Drag and drop interaction (Smart GWT)
/*
* SmartGWT (GWT for SmartClient)
* Copyright 2008 and beyond, Isomorphic Software, Inc.
*
* SmartGWT is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License version 3
* as published by the Free Software Foundation. SmartGWT is also
* available under typical commercial license terms - see
* http://smartclient.com/license
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package com.smartgwt.sample.showcase.client;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.ui.RootPanel;
import com.smartgwt.client.types.Alignment;
import com.smartgwt.client.types.DragAppearance;
import com.smartgwt.client.types.Overflow;
import com.smartgwt.client.types.Visibility;
import com.smartgwt.client.util.EventHandler;
import com.smartgwt.client.widgets.Canvas;
import com.smartgwt.client.widgets.Img;
import com.smartgwt.client.widgets.Label;
import com.smartgwt.client.widgets.events.DropMoveEvent;
import com.smartgwt.client.widgets.events.DropMoveHandler;
import com.smartgwt.client.widgets.events.DropOutEvent;
import com.smartgwt.client.widgets.events.DropOutHandler;
import com.smartgwt.client.widgets.events.DropOverEvent;
import com.smartgwt.client.widgets.events.DropOverHandler;
public class Showcase implements EntryPoint{
public void onModuleLoad() {
RootPanel.get().add(getViewPanel());
}
public Canvas getViewPanel() {
Canvas canvas = new Canvas();
final Img img = new Img("pieces/48/pawn_green.png", 48, 48) {
protected boolean setDragTracker() {
Canvas c = new Canvas();
String html = Canvas.imgHTML("pieces/24/pawn_green.png", 24, 24, null, null, null);
EventHandler.setDragTracker(html);
return false;
}
};
img.setCanDrag(true);
img.setCanDrop(true);
img.setDragAppearance(DragAppearance.TRACKER);
final DropLabel label = new DropLabel();
label.setLeft(100);
label.setWidth(300);
label.setHeight(300);
label.setBackgroundColor("lightblue");
label.setAlign(Alignment.CENTER);
label.setContents("Show Drop Reticle");
label.setOverflow(Overflow.HIDDEN);
label.setCanAcceptDrop(true);
canvas.addChild(img);
canvas.addChild(label);
return canvas;
}
class DropLabel extends Label {
private Canvas crossHairX;
private Canvas crossHairY;
protected void onInit() {
crossHairX = createCrossHair();
crossHairY = createCrossHair();
addChild(crossHairX);
addChild(crossHairY);
this.addDropOverHandler(new DropOverHandler() {
public void onDropOver(DropOverEvent event) {
getCrossHairX().show();
getCrossHairY().show();
updateCrossHairs();
}
});
this.addDropMoveHandler(new DropMoveHandler() {
public void onDropMove(DropMoveEvent event) {
updateCrossHairs();
}
});
this.addDropOutHandler(new DropOutHandler() {
public void onDropOut(DropOutEvent event) {
getCrossHairX().hide();
getCrossHairY().hide();
}
});
}
private Canvas createCrossHair() {
Canvas canvas = new Canvas();
canvas.setWidth(this.getWidth() + 2);
canvas.setHeight(this.getHeight() + 2);
canvas.setBorder("1px solid black");
canvas.setVisibility(Visibility.HIDDEN);
return canvas;
}
public Canvas getCrossHairX() {
return crossHairX;
}
public Canvas getCrossHairY() {
return crossHairY;
}
public void updateCrossHairs() {
int x = getOffsetX();
int y = getOffsetY();
// crossHairX is the -X and +Y axis of the crossHair
crossHairX.setLeft(x - getWidth() - 1);
crossHairX.setTop(y - getHeight() - 1);
// crossHairY is +X, -Y
crossHairY.setLeft(x);
crossHairY.setTop(y);
}
}
}
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