android 文件的下载

个人开发，如果有什么错误或是各位高手有更好的实现方法请不吝赐教，这厢表示强烈感谢

文件下载步骤：

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

获得一个输入流InputStream对象 urlConn.getInputStream()

访问网络权限 android.permission.INTERNET (允许程序访问网络)写入AndroidManifest.xml 的<uses-permission android:name="" />标签内
如果要访问SD，要再加入访问SD卡的权限：android.permission.WRITE_EXTERNAL_STORAGE

访问SDCARD

得到当前SD卡的目录：
Environment.getExternalStorageDirectory()

完整工具类代码：

HttpDownloader.java

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;
	public static final int FILEEXIST = 1;//文件已经存在
	public static final int DOWNLOADFAIL = -1;//文件下载失败
	public static final int DOWNLOADSUCCESS = 0;//文件下载成功
	
	/**
	 * 下载 text文本文件
	 * @param urlStr
	 * @return
	 */
	public String download(String urlStr){
		StringBuffer sb = new StringBuffer("");
		String line = null;
		BufferedReader buffer = null;
		try {
			url = new URL(urlStr);
			HttpURLConnection urlConn = (HttpURLConnection)url.openConnection();
			buffer = new BufferedReader(new InputStreamReader(urlConn.getInputStream()));
			while ((line = buffer.readLine()) != null) {
				sb.append(line + "\n");
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return "";
		}finally{
			try {
				buffer.close();
			} catch (Exception e) {
				return sb.toString();
			}
		}
		return sb.toString();
	}
	
	/**
	 * 下载文件，原文件名默认为原文件名
	 * @param urlStr 现在的文件的链接
	 * @param path 下载的文件存放到SD的目录
	 * @param cover 当文件存在时是否覆盖，true覆盖
	 * @return
	 */
	public int download(String urlStr, String path, boolean cover){
		File oldFile = new File(urlStr);
		return download(urlStr, path, oldFile.getName(), cover);
	}
	
	/**
	 * 下载文件
	 * @param urlStr 现在的文件的链接
	 * @param path 下载的文件存放到SD的目录
	 * @param fileName 文件名
	 * @param cover 当文件存在时是否覆盖，true覆盖
	 * @return
	 */
	public int download(String urlStr, String path, String fileName, boolean cover){
		InputStream inputStream = null;
		if(FileUtils.isFileExist(path + fileName) && !cover){
			return FILEEXIST;
		}
		try {
			inputStream = getInputStreamFromUrl(urlStr);	
			File resultFile = FileUtils.writData2SDFromInputStream(path, fileName, inputStream);
			if(resultFile == null){
				return DOWNLOADFAIL;
			}
		} catch (MalformedURLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return DOWNLOADFAIL;
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			//网络文件未找到
			return DOWNLOADFAIL;
		}
		try {
			inputStream.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return DOWNLOADSUCCESS;
	}
	

	/**
	 * 根据url地址得到输入流
	 * @param urlStr
	 * @throws MalformedURLException
	 * @throws IOException
	 */
	public InputStream getInputStreamFromUrl(String urlStr)throws MalformedURLException,IOException{
		HttpURLConnection urlConn = null;
		InputStream resInput = null;
		url = new URL(urlStr);
		urlConn = (HttpURLConnection)url.openConnection();
		resInput = urlConn.getInputStream();
		return resInput;
	}
}

文件工具类FileUtils.java：

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 static String SDPATH;
	
	static{
		SDPATH = Environment.getExternalStorageDirectory() + File.separator;
	}
	
	
	/**
	 * 在SD卡上创建文件
	 * @param fileName
	 * @return
	 * @throws IOException
	 */
	public static File creatFileOnSD(String fileName) throws IOException{
		File file = new File(SDPATH + fileName);
		file.createNewFile();
		return file;
	}
	
	/**
	 * 在SD卡上创建目录
	 * @param dirName
	 * @return
	 */
	public static File creatDirOnSD(String dirName){
		File dir = new File(SDPATH + dirName);
		dir.mkdir();
		return dir;
	}
	
	/**
	 * 判断文件在SD卡上是否存在
	 * @param fileName
	 * @return
	 */
	public static boolean isFileExist(String fileName){
		File file = new File(SDPATH + fileName);
		return file.exists();
	}
	
	/**
	 * 将输入流里的数据写入SD卡中
	 * @param path 写入文件存放路径
	 * @param fileName 生成的文件名
	 * @param input 输入流
	 * @return
	 */
	public static File writData2SDFromInputStream(String path, String fileName,InputStream inputStream){
		File file = null;
		OutputStream output = null;
		try {
			creatDirOnSD(path);
			file = creatFileOnSD(path + fileName);
			output = new FileOutputStream(file);
			//每4K输出一次
			byte buffer[] = new byte[4 * 1024];
			while(inputStream.read(buffer) != -1){
				output.write(buffer);
			}
			//清除缓存
			output.flush();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return null;
		}finally{
			try {
				output.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		return file;
	}
}

Activity的代码：

btnDownloadTxt.setOnClickListener(new OnClickListener() {
	@Override
	public void onClick(View v) {
		// 得到text内容
		HttpDownloader httpDownloader = new HttpDownloader();
		String res = httpDownloader.download("http://192.168.2.15:6060/tianfangUploadImg/text/news/ttt");
		
		System.out.println(res);
	}
});

btnDownloadMp3.setOnClickListener(new OnClickListener() {
	@Override
	public void onClick(View v) {
		// TODO Auto-generated method stub
		HttpDownloader httpDownloader = new HttpDownloader();
		int res = httpDownloader.download("http://127.0.0.1:6060/test/sounds/test.mp3", "mp3/", "newMap3.mp3", true);
		if(HttpDownloader.DOWNLOADSUCCESS == res){
			System.out.println("下载成功");
		}
		if(HttpDownloader.DOWNLOADFAIL == res){
			System.out.println("下载失败");
		}
		if(HttpDownloader.FILEEXIST == res){
			System.out.println("文件已存在");
		}
	}
});

在网上查看有些高手说用android访问本机电脑服务器可用ip：10.0.2.2

如果你想在模拟器simulator上面访问你的电脑，那么就使用android内置的IP10.0.2.2吧， 10.0.2.2 是模拟器设置的特定ip，是你的电脑的别名alias

记住，在模拟器上用10.0.2.2访问你的电脑本机