Android实现多线程下载文件的方法

2019-10-24 20:35:41

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这篇文章主要介绍了Android实现多线程下载文件的方法,以实例形式较为详细的分析了Android多线程文件传输及合并等操作的相关技巧,具有一定参考借鉴价值,需要的朋友可以参考下

本文实例讲述了Android实现多线程下载文件的方法。分享给大家供大家参考。具体如下：

多线程下载大概思路就是通过Range 属性实现文件分段，然后用RandomAccessFile 来读写文件，最终合并为一个文件

首先看下效果图：

创建工程 ThreadDemo

首先布局文件 threaddemo.xml

<?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="fill_parent"

>

<TextView

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="下载地址"

/>

<TextView

android:id="@+id/downloadurl"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:lines="5"

/>

<TextView

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="线程数"

/>

<EditText

android:id="@+id/downloadnum"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

/>

<ProgressBar

android:id="@+id/downloadProgressBar"

android:layout_width="fill_parent"

style="?android:attr/progressBarStyleHorizontal"

android:layout_height="wrap_content"

/>

<TextView

android:id="@+id/downloadinfo"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="下载进度 0"

/>

<Button

android:id="@+id/downloadbutton"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="开始下载"

/>

</LinearLayout>

<?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="fill_parent" >

<TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="下载地址" />

<TextViewandroid:id="@+id/downloadurl"android:layout_width="fill_parent" android:layout_height="wrap_content" android:lines="5"/>

<TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="线程数" />

<EditTextandroid:id="@+id/downloadnum"android:layout_width="fill_parent" android:layout_height="wrap_content" />

<ProgressBarandroid:id="@+id/downloadProgressBar"android:layout_width="fill_parent" style="?android:attr/progressBarStyleHorizontal" android:layout_height="wrap_content" />

<TextViewandroid:id="@+id/downloadinfo"android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="下载进度 0"/>

<Buttonandroid:id="@+id/downloadbutton"android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="开始下载"/>

</LinearLayout>

主界面 Acitivity

public class ThreadDownloadDemo extends Activity {

private TextView downloadurl;

private EditText downloadnum;

private Button downloadbutton;

private ProgressBar downloadProgressBar;

private TextView downloadinfo;

private int downloadedSize = 0;

private int fileSize = 0;

private long downloadtime;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.threaddemo);

downloadurl = (TextView) findViewById(R.id.downloadurl);

downloadurl.setText("http://file16.top100.cn/201105110911/AA5CC27CBE34DEB50A194581D1300881/Special_323149/%E8%8D%B7%E5%A1%98%E6%9C%88%E8%89%B2.mp3");

downloadnum = (EditText) findViewById(R.id.downloadnum);

downloadinfo = (TextView) findViewById(R.id.downloadinfo);

downloadbutton = (Button) findViewById(R.id.downloadbutton);

downloadProgressBar = (ProgressBar) findViewById(R.id.downloadProgressBar);

downloadProgressBar.setVisibility(View.VISIBLE);

downloadProgressBar.setMax(100);

downloadProgressBar.setProgress(0);

downloadbutton.setOnClickListener(new OnClickListener() {

public void onClick(View v) {

download();

downloadtime = SystemClock.currentThreadTimeMillis();

}

});

}

private void download() {

// 获取SD卡目录

String dowloadDir = Environment.getExternalStorageDirectory()

+ "/threaddemodownload/";

File file = new File(dowloadDir);

//创建下载目录

if (!file.exists()) {

file.mkdirs();

}

//读取下载线程数，如果为空，则单线程下载

int downloadTN = Integer.valueOf("".equals(downloadnum.getText()

.toString()) ? "1" : downloadnum.getText().toString());

String fileName = "hetang.mp3";

//开始下载前把下载按钮设置为不可用

downloadbutton.setClickable(false);

//进度条设为0

downloadProgressBar.setProgress(0);

//启动文件下载线程

new downloadTask("http://file16.top100.cn/201105110911/AA5CC27CBE34DEB50A194581D1300881/Special_323149/%E8%8D%B7%E5%A1%98%E6%9C%88%E8%89%B2.mp3", Integer

.valueOf(downloadTN), dowloadDir + fileName).start();

}

Handler handler = new Handler() {

@Override

public void handleMessage(Message msg) {

//当收到更新视图消息时，计算已完成下载百分比，同时更新进度条信息

int progress = (Double.valueOf((downloadedSize * 1.0 / fileSize * 100))).intValue();

if (progress == 100) {

downloadbutton.setClickable(true);

downloadinfo.setText("下载完成！");

Dialog mdialog = new AlertDialog.Builder(ThreadDownloadDemo.this)

.setTitle("提示信息")

.setMessage("下载完成，总用时为:"+(SystemClock.currentThreadTimeMillis()-downloadtime)+"毫秒")

.setNegativeButton("确定", new DialogInterface.OnClickListener(){

@Override

public void onClick(DialogInterface dialog, int which) {

dialog.dismiss();

}

})

.create();

mdialog.show();

} else {

downloadinfo.setText("当前进度:" + progress + "%");

}

downloadProgressBar.setProgress(progress);

}

};

public class downloadTask extends Thread {

private int blockSize, downloadSizeMore;

private int threadNum = 5;

String urlStr, threadNo, fileName;

public downloadTask(String urlStr, int threadNum, String fileName) {

this.urlStr = urlStr;

this.threadNum = threadNum;

this.fileName = fileName;

}

@Override

public void run() {

FileDownloadThread[] fds = new FileDownloadThread[threadNum];

try {

URL url = new URL(urlStr);

URLConnection conn = url.openConnection();

//防止返回-1

InputStream in = conn.getInputStream();

//获取下载文件的总大小

fileSize = conn.getContentLength();

Log.i("bb", "======================fileSize:"+fileSize);

//计算每个线程要下载的数据量

blockSize = fileSize / threadNum;

// 解决整除后百分比计算误差

downloadSizeMore = (fileSize % threadNum);

File file = new File(fileName);

for (int i = 0; i < threadNum; i++) {

Log.i("bb", "======================i:"+i);

//启动线程，分别下载自己需要下载的部分

FileDownloadThread fdt = new FileDownloadThread(url, file, i * blockSize, (i + 1) * blockSize - 1);

fdt.setName("Thread" + i);

fdt.start();

fds[i] = fdt;

}

boolean finished = false;

while (!finished) {

// 先把整除的余数搞定

downloadedSize = downloadSizeMore;

finished = true;

for (int i = 0; i < fds.length; i++) {

downloadedSize += fds[i].getDownloadSize();

if (!fds[i].isFinished()) {

finished = false;

}

}

handler.sendEmptyMessage(0);

//线程暂停一秒

sleep(1000);

}

} catch (Exception e) {

e.printStackTrace();

}

}

}

}

public class ThreadDownloadDemo extends Activity {

private TextView downloadurl;

private EditText downloadnum;

private Button downloadbutton;

private ProgressBar downloadProgressBar;

private TextView downloadinfo;

private int downloadedSize = 0;

private int fileSize = 0;

private long downloadtime;

@Overridepublic void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.threaddemo);

downloadurl = (TextView) findViewById(R.id.downloadurl);

downloadurl.setText("http://file16.top100.cn/201105110911/AA5CC27CBE34DEB50A194581D1300881/Special_323149/%E8%8D%B7%E5%A1%98%E6%9C%88%E8%89%B2.mp3");

downloadnum = (EditText) findViewById(R.id.downloadnum);

downloadinfo = (TextView) findViewById(R.id.downloadinfo);

downloadbutton = (Button) findViewById(R.id.downloadbutton);

downloadProgressBar = (ProgressBar) findViewById(R.id.downloadProgressBar);

downloadProgressBar.setVisibility(View.VISIBLE);

downloadProgressBar.setMax(100);

downloadProgressBar.setProgress(0);

downloadbutton.setOnClickListener(new OnClickListener() {

public void onClick(View v) {download();

downloadtime = SystemClock.currentThreadTimeMillis();

}

}

);

}

private void download() {// 获取SD卡目录

String dowloadDir = Environment.getExternalStorageDirectory()+ "/threaddemodownload/";

File file = new File(dowloadDir);

//创建下载目录

if (!file.exists()) {file.mkdirs();

}//读取下载线程数，如果为空，则单线程下载

int downloadTN = Integer.valueOf("".equals(downloadnum.getText().toString()) ? "1" : downloadnum.getText().toString());

String fileName = "hetang.mp3";

//开始下载前把下载按钮设置为不可用

downloadbutton.setClickable(false);

//进度条设为0

downloadProgressBar.setProgress(0);

//启动文件下载线程

new downloadTask("http://file16.top100.cn/201105110911/AA5CC27CBE34DEB50A194581D1300881/Special_323149/%E8%8D%B7%E5%A1%98%E6%9C%88%E8%89%B2.mp3", Integer.valueOf(downloadTN), dowloadDir + fileName).start();

}

Handler handler = new Handler() {@Overridepublic void handleMessage(Message msg) {

//当收到更新视图消息时，计算已完成下载百分比，同时更新进度条信息

int progress = (Double.valueOf((downloadedSize * 1.0 / fileSize * 100))).intValue();

if (progress == 100) {downloadbutton.setClickable(true);

downloadinfo.setText("下载完成！");

Dialog mdialog = new AlertDialog.Builder(ThreadDownloadDemo.this).setTitle("提示信息").setMessage("下载完成，总用时为:"+(SystemClock.currentThreadTimeMillis()-downloadtime)+"毫秒").setNegativeButton("确定", new DialogInterface.OnClickListener(){@Overridepublic void onClick(DialogInterface dialog, int which) {dialog.dismiss();

}}).create();

mdialog.show();

} else {

downloadinfo.setText("当前进度:" + progress + "%");

}

downloadProgressBar.setProgress(progress);

}

};

public class downloadTask extends Thread {private int blockSize, downloadSizeMore;

private int threadNum = 5;

String urlStr, threadNo, fileName;

public downloadTask(String urlStr, int threadNum, String fileName) {

this.urlStr = urlStr;

this.threadNum = threadNum;

this.fileName = fileName;

}

@Overridepublic void run() {

FileDownloadThread[] fds = new FileDownloadThread[threadNum];

try {URL url = new URL(urlStr);

URLConnection conn = url.openConnection();

//防止返回-1

InputStream in = conn.getInputStream();

//获取下载文件的总大小

fileSize = conn.getContentLength();

Log.i("bb", "======================fileSize:"+fileSize);

//计算每个线程要下载的数据量

blockSize = fileSize / threadNum;

// 解决整除后百分比计算误差

downloadSizeMore = (fileSize % threadNum);

File file = new File(fileName);

for (int i = 0; i < threadNum; i++) {

Log.i("bb", "======================i:"+i);

//启动线程，分别下载自己需要下载的部分

FileDownloadThread fdt = new FileDownloadThread(url, file, i * blockSize, (i + 1) * blockSize - 1);

fdt.setName("Thread" + i);

fdt.start();

fds[i] = fdt;

}

boolean finished = false;

while (!finished) {

// 先把整除的余数搞定

downloadedSize = downloadSizeMore;

finished = true;

for (int i = 0; i < fds.length; i++) {

downloadedSize += fds[i].getDownloadSize();

if (!fds[i].isFinished()) {

finished = false;

}

}

handler.sendEmptyMessage(0);

//线程暂停一秒sleep(1000);

}

}

catch (Exception e) {

e.printStackTrace();

}

}

}

}

这里启动线程将文件分割为几个部分，每一个部分再启动一个线程去下载数据

下载文件的线程

public class FileDownloadThread extends Thread{

private static final int BUFFER_SIZE=1024;

private URL url;

private File file;

private int startPosition;

private int endPosition;

private int curPosition;

//标识当前线程是否下载完成

private boolean finished=false;

private int downloadSize=0;

public FileDownloadThread(URL url,File file,int startPosition,int endPosition){

this.url=url;

this.file=file;

this.startPosition=startPosition;

this.curPosition=startPosition;

this.endPosition=endPosition;

}

@Override

public void run() {

BufferedInputStream bis = null;

RandomAccessFile fos = null;

byte[] buf = new byte[BUFFER_SIZE];

URLConnection con = null;

try {

con = url.openConnection();

con.setAllowUserInteraction(true);

//设置当前线程下载的起止点

con.setRequestProperty("Range", "bytes=" + startPosition + "-" + endPosition);

Log.i("bb", Thread.currentThread().getName()+" bytes=" + startPosition + "-" + endPosition);

//使用java中的RandomAccessFile 对文件进行随机读写操作

fos = new RandomAccessFile(file, "rw");

//设置写文件的起始位置

fos.seek(startPosition);

bis = new BufferedInputStream(con.getInputStream());

//开始循环以流的形式读写文件

while (curPosition < endPosition) {

int len = bis.read(buf, 0, BUFFER_SIZE);

if (len == -1) {

break;

}

fos.write(buf, 0, len);

curPosition = curPosition + len;

if (curPosition > endPosition) {

downloadSize+=len - (curPosition - endPosition) + 1;

} else {

downloadSize+=len;

}

}

//下载完成设为true

this.finished = true;

bis.close();

fos.close();

} catch (IOException e) {

e.printStackTrace();

}

}

public boolean isFinished(){

return finished;

}

public int getDownloadSize() {

return downloadSize;

}

}

public class FileDownloadThread extends Thread{

private static final int BUFFER_SIZE=1024;

private URL url;

private File file;

private int startPosition;

private int endPosition;

private int curPosition;//标识当前线程是否下载完成

private boolean finished=false;

private int downloadSize=0;

public FileDownloadThread(URL url,File file,int startPosition,int endPosition){

this.url=url;

this.file=file;

this.startPosition=startPosition;

this.curPosition=startPosition;

this.endPosition=endPosition;

}

@Overridepublic void run() {

BufferedInputStream bis = null;

RandomAccessFile fos = null;

byte[] buf = new byte[BUFFER_SIZE];

URLConnection con = null;

try {

con = url.openConnection();

con.setAllowUserInteraction(true);

//设置当前线程下载的起止点

con.setRequestProperty("Range", "bytes=" + startPosition + "-" + endPosition);

Log.i("bb", Thread.currentThread().getName()+" bytes=" + startPosition + "-" + endPosition);

//使用java中的RandomAccessFile 对文件进行随机读写操作

fos = new RandomAccessFile(file, "rw");

//设置写文件的起始位置

fos.seek(startPosition);

bis = new BufferedInputStream(con.getInputStream());

//开始循环以流的形式读写文件

while (curPosition < endPosition) {

int len = bis.read(buf, 0, BUFFER_SIZE);

if (len == -1) {

break;

}

fos.write(buf, 0, len);

curPosition = curPosition + len;

if (curPosition > endPosition) {

downloadSize+=len - (curPosition - endPosition) + 1;

} else {

downloadSize+=len;

}

}

//下载完成设为true

this.finished = true;

bis.close();

fos.close();

} catch (IOException e) {

e.printStackTrace();

}

}

public boolean isFinished(){return finished;}

public int getDownloadSize() {return downloadSize;}

}

这里通过RandomAccessFile 的seek方法定位到相应的位置并实时记录下载量

当然这里需要联网和访问SD卡所以要加上相应的权限

<uses-permission android:name="android.permission.INTERNET" />

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>

<uses-permission android:name="android.permission.INTERNET" /><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>