1. Overview

When developing Android applications inovlving multiple Fragments and Activities, managing navigation becomes a critical task. This article explores four distinct Fragment navigation scenarios:

• 1. Navigating between Fragments within the same Activity
• 2. Launching a new Activity from a Fragment
• 3. Starting a specific Fargment in a new Activity from another Activity
• 4. Starting a Fragment in a new Activity from another Fragment

2. Setup

2.1 Layout Configuration

In the MainActivity layout, define a container for hosting Fragments:

<FrameLayout
    android:id="@+id/fragment_container"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1" />

2.2 Creating Fragment Classes

Create a Fragment class that inflates a layout and sets up click listeners:

public class MyFragment extends Fragment {
    private View contentView;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        if (contentView == null) {
            contentView = inflater.inflate(R.layout.my_fragment, container, false);
            Button btnNavigate = contentView.findViewById(R.id.my_button);
            Button btnBack = contentView.findViewById(R.id.my_return);
            Button btnLaunchActivity = contentView.findViewById(R.id.my_other);
            btnNavigate.setOnClickListener(this::onButtonClick);
            btnBack.setOnClickListener(this::onButtonClick);
            btnLaunchActivity.setOnClickListener(this::onButtonClick);
        }
        return contentView;
    }

    public void onButtonClick(View view) {
        // Navigation logic will be implemented here
    }
}

2.3 Initial Fragment Display

Load the initial Fragment into the container in MainActivity:

getSupportFragmentManager()
    .beginTransaction()
    .replace(R.id.fragment_container, new MyFragment())
    .addToBackStack(null)
    .commit();

3. Fragment Navigation Scenarios

3.1 Switching Between Fragments in the Same Activity

To navigate from one Fragment to another within the same Activity:

getActivity().getSupportFragmentManager()
    .beginTransaction()
    .replace(R.id.fragment_container, new TargetFragment())
    .addToBackStack(null)
    .commit();

3.2 Launching a New Activity from a Fragment

Standard Activity launch from a Fragment:

Intent intent = new Intent(getActivity(), TargetActivity.class);
startActivity(intent);

3.3 Launching a Specific Fragment in a New Activity

Pass a parameter to the target Activity to display a specific Fragment:

Intent intent = new Intent(OtherActivity.this, MainActivity.class);
intent.putExtra("fragment_id", 1);
startActivity(intent);

In the target Activity:

int fragmentId = getIntent().getIntExtra("fragment_id", 0);
if (fragmentId == 1) {
    getSupportFragmentManager()
        .beginTransaction()
        .replace(R.id.fragment_container, new TargetFragment())
        .addToBackStack(null)
        .commit();
}

3.4 Launching a Fragment in Another Activity from a Fragment

Similar to the previous example, but initiated from a Fragment:

Intent intent = new Intent(getActivity(), TargetActivity.class);
intent.putExtra("fragment_id", 1);
startActivity(intent);