playn.core.AssetWatcher Maven / Gradle / Ivy
/**
* Copyright 2011 The PlayN Authors
*
* 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 playn.core;
/**
* A utility class that helps keep track of image loading.
*
* To use: create a new {@link AssetWatcher}, then add images using
* {@link AssetWatcher#add(Image)} and finally call {@link AssetWatcher#start()}.
*/
public class AssetWatcher {
/**
* Listener interface for AssetWatcher.
*/
public interface Listener {
/**
* Called when all assets are done loading (or had an error).
*/
void done();
/**
* Called for each asset that failed to load.
*/
void error(Throwable e);
}
private int total, loaded, errors;
private boolean start;
private final Listener listener;
@SuppressWarnings("rawtypes")
private ResourceCallback callback = new ResourceCallback() {
@Override
public void done(Object resource) {
++loaded;
maybeDone();
}
@Override
public void error(Throwable e) {
++errors;
if (listener != null)
listener.error(e);
maybeDone();
}
};
/**
* Creates a new watcher without a listener.
*/
public AssetWatcher() {
this(null);
start();
}
/**
* Creates a new watcher with the given listener.
*
* Note: must call {@link AssetWatcher#start()} after adding your resources.
*/
public AssetWatcher(Listener listener) {
this.listener = listener;
}
/**
* Adds an image resource to be watched.
*/
@SuppressWarnings("unchecked")
public void add(Image image) {
Asserts.checkState(!start || listener == null);
++total;
image.addCallback(callback);
}
/**
* Whether all resources have completed loading, either successfully or in error.
*/
public boolean isDone() {
return start && (loaded + errors == total);
}
/**
* Done adding resources; {@link Listener#done()} will be called as soon as all assets are done
* being loaded.
*
* There is no need to call this method if there is no listener. {@link #isDone()} will return
* true as soon as all pending assets are loaded.
*/
public void start() {
start = true;
maybeDone();
}
private void maybeDone() {
if (isDone()) {
if (listener != null) {
listener.done();
}
}
}
}