/*
* Copyright (C) 2013 www.418log.org
*
* 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.ab.bitmap;
import java.util.ArrayList;
import java.util.List;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import com.ab.global.AbAppData;
import com.ab.util.AbFileUtil;
import com.ab.util.AbStrUtil;
// TODO: Auto-generated Javadoc
/**
* 描述：图片下载线程，按队列下载（先检查SD卡是否存在相同文件，不存在则下载，最后再从SD卡中读取）.
*
* @author zhaoqp
* @date 2011-12-10
* @version v1.0
*/
public class AbImageDownloadQueue extends Thread {
/** The tag. */
private static String TAG = "AbImageDownloadQueue";
/** The Constant D. */
private static final boolean D = AbAppData.DEBUG;
/** 下载队列. */
private List<AbImageDownloadItem> queue;
/** 图片下载线程单例类. */
private static AbImageDownloadQueue imageDownloadThread = null;
/** 控制释放. */
private static boolean stop = false;
/** 下载完成后的消息句柄. */
private static Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
//if(D)Log.d(TAG, "任务callback handleMessage...");
AbImageDownloadItem item = (AbImageDownloadItem)msg.obj;
item.listener.update(item.bitmap, item.imageUrl);
}
};
/**
* 构造图片下载线程队列.
*/
private AbImageDownloadQueue() {
stop = false;
queue = new ArrayList<AbImageDownloadItem>();
}
/**
* 单例构造图片下载线程.
*
* @return single instance of AbImageDownloadQueue
*/
public static AbImageDownloadQueue getInstance() {
if (imageDownloadThread == null) {
imageDownloadThread = new AbImageDownloadQueue();
imageDownloadThread.setName("AbImageDownloadQueue-1");
//创建后立刻运行
imageDownloadThread.start();
}
return imageDownloadThread;
}
/**
* 开始一个下载任务.
*
* @param item 图片下载单位
* @return Bitmap 下载完成后得到的Bitmap
*/
public void download(AbImageDownloadItem item) {
//检查图片路径
String imageUrl = item.imageUrl;
if(AbStrUtil.isEmpty(imageUrl)){
if(D)Log.d(TAG, "图片URL为空，请先判断");
}else{
imageUrl = imageUrl.trim();
}
//从缓存中获取这个Bitmap.
String cacheKey = AbImageCache.getCacheKey(imageUrl, item.width, item.height, item.type);
item.bitmap = AbImageCache.getBitmapFromCache(cacheKey);
if(item.bitmap == null){
addDownloadItem(item);
}else{
if(D) Log.d(TAG, "从内存缓存中得到图片:"+cacheKey+","+item.bitmap);
if (item.listener != null) {
Message msg = handler.obtainMessage();
msg.obj = item;
handler.sendMessage(msg);
}
}
}
/**
* 描述：添加到图片下载线程队列.
*
* @param item 图片下载单位
*/
private synchronized void addDownloadItem(AbImageDownloadItem item) {
queue.add(item);
//添加了下载项就激活本线程
this.notify();
}
/**
* 开始一个下载任务并清除原来队列.
*
* @param item 下载单位
*/
public void downloadBeforeClean(AbImageDownloadItem item) {
queue.clear();
addDownloadItem(item);
}
/**
* 描述：线程运行.
*
* @see java.lang.Thread#run()
*/
@Override
public void run() {
while(!stop) {
try {
if(D)Log.d(TAG, "图片下载队列大小："+queue.size());
while(queue.size() > 0) {
AbImageDownloadItem item = queue.remove(0);
//缓存图片路径
String cacheKey = AbImageCache.getCacheKey(item.imageUrl, item.width, item.height, item.type);
//逻辑：判断这个任务是否有其他线程再执行，如果有等待，直到下载完成唤醒显示
Runnable runnable = AbImageCache.getRunRunnableFromCache(cacheKey);
if(runnable != null){
//线程等待通知后显示
if(D) Log.d(TAG, "等待:"+cacheKey+","+item.imageUrl);
AbImageCache.addToWaitRunnableCache(cacheKey, this);
synchronized(this){
this.wait();
}
if(D) Log.d(TAG, "我醒了:"+item.imageUrl);
//直接获取
item.bitmap = AbImageCache.getBitmapFromCache(cacheKey);
}else{
//增加下载中的线程记录
if(D) Log.d(TAG, "增加图片下载中:"+cacheKey+","+item.imageUrl);
AbImageCache.addToRunRunnableCache(cacheKey, this);
item.bitmap = AbFileUtil.getBitmapFromSDCache(item.imageUrl,item.type,item.width,item.height);
//增加到下载完成的缓存，删除下载中的记录和等待的记录，同时唤醒所有等待列表中key与其key相同的线程
AbImageCache.addBitmapToCache(cacheKey,item.bitmap);
}
//需要执行回调来显示图片
if (item.listener != null) {
//交由UI线程处理
Message msg = handler.obtainMessage();
msg.obj = item;
handler.sendMessage(msg);
}
}
//停止
if(stop){
queue.clear();
return;
}
//没有下载项时等待
synchronized(this) {
this.wait();
}
} catch (Exception e) {
e.printStackTrace();
}finally{
}
}
}
/**
*
* 描述：终止队列释放线程
* @throws
*/
public void stopQueue(){
try {
stop = true;
imageDownloadThread = null;
this.interrupt();
} catch (Exception e) {
e.printStackTrace();
}
}
}