Android文件下载

看了mars老师的Android视频，真心不错，文件下载的方法，整理一下。

一、文件下载方法：

1. 使用HTTP协议下载文件

2. 将下载的文件写入SDCARD

二、文件下载的具体步骤：

1. 创建一个HttpURLConnection对象

HttpURLConnection urlConn

= (HttpURLConnection)url.openConnection();

2. 获得一个InputStream对象

urlConn.getInputStream()

3. 访问网络的权限

Android：permission.INTERNET

访问SDCARD

得到当前设备SD卡的目录

Environment.getExternalStorageDirectory()

访问SD卡的权限

Android.permission.WRITE_EXTERNAL_STORAGE

具体代码如下：

布局文件：

<?xml version="1.0" encoding="utf-8"?>

FileUtils类：

package 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() {SDPATH = Environment.getExternalStorageDirectory() + "/";}public File creatSDFile(String fileName) throws IOException{File file = new File(SDPATH + fileName);file.createNewFile();return file;}public File creatSDDir(String dirName) {File dir = new File(SDPATH + dirName);dir.mkdirs();return dir;}public boolean isFileExist(String fileName) {File file = new File(SDPATH + fileName);return file.exists();}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);}}catch(Exception e) {e.printStackTrace();}finally{try{output.close();}catch(Exception e){e.printStackTrace();}}return file;}}

HttpDownLoader类：

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;import javax.net.ssl.HttpsURLConnection;public class HttpDownLoader {private URL url = null;public String download(String urlStr){StringBuffer sb = new StringBuffer();String line = null;BufferedReader buffer = null;try{url = new URL(urlStr);HttpURLConnection urlConn =  (HttpsURLConnection) url.openConnection();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();}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();} finally {try{inputStream.close();}catch (Exception e){e.printStackTrace();}}return 0;}public InputStream getInputStreamFromUrl(String urlStr)        throws MalformedURLException, IOException{url = new URL(urlStr);HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();InputStream inputStream = urlConn.getInputStream();return inputStream;}}

DownLoad类：

import 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 DownLoad extends Activity{private Button downloadTxtButton;private Button downloadMp3Button;@Overrideprotected void onCreate(Bundle savedInstanceState) {// TODO Auto-generated method stubsuper.onCreate(savedInstanceState);setContentView(R.layout.activity_main);downloadTxtButton = (Button)findViewById(R.id.downloadText);downloadTxtButton.setOnClickListener(new DownloadTxtListener());downloadMp3Button = (Button)findViewById(R.id.downloadMp3);downloadMp3Button.setOnClickListener(new DownloadMp3ButtonListener());}class DownloadTxtListener implements OnClickListener{@Overridepublic void onClick(View arg0) {HttpDownLoader httpDownloader = new HttpDownLoader();String lrc = httpDownloader.download("http://...");System.out.println(lrc);}}class DownloadMp3ButtonListener implements OnClickListener{@Overridepublic void onClick(View v) {HttpDownLoader httpDownloader = new HttpDownLoader();int result = httpDownloader.downFile("http://...", "/voal","a1.mp3");System.out.println(result);}}}

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