How is it possible to create a fragment with an Object parameter?

Question

I would like to create a Fragment, and have a complex type (MyClass) as its parameter. The guide does not really mention it. I was able to find some examples with Bundle, but those only contain simple parameters, like String and Integer.

Answer 1

You can create a static method named getInstance() or createInstance() or what ever you like for creating Fragment with some value

Java Version:

public static MyFragment newInstance(int arg) {

    Bundle args = new Bundle();
    args.putInt("ARG", arg);

    MyFragment fragment = new MyFragment();
    fragment.setArguments(args);
    return fragment;
}

Kotlin Version:

class MyFragment : Fragment() {
    companion object {
       fun newInstance(arg: Int): MyFragment {
            val args = Bundle()
            args.putInt("ARG", arg)
            val fragment = MyFragment()
            fragment.arguments = args
            return fragment
        }
    }
}

I was able to find some examples with Bundle, but those only contain simple parameters, like String and Integer.

To pass custom object in Bundle you can use make your class Parcelable or Serializable. For Parcelable you can use putParcelable method to store your object in Bundle.

For Parcelable and Serializable in Android check this thread.

You will find some plugin in Android Studio that will auto generate Parcelable implementation code for your class

Another approach is convert your object to String using Gson and put that String in Bundle.

For Gson check this post

Answer 2

Your best bet is probably serializing the complex class and deserializing it again in the fragment.

So something like

bundle.putString("object_key", gson.toJson(yourClassInstance));

And then deserialize it with

Type yourClassType = new TypeToken<YourClass>() {}.getType();
YourClass yourClassInstance = gson.fromJson(bundle.getString("object_key"), yourClassType);

or, if your class isn't generic:

gson.fromJson(bundle.getString("object_key"), YourClass.class);

For more information, see the Gson docs