add onPrepare method

README.md

@@ -89,7 +89,16 @@ builder.onComplete((player, text) -> {
         return AnvilGUI.Response.text("Incorrect.");   
     }                                                  
 });                                                    
-```                                                    
+```                           
+
+#### `onPrepare(BiConsumer<Player, String>)`
+Takes a `BiConsumer<Player, String>` argument that is called when a player changes the input field of the anvil, i.e. when typing or undoing characters.
+It uses the [PrepareAnvilEvent](https://hub.spigotmc.org/javadocs/bukkit/org/bukkit/event/inventory/PrepareAnvilEvent.html), so it will only have an effect on MC versions >= 1.9.
+```java
+builder.onPrepare((player, text) -> {
+	player.sendMessage("Current input: " + text);
+});
+```
 
 #### `preventClose()` 
 Tells the AnvilGUI to prevent the user from pressing escape to close the inventory.

api/pom.xml

@@ -16,7 +16,7 @@
         <dependency>
             <groupId>org.spigotmc</groupId>
             <artifactId>spigot</artifactId>
-            <version>1.8-R0.1-SNAPSHOT</version>
+            <version>1.19-R0.1-SNAPSHOT</version>
             <scope>provided</scope>
         </dependency>
         <dependency>

api/src/main/java/net/wesjd/anvilgui/AnvilGUI.java

@@ -1,24 +1,34 @@
 package net.wesjd.anvilgui;
 
 
+import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
 import java.util.function.Consumer;
 import net.wesjd.anvilgui.version.VersionMatcher;
 import net.wesjd.anvilgui.version.VersionWrapper;
+import net.wesjd.anvilgui.version.Wrapper1_7_R4;
+import net.wesjd.anvilgui.version.Wrapper1_8_R1;
+import net.wesjd.anvilgui.version.Wrapper1_8_R2;
+import net.wesjd.anvilgui.version.Wrapper1_8_R3;
 import org.apache.commons.lang.Validate;
 import org.bukkit.Bukkit;
 import org.bukkit.Material;
 import org.bukkit.entity.Player;
+import org.bukkit.event.Event;
+import org.bukkit.event.EventException;
 import org.bukkit.event.EventHandler;
+import org.bukkit.event.EventPriority;
 import org.bukkit.event.HandlerList;
 import org.bukkit.event.Listener;
 import org.bukkit.event.inventory.InventoryAction;
 import org.bukkit.event.inventory.InventoryClickEvent;
 import org.bukkit.event.inventory.InventoryCloseEvent;
 import org.bukkit.event.inventory.InventoryDragEvent;
+import org.bukkit.event.inventory.PrepareAnvilEvent;
 import org.bukkit.inventory.Inventory;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.inventory.meta.ItemMeta;
+import org.bukkit.plugin.EventExecutor;
 import org.bukkit.plugin.Plugin;
 
 /**
@@ -75,6 +85,10 @@ public class AnvilGUI {
      * An {@link Consumer} that is called when the {@link Slot#INPUT_RIGHT} slot has been clicked
      */
     private final Consumer<Player> inputRightClickListener;
+    /**
+     * An {@link BiConsumer} that is called when the string of the anvil input has been changed.
+     */
+    private final BiConsumer<Player, String> prepareListener;
 
     /**
      * The container id of the inventory, used for NMS methods
@@ -106,7 +120,7 @@ public class AnvilGUI {
      */
     @Deprecated
     public AnvilGUI(Plugin plugin, Player holder, String insert, BiFunction<Player, String, String> biFunction) {
-        this(plugin, holder, "Repair & Name", insert, null, null, false, null, null, null, (player, text) -> {
+        this(plugin, holder, "Repair & Name", insert, null, null, false, null, null, null, null, (player, text) -> {
             String response = biFunction.apply(player, text);
             if (response != null) {
                 return Response.text(response);
@@ -126,6 +140,7 @@ public AnvilGUI(Plugin plugin, Player holder, String insert, BiFunction<Player,
      * @param inputLeft        The material of the item in the first slot of the anvilGUI
      * @param preventClose     Whether to prevent the inventory from closing
      * @param closeListener    A {@link Consumer} when the inventory closes
+     * @param prepareListener  A {@link BiConsumer} that is called when the player changes the text of the item name field
      * @param completeFunction A {@link BiFunction} that is called when the player clicks the {@link Slot#OUTPUT} slot
      */
     private AnvilGUI(
@@ -139,6 +154,7 @@ private AnvilGUI(
             Consumer<Player> closeListener,
             Consumer<Player> inputLeftClickListener,
             Consumer<Player> inputRightClickListener,
+            BiConsumer<Player, String> prepareListener,
             BiFunction<Player, String, Response> completeFunction) {
         this.plugin = plugin;
         this.player = player;
@@ -149,6 +165,7 @@ private AnvilGUI(
         this.closeListener = closeListener;
         this.inputLeftClickListener = inputLeftClickListener;
         this.inputRightClickListener = inputRightClickListener;
+        this.prepareListener = prepareListener;
         this.completeFunction = completeFunction;
 
         if (itemText != null) {
@@ -171,7 +188,7 @@ private void openInventory() {
         WRAPPER.handleInventoryCloseEvent(player);
         WRAPPER.setActiveContainerDefault(player);
 
-        Bukkit.getPluginManager().registerEvents(listener, plugin);
+        this.registerEvents();
 
         final Object container = WRAPPER.newContainerAnvil(player, inventoryTitle);
 
@@ -229,6 +246,41 @@ public Inventory getInventory() {
         return inventory;
     }
 
+    private void registerEvents() {
+        Bukkit.getPluginManager().registerEvents(listener, plugin);
+
+        // registering the AnvilPrepareEvent listener externally since this event is not
+        // available for MC 1.7 and 1.8.
+        if (!(WRAPPER.getClass() == Wrapper1_7_R4.class
+                || WRAPPER.getClass() == Wrapper1_8_R1.class
+                || WRAPPER.getClass() == Wrapper1_8_R2.class
+                || WRAPPER.getClass() == Wrapper1_8_R3.class)) {
+
+            Bukkit.getPluginManager()
+                    .registerEvent(
+                            PrepareAnvilEvent.class,
+                            listener,
+                            EventPriority.NORMAL,
+                            new EventExecutor() {
+                                @Override
+                                public void execute(Listener listener, Event event) throws EventException {
+                                    PrepareAnvilEvent prepareEvent = (PrepareAnvilEvent) event;
+
+                                    if (prepareEvent.getInventory().equals(inventory)) {
+                                        Player player =
+                                                (Player) prepareEvent.getView().getPlayer();
+                                        if (prepareListener != null) {
+                                            prepareListener.accept(
+                                                    player,
+                                                    prepareEvent.getInventory().getRenameText());
+                                        }
+                                    }
+                                }
+                            },
+                            plugin);
+        }
+    }
+
     /**
      * Simply holds the listeners for the GUI
      */
@@ -313,6 +365,10 @@ public static class Builder {
          * An {@link Consumer} that is called when the {@link Slot#INPUT_RIGHT} slot has been clicked
          */
         private Consumer<Player> inputRightClickListener;
+        /**
+         * An {@link BiConsumer} that is called when the string of the anvil input has been changed
+         */
+        private BiConsumer<Player, String> prepareListener;
         /**
          * An {@link BiFunction} that is called when the anvil output slot has been clicked
          */
@@ -383,6 +439,17 @@ public Builder onRightInputClick(Consumer<Player> inputRightClickListener) {
             return this;
         }
 
+        /**
+         * Listens for changes in the input field of the anvil. Ineffective for MC versions 1.7.* and 1.8.*
+         *
+         * @param prepareListener An {@link BiConsumer} that is called when the string of the input field is changed
+         * @return The {@link Builder} instance
+         */
+        public Builder onPrepare(BiConsumer<Player, String> prepareListener) {
+            this.prepareListener = prepareListener;
+            return this;
+        }
+
         /**
          * Handles the inventory output slot when it is clicked
          *
@@ -494,6 +561,7 @@ public AnvilGUI open(Player player) {
                     closeListener,
                     inputLeftClickListener,
                     inputRightClickListener,
+                    prepareListener,
                     completeFunction);
         }
     }