I am creating an app with Fragments and in one of them, I created a non-default constructor and got this warning:
Avoid non-default constructors in fragments: use a default constructor plus Fragment#setArguments(Bundle) instead
Can someone tell me why this is not a good idea?
Can you also suggest how I would accomplish this:
public static class MenuFragment extends ListFragment {
public ListView listView1;
Categories category;
//this is my "non-default" constructor
public MenuFragment(Categories category){
this.category = category;
}....
Without using the non-default constructor?
It seems like none of the answers actually answer "why use bundle for passing parameters rather than non default constructors"
The reason why you should be passing parameters through bundle is because when the system restores a fragment (e.g on config change), it will automatically restore your bundle.
The callbacks like onCreate or onCreateView should read the parameters from the bundle - this way you are guaranteed to restore the state of the fragment correctly to the same state the fragment was initialised with (note this state can be different from the onSaveInstanceState bundle that is passed to the onCreate/onCreateView)
The recommendation of using the static newInstance() method is just a recommendation. You can use a non default constructor but make sure you populate the initialisation parameters in the bundle inside the body of that constructor. And read those parameters in the onCreate() or onCreateView() methods.
Make a bundle object and insert your data (in this example your Category object). Be careful, you can't pass this object directly into the bundle, unless it's serializable.
I think it's better to build your object in the fragment, and put only an id or something else into bundle. This is the code to create and attach a bundle:
Bundle args = new Bundle();
args.putLong("key", value);
yourFragment.setArguments(args);
After that, in your fragment access data:
Type value = getArguments().getType("key");
That's all.
Your Fragment shouldn't have constructors because of how the FragmentManager instantiates it.
You should have a newInstance() static method defined with the parameters you need, then bundle them and set them as the arguments of the fragment, which you can later access with the Bundle parameter.
For example:
public static MyFragment newInstance(int title, String message) {
MyFragment fragment = new MyFragment();
Bundle bundle = new Bundle(2);
bundle.putInt(EXTRA_TITLE, title);
bundle.putString(EXTRA_MESSAGE, message);
fragment.setArguments(bundle);
return fragment ;
}
And read these arguments at onCreate:
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
title = getArguments().getInt(EXTRA_TITLE);
message = getArguments().getString(EXTRA_MESSAGE);
//...
}
This way, if detached and re-attached, the object state can be stored through the arguments, much like bundles attached to Intents.
If you use parameter for some class. try this
SomeClass mSomeInstance;
public static final MyFragment newInstance(SomeClass someInstance){
MyFragment f = new MyFragment();
f.mSomeInstance = someInstance;
return f;
}
I think, there is no difference between static constructor and two constructors (empty and parametrized one that stores arguments into a Fragment's arguments bundle), most probably, this rule of thumb is created to reduce probability of forgetting to implement no-arg constructor in Java, which is not implicitly generated when overload present.
In my projects I use Kotlin, and implement fragments with a primary no-arg constructor and secondary constructor for arguments which just stores them into a bundle and sets it as Fragment arguments, everything works fine.
If fragment uses non-default constructors after configuration changing the fragment will lose all data.
Related
I know with Fragments we cannot use its constructor because the system needs the empty one. So to pass data we need to use a static method and bundles like
public static A newInstance(int myInt){
A myA = new A();
Bundle args = new Bundle();
args.putInt("myInt", someInt);
myA.setArguments(args);
return myA;
}
Okay so far so good.
But what if I want to generify this?
public abstract class C{
private int myInt;
//Here I cannot use the newInstance because I cannot create an instance of an abstract class
}
The outcome should be that I have constructs like this
public class A extends C{
//Some stuff that needs myInt which is stored in superclass because every subclass fragment needs it
}
public class B extends C{
//Some completly other stuff that also needs myInt
}
Both A and B need myInt so I would like to have a newInstance method provided by the superclass that I can call and the outcome should be a instance of A or B. How to do this/Is this possible?
In class C you can store the instance variable myInt, and then override onCreate() and in that extract the myInt value from the arguments bundle.
When creating a new A (A.getInstance(...)), you need to put the myInt value in the argument bundle. You need to do the same thing when creating a new B. To avoid copy-pasting code, you can add a helper method in C called (for example) createArgumentsBundle(myInt), that creates a new bundle with myInt in it and then send back the bundle.
It is not mandatory to have a static method in fragment class to create it's instance. You can create it from outside as well. A Parent class usually is not supposed to know about its child classes.
Retrieve the Bundle arguments from the base class C and set myInt there.
A and B will get the access. Make sure myInt has a protected access modifier.
I'm looking to find a solution on how to inject fragment and pass arguments to it.
And i didn't find any proper solution because injecting the fragment means by the constructor which is not safe for states.
Is there any way to do this, without calling the newInstance pattern ?
Thanks,
Best.
Because Android manages the lifecycle of your Fragment, you should separate the problems of passing state into the Fragment through its bundle and injecting the Fragment with injectable deps. Usually, the best way to separate these is by providing a static factory method, which you might be calling the newInstance pattern.
public class YourFragment extends Fragment {
// Fragments must have public no-arg constructors that Android can call.
// Ideally, do not override the default Fragment constructor, but if you do
// you should definitely not take constructor parameters.
#Inject FieldOne fieldOne;
#Inject FieldTwo fieldTwo;
public static YourFragment newInstance(String arg1, int arg2) {
YourFragment yourFragment = new YourFragment();
Bundle bundle = new Bundle();
bundle.putString("arg1", arg1);
bundle.putInt("arg2", arg2);
yourFragment.setArguments(bundle);
return yourFragment;
}
#Override public void onAttach(Context context) {
// Inject here, now that the Fragment has an Activity.
// This happens automatically if you subclass DaggerFragment.
AndroidSupportInjection.inject(this);
}
#Override public void onCreate(Bundle bundle) {
// Now you can unpack the arguments/state from the Bundle and use them.
String arg1 = bundle.getString("arg1");
String arg2 = bundle.getInt("arg2");
// ...
}
}
Note that this is a different type of injection than you may be used to: Rather than getting a Fragment instance by injecting it, you are telling the Fragment to inject itself later once it has been attached to an Activity. This example uses dagger.android for that injection, which uses subcomponents and members-injection methods to inject #Inject-annotated fields and methods even when Android creates the Fragment instance outside of Dagger's control.
Also note that Bundle is a general key-value store; I've used "arg1" and "arg2" instead of coming up with more creative names, but you can use any String keys you'd like. See Bundle and its superclass BaseBundle to see all of the data types Bundle supports in its get and put methods. This Bundle is also useful for saving Fragment data; if your app is interrupted by a phone call and Android destroys your Activity to save memory, you can use onSaveInstanceState to put form field data into the Bundle and then restore that information in onCreate.
Finally, note that you don't need to create a static factory method like newInstance; you could also have your consumers create a new YourFragment() instance and pass in a particular Bundle design themselves. However, at that point the Bundle structure becomes a part of your API, which you may not want. By creating a static factory method (or Factory object or other structure), you allow the Bundle design to be an implementation detail of your Fragment, and provide a documented and well-kept structure for consumers to create new instances.
I have the following constructor inside a fragment:-
public PlaceDialogFragment(Place place, DisplayMetrics dm){
super();
this.mPlace = place;
this.mMetrics = dm;
}
I have also tried this:-
public static final DialogFragment newInstance(Place place, DisplayMetrics dm)
{
DialogFragment fragment = new DialogFragment();
Bundle bundle = new Bundle(2);
bundle.putParcelable("Place", place);
bundle.putLong("Metrics", dm);
fragment.setArguments(bundle);
return fragment ;
}
But There is an error on bundle.putLong("Metrics", dm) line
Here Place is a class which implements the Parceable interface
But i get an error saying:-
Avoid non-default constructors in fragments: use a default constructor plus Fragment#setArguments(Bundle) instead
Any suggestions how to resolve this?
The reason you should use default constructors and pass arguments as bundles is because when the system restores your fragment state, it's gonna call the default constructor and restore the bundle. If you get your parameters from the bundle, then you can restore the state correctly.
Using your current method, everything you do in your custom constructor will be lost when the fragment is recreated.
See this answer for an example.
Use setArguments instead, while transacting the fragment, pass the constructor params in bundle, then use them in fragment using getArguments()
How to use setArguments() and getArguments() methods in Fragments?
What's the point of setArguments?
http://developer.android.com/reference/android/app/Fragment.html
You added :
bundle.putLong("Metrics", dm);
Do like this:
bundle.putFloat("Metrics_density", dm.density);
Refer to DisplatMetrics documentation and add arguments separately, or add DisplayMetrics object as static in your Application memory, and use it from anywhere.
DisplayMetrics is not a Long object, not even parcelable, add relevant DisplayMetrics fields in bundle instead.
public static final PlaceDialogFragment newInstance(Place place, DisplayMetrics dm)
{
PlaceDialogFragment fragment = new DialogFragment();
Bundle bundle = new Bundle(2);
bundle.putParcelable("Place", place);
bundle.putFloat("Metrics_density", dm.density);
//bundle.putFloat("Metrics_other", dm.<other fields>);
fragment.setArguments(bundle);
return fragment ;
}
Note : Don't use public constructor with parameters.
The error message is right!
Avoid the use of Parameterized constructors to Fragment/Activity..
You can do "quick-fix" by going into Lint settings and excluding the rule + adding a default constructor. But quick fix is not the way. This will result in problem.
Consider this case, you just rotate the screen, then your fragment gets destroyed and recreated when you call super.onCreate(savedState) of your activity, which will call default constructor => this results in NullPointerException.
So respect the Android Lint, make use of setArguments() to pass the instance of Place. If Place is your model class, make it Parcelable
you can get arguments by calling getArguments() inside your fragment
Ideally, a fragment needs to reconstruct itself using only its arguments. A parameterised constructor does not work well for this as the parameters are lost in the case of a (for example) device orientation change (although you can mitigate this with a call to setRetainInstance).
Use a static method instead of a constructor to create your fragment.
e.g.
public static MyFragment newInstance() {
MyFragment f = new FragStateList_();
Bundle args = new Bundle();
args.putInt("someInt", someInt);
args.putString("someString", someString);
f.setArguments(args);
return f;
}
You should then include a default constructor so the system car re-create your fragment when it needs to.
In your updated question, you are attempting to place a DisplayMetrics objects into the bundle as a Long. The types are not compatible. Do not pass in the DisplayMetrics. Instead, try this in your fragment to get the DisplayMetrics object.
DisplayMetrics metrics = new DisplayMetrics();
getActivity().getWindowManager().getDefaultDisplay().getMetrics(metrics);
Ideally, a fragment needs to reconstruct itself using only its arguments. A parameterised constructor does not work well for this as the parameters are lost in the case of a (for example) device orientation change (although you can mitigate this with a call to setRetainInstance).
Like Kuffs wrote, the proper way to do this is to have a static method that calls a (default) constructor and after it is initialized, it adds your custom values. You can place arguments in that method, for example:
public static PlaceDialogFragment newInstance(Place place, DisplayMetrics dm) {
PlaceDialogFragment f = new PlaceDialogFragment(); //alternatively new Fragment()
f.mPlace = place;
f.mMetrics = dm;
return f;
}
Then from you Activity, you call it like:
PlaceDialogFragment pdf = PlaceDialogFragment.newInstance(param1, param2);
I recently grew tired of constantly having to know String keys to pass arguments into Bundles when creating my Fragments. So I decided to make constructors for my Fragments that would take the parameters I wanted to set, and put those variables into the Bundles with the correct String keys, therefore eliminating the need for other Fragments and Activities needing to know those keys.
public ImageRotatorFragment() {
super();
Log.v(TAG, "ImageRotatorFragment()");
}
public ImageRotatorFragment(int imageResourceId) {
Log.v(TAG, "ImageRotatorFragment(int imageResourceId)");
// Get arguments passed in, if any
Bundle args = getArguments();
if (args == null) {
args = new Bundle();
}
// Add parameters to the argument bundle
args.putInt(KEY_ARG_IMAGE_RES_ID, imageResourceId);
setArguments(args);
}
And then I pull out those arguments like normal.
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.v(TAG, "onCreate");
// Set incoming parameters
Bundle args = getArguments();
if (args != null) {
mImageResourceId = args.getInt(KEY_ARG_IMAGE_RES_ID, StaticData.getImageIds()[0]);
}
else {
// Default image resource to the first image
mImageResourceId = StaticData.getImageIds()[0];
}
}
However, Lint took issue with this, saying not to have subclasses of Fragment with constructors with other parameters, requiring me to use #SuppressLint("ValidFragment") to even run the app. The thing is, this code works perfectly fine. I can use ImageRotatorFragment(int imageResourceId) or the old school method ImageRotatorFragment() and call setArguments() manually on it. When Android needs to recreate the Fragment (orientation change or low memory), it calls the ImageRotatorFragment() constructor and then passes the same argument Bundle with my values, which get set correctly.
So I have been searching for the "suggested" approach and see a lot of examples using newInstance() to create Fragments with parameters, which seems to do the same thing my constructor is. So I made my own to test it, and it works just as flawlessly as before, minus Lint whining about it.
public static ImageRotatorFragment newInstance(int imageResourceId) {
Log.v(TAG, "newInstance(int imageResourceId)");
ImageRotatorFragment imageRotatorFragment = new ImageRotatorFragment();
// Get arguments passed in, if any
Bundle args = imageRotatorFragment.getArguments();
if (args == null) {
args = new Bundle();
}
// Add parameters to the argument bundle
args.putInt(KEY_ARG_IMAGE_RES_ID, imageResourceId);
imageRotatorFragment.setArguments(args);
return imageRotatorFragment;
}
I personally find that using constructors is a much more common practice than knowing to use newInstance() and passing parameters. I believe you can use this same constructor technique with Activities and Lint will not complain about it. So basically my question is, why does Google not want you to use constructors with parameters for Fragments?
My only guess is so you don't try to set an instance variable without using the Bundle, which won't get set when the Fragment gets recreated. By using a static newInstance() method, the compiler won't let you access an instance variable.
public ImageRotatorFragment(int imageResourceId) {
Log.v(TAG, "ImageRotatorFragment(int imageResourceId)");
mImageResourceId = imageResourceId;
}
I still don't feel like this is enough reason to disallow the use of parameters in constructors. Anyone else have insight into this?
I personally find that using constructors is a much more common practice than knowing to use newInstance() and passing parameters.
The factory method pattern is used fairly frequently in modern software development.
So basically my question is, why does Google not want you to use constructors with parameters for Fragments?
You answered your own question:
My only guess is so you don't try to set an instance variable without using the Bundle, which won't get set when the Fragment gets recreated.
Correct.
I still don't feel like this is enough reason to disallow the use of parameters in constructors.
You are welcome to your opinion. You are welcome to disable this Lint check, either on a per-constructor or per-workspace fashion.
Android only recreates fragments it kills using default constructor, so any initialization we do in additional constructors will be lost.Hence data will be lost.
I have seen two general practices to instantiate a new Fragment in an application:
Fragment newFragment = new MyFragment();
and
Fragment newFragment = MyFragment.newInstance();
The second option makes use of a static method newInstance() and generally contains the following method.
public static Fragment newInstance()
{
MyFragment myFragment = new MyFragment();
return myFragment;
}
At first, I thought the main benefit was the fact that I could overload the newInstance() method to give flexibility when creating new instances of a Fragment - but I could also do this by creating an overloaded constructor for the Fragment.
Did I miss something?
What are the benefits of one approach over the other? Or is it just good practice?
If Android decides to recreate your Fragment later, it's going to call the no-argument constructor of your fragment. So overloading the constructor is not a solution.
With that being said, the way to pass stuff to your Fragment so that they are available after a Fragment is recreated by Android is to pass a bundle to the setArguments method.
So, for example, if we wanted to pass an integer to the fragment we would use something like:
public static MyFragment newInstance(int someInt) {
MyFragment myFragment = new MyFragment();
Bundle args = new Bundle();
args.putInt("someInt", someInt);
myFragment.setArguments(args);
return myFragment;
}
And later in the Fragment onCreate() you can access that integer by using:
getArguments().getInt("someInt", 0);
This Bundle will be available even if the Fragment is somehow recreated by Android.
Also note: setArguments can only be called before the Fragment is attached to the Activity.
This approach is also documented in the android developer reference: https://developer.android.com/reference/android/app/Fragment.html
The only benefit in using the newInstance() that I see are the following:
You will have a single place where all the arguments used by the fragment could be bundled up and you don't have to write the code below everytime you instantiate a fragment.
Bundle args = new Bundle();
args.putInt("someInt", someInt);
args.putString("someString", someString);
// Put any other arguments
myFragment.setArguments(args);
Its a good way to tell other classes what arguments it expects to work faithfully(though you should be able to handle cases if no arguments are bundled in the fragment instance).
So, my take is that using a static newInstance() to instantiate a fragment is a good practice.
There is also another way:
Fragment.instantiate(context, MyFragment.class.getName(), myBundle)
While #yydl gives a compelling reason on why the newInstance method is better:
If Android decides to recreate your Fragment later, it's going to call
the no-argument constructor of your fragment. So overloading the
constructor is not a solution.
it's still quite possible to use a constructor. To see why this is, first we need to see why the above workaround is used by Android.
Before a fragment can be used, an instance is needed. Android calls YourFragment() (the no arguments constructor) to construct an instance of the fragment. Here any overloaded constructor that you write will be ignored, as Android can't know which one to use.
In the lifetime of an Activity the fragment gets created as above and destroyed multiple times by Android. This means that if you put data in the fragment object itself, it will be lost once the fragment is destroyed.
To workaround, android asks that you store data using a Bundle (calling setArguments()), which can then be accessed from YourFragment. Argument bundles are protected by Android, and hence are guaranteed to be persistent.
One way to set this bundle is by using a static newInstance method:
public static YourFragment newInstance (int data) {
YourFragment yf = new YourFragment()
/* See this code gets executed immediately on your object construction */
Bundle args = new Bundle();
args.putInt("data", data);
yf.setArguments(args);
return yf;
}
However, a constructor:
public YourFragment(int data) {
Bundle args = new Bundle();
args.putInt("data", data);
setArguments(args);
}
can do exactly the same thing as the newInstance method.
Naturally, this would fail, and is one of the reasons Android wants you to use the newInstance method:
public YourFragment(int data) {
this.data = data; // Don't do this
}
As further explaination, here's Android's Fragment Class:
/**
* Supply the construction arguments for this fragment. This can only
* be called before the fragment has been attached to its activity; that
* is, you should call it immediately after constructing the fragment. The
* arguments supplied here will be retained across fragment destroy and
* creation.
*/
public void setArguments(Bundle args) {
if (mIndex >= 0) {
throw new IllegalStateException("Fragment already active");
}
mArguments = args;
}
Note that Android asks that the arguments be set only at construction, and guarantees that these will be retained.
EDIT: As pointed out in the comments by #JHH, if you are providing a custom constructor that requires some arguments, then Java won't provide your fragment with a no arg default constructor. So this would require you to define a no arg constructor, which is code that you could avoid with the newInstance factory method.
EDIT: Android doesn't allow using an overloaded constructor for fragments anymore. You must use the newInstance method.
Some kotlin code:
companion object {
fun newInstance(first: String, second: String) : SampleFragment {
return SampleFragment().apply {
arguments = Bundle().apply {
putString("firstString", first)
putString("secondString", second)
}
}
}
}
And you can get arguments with this:
val first: String by lazy { arguments?.getString("firstString") ?: "default"}
val second: String by lazy { arguments?.getString("secondString") ?: "default"}
I disagree with yydi answer saying:
If Android decides to recreate your Fragment later, it's going to call
the no-argument constructor of your fragment. So overloading the
constructor is not a solution.
I think it is a solution and a good one, this is exactly the reason it been developed by Java core language.
Its true that Android system can destroy and recreate your Fragment. So you can do this:
public MyFragment() {
// An empty constructor for Android System to use, otherwise exception may occur.
}
public MyFragment(int someInt) {
Bundle args = new Bundle();
args.putInt("someInt", someInt);
setArguments(args);
}
It will allow you to pull someInt from getArguments() latter on, even if the Fragment been recreated by the system. This is more elegant solution than static constructor.
For my opinion static constructors are useless and should not be used. Also they will limit you if in the future you would like to extend this Fragment and add more functionality to the constructor. With static constructor you can't do this.
Update:
Android added inspection that flag all non-default constructors with an error.
I recommend to disable it, for the reasons mentioned above.
I'm lately here. But somethings I just known that might help you a bit.
If you are using Java, there is nothing much to change. But for Kotlin developers, here is some following snippet I think that can make you a basement to run on:
Parent fragment:
inline fun <reified T : SampleFragment> newInstance(text: String): T {
return T::class.java.newInstance().apply {
arguments = Bundle().also { it.putString("key_text_arg", text) }
}
}
Normal call
val f: SampleFragment = SampleFragment.newInstance("ABC")
// or val f = SampleFragment.newInstance<SampleFragment>("ABC")
You can extend the parent init operation in child fragment class by:
fun newInstance(): ChildSampleFragment {
val child = UserProfileFragment.newInstance<ChildSampleFragment>("XYZ")
// Do anything with the current initialized args bundle here
// with child.arguments = ....
return child
}
Happy coding.
Best practice to instance fragments with arguments in android is to have static factory method in your fragment.
public static MyFragment newInstance(String name, int age) {
Bundle bundle = new Bundle();
bundle.putString("name", name);
bundle.putInt("age", age);
MyFragment fragment = new MyFragment();
fragment.setArguments(bundle);
return fragment;
}
You should avoid setting your fields with the instance of a fragment. Because whenever android system recreate your fragment, if it feels that the system needs more memory, than it will recreate your fragment by using constructor with no arguments.
You can find more info about best practice to instantiate fragments with arguments here.
Since the questions about best practice, I would add, that very often good idea to use hybrid approach for creating fragment when working with some REST web services
We can't pass complex objects, for example some User model, for case of displaying user fragment
But what we can do, is to check in onCreate that user!=null and if not - then bring him from data layer, otherwise - use existing.
This way we gain both ability to recreate by userId in case of fragment recreation by Android and snappiness for user actions, as well as ability to create fragments by holding to object itself or only it's id
Something likes this:
public class UserFragment extends Fragment {
public final static String USER_ID="user_id";
private User user;
private long userId;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
userId = getArguments().getLong(USER_ID);
if(user==null){
//
// Recreating here user from user id(i.e requesting from your data model,
// which could be services, direct request to rest, or data layer sitting
// on application model
//
user = bringUser();
}
}
public static UserFragment newInstance(User user, long user_id){
UserFragment userFragment = new UserFragment();
Bundle args = new Bundle();
args.putLong(USER_ID,user_id);
if(user!=null){
userFragment.user=user;
}
userFragment.setArguments(args);
return userFragment;
}
public static UserFragment newInstance(long user_id){
return newInstance(null,user_id);
}
public static UserFragment newInstance(User user){
return newInstance(user,user.id);
}
}
use this code 100% fix your problem
enter this code in firstFragment
public static yourNameParentFragment newInstance() {
Bundle args = new Bundle();
args.putBoolean("yourKey",yourValue);
YourFragment fragment = new YourFragment();
fragment.setArguments(args);
return fragment;
}
this sample send boolean data
and in SecendFragment
yourNameParentFragment name =yourNameParentFragment.newInstance();
Bundle bundle;
bundle=sellDiamondFragments2.getArguments();
boolean a= bundle.getBoolean("yourKey");
must value in first fragment is static
happy code
Ideally we shouldn't pass anything in the fragment constructor, fragment constructor should be empty or default.
Now the second question is, what if we want to pass interface variable or parameters-
We should use Bundle to pass data.
For Interface we can putParceble in bundle and make that interface implement parceble
If possible we can implement that interface in activity and in fragment we can initialize listener in OnAttach where we have context[ (context) Listener].
So that during configuration change (e.g. Font change) the Activity recreation listener won't go uninitialize and we can avoid a null pointer exception.
Best way to instantiate the fragment is use default Fragment.instantiate method or create factory method to instantiate the the fragment
Caution: always create one empty constructor in fragment other while restoring fragment memory will throw run-time exception.
You can use smth like this:
val fragment = supportFragmentManager.fragmentFactory.instantiate(classLoader, YourFragment::class.java.name)
because this answer now is Deprecated
Create an instance of the fragment using kotlin code.
Write in activity
val fragment = YourFragment.newInstance(str = "Hello",list = yourList)
Write in fragment
fun newInstance(str: String, list: ArrayList<String>): Fragment {
val fragment = YourFragment()
fragment.arguments = Bundle().apply {
putSerializable("KEY_STR", str)
putSerializable("KEY_LIST", list)
}
return fragment
}
Using the same fragment retrieve the data from bundle
val str = arguments?.getString("KEY_STR") as? String
val list = arguments?.getSerializable("KEY_LIST") as? ArrayList<String>
setArguments() is useless. It only brings a mess.
public class MyFragment extends Fragment {
public String mTitle;
public String mInitialTitle;
public static MyFragment newInstance(String param1) {
MyFragment f = new MyFragment();
f.mInitialTitle = param1;
f.mTitle = param1;
return f;
}
#Override
public void onSaveInstanceState(Bundle state) {
state.putString("mInitialTitle", mInitialTitle);
state.putString("mTitle", mTitle);
super.onSaveInstanceState(state);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle state) {
if (state != null) {
mInitialTitle = state.getString("mInitialTitle");
mTitle = state.getString("mTitle");
}
...
}
}
I believe I have a much simpeler solution for this.
public class MyFragment extends Fragment{
private String mTitle;
private List<MyObject> mObjects;
public static MyFragment newInstance(String title, List<MyObject> objects)
MyFragment myFrag = new MyFragment();
myFrag.mTitle = title;
myFrag.mObjects = objects;
return myFrag;
}