NewPipe/app/src/main/java/org/schabi/newpipe/local/BaseLocalListFragment.java

package org.schabi.newpipe.local;

import android.content.SharedPreferences;
import android.content.res.Configuration;
import android.content.res.Resources;
import android.os.Bundle;
import android.preference.PreferenceManager;
import androidx.fragment.app.Fragment;
import androidx.appcompat.app.ActionBar;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;

import org.schabi.newpipe.R;
import org.schabi.newpipe.fragments.BaseStateFragment;
import org.schabi.newpipe.fragments.list.ListViewContract;

import static org.schabi.newpipe.util.AnimationUtils.animateView;

/**
 * This fragment is design to be used with persistent data such as
 * {@link org.schabi.newpipe.database.LocalItem}, and does not cache the data contained
 * in the list adapter to avoid extra writes when the it exits or re-enters its lifecycle.
 *
 * This fragment destroys its adapter and views when {@link Fragment#onDestroyView()} is
 * called and is memory efficient when in backstack.
 * */
public abstract class BaseLocalListFragment<I, N> extends BaseStateFragment<I>
        implements ListViewContract<I, N>, SharedPreferences.OnSharedPreferenceChangeListener {

    /*//////////////////////////////////////////////////////////////////////////
    // Views
    //////////////////////////////////////////////////////////////////////////*/

    protected View headerRootView;
    protected View footerRootView;

    protected LocalItemListAdapter itemListAdapter;
    protected RecyclerView itemsList;
    private int updateFlags = 0;

    private static final int LIST_MODE_UPDATE_FLAG = 0x32;

    /*//////////////////////////////////////////////////////////////////////////
    // Lifecycle - Creation
    //////////////////////////////////////////////////////////////////////////*/

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
        PreferenceManager.getDefaultSharedPreferences(activity)
                .registerOnSharedPreferenceChangeListener(this);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        PreferenceManager.getDefaultSharedPreferences(activity)
                .unregisterOnSharedPreferenceChangeListener(this);
    }

    @Override
    public void onResume() {
        super.onResume();
        if (updateFlags != 0) {
            if ((updateFlags & LIST_MODE_UPDATE_FLAG) != 0) {
                final boolean useGrid = isGridLayout();
                itemsList.setLayoutManager(useGrid ? getGridLayoutManager() : getListLayoutManager());
                itemListAdapter.setGridItemVariants(useGrid);
                itemListAdapter.notifyDataSetChanged();
            }
            updateFlags = 0;
        }
    }

    /*//////////////////////////////////////////////////////////////////////////
    // Lifecycle - View
    //////////////////////////////////////////////////////////////////////////*/

    protected View getListHeader() {
        return null;
    }

    protected View getListFooter() {
        return activity.getLayoutInflater().inflate(R.layout.pignate_footer, itemsList, false);
    }

    protected RecyclerView.LayoutManager getGridLayoutManager() {
        final Resources resources = activity.getResources();
        int width = resources.getDimensionPixelSize(R.dimen.video_item_grid_thumbnail_image_width);
        width += (24 * resources.getDisplayMetrics().density);
        final int spanCount = (int) Math.floor(resources.getDisplayMetrics().widthPixels / (double)width);
        final GridLayoutManager lm = new GridLayoutManager(activity, spanCount);
        lm.setSpanSizeLookup(itemListAdapter.getSpanSizeLookup(spanCount));
        return lm;
    }

    protected RecyclerView.LayoutManager getListLayoutManager() {
        return new LinearLayoutManager(activity);
    }

    @Override
    protected void initViews(View rootView, Bundle savedInstanceState) {
        super.initViews(rootView, savedInstanceState);

        itemListAdapter = new LocalItemListAdapter(activity);

        final boolean useGrid = isGridLayout();
        itemsList = rootView.findViewById(R.id.items_list);
        itemsList.setLayoutManager(useGrid ? getGridLayoutManager() : getListLayoutManager());

        itemListAdapter.setGridItemVariants(useGrid);
        itemListAdapter.setHeader(headerRootView = getListHeader());
        itemListAdapter.setFooter(footerRootView = getListFooter());

        itemsList.setAdapter(itemListAdapter);
    }

    @Override
    protected void initListeners() {
        super.initListeners();
    }

    /*//////////////////////////////////////////////////////////////////////////
    // Lifecycle - Menu
    //////////////////////////////////////////////////////////////////////////*/

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        super.onCreateOptionsMenu(menu, inflater);
        if (DEBUG) Log.d(TAG, "onCreateOptionsMenu() called with: menu = [" + menu +
                "], inflater = [" + inflater + "]");

        final ActionBar supportActionBar = activity.getSupportActionBar();
        if (supportActionBar == null) return;

        supportActionBar.setDisplayShowTitleEnabled(true);
    }

    /*//////////////////////////////////////////////////////////////////////////
    // Lifecycle - Destruction
    //////////////////////////////////////////////////////////////////////////*/

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        itemsList = null;
        itemListAdapter = null;
    }

    /*//////////////////////////////////////////////////////////////////////////
    // Contract
    //////////////////////////////////////////////////////////////////////////*/

    @Override
    public void startLoading(boolean forceLoad) {
        super.startLoading(forceLoad);
        resetFragment();
    }

    @Override
    public void showLoading() {
        super.showLoading();
        if (itemsList != null) animateView(itemsList, false, 200);
        if (headerRootView != null) animateView(headerRootView, false, 200);
    }

    @Override
    public void hideLoading() {
        super.hideLoading();
        if (itemsList != null) animateView(itemsList, true, 200);
        if (headerRootView != null) animateView(headerRootView, true, 200);
    }

    @Override
    public void showError(String message, boolean showRetryButton) {
        super.showError(message, showRetryButton);
        showListFooter(false);

        if (itemsList != null) animateView(itemsList, false, 200);
        if (headerRootView != null) animateView(headerRootView, false, 200);
    }

    @Override
    public void showEmptyState() {
        super.showEmptyState();
        showListFooter(false);
    }

    @Override
    public void showListFooter(final boolean show) {
        if (itemsList == null) return;
        itemsList.post(() -> {
            if (itemListAdapter != null) itemListAdapter.showFooter(show);
        });
    }

    @Override
    public void handleNextItems(N result) {
        isLoading.set(false);
    }

    /*//////////////////////////////////////////////////////////////////////////
    // Error handling
    //////////////////////////////////////////////////////////////////////////*/

    protected void resetFragment() {
        if (itemListAdapter != null) itemListAdapter.clearStreamItemList();
    }

    @Override
    protected boolean onError(Throwable exception) {
        resetFragment();
        return super.onError(exception);
    }

    @Override
    public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
        if (key.equals(getString(R.string.list_view_mode_key))) {
            updateFlags |= LIST_MODE_UPDATE_FLAG;
        }
    }

    protected boolean isGridLayout() {
        final String list_mode = PreferenceManager.getDefaultSharedPreferences(activity).getString(getString(R.string.list_view_mode_key), getString(R.string.list_view_mode_value));
        if ("auto".equals(list_mode)) {
            final Configuration configuration = getResources().getConfiguration();
            return configuration.orientation == Configuration.ORIENTATION_LANDSCAPE
                    && configuration.isLayoutSizeAtLeast(Configuration.SCREENLAYOUT_SIZE_LARGE);
        } else {
            return "grid".equals(list_mode);
        }
    }
}