
fragment_a.xml
<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">
<EditText
android:id="#+id/editText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button" />
</LinearLayout>
fragment_b.xml
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/textView"
android:layout_width="match_parent"
android:layout_height="match_parent" />

Fragments in back stack retain their state in a Bundle. This includes the view hierarchy state with the current contents of EditTexts and such.

To destroy The Fragment .. Use This onDestroyView
or in onDetach
if (fragment != null) {
fragment = new YourFragment();
FragmentTransaction ft = getActivity().getFragmentManager().beginTransaction();
ft.remove(fragment);
ft.commit();
}

Android - Navigation drawer fragments

I have implemented navigation drawer in my android app. but now I want to be able to change the layout using fragments when the user clicks any list item in the navigation bar.
Here is what I have got so far:
XML
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/drawer_layout"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<FrameLayout
android:id="#+id/content_frame"
android:layout_width="match_parent"
android:background="#000000"
android:layout_height="match_parent" >
</FrameLayout>
<ListView android:id="#+id/left_drawer"
android:layout_width="220dp"
android:layout_height="match_parent"
android:layout_gravity="start"
android:choiceMode="singleChoice"
android:divider="#android:color/transparent"
android:dividerHeight="0dp"
android:background="#111"/>
</android.support.v4.widget.DrawerLayout>
Java File
public class MainActivity extends Activity {
final String[] data ={"one","two","three"};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, data);
final DrawerLayout drawer = (DrawerLayout)findViewById(R.id.drawer_layout);
final ListView navList = (ListView) findViewById(R.id.left_drawer);
navList.setAdapter(adapter);
navList.setOnItemClickListener(new AdapterView.OnItemClickListener(){
#Override
public void onItemClick(AdapterView<?> parent, View view, final int pos,long id){
drawer.setDrawerListener( new DrawerLayout.SimpleDrawerListener(){
#Override
public void onDrawerClosed(View drawerView){
super.onDrawerClosed(drawerView);
}
});
drawer.closeDrawer(navList);
}
});
}
}
Using the above code, I implemented navigation drawer in my app and I see "one", "two" and "Three" list items in the navigation drawer but nothing happens when I click on them except the drawer closes.
So, my question is :
How do I add the fragment functionality to the above given code?
I am beginner. Thanks in advance!

On click have
selectItem(pos);
Then
public void selectItem(int position)
{
switch(position)
{
case 0:
// fragment1
// use fragment transaction and add the fragment to the container
FragmentManager fragmentManager = getFragmentManager()
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
Fragment1 fragment = new Fragment1();
fragmentTransaction.add(R.id.content_frame, fragment);
fragmentTransaction.commit();
break;
case 1:
// fragment2
break;
case 2:
// fragment2
break;
}
}

use This:
public class MenuFragmentActivity extends FragmentActivity{
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.base_layout);
addFragments(new Sample(), false, false,
AndyConstants.CONTENT_PAGE);
}
public void addFragments(Fragment fragment, boolean animate,
boolean addToBackStack, String tag) {
FragmentManager manager = getSupportFragmentManager();
FragmentTransaction ft = manager.beginTransaction();
if (animate) {
ft.setCustomAnimations(R.anim.fragment_from_right,
R.anim.fragment_from_left, R.anim.fragment_from_right,
R.anim.fragment_from_left);
}
if (addToBackStack) {
ft.addToBackStack(tag);
}
ft.replace(R.id.content_frame, fragment);
ft.commit();
}
}
For Fragment:
public class Sample extends Fragment {
#Override
public void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
View view = inflater.inflate(R.layout.page, container, false);
return view;
}
}

After generate a Navigation Drawer Activity by File->New->Activity->Navigation Drawer Activity, here are 3 steps
First, go to app_bar_main.xml then
replace
<include layout="#layout/content_main"/>
by
<FrameLayout
android:id="#+id/frame_content"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
/>
Second, go to MainActivity -> onNavigationItemSelected then modify it like
public boolean onNavigationItemSelected(#NonNull MenuItem item) {
int id = item.getItemId();
Fragment fragment = null;
if (id == R.id.nav_camera) {
fragment = CameraFragment.newInstance();
} else if (id == R.id.nav_gallery) {
fragment = GalleryFragment.newInstance();
} else if (id == R.id.nav_slideshow) {
fragment = SlideShowFragment.newInstance();
}
FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frame_content, fragment).commit();
setTitle(item.getTitle());
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
Finally, create Fragment class, example a Fragment
public class CameraFragment extends Fragment{
public static CameraFragment newInstance() {
Bundle args = new Bundle();
CameraFragment fragment = new CameraFragment();
fragment.setArguments(args);
return fragment;
}
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container,
#Nullable Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_camera, null, false);
return rootView;
}
}
Demo project