Created GuiEntryListEntry interface for GuiEntryList contained classes to avoid toString() methods from having to be abused

Created GuiFileChooser and according Listeners
Added (non-functional) GuiAssetAdder for CustomImageObjects

src/main/java/eu/crushedpixel/replaymod/gui/elements/GuiFileChooser.java

@@ -0,0 +1,90 @@
+package eu.crushedpixel.replaymod.gui.elements;
+
+import eu.crushedpixel.replaymod.gui.elements.listeners.FileChooseListener;
+import lombok.Getter;
+import lombok.Setter;
+import net.minecraft.client.Minecraft;
+import net.minecraft.client.gui.GuiButton;
+
+import java.awt.*;
+import java.io.File;
+import java.io.FilenameFilter;
+import java.util.ArrayList;
+import java.util.List;
+
+public class GuiFileChooser extends GuiButton {
+
+    @Getter
+    @Setter
+    private File selectedFile;
+
+    private String baseString;
+
+    private String[] allowedExtensions = null;
+
+    private List<FileChooseListener> listeners = new ArrayList<FileChooseListener>();
+
+    public GuiFileChooser(int buttonId, int x, int y, String buttonText, File selectedFile, String[] allowedExtensions) {
+        super(buttonId, x, y, buttonText);
+        this.selectedFile = selectedFile;
+
+        this.baseString = buttonText;
+        updateDisplayString();
+
+        this.allowedExtensions = allowedExtensions;
+    }
+
+    public void registerListener(FileChooseListener listener) {
+        this.listeners.add(listener);
+    }
+
+    protected void updateDisplayString() {
+        this.displayString = baseString + (selectedFile == null ? "-" : selectedFile.getName());
+    }
+
+    @Override
+    public boolean mousePressed(Minecraft mc, int mouseX, int mouseY) {
+        boolean success = super.mousePressed(mc, mouseX, mouseY);
+        if (success) {
+            new Thread(new Runnable() {
+                @Override
+                public void run() {
+                    Frame frame = new Frame();
+                    FileDialog fileDialog = new FileDialog(frame);
+
+                    fileDialog.setFilenameFilter(new FilenameFilter() {
+                        @Override
+                        public boolean accept(File dir, String name) {
+                            if(allowedExtensions == null) return true;
+                            for(String extension : allowedExtensions) {
+                                String[] split = name.split("\\.");
+                                String ext = split[split.length-1];
+                                if(extension.equalsIgnoreCase(ext)) return true;
+                            }
+
+                            return false;
+                        }
+                    });
+
+                    //frame.setVisible(true);
+                    fileDialog.setVisible(true);
+
+                    String filename = fileDialog.getFile();
+                    if(filename != null) {
+                        selectedFile = new File(filename);
+
+                        updateDisplayString();
+
+                        for(FileChooseListener listener : listeners) {
+                            listener.onFileChosen(selectedFile);
+                        }
+                    }
+
+                    frame.dispose();
+                }
+            }, "replaymod-file-chooser").start();
+        }
+        return success;
+    }
+
+}