下载文件

来源：互联网发布：淘宝店主的故事编辑：程序博客网时间：2024/05/29 17:10

1.下载工具类，将要下载的文件保存到SD卡中

package com.huo;

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 DownloadUtils {

private String SDPATH;

public String getSDPATH() {
return SDPATH;
}

/* 获取外部存储设备目录*/
public DownloadUtils() {
   /*Environment.getExternalStorageState()方法用于获取SDCard的状态，
       *如果手机装有SDCard，并且可以进行读写，那么方法返回的状态等于Environment.MEDIA_MOUNTED*/
   if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
   /*获取SD卡的存储路径*/
    SDPATH = Environment.getExternalStorageDirectory() + "/";

}
}

/*在SD卡上创建文件*/
public File createSDFile(String filename) throws IOException{
  File file = new File(SDPATH + filename);
  file.createNewFile();
  return file;
}

/*创建SD卡目录*/
public File createSDir(String dirname){
  File dir = new File(SDPATH + dirname);
  dir.mkdir();
  return dir;
}

/*判断SD卡上文件是否存在*/
public boolean isFileExist(String filename){
  File file = new File(SDPATH + filename);
  return file.exists();
}

/*从输入流中读出数据写入到SD卡中,从输入流中读取数据，保存到字节数组中，然后将数据写入到输出流中
* @param dirname 存储路径
* @param filename 文件名
* @param is 输入流
* */

public File write2SDFromInput(String path,String filename,InputStream is){
          File file = null;
          OutputStream os = null;
          try {
              createSDir(path);
              file = createSDFile(path + filename);
              /*创建一个向指定 File 对象表示的文件中写入数据的文件输出流*/
              os = new FileOutputStream(file);
              byte[] buffer = new byte[4*1024];
              while((is.read(buffer)) != -1){
              os.write(buffer);
              }
              os.flush();
          }
          catch (Exception e) {
              e.printStackTrace();
          }
          finally{
              try {
              os.close();
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }
          return file;
      }

}

===========================================

2.实现文件下载

package com.huo;

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;

public class Downloader {

private URL url = null;

public String downloadTXTFile(String httpUrl){
BufferedReader buffer = null;
  StringBuffer sb = new StringBuffer();
  String line = null;

   /*获取URL对象*/
   try {
    url = new URL(httpUrl);
    /*获取HttpURLConnection对象*/
    HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
    /*创建BufferedReader,用来读取数据*/
    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 (IOException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
   }

  return sb.toString();
}

/*
* 下载文件
* 0代表下载成功
* 1代表该文件以存在
* -1代表下载失败
* */

public int downloadFile(String urlStr,String path,String filename){

  InputStream is = null;

  try{
   DownloadUtils downloadUtils = new DownloadUtils();
   /*判断该文件是否存在*/
   if(downloadUtils.isFileExist(path + filename)){
    return 1;
   }
   else{
    is = getInputStreamFromURL(urlStr);
    File resultFile = downloadUtils.write2SDFromInput(path, filename, is);
    if(resultFile == null){
     return -1;
    }
   }
  }catch(Exception e){
   e.printStackTrace();
   return -1;
  }
//  finally{
//   try {
//    is.close();
//   } catch (IOException e) {
//    e.printStackTrace();
//   }
//  }
  return 0;
}

/*根据URL,取得输入流*/
public InputStream getInputStreamFromURL(String urlStr){

  InputStream is = null;
  try {
   url = new URL(urlStr);
   HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
   is = httpConn.getInputStream();
  } catch (Exception e) {
   e.printStackTrace();
  }
  return is;
}
}

=============================================

3.Activity

package com.huo;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class DownloadActivity extends Activity {

Button button01;
Button button02;
Downloader downloader = null;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        button01 = (Button) findViewById(R.id.Button01);
        button01.setOnClickListener(new View.OnClickListener() {

   @Override
   public void onClick(View v) {
    downloader = new Downloader();
    String str = downloader.downloadTXTFile("http://10.0.2.2:8080/oa/aaa.txt");
    System.out.println(str);
   }
  });

        button02 = (Button) findViewById(R.id.Button02);
        button02.setOnClickListener(new View.OnClickListener() {

   @Override
   public void onClick(View v) {
    downloader = new Downloader();
    int result = downloader.downloadFile("http://10.0.2.2:8080/oa/aaa.txt",
           "voa/","aaa.txt");
    System.out.println(result);
   }
  });
    }


}