让我们看一下代码的实现方法。
package com.smart.db;
import java.util.HashMap;
import java.util.Map;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
/**
* 业务bean
*
*/
public class FileService {
private DBOpenHelper openHelper;
public FileService(Context context) {
openHelper = new DBOpenHelper(context);
}
/**
* 获取每条线程已经下载的文件长度
* @param path
* @return
*/
public Map<Integer, Integer> getData(String path){
SQLiteDatabase db = openHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select threadid, downlength from SmartFileDownlog where downpath=?", new String[]{path});
Map<Integer, Integer> data = new HashMap<Integer, Integer>();
while(cursor.moveToNext()){
data.put(cursor.getInt(0), cursor.getInt(1));
}
cursor.close();
db.close();
return data;
}
/**
* 保存每条线程已经下载的文件长度
* @param path
* @param map
*/
public void save(String path, Map<Integer, Integer> map){//int threadid, int position
SQLiteDatabase db = openHelper.getWritableDatabase();
db.beginTransaction();
try{
for(Map.Entry<Integer, Integer> entry : map.entrySet()){
db.execSQL("insert into SmartFileDownlog(downpath, threadid, downlength) values(?,?,?)",
new Object[]{path, entry.getKey(), entry.getValue()});
}
db.setTransactionSuccessful();
}finally{
db.endTransaction();
}
db.close();
}
/**
* 实时更新每条线程已经下载的文件长度
* @param path
* @param map
*/
public void update(String path, Map<Integer, Integer> map){
SQLiteDatabase db = openHelper.getWritableDatabase();
db.beginTransaction();
try{
for(Map.Entry<Integer, Integer> entry : map.entrySet()){
db.execSQL("update SmartFileDownlog set downlength=? where downpath=? and threadid=?",
new Object[]{entry.getValue(), path, entry.getKey()});
}
db.setTransactionSuccessful();
}finally{
db.endTransaction();
}
db.close();
}
/**
* 当文件下载完成后，删除对应的下载记录
* @param path
*/
public void delete(String path){
SQLiteDatabase db = openHelper.getWritableDatabase();
db.execSQL("delete from SmartFileDownlog where downpath=?", new Object[]{path});
db.close();
}
}
package com.smart.impl;
import java.io.File;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import android.content.Context;
import android.util.Log;
import com.smart.db.FileService;
/**
* 文件下载器
* @author lihuoming@sohu.com
*/
public class SmartFileDownloader {
private static final String TAG = "SmartFileDownloader";
private Context context;
private FileService fileService;
/* 已下载文件长度 */
private int downloadSize = 0;
/* 原始文件长度 */
private int fileSize = 0;
/* 线程数 */
private SmartDownloadThread[] threads;
/* 本地保存文件 */
private File saveFile;
/* 缓存各线程下载的长度*/
private Map<Integer, Integer> data = new ConcurrentHashMap<Integer, Integer>();
/* 每条线程下载的长度 */
private int block;
/* 下载路径 */
private String downloadUrl;
/**
* 获取线程数
*/
public int getThreadSize() {
return threads.length;
}
/**
* 获取文件大小
* @return
*/
public int getFileSize() {
return fileSize;
}
/**
* 累计已下载大小
* @param size
*/
protected synchronized void append(int size) {
downloadSize += size;
}
/**
* 更新指定线程最后下载的位置
* @param threadId 线程id
* @param pos 最后下载的位置
*/
protected void update(int threadId, int pos) {
this.data.put(threadId, pos);
}
/**
* 保存记录文件
*/
protected synchronized void saveLogFile() {
this.fileService.update(this.downloadUrl, this.data);
}
/**
* 构建文件下载器
* @param downloadUrl 下载路径
* @param fileSaveDir 文件保存目录
* @param threadNum 下载线程数
*/
public SmartFileDownloader(Context context, String downloadUrl, File fileSaveDir, int threadNum) {
try {
this.context = context;
this.downloadUrl = downloadUrl;
fileService = new FileService(this.context);
URL url = new URL(this.downloadUrl);
if(!fileSaveDir.exists()) fileSaveDir.mkdirs();
this.threads = new SmartDownloadThread[threadNum];
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(5*1000);
conn.setRequestMethod("GET");
conn.setRequestProperty("Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*");
conn.setRequestProperty("Accept-Language", "zh-CN");
conn.setRequestProperty("Referer", downloadUrl);
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");
conn.setRequestProperty("Connection", "Keep-Alive");
conn.connect();
printResponseHeader(conn);
if (conn.getResponseCode()==200) {
this.fileSize = conn.getContentLength();//根据响应获取文件大小
if (this.fileSize <= 0) throw new RuntimeException("Unkown file size ");
String filename = getFileName(conn);
this.saveFile = new File(fileSaveDir, filename);/* 保存文件 */
Map<Integer, Integer> logdata = fileService.getData(downloadUrl);
if(logdata.size()>0){
for(Map.Entry<Integer, Integer> entry : logdata.entrySet())
data.put(entry.getKey(), entry.getValue());
}
this.block = (this.fileSize % this.threads.length)==0? this.fileSize / this.threads.length : this.fileSize / this.threads.length + 1;
if(this.data.size()==this.threads.length){
for (int i = 0; i < this.threads.length; i++) {
this.downloadSize += this.data.get(i+1);
}
print("已经下载的长度"+ this.downloadSize);
}
}else{
throw new RuntimeException("server no response ");
}
} catch (Exception e) {
print(e.toString());
throw new RuntimeException("don't connection this url");
}
}
/**
* 获取文件名
*/
private String getFileName(HttpURLConnection conn) {
String filename = this.downloadUrl.substring(this.downloadUrl.lastIndexOf('/') + 1);
if(filename==null || "".equals(filename.trim())){//如果获取不到文件名称
for (int i = 0;; i++) {
String mine = conn.getHeaderField(i);
if (mine == null) break;
if("content-disposition".equals(conn.getHeaderFieldKey(i).toLowerCase())){
Matcher m = Pattern.compile(".*filename=(.*)").matcher(mine.toLowerCase());
if(m.find()) return m.group(1);
}
}
filename = UUID.randomUUID()+ ".tmp";//默认取一个文件名
}
return filename;
}
/**
* 开始下载文件
* @param listener 监听下载数量的变化,如果不需要了解实时下载的数量,可以设置为null
* @return 已下载文件大小
* @throws Exception
*/
public int download(SmartDownloadProgressListener listener) throws Exception{
try {
RandomAccessFile randOut = new RandomAccessFile(this.saveFile, "rw");
if(this.fileSize>0) randOut.setLength(this.fileSize);
randOut.close();
URL url = new URL(this.downloadUrl);
if(this.data.size() != this.threads.length){
this.data.clear();//清除数据
for (int i = 0; i < this.threads.length; i++) {
this.data.put(i+1, 0);
}
}
for (int i = 0; i < this.threads.length; i++) {
int downLength = this.data.get(i+1);
if(downLength < this.block && this.downloadSize<this.fileSize){ //该线程未完成下载时,继续下载
this.threads = new SmartDownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
this.threads.setPriority(7);
this.threads.start();
}else{
this.threads = null;
}
}
this.fileService.save(this.downloadUrl, this.data);
boolean notFinish = true;//下载未完成
while (notFinish) {// 循环判断是否下载完毕
Thread.sleep(900);
notFinish = false;//假定下载完成
for (int i = 0; i < this.threads.length; i++){
if (this.threads != null && !this.threads.isFinish()) {
notFinish = true;//下载没有完成
if(this.threads.getDownLength() == -1){//如果下载失败,再重新下载
this.threads = new SmartDownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
this.threads.setPriority(7);
this.threads.start();
}
}
}
if(listener!=null) listener.onDownloadSize(this.downloadSize);
}
fileService.delete(this.downloadUrl);
} catch (Exception e) {
print(e.toString());
throw new Exception("file download fail");
}
return this.downloadSize;
}
/**
* 获取Http响应头字段
* @param http
* @return
*/
public static Map<String, String> getHttpResponseHeader(HttpURLConnection http) {
Map<String, String> header = new LinkedHashMap<String, String>();
for (int i = 0;; i++) {
String mine = http.getHeaderField(i);
if (mine == null) break;
header.put(http.getHeaderFieldKey(i), mine);
}
return header;
}
/**
* 打印Http头字段
* @param http
*/
public static void printResponseHeader(HttpURLConnection http){
Map<String, String> header = getHttpResponseHeader(http);
for(Map.Entry<String, String> entry : header.entrySet()){
String key = entry.getKey()!=null ? entry.getKey()+ ":" : "";
print(key+ entry.getValue());
}
}
//打印日志
private static void print(String msg){
Log.i(TAG, msg);
}
}
package com.smart.impl;
import java.io.File;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import android.util.Log;
public class SmartDownloadThread extends Thread {
private static final String TAG = "SmartDownloadThread";
private File saveFile;
private URL downUrl;
private int block;
/* *下载开始位置 */
private int threadId = -1;
private int downLength;
private boolean finish = false;
private SmartFileDownloader downloader;
public SmartDownloadThread(SmartFileDownloader downloader, URL downUrl, File saveFile, int block, int downLength, int threadId) {
this.downUrl = downUrl;
this.saveFile = saveFile;
this.block = block;
this.downloader = downloader;
this.threadId = threadId;
this.downLength = downLength;
}
@Override
public void run() {
if(downLength < block){//未下载完成
try {
HttpURLConnection http = (HttpURLConnection) downUrl.openConnection();
http.setConnectTimeout(5 * 1000);
http.setRequestMethod("GET");
http.setRequestProperty("Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*");
http.setRequestProperty("Accept-Language", "zh-CN");
http.setRequestProperty("Referer", downUrl.toString());
http.setRequestProperty("Charset", "UTF-8");
int startPos = block * (threadId - 1) + downLength;//开始位置
int endPos = block * threadId -1;//结束位置
http.setRequestProperty("Range", "bytes=" + startPos + "-"+ endPos);//设置获取实体数据的范围
http.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");
http.setRequestProperty("Connection", "Keep-Alive");
InputStream inStream = http.getInputStream();
byte[] buffer = new byte[1024];
int offset = 0;
print("Thread " + this.threadId + " start download from position "+ startPos);
RandomAccessFile threadfile = new RandomAccessFile(this.saveFile, "rwd");
threadfile.seek(startPos);
while ((offset = inStream.read(buffer, 0, 1024)) != -1) {
threadfile.write(buffer, 0, offset);
downLength += offset;
downloader.update(this.threadId, downLength);
downloader.saveLogFile();
downloader.append(offset);
}
threadfile.close();
inStream.close();
print("Thread " + this.threadId + " download finish");
this.finish = true;
} catch (Exception e) {
this.downLength = -1;
print("Thread "+ this.threadId+ ":"+ e);
}
}
}
private static void print(String msg){
Log.i(TAG, msg);
}
/**
* 下载是否完成
* @return
*/
public boolean isFinish() {
return finish;
}
/**
* 已经下载的内容大小
* @return 如果返回值为-1,代表下载失败
*/
public long getDownLength() {
return downLength;
}
}
package com.smart.activoty.download;
import java.io.File;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import com.smart.impl.SmartDownloadProgressListener;
import com.smart.impl.SmartFileDownloader;
public class SmartDownloadActivity extends Activity {
private ProgressBar downloadbar;
private EditText pathText;
private TextView resultView;
private Handler handler = new Handler(){
@Override//信息
public void handleMessage(Message msg) {
switch (msg.what) {
case 1:
int size = msg.getData().getInt("size");
downloadbar.setProgress(size);
float result = (float)downloadbar.getProgress()/ (float)downloadbar.getMax();
int p = (int)(result*100);
resultView.setText(p+"%");
if(downloadbar.getProgress()==downloadbar.getMax())
Toast.makeText(SmartDownloadActivity.this, R.string.success, 1).show();
break;
case -1:
Toast.makeText(SmartDownloadActivity.this, R.string.error, 1).show();
break;
}
}
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button button = (Button)this.findViewById(R.id.button);
downloadbar = (ProgressBar)this.findViewById(R.id.downloadbar);
pathText = (EditText)this.findViewById(R.id.path);
resultView = (TextView)this.findViewById(R.id.result);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String path = pathText.getText().toString();
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
File dir = Environment.getExternalStorageDirectory();//文件保存目录
download(path, dir);
}else{
Toast.makeText(SmartDownloadActivity.this, R.string.sdcarderror, 1).show();
}
}
});
}
//对于UI控件的更新只能由主线程(UI线程)负责，如果在非UI线程更新UI控件，更新的结果不会反映在屏幕上，某些控件还会出错
private void download(final String path, final File dir){
new Thread(new Runnable() {
@Override
public void run() {
try {
SmartFileDownloader loader = new SmartFileDownloader(SmartDownloadActivity.this, path, dir, 3);
int length = loader.getFileSize();//获取文件的长度
downloadbar.setMax(length);
loader.download(new SmartDownloadProgressListener(){
@Override
public void onDownloadSize(int size) {//可以实时得到文件下载的长度
Message msg = new Message();
msg.what = 1;
msg.getData().putInt("size", size);
handler.sendMessage(msg);
}});
} catch (Exception e) {
Message msg = new Message();//信息提示
msg.what = -1;
msg.getData().putString("error", "下载失败");//如果下载错误，显示提示失败！
handler.sendMessage(msg);
}
}
}).start();//开始
}
}
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