Deduplicate code to initialize ClickListeners on playlist controls

Add the separate utility class PlayButtonHelper to handle the initialization of the listeners.
The ClickListeners on playlist controls had different behaviours. This commit fixes that.

The commit also refactors the way how the app determines whether it is started for the first time. The previous version was not clean and recent in this PR caused it to fail.

app/src/main/java/org/schabi/newpipe/util/PlayButtonHelper.java

@@ -0,0 +1,90 @@
+package org.schabi.newpipe.util;
+
+import android.content.Context;
+import android.widget.Toast;
+
+import androidx.annotation.NonNull;
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.preference.PreferenceManager;
+
+import org.schabi.newpipe.R;
+import org.schabi.newpipe.databinding.PlaylistControlBinding;
+import org.schabi.newpipe.fragments.list.playlist.PlaylistControlViewHolder;
+import org.schabi.newpipe.player.PlayerType;
+
+/**
+ * Utility class for play buttons and their respective click listeners.
+ */
+public final class PlayButtonHelper {
+
+    private PlayButtonHelper() {
+        // utility class
+    }
+
+    /**
+     * <p>Initialize {@link android.view.View.OnClickListener OnClickListener}
+     * and {@link android.view.View.OnLongClickListener OnLongClickListener} for playlist control
+     * buttons defined in {@code R.layout.playlist_control}.</p>
+     *
+     * @param activity The activity to use for the {@link android.widget.Toast Toast}.
+     * @param playlistControlBinding The binding of the
+     *        {@link R.layout.playlist_control playlist control layout}.
+     * @param fragment The fragment to get the play queue from.
+     */
+    public static void initPlaylistControlClickListener(
+            @NonNull final AppCompatActivity activity,
+            @NonNull final PlaylistControlBinding playlistControlBinding,
+            @NonNull final PlaylistControlViewHolder fragment) {
+        // click listener
+        playlistControlBinding.playlistCtrlPlayAllButton.setOnClickListener(view -> {
+            NavigationHelper.playOnMainPlayer(activity, fragment.getPlayQueue());
+            showHoldToAppendToastIfNeeded(activity);
+        });
+        playlistControlBinding.playlistCtrlPlayPopupButton.setOnClickListener(view -> {
+            NavigationHelper.playOnPopupPlayer(activity, fragment.getPlayQueue(), false);
+            showHoldToAppendToastIfNeeded(activity);
+        });
+        playlistControlBinding.playlistCtrlPlayBgButton.setOnClickListener(view -> {
+            NavigationHelper.playOnBackgroundPlayer(activity, fragment.getPlayQueue(), false);
+            showHoldToAppendToastIfNeeded(activity);
+        });
+
+        // long click listener
+        playlistControlBinding.playlistCtrlPlayPopupButton.setOnLongClickListener(view -> {
+            NavigationHelper.enqueueOnPlayer(activity, fragment.getPlayQueue(), PlayerType.POPUP);
+            return true;
+        });
+        playlistControlBinding.playlistCtrlPlayBgButton.setOnLongClickListener(view -> {
+            NavigationHelper.enqueueOnPlayer(activity, fragment.getPlayQueue(), PlayerType.AUDIO);
+            return true;
+        });
+    }
+
+    /**
+     * <p>Show the "hold to append" toast if the corresponding preference is enabled.</p>
+     *
+     * @param context The context to show the toast.
+     */
+    private static void showHoldToAppendToastIfNeeded(@NonNull final Context context) {
+        if (shouldShowHoldToAppendTip(context)) {
+            Toast.makeText(context, R.string.hold_to_append, Toast.LENGTH_SHORT).show();
+        }
+
+    }
+
+    /**
+     * <p>Check if the "hold to append" toast should be shown.</p>
+     *
+     * <p>
+     * The tip is shown if the corresponding preference is enabled.
+     * This is the default behaviour.
+     * </p>
+     *
+     * @param context The context to get the preference.
+     * @return {@code true} if the tip should be shown, {@code false} otherwise.
+     */
+    public static boolean shouldShowHoldToAppendTip(@NonNull final Context context) {
+        return PreferenceManager.getDefaultSharedPreferences(context)
+                .getBoolean(context.getString(R.string.show_hold_to_append_key), true);
+    }
+}