Create ChallengesUserListGUI that will display user heads in rows and allows to select specific user.

src/main/java/world/bentobox/challenges/panel/admin/ChallengesUserListGUI.java

@@ -0,0 +1,243 @@
+package world.bentobox.challenges.panel.admin;
+
+
+import org.bukkit.Bukkit;
+import org.bukkit.Material;
+import org.bukkit.OfflinePlayer;
+import org.bukkit.World;
+import org.bukkit.entity.Player;
+import java.util.ArrayList;
+import java.util.List;
+
+import world.bentobox.bentobox.api.panels.PanelItem;
+import world.bentobox.bentobox.api.panels.builders.PanelBuilder;
+import world.bentobox.bentobox.api.panels.builders.PanelItemBuilder;
+import world.bentobox.bentobox.api.user.User;
+import world.bentobox.challenges.ChallengesAddon;
+import world.bentobox.challenges.panel.CommonGUI;
+
+
+/**
+ * This class contains methods that allows to select specific user.
+ */
+public class ChallengesUserListGUI extends CommonGUI
+{
+// ---------------------------------------------------------------------
+// Section: Variables
+// ---------------------------------------------------------------------
+
+	/**
+	 * List with players that should be in GUI.
+	 */
+	private List<Player> onlineUsers;
+
+	/**
+	 * Current index of view mode
+	 */
+	private int modeIndex = 2;
+
+
+	/**
+	 * This allows to switch which users should be in the list.
+	 */
+	private enum ViewMode
+	{
+		ONLINE,
+		OFFLINE,
+		IN_WORLD
+	}
+
+
+// ---------------------------------------------------------------------
+// Section: Constructors
+// ---------------------------------------------------------------------
+
+
+	/**
+	 * {@inheritDoc}
+	 */
+	public ChallengesUserListGUI(ChallengesAddon addon,
+		World world,
+		User user, String topLabel, String permissionPrefix)
+	{
+		this(addon, world, user, topLabel, permissionPrefix, null);
+	}
+
+
+	/**
+	 * {@inheritDoc}
+	 */
+	public ChallengesUserListGUI(ChallengesAddon addon,
+		World world,
+		User user,
+		String topLabel,
+		String permissionPrefix,
+		CommonGUI parentPanel)
+	{
+		super(addon, world, user, topLabel, permissionPrefix, parentPanel);
+		this.onlineUsers = this.collectUsers(ViewMode.IN_WORLD);
+	}
+
+
+// ---------------------------------------------------------------------
+// Section: Methods
+// ---------------------------------------------------------------------
+
+
+	@Override
+	public void build()
+	{
+		PanelBuilder panelBuilder = new PanelBuilder().user(this.user).name(
+			this.user.getTranslation("challenges.gui.admin.choose-user-title"));
+
+		int MAX_ELEMENTS = 45;
+		if (this.pageIndex < 0)
+		{
+			this.pageIndex = 0;
+		}
+		else if (this.pageIndex > (this.onlineUsers.size() / MAX_ELEMENTS))
+		{
+			this.pageIndex = this.onlineUsers.size() / MAX_ELEMENTS;
+		}
+
+		int playerIndex = MAX_ELEMENTS * this.pageIndex;
+
+		while (playerIndex < ((this.pageIndex + 1) * MAX_ELEMENTS) &&
+			playerIndex < this.onlineUsers.size())
+		{
+			panelBuilder.item(this.createPlayerIcon(this.onlineUsers.get(playerIndex)));
+			playerIndex++;
+		}
+
+		int nextIndex = playerIndex % MAX_ELEMENTS == 0 ?
+			MAX_ELEMENTS :
+			(((playerIndex % MAX_ELEMENTS) - 1) / 9 + 1) * 9;
+
+		if (playerIndex > MAX_ELEMENTS)
+		{
+			panelBuilder.item(nextIndex, this.getButton(CommonButtons.PREVIOUS));
+		}
+
+		if (playerIndex < this.onlineUsers.size())
+		{
+			panelBuilder.item(nextIndex + 8, this.getButton(CommonButtons.NEXT));
+		}
+
+		if (this.returnButton != null)
+		{
+			panelBuilder.item(nextIndex + 6, this.returnButton);
+		}
+
+		panelBuilder.item(nextIndex + 3, this.createToggleButton());
+
+		panelBuilder.build();
+	}
+
+
+	/**
+	 * This method creates button for given user. If user has island it will add valid click handler.
+	 * @param player Player which button must be created.
+	 * @return Player button.
+	 */
+	private PanelItem createPlayerIcon(Player player)
+	{
+		if (this.addon.getIslands().hasIsland(this.world, player.getUniqueId()))
+		{
+			return new PanelItemBuilder().name(player.getName()).icon(player.getName()).clickHandler(
+				(panel, user1, clickType, slot) -> {
+					// TODO Add operations that should be called from here
+
+					return true;
+				}).build();
+		}
+		else
+		{
+			return new PanelItemBuilder().
+				name(player.getName()).
+				icon(Material.BARRIER).
+				description(this.user.getTranslation("general.errors.player-has-no-island")).
+				clickHandler((panel, user1, clickType, slot) -> false).
+				build();
+		}
+	}
+
+
+	/**
+	 * This method collects users based on view mode.
+	 * @param mode Given view mode.
+	 * @return List with players in necessary view mode.
+	 */
+	private List<Player> collectUsers(ViewMode mode)
+	{
+		if (mode.equals(ViewMode.ONLINE))
+		{
+			return new ArrayList<>(Bukkit.getOnlinePlayers());
+		}
+		else if (mode.equals(ViewMode.OFFLINE))
+		{
+			List<Player> offlinePlayer = new ArrayList<>(Bukkit.getOfflinePlayers().length);
+
+			for (int index = 0; index < Bukkit.getOfflinePlayers().length; index++)
+			{
+				OfflinePlayer player = Bukkit.getOfflinePlayers()[index];
+				offlinePlayer.add(player.getPlayer());
+			}
+
+			return offlinePlayer;
+		}
+		else
+		{
+			return  new ArrayList<>(this.world.getPlayers());
+		}
+	}
+
+
+	/**
+	 * This method creates Player List view Mode toggle button.
+	 * @return Button that toggles through player view mode.
+	 */
+	private PanelItem createToggleButton()
+	{
+		List<String> values = new ArrayList<>(ViewMode.values().length);
+
+		for (int i = 0; i < ViewMode.values().length; i++)
+		{
+			values.add((this.modeIndex == i ? "§2" : "§c") +
+				this.user.getTranslation("challenges.gui.admin.descriptions." +
+					ViewMode.values()[i].name().toLowerCase()));
+		}
+
+		return new PanelItemBuilder().
+			name(this.user.getTranslation("challenges.gui.admin.buttons.toggle-users",
+				"[value]",
+				this.user.getTranslation("challenges.gui.admin.descriptions." + ViewMode.values()[this.modeIndex].name().toLowerCase()))).
+			description(values).
+			icon(Material.STONE_BUTTON).
+			clickHandler(
+				(panel, user1, clickType, slot) -> {
+					if (clickType.isRightClick())
+					{
+						this.modeIndex--;
+
+						if (this.modeIndex < 0)
+						{
+							this.modeIndex = ViewMode.values().length - 1;
+						}
+					}
+					else
+					{
+						this.modeIndex++;
+
+						if (this.modeIndex >= ViewMode.values().length)
+						{
+							this.modeIndex = 0;
+						}
+					}
+
+					this.onlineUsers = this.collectUsers(ViewMode.values()[this.modeIndex]);
+					this.pageIndex = 0;
+					this.build();
+					return true;
+				}).build();
+	}
+}