(转自Mars) Android 文件下载类 HttpDownloader,内存卡操作类 FileUtils

HttpDownloader.java

package mars.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

package mars.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;
    }

}

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="mars.download"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".Download"
                  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>
    <uses-sdk android:minSdkVersion="4" />
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
</manifest>