How to add rows to RecycleView?

Question

Android

I'm trying to study RecycleView, but I can't figure out how to add a line to the end of RecycleView from MainActivty to an already existing and displayed RecycleView? Or should it be done elsewhere?

public class MainActivity extends SampleActivityBase {

    public static final String TAG = "MainActivity";

    private boolean mLogShown;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (savedInstanceState == null) {
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            RecyclerViewFragment fragment = new RecyclerViewFragment();
            transaction.replace(R.id.sample_content_fragment, fragment);
            transaction.commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        MenuItem logToggle = menu.findItem(R.id.menu_toggle_log);
        logToggle.setVisible(findViewById(R.id.sample_output) instanceof ViewAnimator);
        logToggle.setTitle(mLogShown ? R.string.sample_hide_log : R.string.sample_show_log);

        return super.onPrepareOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch(item.getItemId()) {
            case R.id.menu_toggle_log:
                mLogShown = !mLogShown;
                ViewAnimator output = (ViewAnimator) findViewById(R.id.sample_output);
                if (mLogShown) {
                    output.setDisplayedChild(1);
                } else {
                    output.setDisplayedChild(0);
                }
                supportInvalidateOptionsMenu();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /** Create a chain of targets that will receive log data */
    @Override
    public void initializeLogging() {
        // Wraps Android's native log framework.
        LogWrapper logWrapper = new LogWrapper();
        // Using Log, front-end to the logging chain, emulates android.util.log method signatures.
        Log.setLogNode(logWrapper);

        // Filter strips out everything except the message text.
        MessageOnlyLogFilter msgFilter = new MessageOnlyLogFilter();
        logWrapper.setNext(msgFilter);

        // On screen logging via a fragment with a TextView.
        LogFragment logFragment = (LogFragment) getSupportFragmentManager()
                .findFragmentById(R.id.log_fragment);
        msgFilter.setNext(logFragment.getLogView());

        Log.i(TAG, "Ready");
    }
    }

Adapter

public class CustomAdapter extends RecyclerView.Adapter<CustomAdapter.ViewHolder> {
    private static final String TAG = "CustomAdapter";

    private String[] mDataSet;

    // BEGIN_INCLUDE(recyclerViewSampleViewHolder)
    /**
     * Provide a reference to the type of views that you are using (custom ViewHolder)
     */
    public static class ViewHolder extends RecyclerView.ViewHolder {
        private final TextView textView;

        public ViewHolder(View v) {
            super(v);
            // Define click listener for the ViewHolder's View.
            v.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Log.d(TAG, "Element " + getAdapterPosition() + " clicked.");
                }
            });
            textView = (TextView) v.findViewById(R.id.textView);
        }

        public TextView getTextView() {
            return textView;
        }
    }
    // END_INCLUDE(recyclerViewSampleViewHolder)

    /**
     * Initialize the dataset of the Adapter.
     *
     * @param dataSet String[] containing the data to populate views to be used by RecyclerView.
     */
    public CustomAdapter(String[] dataSet) {
        mDataSet = dataSet;
    }

    // BEGIN_INCLUDE(recyclerViewOnCreateViewHolder)
    // Create new views (invoked by the layout manager)
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int viewType) {
        // Create a new view.
        View v = LayoutInflater.from(viewGroup.getContext())
                .inflate(R.layout.text_row_item, viewGroup, false);

        return new ViewHolder(v);
    }
    
    @Override
    public void onBindViewHolder(ViewHolder viewHolder, final int position) {
        Log.d(TAG, "Element " + position + " set.");

        // Get element from your dataset at this position and replace the contents of the view
        // with that element
        viewHolder.getTextView().setText(mDataSet[position]);
    }

    @Override
    public int getItemCount() {
        return mDataSet.length;
    }
    }

Fragment

public class RecyclerViewFragment extends Fragment {

    private static final String TAG = "RecyclerViewFragment";
    private static final String KEY_LAYOUT_MANAGER = "layoutManager";
    private static final int SPAN_COUNT = 2;
    private static final int DATASET_COUNT = 60;

    private enum LayoutManagerType {
        GRID_LAYOUT_MANAGER,
        LINEAR_LAYOUT_MANAGER
    }

    protected LayoutManagerType mCurrentLayoutManagerType;

    protected RadioButton mLinearLayoutRadioButton;
    protected RadioButton mGridLayoutRadioButton;

    protected RecyclerView mRecyclerView;
    protected CustomAdapter mAdapter;
    protected RecyclerView.LayoutManager mLayoutManager;
    protected String[] mDataset;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Initialize dataset, this data would usually come from a local content provider or
        // remote server.
        initDataset();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.recycler_view_frag, container, false);
        rootView.setTag(TAG);

        // BEGIN_INCLUDE(initializeRecyclerView)
        mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerView);

        // LinearLayoutManager is used here, this will layout the elements in a similar fashion
        // to the way ListView would layout elements. The RecyclerView.LayoutManager defines how
        // elements are laid out.
        mLayoutManager = new LinearLayoutManager(getActivity());

        mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;

        if (savedInstanceState != null) {
            // Restore saved layout manager type.
            mCurrentLayoutManagerType = (LayoutManagerType) savedInstanceState
                    .getSerializable(KEY_LAYOUT_MANAGER);
        }
        setRecyclerViewLayoutManager(mCurrentLayoutManagerType);

        mAdapter = new CustomAdapter(mDataset);
        // Set CustomAdapter as the adapter for RecyclerView.
        mRecyclerView.setAdapter(mAdapter);
        // END_INCLUDE(initializeRecyclerView)

        mLinearLayoutRadioButton = (RadioButton) rootView.findViewById(R.id.linear_layout_rb);
        mLinearLayoutRadioButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                setRecyclerViewLayoutManager(LayoutManagerType.LINEAR_LAYOUT_MANAGER);
            }
        });

        mGridLayoutRadioButton = (RadioButton) rootView.findViewById(R.id.grid_layout_rb);
        mGridLayoutRadioButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                setRecyclerViewLayoutManager(LayoutManagerType.GRID_LAYOUT_MANAGER);
            }
        });

        return rootView;
    }

 
    public void setRecyclerViewLayoutManager(LayoutManagerType layoutManagerType) {
        int scrollPosition = 0;

        // If a layout manager has already been set, get current scroll position.
        if (mRecyclerView.getLayoutManager() != null) {
            scrollPosition = ((LinearLayoutManager) mRecyclerView.getLayoutManager())
                    .findFirstCompletelyVisibleItemPosition();
        }

        switch (layoutManagerType) {
            case GRID_LAYOUT_MANAGER:
                mLayoutManager = new GridLayoutManager(getActivity(), SPAN_COUNT);
                mCurrentLayoutManagerType = LayoutManagerType.GRID_LAYOUT_MANAGER;
                break;
            case LINEAR_LAYOUT_MANAGER:
                mLayoutManager = new LinearLayoutManager(getActivity());
                mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
                break;
            default:
                mLayoutManager = new LinearLayoutManager(getActivity());
                mCurrentLayoutManagerType = LayoutManagerType.LINEAR_LAYOUT_MANAGER;
        }

        mRecyclerView.setLayoutManager(mLayoutManager);
        mRecyclerView.scrollToPosition(scrollPosition);
    }

    @Override
    public void onSaveInstanceState(Bundle savedInstanceState) {
        // Save currently selected layout manager.
        savedInstanceState.putSerializable(KEY_LAYOUT_MANAGER, mCurrentLayoutManagerType);
        super.onSaveInstanceState(savedInstanceState);
    }

    /**
     * Generates Strings for RecyclerView's adapter. This data would usually come
     * from a local content provider or remote server.
     */
    private void initDataset() {
        mDataset = new String[DATASET_COUNT];
        for (int i = 0; i < DATASET_COUNT; i++) {
            mDataset[i] = "This is element #" + i;
        }
    }
    }

Answer 1

Это нужно делать во фрагменте.
В адаптере вместо массива используй список(List, ArrayList). Добавляй в список свои строки и вызывай у адаптера notifyDatasetChanged(лучше, конечно, использовать DiffUtil и вызывать таким образом другие notify* методы).