Develop Reference

How to use SupportFragmentManager on a Fragment

I'm trying to use support fragment manager in a fragment but it says SupportFragmentManager doesn't exist in the current context.
Here's my code
private void Adapter_RateItemClick(object sender, DriversAdapterClickEventArgs e)
{
RatingFragment editAluminiFragment = new RatingFragment();
var trans = SupportFragmentManager.BeginTransaction();
editAluminiFragment.Show(trans, "Rate");
}
I used
using FragmentManager = Android.Support.V4.App.FragmentManager;
?
what should I do next

Firstly, there is documentation AndroidX Fragment class (it is similar for support v4, but you definitely should switch to AndroidX if you can). And as you can see there, there are two methods for working with fragments: getChildFragmentManager and getParentFragmentManager. I suppose you want to use child fragment manager to show some dialog, so in your case it will be
private void Adapter_RateItemClick(Object sender, DriversAdapterClickEventArgs e)
{
RatingFragment editAluminiFragment = new RatingFragment();
editAluminiFragment.Show(getChildFragmentManager(), "Rate");
}

Android prevent DialogFragment opening twice

I am trying to prevent my DialogFragment opening twice. Here is what I do:
I try to keep only one instance of my fragment. I create and add my fragment like this:
//MyFragment.java
public static MyFragment mInstance;
public static void instantiateFragment() {
MyFragment myFragment = MyFragment.getInstance();
if(!myFragment.isAdded()) {
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(myFragment, TAG);
ft.commit();
}
}
private static MyFragment getInstance() {
if(mInstance == null) {
mInstance = new MyFragment();
}
return mInstance;
}
And when a button is clicked, I intentionally try to add fragment twice like this:
MyFragment.instantiateFragment();
MyFragment.instantiateFragment();
But I get IllegalStateException: Fragment already added. Any ideas about that?
Thanks.

Indeed it's a problem with asynchronous commit of transactions, so as #Android jack stated you can use executePendingTransactions() like in this answer,
or even better use commitNow(),
or try something like this:
public static void instantiateFragment() {
Fragment myFragment = getSupportFragmentManager().findFragmentByTag(TAG);
if (myFragment == null) {
myFragment = MyFragment.getInstance();
FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
ft.add(myFragment, TAG);
ft.commit();
}
}

I think this has to do with the asynchronous behaviour of fragment transactions.Fragment Transactions are committed asynchronously. So at first call, your fragment is added but it is committed asynchronously.Again in your next call your fragment is not added as it is not committed yet so !myFragment.isAdded() returns false.Then while adding the fragment the previous transaction is committed due to which it raises exception.
Try to use this
getFragmentManager().executePendingTransactions();
before your (!myFragment.isAdded()) code.

How to get all sub/inner/nested Fragments of a Fragment?

It looks like it's possible to get all fragments of an Activity pretty easily. But how can I get all subfragments for a given fragment ?
This question is also related to getParentFragment API 16

You can do it in the same way -- just use the FragmentManager obtained using the Fragment instance's getChildFragmentManager() instead of the Activity FragmentManager. Of course, this assumes you're using a recompiled version of the support library with getFragments() not hidden, or are using reflection to get invoke that method.

The following solution is not perfect but it works in some extent :
If Android SDK is 17+, then it works fine
below SDK 17 it works for fragments at the root level (added directly to activity), and also works fine for fragments of level 1 (added to a fragment at root level).
for fragments of level >= 2, then it will always return a fragment of root level. It means that it is not possible to return the real parent of a fragment whose level is >=2, it will always return its ancestor at the root level.
And, unfortunately, it means you must have access to the activity class, so this solution is not really generic.
Here is the solution. The MyActivity class is given below.
public static Fragment getParentFragment(Fragment fragment) {
if( Build.VERSION.SDK_INT > Build.VERSION_CODES.JELLY_BEAN)
return fragment.getParentFragment();
MyActivity activity = (MyActivity)fragment.getActivity();
List<Fragment> fragmentList = activity.getActiveFragments();
if( fragmentList.contains( fragment) ) {
return null;
}
for( Fragment fragmentLevel1 : fragmentList ) {
if( fragmentLevel1.getFragmentManager() == fragment.getFragmentManager() ) {
return fragmentLevel1;
}
}
//this is not supposed to happen, it might be better to throw an exception
return null;
}
Where MyActivity is based on : Is there a way to get references for all currently active fragments in an Activity?
public class MyActivity {
List<WeakReference<Fragment>> fragList = new ArrayList<WeakReference<Fragment>>();
#Override
public void onAttachFragment (Fragment fragment) {
fragList.add(new WeakReference(fragment));
}
public List<Fragment> getActiveFragments() {
ArrayList<Fragment> ret = new ArrayList<Fragment>();
for(WeakReference<Fragment> ref : fragList) {
Fragment f = ref.get();
if(f != null) {
if(f.isVisible()) {
ret.add(f);
}
}
}
return ret;
}
}

JUnit testing for Android app with fragments

My Android App was built on Single Activity, multiple fragments based model.
I need to do unit testing for the app. I could write unit testcases for app which contains all activities using ActivityInstrumentationTestCase2 JUnit but not for app which contains fragments.
Please suggest the way to write JUnit testcases for fragments.
Thank you

See Android: Testing fragments
Copied for your reading pleasure with edits made for getFragmentManager() vs getSupportFragmentManager() and android:exported="false":
If you want to test a fragment in isolation, you need to create a Test FragmentActivity so your test can use that. The test activity will look something like this. Remember to declare it in your application’s manifest:
public class TestFragmentActivity extends FragmentActivity {
#Override
protected void onCreate(Bundle arg0) {
super.onCreate(arg0);
setContentView(R.layout.activity_fortests);
}
}
Layout:
<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"
>
<LinearLayout
android:id="#+id/activity_test_fragment_linearlayout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
/>
</RelativeLayout>
AndroidManifest:
...
<activity
android:name="your.package.name.TestFragmentActivity"
android:exported="false" />
...
Then in your test project, you can have a class like this to start the fragment:
public class FrameworkObjectsGeneratorFragmentTest
extends ActivityInstrumentationTestCase2<TestFragmentActivity> {
private TestFragmentActivity mActivity;
public FrameworkObjectsGeneratorFragmentTest() {
super(TestFragmentActivity.class);
}
#Override
protected void setUp() throws Exception {
super.setUp();
mActivity = getActivity();
}
private Fragment startFragment(Fragment fragment) {
FragmentTransaction transaction = mActivity.getFragmentManager().beginTransaction();
transaction.add(R.id.activity_test_fragment_linearlayout, fragment, "tag");
transaction.commit();
getInstrumentation().waitForIdleSync();
Fragment frag = mActivity.getFragmentManager().findFragmentByTag("tag");
return frag;
}
public void testFragment() {
FrameworkObjectsGeneratorFragment fragment = new FrameworkObjectsGeneratorFragment() {
//Override methods and add assertations here.
};
Fragment frag = startFragment(fragment);
}
}
The startFragment() method adds a fragment you specify to the ViewGroup in the TestActivity.
The good thing about testing fragments, as opposed to Activities, is that you can extends the Fragment to override protected fields and methods within which you can add assertions.
NOTE: Call getSupportFragmentManager() if you are using the support library.

java.lang.IllegalStateException: Activity has been destroyed

Working with Robolectric , I'm very new to android. I made a first test class using Activity. It worked nicely.
Now I want make a test for fragment.
#RunWith(RobolectricTestRunner.class)
public class LoginFragmentTest {
private LoginFragment fragment;
#Before
public void setup() {
fragment = new LoginFragment();
startFragment(fragment);
assertThat(fragment, notNullValue());
assertThat(fragment.getActivity(), notNullValue());
}
private void startFragment(LoginFragment fragment) {
FragmentManager fragmentManager = new FragmentActivity().getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(fragment, null);
fragmentTransaction.commit();
}
#Test
public void login() {
EditText idEditText = (EditText)fragment.getActivity().findViewById(R.id.main_id);
assertThat(idEditText, notNullValue());
}
}
This is my first test class for Fragment class. It throws
"java.lang.IllegalStateException: Activity has been destroyed" in startFragment#fragmentTransaction.commit().
Anyone knows how to fix this ?
You can find whole source from https://github.com/msbaek/frame-test
Thanks in advance !!

In my case, specifically, my problem was when creating the activity.
I was using
activity = Robolectric.buildActivity(MyActivity.class).get();
And it should be
activity = Robolectric.buildActivity(MyActivity.class).create().get();
Hope it helps someone :D

#RunWith(RobolectricTestRunner.class)
public class LoginFragmentTest {
private LoginFragment fragment;
#Before
public void setup() {
fragment = new LoginFragment();
startFragment();
assertThat(fragment, notNullValue());
assertThat(fragment.getActivity(), notNullValue());
}
private void startFragment() {
FragmentActivity activity = new FragmentActivity();
shadowOf(activity).callOnCreate(null);
shadowOf(activity).callOnStart();
shadowOf(activity).callOnResume();
FragmentManager fragmentManager = activity.getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.add(fragment, null);
fragmentTransaction.commit();
}
#Test
public void login() {
EditText idEditText = (EditText) fragment.getView().findViewById(R.id.main_id);
assertThat(idEditText, notNullValue());
}
}
This is working version. Following 3 lines are important(it's from robolectric source - DialogFragmentTest).
shadowOf(activity).callOnCreate(null);
shadowOf(activity).callOnStart();
shadowOf(activity).callOnResume();

The fragments are supposed to be displayed from an Activity. The flow should be:
allocate a new fragment object in a FragmentActivity class
get the fragment manager to add the newly allocated fragment
In your case you do not have a connection to a real activity. You allocate a FragmentActivity with new FragmentActivity() and try to get the support manager. While this compiles there is no "real" activity able to manage your fragment. Fragments can be added on activities already displayed and here it's not the case.
I recommend reading this page as it explains these things very well: http://developer.android.com/guide/components/fragments.html

That happened for me when I used fragmentTransaction.commitAllowingStateLoss(); from sub Fragment whose parent fragment had setRetainInstance(true); I had activity as property what lead to leaking activity on rotation.