Make Grid rows draggable (#8690)

It is possible to customize the drag data for each row. (#8706)

Fixes #8396

1 files changed, 125 insertions, 0 deletions

diff --git a/server/src/main/java/com/vaadin/ui/GridDragSourceExtension.java b/server/src/main/java/com/vaadin/ui/GridDragSourceExtension.java
new file mode 100644
index 0000000000..9f7e9ec67d
--- /dev/null
+++ b/server/src/main/java/com/vaadin/ui/GridDragSourceExtension.java
@@ -0,0 +1,125 @@
+/*
+ * Copyright 2000-2016 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.ui;
+
+import java.util.Optional;
+
+import com.vaadin.data.provider.DataGenerator;
+import com.vaadin.event.dnd.DragSourceExtension;
+import com.vaadin.server.SerializableFunction;
+import com.vaadin.shared.ui.grid.GridDragSourceExtensionState;
+
+import elemental.json.JsonObject;
+
+/**
+ * Makes a Grid's rows draggable for HTML5 drag and drop functionality.
+ *
+ * @param <T>
+ *         The Grid bean type.
+ * @author Vaadin Ltd.
+ * @since
+ */
+public class GridDragSourceExtension<T> extends DragSourceExtension<Grid<T>> {
+
+    /**
+     * Drag data generator that appends drag data to each row.
+     */
+    private DataGenerator<T> dragDataGenerator;
+
+    /**
+     * Drag data generator function that is executed for each row.
+     */
+    private SerializableFunction<T, JsonObject> generatorFunction;
+
+    /**
+     * Extends a Grid and makes it's rows draggable.
+     *
+     * @param target
+     *         Grid to be extended.
+     */
+    public GridDragSourceExtension(Grid<T> target) {
+        super(target);
+
+        // Create drag data generator
+        dragDataGenerator = this::generateDragData;
+
+        // Add drag data generator to Grid
+        target.addDataGenerator(dragDataGenerator);
+    }
+
+    /**
+     * Drag data generator. Appends drag data to row data json if generator
+     * function is set by the user of this extension.
+     *
+     * @param item
+     *         Row item for data generation.
+     * @param jsonObject
+     *         Row data in json format.
+     */
+    private void generateDragData(T item, JsonObject jsonObject) {
+        Optional.ofNullable(generatorFunction).ifPresent(generator -> jsonObject
+                .put(GridDragSourceExtensionState.JSONKEY_DRAG_DATA,
+                        generator.apply(item)));
+    }
+
+    /**
+     * Sets a generator function for customizing drag data. The function is
+     * executed for each item in the Grid during data generation. Return a
+     * {@link JsonObject} to be appended to the row data.
+     * <p>
+     * Example:
+     * <pre>
+     *     dragSourceExtension.setDragDataGenerator(item -> {
+     *         JsonObject dragData = Json.createObject();
+     *         dragData.put("someKey", item.getValue());
+     *         return dragData;
+     *     });
+     * </pre>
+     *
+     * @param generator
+     *         Function to be executed on row data generation.
+     */
+    public void setDragDataGenerator(
+            SerializableFunction<T, JsonObject> generator) {
+        generatorFunction = generator;
+    }
+
+    /**
+     * Returns the generator function for customizing drag data.
+     *
+     * @return Drag data generator function.
+     */
+    public SerializableFunction<T, JsonObject> getDragDataGenerator() {
+        return generatorFunction;
+    }
+
+    @Override
+    public void remove() {
+        super.remove();
+
+        getParent().removeDataGenerator(dragDataGenerator);
+    }
+
+    @Override
+    protected GridDragSourceExtensionState getState() {
+        return (GridDragSourceExtensionState) super.getState();
+    }
+
+    @Override
+    protected GridDragSourceExtensionState getState(boolean markAsDirty) {
+        return (GridDragSourceExtensionState) super.getState(markAsDirty);
+    }
+}