android_文件下载

转载自：http://blog.csdn.net/ycwol/article/details/44546337

android 在网络上下载文件

步骤 :

1.使用HTTP协议下载文件

- 创建一个HttpURLConnection对象 : HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();

- 获取一个InputStream对象 : urlConn.getInputStream()

- 访问网络的权限 : android.permission.INTERNET

2.将下载的文件写入SDCARD

- 得到当前设备SD卡的目录 : Environment.getExternalStrageDirectory()

- 访问SD卡的权限 : android.permission.WRITE_EXTERNAL_STORAGE

代码 :

activity_main.xml

[html] view
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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:paddingBottom="@dimen/activity_vertical_margin"

android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

tools:context=".MainActivity" >



<Button

android:id="@+id/btn_txt"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="download lrc" />



<Button

android:id="@+id/btn_mp3"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_below="@id/btn_txt"

android:text="download mp3" />



</RelativeLayout>

MainActivity.java

[java] view
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package com.chay.download;



import com.chay.utils.HttpDownloader;



import android.app.Activity;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;



public class MainActivity extends Activity {



String urlStr_txt = "http://192.168.56.1:8080/mp3/wan.lrc";

String urlStr_mp3 = "http://192.168.56.1:8080/mp3/wan.mp3";

String path = "mp3/";

String fileName = "wan.mp3";

private Button downloadTxtButton;

private Button downloadMp3Button;



@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

downloadTxtButton = (Button) findViewById(R.id.btn_txt);

downloadTxtButton.setOnClickListener(new DownloadTxtListener());

downloadMp3Button = (Button) findViewById(R.id.btn_mp3);

downloadMp3Button.setOnClickListener(new DownloadMp3Listener());

}



//下载歌词文件按钮监听器

class DownloadTxtListener implements OnClickListener {

@Override

public void onClick(View v) {

Thread t = new DownloadTxtThread();

t.start();

System.out.println("txt--->");

}

}

//下载歌词文件线程

class DownloadTxtThread extends Thread{

@Override

public void run() {

HttpDownloader httpDownloader = new HttpDownloader();

String lrc = httpDownloader.download(urlStr_txt);

System.out.println(lrc);

}

}

//下载MP3文件按钮监听器

class DownloadMp3Listener implements OnClickListener {

@Override

public void onClick(View v) {

Thread h = new DownMp3Thread();

h.start();

System.out.println("mp3--->");

}

}

//下载MP3文件线程

class DownMp3Thread extends Thread{

@Override

public void run() {

HttpDownloader httpDownloader = new HttpDownloader();

int result = httpDownloader.downFile(urlStr_mp3, path, fileName);

System.out.println(result);

}

}

}

工具类:

HttpDownloader.java

[java] view
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package com.chay.utils;



import java.io.BufferedReader;

import java.io.File;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;



public class HttpDownloader {

private URL url = null;



/**

* 根据URL下载文件，前提是这个文件当中的内容是文本，函数的返回值就是文件当中的内容

* 1.创建一个URL对象

* 2.通过URL对象，创建一个HttpURLConnection对象

* 3.得到InputStram

* 4.从InputStream当中读取数据

* @param urlStr

* @return

*/

public String download(String urlStr) {

StringBuffer sb = new StringBuffer();

String line = null;

BufferedReader buffer = null;

try {

// 创建一个URL对象

url = new URL(urlStr);

// 创建一个Http连接

HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();

// 使用IO流读取数据

buffer = new BufferedReader(new InputStreamReader(urlConn.getInputStream()));

while ((line = buffer.readLine()) != null) {

sb.append(line);

}

} catch (Exception e) {

e.printStackTrace();

} finally {

try {

buffer.close();

} catch (Exception e) {

e.printStackTrace();

}

}

return sb.toString();

}



/**

* 该函数返回整形 -1：代表下载文件出错 0：代表下载文件成功 1：代表文件已经存在

*/

public int downFile(String urlStr, String path, String fileName) {

InputStream inputStream = null;

try {

FileUtils fileUtils = new FileUtils();



if (fileUtils.isFileExist(path + fileName)) {

return 1;

} else {

inputStream = getInputStreamFromUrl(urlStr);

File resultFile = fileUtils.write2SDFromInput(path,fileName, inputStream);

if (resultFile == null) {

return -1;

}

}

} catch (Exception e) {

e.printStackTrace();

return -1;

} finally {

try {

inputStream.close();

} catch (Exception e) {

e.printStackTrace();

}

}

return 0;

}



/**

* 根据URL得到输入流

*

* @param urlStr

* @return

* @throws MalformedURLException

* @throws IOException

*/

public InputStream getInputStreamFromUrl(String urlStr)

throws MalformedURLException, IOException {

url = new URL(urlStr);

HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();

InputStream inputStream = urlConn.getInputStream();

return inputStream;

}

}

FileUtils.java

[java] view
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package com.chay.utils;



import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;



import android.os.Environment;



public class FileUtils {

private String SDPATH;



public String getSDPATH() {

return SDPATH;

}

public FileUtils() {

//得到当前外部存储设备的目录

// /SDCARD

SDPATH = Environment.getExternalStorageDirectory() + "/";

}

/**

* 在SD卡上创建文件

*

* @throws IOException

*/

public File creatSDFile(String fileName) throws IOException {

File file = new File(SDPATH + fileName);

file.createNewFile();

return file;

}



/**

* 在SD卡上创建目录

*

* @param dirName

*/

public File creatSDDir(String dirName) {

File dir = new File(SDPATH + dirName);

dir.mkdirs();

return dir;

}



/**

* 判断SD卡上的文件夹是否存在

*/

public boolean isFileExist(String fileName){

File file = new File(SDPATH + fileName);

return file.exists();

}



/**

* 将一个InputStream里面的数据写入到SD卡中

*/

public File write2SDFromInput(String path,String fileName,InputStream input){

File file = null;

OutputStream output = null;

try{

creatSDDir(path);

file = creatSDFile(path + fileName);

output = new FileOutputStream(file);

byte buffer [] = new byte[4 * 1024];

while((input.read(buffer)) != -1){

output.write(buffer);

}

output.flush();

}

catch(Exception e){

e.printStackTrace();

}

finally{

try{

output.close();

}

catch(Exception e){

e.printStackTrace();

}

}

return file;

}

}

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