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/*
* 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.event.dnd;
import java.util.Objects;
import com.vaadin.server.AbstractExtension;
import com.vaadin.shared.Registration;
import com.vaadin.shared.ui.dnd.DropEffect;
import com.vaadin.shared.ui.dnd.DropTargetRpc;
import com.vaadin.shared.ui.dnd.DropTargetState;
import com.vaadin.ui.AbstractComponent;
/**
* Extension to add drop target functionality to a widget for using HTML5 drag
* and drop.
*
* @param <T>
* Type of the component to be extended.
* @author Vaadin Ltd
* @since 8.1
*/
public class DropTargetExtension<T extends AbstractComponent> extends
AbstractExtension {
/**
* Extends {@code target} component and makes it a drop target.
*
* @param target
* Component to be extended.
*/
public DropTargetExtension(T target) {
registerRpc((DropTargetRpc) (dataTransferText, dropEffect) -> {
DropEvent<T> event = new DropEvent<>(target, dataTransferText,
dropEffect, getUI().getActiveDragSource());
fireEvent(event);
});
super.extend(target);
}
/**
* Sets the drop effect for the current drop target. Used for the client
* side {@code DataTransfer.dropEffect} parameter.
* <p>
* Default value is browser dependent and can depend on e.g. modifier keys.
*
* @param dropEffect
* The drop effect to be set. Cannot be {@code null}.
*/
public void setDropEffect(DropEffect dropEffect) {
if (dropEffect == null) {
throw new IllegalArgumentException("Drop effect cannot be null.");
}
if (!Objects.equals(getState(false).dropEffect, dropEffect)) {
getState().dropEffect = dropEffect;
}
}
/**
* Returns the drop effect for the current drop target.
*
* @return The drop effect of this drop target.
*/
public DropEffect getDropEffect() {
return getState(false).dropEffect;
}
/**
* Sets criteria to allow dragover event on the current drop target. The
* script executes when dragover event happens and stops the event in case
* the script returns {@code false}.
* <p>
* <b>IMPORTANT:</b> Construct the criteria script carefully and do not
* include untrusted sources such as user input. Always keep in mind that
* the script is executed on the client as is.
* <p>
* Example:
* <pre>
* target.setDropCriteria(
* // If dragged source contains a URL, allow it to be dragged over
* "if (event.dataTransfer.types.includes('text/uri-list')) {" +
* " return true;" +
* "}" +
*
* // Otherwise cancel the event"
* "return false;");
* </pre>
*
* @param criteriaScript
* JavaScript to be executed when dragover event happens or {@code
* null} to clear.
*/
public void setDragOverCriteria(String criteriaScript) {
if (!Objects.equals(getState(false).dragOverCriteria, criteriaScript)) {
getState().dragOverCriteria = criteriaScript;
}
}
/**
* Returns the criteria for allowing dragover event on the current drop
* target.
*
* @return JavaScript that executes when dragover event happens.
*/
public String getDragOverCriteria() {
return getState(false).dragOverCriteria;
}
/**
* Sets criteria to allow drop event on the current drop target. The script
* executes when drop event happens and stops the event in case the script
* returns {@code false}.
* <p>
* <b>IMPORTANT:</b> Construct the criteria script carefully and do not
* include untrusted sources such as user input. Always keep in mind that
* the script is executed on the client as is.
* <p>
* Example:
* <pre>
* target.setDropCriteria(
* // If dragged source contains a URL, allow it to be dropped
* "if (event.dataTransfer.types.includes('text/uri-list')) {" +
* " return true;" +
* "}" +
*
* // Otherwise cancel the event"
* "return false;");
* </pre>
*
* @param criteriaScript
* JavaScript to be executed when drop event happens or {@code null}
* to clear.
*/
public void setDropCriteria(String criteriaScript) {
if (!Objects.equals(getState(false).dropCriteria, criteriaScript)) {
getState().dropCriteria = criteriaScript;
}
}
/**
* Returns the criteria for allowing drop event on the current drop target.
*
* @return JavaScript that executes when drop event happens.
*/
public String getDropCriteria() {
return getState(false).dropCriteria;
}
/**
* Attaches drop listener for the current drop target. {@link
* DropListener#drop(DropEvent)} is called when drop event happens on the
* client side.
*
* @param listener
* Listener to handle drop event.
* @return Handle to be used to remove this listener.
*/
public Registration addDropListener(DropListener<T> listener) {
return addListener(DropEvent.class, listener, DropListener.DROP_METHOD);
}
@Override
protected DropTargetState getState() {
return (DropTargetState) super.getState();
}
@Override
protected DropTargetState getState(boolean markAsDirty) {
return (DropTargetState) super.getState(markAsDirty);
}
/**
* Returns the component this extension is attached to.
*
* @return Extended component.
*/
@Override
@SuppressWarnings("unchecked")
public T getParent() {
return (T) super.getParent();
}
}
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