/*
* Copyright (c) 2012, Codename One and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Codename One designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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 General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Codename One through http://www.codenameone.com/ if you
* need additional information or have any questions.
*/
package com.codename1.components;
import com.codename1.ui.Component;
import com.codename1.ui.Container;
import com.codename1.ui.Display;
import com.codename1.ui.Graphics;
import com.codename1.ui.geom.Dimension;
import com.codename1.ui.layouts.FlowLayout;
/**
* <p>Allows adapting a scroll container to scroll indefinitely (or at least until
* running out of data), this effectively works by showing an infinite progress
* indicator when reaching scroll end then allowing code to fetch additional components.</p>
*
* <p>
* <strong>Warning:</strong> If you call {@link com.codename1.ui.Container#removeAll()} on the container to which an InfiniteScrollAdapter is
* installed, it will disable the infinite scrolling behavior. You can re-enable infinite scrolling by calling {@link #addMoreComponents(com.codename1.ui.Container, com.codename1.ui.Component[], boolean) }
* again.</p>
*
* <p>
* The sample code shows the usage of the nestoria API to fill out an infinitely scrolling list.
* </p>
* <script src="https://gist.github.com/codenameone/af27af111ba766627363.js"></script>
*
* <img src="https://www.codenameone.com/img/developer-guide/components-infinitescrolladapter.png" alt="Sample usage of infinite scroll adapter" /><br><br>
*
*
* @author Shai Almog
*/
public class InfiniteScrollAdapter {
private Container infiniteContainer;
private Runnable fetchMore;
private Component ip;
private int componentLimit = -1;
private InfiniteProgress progress;
class EdgeMarker extends Component {
private boolean top;
public EdgeMarker(boolean top) {
this.top = top;
}
public Dimension calcPreferredSize() {
return new Dimension(1,1);
}
public void paint(Graphics g) {
if(getParent() != null && isInClippingRegion(g)) {
reachedEnd();
}
}
}
private Component endMarker = new EdgeMarker(true);
private InfiniteScrollAdapter() {
progress = new InfiniteProgress();
Container p = new Container(new FlowLayout(Component.CENTER));
p.addComponent(progress);
ip = p;
}
void reachedEnd() {
infiniteContainer.removeComponent(endMarker);
infiniteContainer.addComponent(ip);
infiniteContainer.revalidate();
Display.getInstance().callSerially(fetchMore);
}
/**
* Creates an instance of the InfiniteScrollAdapter that will invoke the fetch more
* callback to fetch additional components, once that method completes its task it
* should add the components via the addMoreComponents() invocation.
* Notice that the container MUST be empty when invoking this method, fetchMore
* will be invoked immediately and you can add your data when ready.
*
* @param cont the container to bind, it MUST be empty and must be scrollable on the Y axis
* @param fetchMore a callback that will be invoked on the EDT to fetch more data (do not block this method)
* @return an instance of this class that can be used to add components
*/
public static InfiniteScrollAdapter createInfiniteScroll(Container cont, Runnable fetchMore) {
return createInfiniteScroll(cont, fetchMore, true);
}
/**
* Creates an instance of the InfiniteScrollAdapter that will invoke the fetch more
* callback to fetch additional components, once that method completes its task it
* should add the components via the addMoreComponents() invocation.
* Notice that the container MUST be empty when invoking this method, fetchMore
* will be invoked immediately and you can add your data when ready.
*
* @param cont the container to bind, it MUST be empty and must be scrollable on the Y axis
* @param fetchMore a callback that will be invoked on the EDT to fetch more data (do not block this method)
* @param fetchOnCreate if true the fetchMore callback is called upon calling this method
* @return an instance of this class that can be used to add components
*/
public static InfiniteScrollAdapter createInfiniteScroll(Container cont, Runnable fetchMore, boolean fetchOnCreate) {
InfiniteScrollAdapter a = new InfiniteScrollAdapter();
cont.putClientProperty("cn1$infinite", a);
a.infiniteContainer = cont;
a.fetchMore = fetchMore;
if(fetchOnCreate){
cont.addComponent(a.ip);
Display.getInstance().callSerially(fetchMore);
}else{
a.infiniteContainer.addComponent(a.endMarker);
}
return a;
}
/**
* Invoke this method to add additional components to the container, if you use
* addComponent/removeComponent you will get undefined behavior.
* This is a convenience method saving the need to keep the InfiniteScrollAdapter as a variable
* @param cnt container to add the components to
* @param components the components to add
* @param areThereMore whether additional components exist
*/
public static void addMoreComponents(Container cnt, Component[] components, boolean areThereMore) {
InfiniteScrollAdapter ia = (InfiniteScrollAdapter)cnt.getClientProperty("cn1$infinite");
ia.addMoreComponents(components, areThereMore);
}
/**
* Invoke this method to add additional components to the container, if you use
* addComponent/removeComponent you will get undefined behavior.
* @param components the components to add
* @param areThereMore whether additional components exist
*/
public void addMoreComponents(Component[] components, boolean areThereMore) {
infiniteContainer.removeComponent(ip);
infiniteContainer.removeComponent(endMarker);
for(Component c : components) {
c.setY(infiniteContainer.getHeight());
infiniteContainer.addComponent(c);
}
if(componentLimit > 0) {
int diff = infiniteContainer.getComponentCount() - componentLimit;
while(diff > 0) {
infiniteContainer.removeComponent(infiniteContainer.getComponentAt(0));
diff--;
}
}
infiniteContainer.revalidate();
if(areThereMore) {
// if this is animated we get redundant calls to reached end
infiniteContainer.addComponent(endMarker);
infiniteContainer.revalidate();
}
}
/**
* The component limit defines the number of components that should be within the infinite scroll adapter,
* if more than component limit is added then the appropriate number of components is removed from the top.
* This prevents running out of memory or performance overhead with too many components...
* Notice that -1 is a special case value for no component limit.
* @return the componentLimit
*/
public int getComponentLimit() {
return componentLimit;
}
/**
* The component limit defines the number of components that should be within the infinite scroll adapter,
* if more than component limit is added then the appropriate number of components is removed from the top.
* This prevents running out of memory or performance overhead with too many components...
* Notice that -1 is a special case value for no component limit.
* @param componentLimit the componentLimit to set
*/
public void setComponentLimit(int componentLimit) {
this.componentLimit = componentLimit;
}
/**
* Lets us manipulate the infinite progress object e.g. set the animation image etc.
* @return the infinite progress component underlying this adapter
*/
public InfiniteProgress getInfiniteProgress() {
return progress;
}
}