先来一张效果图：
主要实现思路：
每一个下载都是通过RandomAccessFile对下载资源的总长进行切割之后，根据我们设置的线程多少进行计算之后开启多线程下载的。而每一个任务都是一个AsyncTask。数据的存储都是通过SQL来进行，保证整个下载任务的断续不受影响。
一：数据库操作的工具类，根据数据库设计而生成的bean类：
public class DBHelper extends SQLiteOpenHelper{
//download.db-->数据库名
public DBHelper(Context context) {
super(context, "download.db", null, 1);
}
/**
* 在download.db数据库下创建一个download_info表存储下载信息
*/
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("create table download_info(_id integer PRIMARY KEY AUTOINCREMENT, thread_id integer, "
+ "start_pos integer, end_pos integer, compelete_size integer,url char)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}数据库操作类，包括查看，保存，更新，获取，以及下载完毕之后的删除操作。
public class Dao {
private static Dao dao=null;
private Context context;
private Dao(Context context) {
this.context=context;
}
public static Dao getInstance(Context context){
if(dao==null){
dao=new Dao(context);
}
return dao;
}
public SQLiteDatabase getConnection() {
SQLiteDatabase sqliteDatabase = null;
try {
sqliteDatabase= new DBHelper(context).getReadableDatabase();
} catch (Exception e) {
}
return sqliteDatabase;
}
/**
* 查看数据库中是否有数据
*/
public synchronized boolean isHasInfors(String urlstr) {
SQLiteDatabase database = getConnection();
int count = -1;
Cursor cursor = null;
try {
String sql = "select count(*) from download_info where url=?";
cursor = database.rawQuery(sql, new String[] { urlstr });
if (cursor.moveToFirst()) {
count = cursor.getInt(0);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != database) {
database.close();
}
if (null != cursor) {
cursor.close();
}
}
return count == 0;
}
/**
* 保存 下载的具体信息
*/
public synchronized void saveInfos(List<DownloadInfo> infos) {
SQLiteDatabase database = getConnection();
try {
for (DownloadInfo info : infos) {
String sql = "insert into download_info(thread_id,start_pos, end_pos,compelete_size,url) values (?,?,?,?,?)";
Object[] bindArgs = { info.getThreadId(), info.getStartPos(),
info.getEndPos(), info.getCompeleteSize(),
info.getUrl() };
database.execSQL(sql, bindArgs);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != database) {
database.close();
}
}
}
/**
* 得到下载具体信息
*/
public synchronized List<DownloadInfo> getInfos(String urlstr) {
List<DownloadInfo> list = new ArrayList<>();
SQLiteDatabase database = getConnection();
Cursor cursor = null;
try {
String sql = "select thread_id, start_pos, end_pos,compelete_size,url from download_info where url=?";
cursor = database.rawQuery(sql, new String[] { urlstr });
while (cursor.moveToNext()) {
DownloadInfo info = new DownloadInfo(cursor.getInt(0),
cursor.getInt(1), cursor.getInt(2), cursor.getInt(3),
cursor.getString(4));
list.add(info);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != database) {
database.close();
}
if (null != cursor) {
cursor.close();
}
}
return list;
}
/**
* 更新数据库中的下载信息
*/
public synchronized void updataInfos(int threadId, int compeleteSize, String urlstr) {
SQLiteDatabase database = getConnection();
try {
String sql = "update download_info set compelete_size=? where thread_id=? and url=?";
Object[] bindArgs = { compeleteSize, threadId, urlstr };
database.execSQL(sql, bindArgs);
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != database) {
database.close();
}
}
}
/**
* 下载完成后删除数据库中的数据
*/
public synchronized void delete(String url) {
SQLiteDatabase database = getConnection();
try {
database.delete("download_info", "url=?", new String[] { url });
} catch (Exception e) {
e.printStackTrace();
} finally {
if (null != database) {
database.close();
}
}
}
}根据数据库设计的字段自己编写的bean类：
public class DownloadInfo {
private int threadId;//下载器id
private int startPos;//开始点
private int endPos;//结束点
private int compeleteSize;//完成度
private String url;//下载器网络标识
public DownloadInfo(int threadId, int startPos, int endPos,
int compeleteSize,String url) {
this.threadId = threadId;
this.startPos = startPos;
this.endPos = endPos;
this.compeleteSize = compeleteSize;
this.url=url;
}
public DownloadInfo() {
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public int getThreadId() {
return threadId;
}
public void setThreadId(int threadId) {
this.threadId = threadId;
}
public int getStartPos() {
return startPos;
}
public void setStartPos(int startPos) {
this.startPos = startPos;
}
public int getEndPos() {
return endPos;
}
public void setEndPos(int endPos) {
this.endPos = endPos;
}
public int getCompeleteSize() {
return compeleteSize;
}
public void setCompeleteSize(int compeleteSize) {
this.compeleteSize = compeleteSize;
}
@Override
public String toString() {
return "DownloadInfo [threadId=" + threadId
+ ", startPos=" + startPos + ", endPos=" + endPos
+ ", compeleteSize=" + compeleteSize +"]";
}
}从DownLoadInfo中获取到的几个数据要返回给activity进行进度的更新的实体类
public class LoadInfo {
public int fileSize;//文件大小
private int complete;//完成度
private String urlstring;//下载器标识
public LoadInfo(int fileSize, int complete, String urlstring) {
this.fileSize = fileSize;
this.complete = complete;
this.urlstring = urlstring;
}
public LoadInfo() {
}
public int getFileSize() {
return fileSize;
}
public void setFileSize(int fileSize) {
this.fileSize = fileSize;
}
public int getComplete() {
return complete;
}
public void setComplete(int complete) {
this.complete = complete;
}
public String getUrlstring() {
return urlstring;
}
public void setUrlstring(String urlstring) {
this.urlstring = urlstring;
}
@Override
public String toString() {
return "LoadInfo [fileSize=" + fileSize + ", complete=" + complete
+ ", urlstring=" + urlstring + "]";
}
}二：编写关键的DownLoader类，所有下载逻辑在这里进行，并连接数据库工具类进行操作。
首先就是构造，我们需要获取到的数据，肯定要包括自己设计的数据库里边的字段的数据，其次肯定还要知道多线程的指定数，
最后就是需要一个在activity中定义好的handler来进行进度的传递。
public DownLoader(String urlstr, String localfile, int threadcount,
Context context, Handler mHandler) {
this.urlstr = urlstr;
this.localfile = localfile;
this.threadcount = threadcount;
this.mHandler = mHandler;
this.context = context;
}那么下载的状态也是必须要提前准备好的
private static final int INIT = 1;//定义三种下载的状态：初始化状态，正在下载状态，暂停状态
private static final int DOWNLOADING = 2;
private static final int PAUSE = 3; /**
*判断是否正在下载
*/
public boolean isdownloading() {
return state == DOWNLOADING;
} //删除数据库中urlstr对应的下载器信息
public void delete(String urlstr) {
Dao.getInstance(context).delete(urlstr);
}
//设置暂停
public void pause() {
state = PAUSE;
}
//重置下载状态
public void reset() {
state = INIT;
}开始进入整个下载的逻辑
首先是判断是否是第一次下载：
/**
* 判断是否是第一次 下载
*/
private boolean isFirst(String urlstr) {
return Dao.getInstance(context).isHasInfors(urlstr);
}如果是第一次下载，就要知道整个下载资源的总长度：
/**
* 初始化
*/
private void init() {
try {
URL url = new URL(urlstr);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setConnectTimeout(5000);
connection.setRequestMethod("GET");
fileSize = connection.getContentLength();
File file = new File(localfile);
if (!file.exists()) {
file.createNewFile();
}
// 本地访问文件
RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");
accessFile.setLength(fileSize);
accessFile.close();
connection.disconnect();
} catch (Exception e) {
e.printStackTrace();
}
}总长度获取到之后，我们就需要通过线程的数量来进行计算每条线程开始的断点的位置，并且将每条线程的任务用bean类进行保存，并存储在list中，然后进行数据库的save。
int range = fileSize / threadcount;
infos = new ArrayList<>();
for (int i = 0; i < threadcount - 1; i++) {
DownloadInfo info = new DownloadInfo(i, i * range, (i + 1)* range - 1, 0, urlstr);
infos.add(info);
}
DownloadInfo info = new DownloadInfo(threadcount - 1,(threadcount - 1) * range, fileSize - 1, 0, urlstr);
infos.add(info);
//保存infos中的数据到数据库
Dao.getInstance(context).saveInfos(infos);那么如果不是第一次下载该资源，就需要先从数据库中获取到下载的信息。因为是断点下载，仅需要通过for循环计算出已下载的资源的总长度
//得到数据库中已有的urlstr的下载器的具体信息
infos = Dao.getInstance(context).getInfos(urlstr);
Log.v("TAG", "not isFirst size=" + infos.size());
int size = 0;//下载资源的总量
int compeleteSize = 0;//已经下载完成的资源总量
for (DownloadInfo info : infos) {
compeleteSize += info.getCompeleteSize();
size += info.getEndPos() - info.getStartPos() + 1;
} /**
* 得到downloader里的信息
* 首先进行判断是否是第一次下载，如果是第一次就要进行初始化，并将下载器的信息保存到数据库中
* 如果不是第一次下载，那就要从数据库中读出之前下载的信息（起始位置，结束为止，文件大小等），并将下载信息返回给下载器
*/
public LoadInfo getDownloaderInfors() {
if (isFirst(urlstr)) {
Log.v("TAG", "isFirst");
init();
int range = fileSize / threadcount;
infos = new ArrayList<>();
for (int i = 0; i < threadcount - 1; i++) {
DownloadInfo info = new DownloadInfo(i, i * range, (i + 1)* range - 1, 0, urlstr);//因为是第一次，所以completeSize为0；
infos.add(info);
}
DownloadInfo info = new DownloadInfo(threadcount - 1,(threadcount - 1) * range, fileSize - 1, 0, urlstr);
infos.add(info);
//保存infos中的数据到数据库
Dao.getInstance(context).saveInfos(infos);
//创建一个LoadInfo对象记载下载器的具体信息
LoadInfo loadInfo = new LoadInfo(fileSize, 0, urlstr);
return loadInfo;
} else {
//得到数据库中已有的urlstr的下载器的具体信息
infos = Dao.getInstance(context).getInfos(urlstr);
Log.v("TAG", "not isFirst size=" + infos.size());
int size = 0;
int compeleteSize = 0;
for (DownloadInfo info : infos) {
compeleteSize += info.getCompeleteSize();//因为已经下载过，所以需要计算出已下载的completeSize进行界面更新。
size += info.getEndPos() - info.getStartPos() + 1;
}
return new LoadInfo(size, compeleteSize, urlstr);
}
}在每次下载任务之前需要先去获取一下getDownloaderInfors（）下载的信息，注意这个信息因为包含数据库操作，且init中需要联网获取资源总长，所以需要在子线程中进行。
接下来开始进行具体的下载工作：
/**
* 利用线程开始下载数据
*/
public void download() {
if (infos != null) {
if (state == DOWNLOADING)
return;
state = DOWNLOADING;
for (DownloadInfo info : infos) {
new MyThread(info.getThreadId(), info.getStartPos(),
info.getEndPos(), info.getCompeleteSize(),
info.getUrl()).start();
}
}
}断点下载就需要将我们前面准备工作中获取到的DownLoadInfo的集合进行遍历，将每一个线程应该从哪儿到哪儿的下载任务区分好，整个线程的逻辑如下：
public class MyThread extends Thread {
private int threadId;
private int startPos;
private int endPos;
private int compeleteSize;
private String urlstr;
public MyThread(int threadId, int startPos, int endPos,
int compeleteSize, String urlstr) {
this.threadId = threadId;
this.startPos = startPos;
this.endPos = endPos;
this.compeleteSize = compeleteSize;
this.urlstr = urlstr;
}
@Override
public void run() {
HttpURLConnection connection = null;
RandomAccessFile randomAccessFile = null;
InputStream is = null;
try {
URL url = new URL(urlstr);
connection = (HttpURLConnection) url.openConnection();
connection.setConnectTimeout(5000);
connection.setRequestMethod("GET");
// 设置范围，格式为Range：bytes x-y;
connection.setRequestProperty("Range", "bytes="+(startPos + compeleteSize) + "-" + endPos);
randomAccessFile = new RandomAccessFile(localfile, "rwd");
randomAccessFile.seek(startPos + compeleteSize);
// 将要下载的文件写到保存在保存路径下的文件中
is = connection.getInputStream();
byte[] buffer = new byte[4096];
int length = -1;
while ((length = is.read(buffer)) != -1) {
randomAccessFile.write(buffer, 0, length);
compeleteSize += length;
// 更新数据库中的下载信息
Dao.getInstance(context).updataInfos(threadId, compeleteSize, urlstr);
// 用消息将下载信息传给进度条，对进度条进行更新
Message message = Message.obtain();
message.what = 1;
message.obj = urlstr;
message.arg1 = length;
mHandler.sendMessage(message);
if (state == PAUSE) {
return;
}
}
} catch (Exception e) {
e.printStackTrace();
}finally {
try {
if (connection!=null)connection.disconnect();
if (randomAccessFile!=null)randomAccessFile.close();
if (is!=null)is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}计算每个线程起始的下载位置，通过randomAccessFile.seek(startPos + compeleteSize)来快进到开始位置。然后进行while循环下载，不断的更新数据库（这一块的数据库操作很频繁，还在想怎么优化，但是感觉怎么优化都不太合适），并通过handler将完成度传递给activity进行界面更新。并且判断当前状态是否是已暂停，已暂停就直接跳出循环停止任务。最后记得关闭流。
这样整个下载工具类就结束了，接下来就是activity中对该类的调用以及界面的更新了、
三：Activity中的代码逻辑
首先是准备工作：
// 固定下载的资源路径，这里可以设置网络上的地址
private static final String URL = "http://download.haozip.com/";
// 固定存放下载的音乐的路径：SD卡目录下
private static final String SD_PATH = "/mnt/sdcard/";
// 存放各个下载器
private Map<String, DownLoader> downloaders = new HashMap<String, DownLoader>();
// 存放与下载器对应的进度条
private Map<String, ProgressBar> ProgressBars = new HashMap<String, ProgressBar>();这里将downloader和progressbar存储在map中，并且将下载的url作为key，这样就保证了数据的唯一。
数据的展示是使用的listview和adapter进行操作：
显示数据的准备：
// 显示listView，这里可以随便添加
private void showListView() {
List<Map<String, String>> data = new ArrayList<Map<String, String>>();
Map<String, String> map = new HashMap<String, String>();
map.put("name", "haozip_v3.1.exe");
data.add(map);
map = new HashMap<String, String>();
map.put("name", "haozip_v3.1_hj.exe");
data.add(map);
map = new HashMap<String, String>();
map.put("name", "haozip_v2.8_x64_tiny.exe");
data.add(map);
map = new HashMap<String, String>();
map.put("name", "haozip_v2.8_tiny.exe");
data.add(map);
DownLoadAdapter adapter=new DownLoadAdapter(this,data);
setListAdapter(adapter);
}adapter中也就是显示一下资源名，这里就不粘贴了。
item中的布局文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<LinearLayout
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="5dip">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:id="@+id/tv_resouce_name"/>
<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="下载"
android:id="@+id/btn_start"
android:onClick="startDownload"/>
<Button
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="暂停"
android:visibility="gone"
android:id="@+id/btn_pause"
android:onClick="pauseDownload"/>
</LinearLayout>
</LinearLayout>直接给每个item的button设置onclick事件，在activity中进行操作。（progressBar是在代码中new出来的，更方便控制）。
/**
* 响应开始下载按钮的点击事件
*/
public void startDownload(View v) {
// 得到textView的内容
LinearLayout layout = (LinearLayout) v.getParent();
String resouceName = ((TextView) layout.findViewById(R.id.tv_resouce_name)).getText().toString();
String urlstr = URL + resouceName;
String localfile = SD_PATH + resouceName;
//设置下载线程数为4，这里是我为了方便随便固定的
String threadcount = "4";
DownloadTask downloadTask=new DownloadTask(v);
downloadTask.execute(urlstr,localfile,threadcount);
};点击开始按钮之后，开启一个AsyncTask来进行下载的逻辑。
class DownloadTask extends AsyncTask<String, Integer, LoadInfo> {
DownLoader downloader=null;
View v=null;
String urlstr=null;
public DownloadTask(final View v){
this.v=v;
}
@Override
protected void onPreExecute() {
Button btn_start=(Button)((View)v.getParent()).findViewById(R.id.btn_start);
Button btn_pause=(Button)((View)v.getParent()).findViewById(R.id.btn_pause);
btn_start.setVisibility(View.GONE);
btn_pause.setVisibility(View.VISIBLE);
}
@Override
protected LoadInfo doInBackground(String... params) {
urlstr=params[0];
String localfile=params[1];
int threadcount=Integer.parseInt(params[2]);
// 初始化一个downloader下载器
downloader = downloaders.get(urlstr);
if (downloader == null) {
downloader = new DownLoader(urlstr, localfile, threadcount, MainActivity.this, mHandler);
downloaders.put(urlstr, downloader);
}
if (downloader.isdownloading())
return null;
// 得到下载信息类的个数组成集合
return downloader.getDownloaderInfors();
}
@Override
protected void onPostExecute(LoadInfo loadInfo) {
if(loadInfo!=null){
// 显示进度条
showProgress(loadInfo, urlstr, v);
// 调用方法开始下载
downloader.download();
}
}
};DownloadTask需要将button这个view通过构造方法传递过来，在准备阶段进行切换，将开始按钮隐藏，暂停按钮开启（当然也可以两个按钮都同时存在，就不用这么麻烦）。
在doInBackground中先进行DownLoader的初始化并且put到map中。这一步在downloader中主要是获取到资源总长以及分段生成DownloadInfo实体类，和保存这些实体类的list集合。最后获取到loadInfo，在下面进行界面的更新。
在onPostExecute（）中先是进行界面的更新（毕竟有可能是下载过数据的），然后开始进行分段下载。
/**
* 显示进度条
*/
private void showProgress(LoadInfo loadInfo, String url, View v) {
ProgressBar bar = ProgressBars.get(url);
if (bar == null) {//new出一个progressBar并进行addView添加到item中
bar = new ProgressBar(this, null, android.R.attr.progressBarStyleHorizontal);
bar.setMax(loadInfo.getFileSize());//根据在上一步骤中获取到的资源总长度设置bar的最大值
bar.setProgress(loadInfo.getComplete());
ProgressBars.put(url, bar);//put到map中
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.FILL_PARENT, 5);
((LinearLayout) ((LinearLayout) v.getParent()).getParent()).addView(bar, params);
}
}最后就是更新ui了，在activity中new一个handler，在Downloader初始化时传递过去，在下载中不断发送进度，在activity中获取到并及时更新：
/**
* 利用消息处理机制适时更新进度条
*/
private Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
if (msg.what == 1) {
String url = (String) msg.obj;
int length = msg.arg1;
ProgressBar bar = ProgressBars.get(url);
if (bar != null) {
// 增加指定的进度
bar.incrementProgressBy(length);
if (bar.getProgress() == bar.getMax()) {
LinearLayout layout = (LinearLayout) bar.getParent();
TextView resouceName=(TextView)layout.findViewById(R.id.tv_resouce_name);
Toast.makeText(MainActivity.this, "["+resouceName.getText()+"]下载完成！", Toast.LENGTH_SHORT).show();
// 下载完成后清除进度条并将map中的数据清空
layout.removeView(bar);
ProgressBars.remove(url);
downloaders.get(url).delete(url);
downloaders.get(url).reset();
downloaders.remove(url);
Button btn_start=(Button)layout.findViewById(R.id.btn_start);
Button btn_pause=(Button)layout.findViewById(R.id.btn_pause);
btn_pause.setVisibility(View.GONE);
btn_start.setVisibility(View.GONE);
}
}
}
}
};这里首先要注意，因为是多线程下载，且传递的message中是每一个线程下载的length，不是总长度，所以这边需要调用
bar.incrementProgressBy(length);方法进行progressBar的更新，不能直接采用setProgress（length）的方法。
最后就是下载完毕之后记得UI得操作，提示用户，以及数据的删除。
附上activity的整体代码以及adapter的代码：
public class DownLoadAdapter extends BaseAdapter{
private LayoutInflater mInflater;
private List<Map<String, String>> data;
private Context context;
private OnClickListener click;
public DownLoadAdapter(Context context,List<Map<String, String>> data) {
this.context=context;
mInflater = LayoutInflater.from(context);
this.data=data;
}
public void refresh(List<Map<String, String>> data) {
this.data=data;
this.notifyDataSetChanged();
}
public void setOnclick(OnClickListener click) {
this.click=click;
}
@Override
public int getCount() {
return data.size();
}
@Override
public Object getItem(int position) {
return data.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
final Map<String, String> bean=data.get(position);
ViewHolder holder = null;
if (convertView == null) {
convertView = mInflater.inflate(R.layout.item, null);
holder = new ViewHolder();
holder.resouceName=(TextView) convertView.findViewById(R.id.tv_resouce_name);
holder.startDownload=(Button) convertView.findViewById(R.id.btn_start);
holder.pauseDownload=(Button) convertView.findViewById(R.id.btn_pause);
convertView.setTag(holder);
} else {
holder = (ViewHolder) convertView.getTag();
}
holder.resouceName.setText(bean.get("name"));
return convertView;
}
public OnClickListener getClick() {
return click;
}
public void setClick(OnClickListener click) {
this.click = click;
}
private class ViewHolder {
public TextView resouceName;
public Button startDownload;
public Button pauseDownload;
}
}public class MainActivity extends AppCompatActivity {
private String[] urls={"http://jzvd.nathen.cn/c494b340ff704015bb6682ffde3cd302/64929c369124497593205a4190d7d128-5287d2089db37e62345123a1be272f8b.mp4",
"http://jzvd.nathen.cn/63f3f73712544394be981d9e4f56b612/69c5767bb9e54156b5b60a1b6edeb3b5-5287d2089db37e62345123a1be272f8b.mp4",
"http://jzvd.nathen.cn/b201be3093814908bf987320361c5a73/2f6d913ea25941ffa78cc53a59025383-5287d2089db37e62345123a1be272f8b.mp4",
"http://jzvd.nathen.cn/d2438fd1c37c4618a704513ad38d68c5/68626a9d53ca421c896ac8010f172b68-5287d2089db37e62345123a1be272f8b.mp4",
"http://jzvd.nathen.cn/25a8d119cfa94b49a7a4117257d8ebd7/f733e65a22394abeab963908f3c336db-5287d2089db37e62345123a1be272f8b.mp4",
"http://jzvd.nathen.cn/7512edd1ad834d40bb5b978402274b1a/9691c7f2d7b74b5e811965350a0e5772-5287d2089db37e62345123a1be272f8b.mp4",
"http://jzvd.nathen.cn/c6e3dc12a1154626b3476d9bf3bd7266/6b56c5f0dc31428083757a45764763b0-5287d2089db37e62345123a1be272f8b.mp4"
};
// 固定存放下载的音乐的路径：SD卡目录下
private static final String SD_PATH = "/mnt/sdcard/";
// 存放各个下载器
private Map<String, DownLoader> downloaders = new HashMap<String, DownLoader>();
// 存放与下载器对应的进度条
private Map<String, ProgressBar> ProgressBars = new HashMap<String, ProgressBar>();
/**
* 利用消息处理机制适时更新进度条
*/
private Handler mHandler = new Handler() {
public void handleMessage(Message msg) {
if (msg.what == 1) {
String url = (String) msg.obj;
int length = msg.arg1;
ProgressBar bar = ProgressBars.get(url);
if (bar != null) {
// 设置进度条按读取的length长度更新
bar.incrementProgressBy(length);
if (bar.getProgress() == bar.getMax()) {
LinearLayout layout = (LinearLayout) bar.getParent();
TextView resouceName=(TextView)layout.findViewById(R.id.tv_resouce_name);
Toast.makeText(MainActivity.this, "["+resouceName.getText()+"]下载完成！", Toast.LENGTH_SHORT).show();
// 下载完成后清除进度条并将map中的数据清空
layout.removeView(bar);
ProgressBars.remove(url);
downloaders.get(url).delete(url);
downloaders.get(url).reset();
downloaders.remove(url);
Button btn_start=(Button)layout.findViewById(R.id.btn_start);
Button btn_pause=(Button)layout.findViewById(R.id.btn_pause);
btn_pause.setVisibility(View.GONE);
btn_start.setVisibility(View.GONE);
}
}
}
}
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
showListView();
}
// 显示listView，这里可以随便添加
private void showListView() {
List<Map<String, String>> data = new ArrayList<Map<String, String>>();
for (int i=0;i<urls.length;i++){
Map<String, String> map = new HashMap<String, String>();
map.put("name", urls[i]);
data.add(map);
}
DownLoadAdapter adapter=new DownLoadAdapter(this,data);
setListAdapter(adapter);
}
private void setListAdapter(DownLoadAdapter adapter) {
ListView listView=findViewById(R.id.list);
listView.setAdapter(adapter);
}
/**
* 响应开始下载按钮的点击事件
*/
public void startDownload(View v) {
// 得到textView的内容
LinearLayout layout = (LinearLayout) v.getParent();
String resouceName = ((TextView) layout.findViewById(R.id.tv_resouce_name)).getText().toString();
String urlstr = resouceName;
String localfile = SD_PATH + resouceName.substring(resouceName.lastIndexOf("/"));
//设置下载线程数为4，这里是我为了方便随便固定的
String threadcount = "4";
DownloadTask downloadTask=new DownloadTask(v);
downloadTask.execute(urlstr,localfile,threadcount);
};
class DownloadTask extends AsyncTask<String, Integer, LoadInfo> {
DownLoader downloader=null;
View v=null;
String urlstr=null;
public DownloadTask(final View v){
this.v=v;
}
@Override
protected void onPreExecute() {
Button btn_start=(Button)((View)v.getParent()).findViewById(R.id.btn_start);
Button btn_pause=(Button)((View)v.getParent()).findViewById(R.id.btn_pause);
btn_start.setVisibility(View.GONE);
btn_pause.setVisibility(View.VISIBLE);
}
@Override
protected LoadInfo doInBackground(String... params) {
urlstr=params[0];
String localfile=params[1];
int threadcount=Integer.parseInt(params[2]);
// 初始化一个downloader下载器
downloader = downloaders.get(urlstr);
if (downloader == null) {
downloader = new DownLoader(urlstr, localfile, threadcount, MainActivity.this, mHandler);
downloaders.put(urlstr, downloader);
}
if (downloader.isdownloading())
return null;
// 得到下载信息类的个数组成集合
return downloader.getDownloaderInfors();
}
@Override
protected void onPostExecute(LoadInfo loadInfo) {
if(loadInfo!=null){
// 显示进度条
showProgress(loadInfo, urlstr, v);
// 调用方法开始下载
downloader.download();
}
}
};
/**
* 显示进度条
*/
private void showProgress(LoadInfo loadInfo, String url, View v) {
ProgressBar bar = ProgressBars.get(url);
if (bar == null) {
bar = new ProgressBar(this, null, android.R.attr.progressBarStyleHorizontal);
bar.setMax(loadInfo.getFileSize());
bar.setProgress(loadInfo.getComplete());
ProgressBars.put(url, bar);
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.FILL_PARENT, 5);
((LinearLayout) ((LinearLayout) v.getParent()).getParent()).addView(bar, params);
}
}
/**
* 响应暂停下载按钮的点击事件
*/
public void pauseDownload(View v) {
LinearLayout layout = (LinearLayout) v.getParent();
String resouceName = ((TextView) layout.findViewById(R.id.tv_resouce_name)).getText().toString();
String urlstr =resouceName;
downloaders.get(urlstr).pause();
Button btn_start=(Button)((View)v.getParent()).findViewById(R.id.btn_start);
Button btn_pause=(Button)((View)v.getParent()).findViewById(R.id.btn_pause);
btn_pause.setVisibility(View.GONE);
btn_start.setVisibility(View.VISIBLE);
}
}