Tag: ViewGroup

Create Fragments

Add fragments to your app.

Create a new class for our Fragment:
public class AppFragment extends Fragment {

    public AppFragment() { // Empty constructor
    }

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { // Essential
        View rootView = inflater.inflate(R.layout.our_fragment, container, false); // Use a custom layout file (see below)

        ImageView imageView = rootView.findViewById(R.id.ourImageView); // Here we find a View within the layout

        imageView.setImageResource(R.drawable.anImage); // And allocate an image to it

        return rootView;
    }
}



Our layout file for the Fragment, our_fragment.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:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/ourImageView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:contentDescription="An Image"
        tools:srcCompat="@drawable/anImage" /> // Placeholder image
</LinearLayout>



Create an instance of our Fragment in the Activity and use FragmentManager to add it to the layout for the Activity:


        AppFragment aFragment = new AppFragment(); // New instance of our custom Fragment

        FragmentManager fragmentManager = getSupportFragmentManager();

        fragmentManager.beginTransaction()
                .add(R.id.fragment_container, aFragment) // Adds the new fragment to an element of the Activity layout (see below)
                .commit();



Our layout file for the Activity, activity_main.xml:


<?xml version="1.0" encoding="utf-8"?>
<ScrollView
    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.example.android.app.MainActivity">

    <LinearLayout
        android:id="@+id/main_activity_linear_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <FrameLayout android:id="@+id/fragment_container" // View that will contain the Fragment
        android:layout_width="match_parent"
        android:layout_height="180dp"
        android:scaleType="centerInside"/>

    </LinearLayout>
</ScrollView>

Customising RecyclerViews according to position +/- orientation

If wanting to set differing layouts for a RecyclerView in a particular ViewHolder position +/- orientation (portrait or landscape), you can do the following:

Use the values, values-port and values-land folders to set booleans (or other) to indicate your preferences for layout according to orientation e.g. in values-port\bools.xml add 
<bool name="use_expanded_layout">false</bool>


 to state that you do not want to use your expanded layout in portrait mode (if desired).

Overriding getViewType will give you the position of the ViewHolder by which you can conditionally set which viewType to use. In your RecyclerView.Adapter file:


private final int CONDENSED_VIEWTYPE_ID = 83; // Randomly generated unique ID to correspond to condensed layout
private final int EXPANDED_VIEWTYPE_ID = 928; // Randomly generated unique ID to correspond to expanded layout
private boolean mUseExpandedLayout; // Declare a variable to determine layout preference
private final Context mContext; // We'll need this

    public RecyclerViewAdapter(@NonNull Context context, RecyclerViewAdapterOnClickHandler clickHandler) { // In the constructor...
        ...
        mContext = context;
        mUseExpandedLayout= context.getResources().getBoolean(R.bool.use_expanded_layout); // ... get the preference from your boolean. If in portrait orientation it will take this value from the values-port\bools.xml file if it exists, otherwise the values\bools.xml file
    }

    @Override
    public int getItemViewType(int position) { // Override getViewType, which gives you the ViewHolder position
        if (!mExpandedLayout || position != 0) { // Use this position to determine which viewType to apply. Here, if the boolean is false or position is not 0...
            return CONDENSED_VIEWTYPE_ID; // ...use the condensed viewType
        }
        return EXPANDED_VIEWTYPE_ID; // Otherwise use the expanded viewType
    }

    @Override
    public RecyclerViewAdapterViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) { // In the onCreateViewHolder override...

        View view;

        if (viewType == CONDENSED_VIEWTYPE_ID) { // ...if the viewType has the condensed ID...
            view = LayoutInflater
                    .from(mContext)
                    .inflate(R.layout.condensed_list_item, viewGroup, false); // ...apply the condensed layout
        } else if (viewType == EXPANDED_VIEWTYPE_ID) { // If the viewType has the expanded ID...
            view = LayoutInflater
                    .from(mContext)
                    .inflate(R.layout.expanded_list_item, viewGroup, false); // ...apply the expanded layout
        } else {
            throw new IllegalArgumentException("Invalid layout type");
        }

        return new RecyclerViewAdapterViewHolder(view); // Creates the ViewHolder with the appropriate layout attached
    }