Implement drag and drop for maintable

src/main/java/org/jabref/gui/BasePanel.java

@@ -1,8 +1,5 @@
 package org.jabref.gui;
 
-import java.awt.datatransfer.Clipboard;
-import java.awt.datatransfer.ClipboardOwner;
-import java.awt.datatransfer.Transferable;
 import java.io.File;
 import java.io.IOException;
 import java.io.StringReader;
@@ -134,7 +131,8 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-public class BasePanel extends StackPane implements ClipboardOwner {
+public class BasePanel extends StackPane {
+
     private static final Logger LOGGER = LoggerFactory.getLogger(BasePanel.class);
 
     private final BibDatabaseContext bibDatabaseContext;
@@ -227,8 +225,10 @@ public BasePanel(JabRefFrame frame, BasePanelPreferences preferences, BibDatabas
 
         this.entryEditor = new EntryEditor(this, preferences.getEntryEditorPreferences(), Globals.getFileUpdateMonitor(), dialogService);
 
-        this.preview = new PreviewPanel(this, getBibDatabaseContext(), preferences.getKeyBindings(), preferences.getPreviewPreferences(), dialogService);
+        this.preview = new PreviewPanel(this, getBibDatabaseContext(), preferences.getKeyBindings(), preferences.getPreviewPreferences(), dialogService, externalFileTypes);
         frame().getGlobalSearchBar().getSearchQueryHighlightObservable().addSearchListener(preview);
+
+
     }
 
     @Subscribe
@@ -680,15 +680,15 @@ public void runCommand(final Actions command) {
      */
     private boolean saveDatabase(File file, boolean selectedOnly, Charset encoding,
                                  SavePreferences.DatabaseSaveType saveType)
-            throws SaveException {
+        throws SaveException {
         SaveSession session;
         final String SAVE_DATABASE = Localization.lang("Save library");
         try {
             SavePreferences prefs = Globals.prefs.loadForSaveFromPreferences()
                                                  .withEncoding(encoding)
-                    .withSaveType(saveType);
+                                                 .withSaveType(saveType);
             BibtexDatabaseWriter<SaveSession> databaseWriter = new BibtexDatabaseWriter<>(
-                    FileSaveSession::new);
+                                                                                          FileSaveSession::new);
             if (selectedOnly) {
                 session = databaseWriter.savePartOfDatabase(bibDatabaseContext, mainTable.getSelectedEntries(), prefs);
             } else {
@@ -700,7 +700,7 @@ private boolean saveDatabase(File file, boolean selectedOnly, Charset encoding,
         // FIXME: not sure if this is really thrown anywhere
         catch (UnsupportedCharsetException ex) {
             frame.getDialogService().showErrorDialogAndWait(Localization.lang("Save library"), Localization.lang("Could not save file.")
-                    + Localization.lang("Character encoding '%0' is not supported.", encoding.displayName()));
+                                                                                               + Localization.lang("Character encoding '%0' is not supported.", encoding.displayName()));
             throw new SaveException("rt");
         } catch (SaveException ex) {
             if (ex.specificEntry()) {
@@ -1145,7 +1145,7 @@ public void entryEditorClosing(EntryEditor editor) {
      */
     public void ensureNotShowingBottomPanel(BibEntry entry) {
         if (((mode == BasePanelMode.SHOWING_EDITOR) && (entryEditor.getEntry() == entry))
-                || ((mode == BasePanelMode.SHOWING_PREVIEW) && (preview.getEntry() == entry))) {
+            || ((mode == BasePanelMode.SHOWING_PREVIEW) && (preview.getEntry() == entry))) {
             closeBottomPane();
         }
     }
@@ -1312,11 +1312,13 @@ private void saveDividerLocation(Number position) {
         }
     }
 
+    /*
     // Method pertaining to the ClipboardOwner interface.
     @Override
     public void lostOwnership(Clipboard clipboard, Transferable contents) {
         // Nothing
     }
+    */
 
     /**
      * Perform necessary cleanup when this BasePanel is closed.
@@ -1500,7 +1502,7 @@ public void listen(EntryAddedEvent addedEntryEvent) {
             if (Globals.prefs.getBoolean(JabRefPreferences.AUTO_ASSIGN_GROUP)) {
                 final List<BibEntry> entries = Collections.singletonList(addedEntryEvent.getBibEntry());
                 Globals.stateManager.getSelectedGroup(bibDatabaseContext).forEach(
-                        selectedGroup -> selectedGroup.addEntriesToGroup(entries));
+                                                                                  selectedGroup -> selectedGroup.addEntriesToGroup(entries));
             }
         }
     }
@@ -1601,8 +1603,8 @@ public void action() {
 
                     Optional<LinkedFile> linkedFile = files.stream()
                                                            .filter(file -> (FieldName.URL.equalsIgnoreCase(file.getFileType())
-                                                                   || FieldName.PS.equalsIgnoreCase(file.getFileType())
-                                                                   || FieldName.PDF.equalsIgnoreCase(file.getFileType())))
+                                                                            || FieldName.PS.equalsIgnoreCase(file.getFileType())
+                                                                            || FieldName.PDF.equalsIgnoreCase(file.getFileType())))
                                                            .findFirst();
 
                     if (linkedFile.isPresent()) {

src/main/java/org/jabref/gui/DragAndDropDataFormats.java

@@ -1,7 +1,11 @@
 package org.jabref.gui;
 
+import java.util.List;
+
 import javafx.scene.input.DataFormat;
 
+import org.jabref.model.entry.BibEntry;
+
 /**
  * Contains all the different {@link DataFormat}s that may occur in JabRef.
  */
@@ -10,4 +14,6 @@ public class DragAndDropDataFormats {
     public static final DataFormat GROUP = new DataFormat("dnd/org.jabref.model.groups.GroupTreeNode");
     public static final DataFormat LINKED_FILE = new DataFormat("dnd/org.jabref.model.entry.LinkedFile");
     public static final DataFormat ENTRIES = new DataFormat("dnd/org.jabref.model.entry.BibEntries");
+    @SuppressWarnings("unchecked") public static final Class<List<BibEntry>> BIBENTRY_LIST_CLASS = (Class<List<BibEntry>>) (Class<?>) List.class;
+
 }

src/main/java/org/jabref/gui/GUIGlobals.java

@@ -6,6 +6,7 @@
 import org.jabref.Globals;
 import org.jabref.gui.icon.IconTheme;
 import org.jabref.gui.keyboard.EmacsKeyBindings;
+import org.jabref.gui.util.CustomLocalDragboard;
 import org.jabref.logic.l10n.Localization;
 import org.jabref.preferences.JabRefPreferences;
 
@@ -16,12 +17,15 @@
  * Static variables for graphics files and keyboard shortcuts.
  */
 public class GUIGlobals {
+
     public static Color editorTextColor;
     public static Color validFieldBackgroundColor;
     public static Color activeBackgroundColor;
     public static Color invalidFieldBackgroundColor;
     public static Font currentFont;
 
+    public static CustomLocalDragboard localDragboard = new CustomLocalDragboard();
+
     public static final int WIDTH_ICON_COL = 16 + 12; // add some additional space to improve appearance
 
     public static final int WIDTH_ICON_COL_RANKING = 5 * 16; // Width of Ranking Icon Column
@@ -58,13 +62,12 @@ public static void init() {
 
         IconTheme.loadFonts();
         GUIGlobals.currentFont = new Font(Globals.prefs.get(JabRefPreferences.FONT_FAMILY),
-                Globals.prefs.getInt(JabRefPreferences.FONT_STYLE), Globals.prefs.getInt(JabRefPreferences.FONT_SIZE));
+                                          Globals.prefs.getInt(JabRefPreferences.FONT_STYLE), Globals.prefs.getInt(JabRefPreferences.FONT_SIZE));
     }
 
     public static void setFont(int size) {
         currentFont = new Font(currentFont.getFamily(), currentFont.getStyle(), size);
         // update preferences
         Globals.prefs.putInt(JabRefPreferences.FONT_SIZE, size);
     }
-
 }