Android HTTP下载文件并保存到本地或SD卡

【Android HTTP下载文件并保存到本地或SD卡】愿君学长松，慎勿作桃李。这篇文章主要讲述Android HTTP下载文件并保存到本地或SD卡相关的知识，希望能为你提供帮助。
想把文件保存到SD卡中，一定要知道SD卡的路径，获取SD卡路径：

Environment.getExternalStorageDirectory()

另外，在保存之前要判断SD卡是否已经安装好，并且可读写：

//判断SDcard是否存在并且可读写 if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){ service.saveToSDCard(filename,filecontent); Toast.makeText(getApplicationContext(), R.string.success, 1).show(); }else{ Toast.makeText(getApplicationContext(), R.string.sdcarderror, 1).show(); }

实例
1. 下载存文本文件和下载如mp3等大容量的文件

文章图片

2.代码编写
androidMainfest.xml中配置
主要是解决网络权限和写SDCard的权限

< ?xml version="1.0" encoding="utf-8"?> < manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.jingling.practice.downloadtest" > < uses-permission android:name="android.permission.INTERNET"/> < uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> < application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > < activity android:name=".MainActivity" android:label="@string/app_name" > < intent-filter> < action android:name="android.intent.action.MAIN" /> < category android:name="android.intent.category.LAUNCHER" /> < /intent-filter> < /activity> < /application> < /manifest>

package util; import android.util.Log; 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.URL; /** * Created by Spring on 2015/11/7. * 下载工具类 */ public class HttpDownloader { private URL url = null; private final String TAG = "TAG"; /** * 读取文本文件 * @param urlStr url路径 * @return 文本信息 * 根据url下载文件，前提是这个文件中的内容是文本， * 1.创建一个URL对象 * 2.通过URL对象，创建一个Http连接 * 3.得到InputStream * 4.从InputStream中得到数据 */ public String download(String urlStr) { StringBuffer sb = new StringBuffer(); String line = null; BufferedReader bufferedReader = null; try { url = new URL(urlStr); //创建http连接 HttpURLConnection urlConn = (HttpURLConnection) url.openConnection(); //使用IO流读取数据 bufferedReader = new BufferedReader(new InputStreamReader(urlConn.getInputStream())); while ((line = bufferedReader.readLine()) != null) { sb.append(line); } } catch (IOException e) { e.printStackTrace(); } finally { try { bufferedReader.close(); } catch (IOException e) { e.printStackTrace(); } } Log.e("TAG","下载txt文件"); Log.e("TAG",sb.toString()); return sb.toString(); }/** * 读取任何文件 * 返回-1 ，代表下载失败。返回0，代表成功。返回1代表文件已经存在 * * @param urlStr * @param path * @param fileName * @return */ public int downlaodFile(String urlStr, String path, String fileName) { InputStream input = null; try { FileUtil fileUtil = new FileUtil(); if (fileUtil.isFileExist(path + fileName)) { return 1; } else { input = getInputStearmFormUrl(urlStr); File resultFile = fileUtil.write2SDFromInput(path,fileName,input); if (resultFile == null) return -1; } } catch (IOException e) { e.printStackTrace(); return -1; } finally { try { input.close(); } catch (IOException e) { e.printStackTrace(); } } return0; }public InputStream getInputStearmFormUrl(String urlStr) throws IOException { url = new URL(urlStr); HttpURLConnection urlConn = (HttpURLConnection) url.openConnection(); InputStream input = urlConn.getInputStream(); return input; } }

FileUtil.java

package util; import android.os.Environment; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; /** * Created by Spring on 2015/11/7. */ public class FileUtil { private String SDPATH; public FileUtil() {}public String getSDPATH() { return SDPATH; }public FileUtil(String SDPATH){ //得到外部存储设备的目录（/SDCARD） SDPATH = Environment.getExternalStorageDirectory() + "/" ; }/** * 在SD卡上创建文件 * @param fileName * @return * @throws java.io.IOException */ public File createSDFile(String fileName) throws IOException { File file = new File(SDPATH + fileName); file.createNewFile(); return file; }/** * 在SD卡上创建目录 * @param dirName 目录名字 * @return 文件目录 */ public File createDir(String dirName){ File dir = new File(SDPATH + dirName); dir.mkdir(); return dir; }/** * 判断文件是否存在 * @param fileName * @return */ 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 { createDir(path); file =createSDFile(path + fileName); output = new FileOutputStream(file); byte [] buffer = new byte[4 * 1024]; while(input.read(buffer) != -1){ output.write(buffer); output.flush(); } } catch (IOException e) { e.printStackTrace(); } finally { try { output.close(); } catch (IOException e) { e.printStackTrace(); } } return file; } }

3.MainActivity

package com.jingling.practice.downloadtest; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.Button; import util.HttpDownloader; public class MainActivity extends Activity { HttpDownloader downloader ; private Button btn_downFile; private Button btn_downMP3; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); btn_downFile = (Button)this.findViewById(R.id.button); btn_downMP3 = (Button)this.findViewById(R.id.button2); btn_downFile.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { downloader = new HttpDownloader(); String urlStr = "http://172.17.54.91:8080/download/down.txt"; downloader.download(urlStr); } }); btn_downMP3.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { String urlStr="http://172.17.54.91:8080/download/1.mp3"; String path="file"; String fileName="2.mp3"; HttpDownloader httpDownloader = new HttpDownloader(); httpDownloader.downlaodFile(urlStr,path,fileName); } }); }}