android之download

有三个java类

Download.java

package tk.download;


import tk.utils.HttpDownloader;
import android.os.Bundle;
import android.R.integer;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class Download extends Activity {
    
    /**
     *创建一个HttpURLConnection对象
     *HttpURLConnection urlConn=(HttpURLConnection)url.openConnection();
     *获得一个InputStream对象
     *urlConn.getInputStream()
     *访问网络的权限(在mainfest中声明)
     *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
     * 
     * /
    /**Called when the activity is first created.*/
    
    private Button downloadTxtButton;
    private Button downloadMp3Button;

    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        downloadMp3Button=(Button)findViewById(R.id.downloadMp3);
        downloadMp3Button.setOnClickListener(new DownloadMp3Listener());
        downloadTxtButton=(Button)findViewById(R.id.downloadTxt);
        downloadTxtButton.setOnClickListener(new DownloadTxtListener());
        
        
    }
    
    class DownloadTxtListener implements OnClickListener{

        @Override
        public void onClick(View v) {
            HttpDownloader httpDownloader=new HttpDownloader();
            System.out.println("begin");
            String lrc = httpDownloader.download("http://125.222.201.90/home/download4.asp?FileName=hello.txt");
            System.out.println(lrc);
            System.out.println("end");
            
            
        }
        
        
    }
    
    class DownloadMp3Listener implements OnClickListener{

        @Override
        public void onClick(View v) {
            HttpDownloader httpDownloader=new HttpDownloader();
            System.out.println("begin");
            int result = httpDownloader.downFile("http://125.222.201.90/home/download4.asp?FileName=Layout_04.apk", "tk/", "test.apk");
            System.out.println(result);
            
        }

    }
    
    

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
}

FileUtils.java

package tk.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() + "/";
        //SDPATH ="/";
    }

/**
* 在SD卡上创建目录
* 
* @param dirName
*/

    public File creatSDDir(String dirName) {
        File file = new File(SDPATH + dirName);
        file.mkdirs();
        return file;
    }

/**
* 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;
    }

 

/**
* 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 inputStream){
    
        File file = null;
        OutputStream outputStream = null;
        
        try{
            creatSDDir(path);
            file = creatSDFile(path + fileName);
            outputStream = new FileOutputStream(file);
            byte buffer [] = new byte[4 * 1024];
            while((inputStream.read(buffer)) != -1){
                
                outputStream.write(buffer);
                
            }
            outputStream.flush();
            
        }catch(Exception e){
            
            e.printStackTrace();
            
        }finally{
            
            try{
                outputStream.close();
            }catch(Exception e){
                e.printStackTrace();
            }
            
        }
        
        return file;
    
    }

}

HttpDownloader.java

package tk.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Inputstream
     * 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Http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; //文件已经存在
            } else {
                inputStream =getInputStreamFromUrl(urlStr);
                if(inputStream==null)return 2;
                File resultFile =fileUtils.write2SDFromInput(path,fileName,inputStream);  
                if (resultFile == null){
                    return -1;  //下载文件出错
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
            return -1;
        } finally {
            try {
                inputStream.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    return 0;
    }
    
     
    
    public InputStream getInputStreamFromUrl(String urlStr) throws MalformedURLException, IOException {
    
        InputStream inputStream=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
           inputStream = urlConn.getInputStream();
           return inputStream;
        }catch (Exception e) {
            e.printStackTrace();
            return null;
        }finally {
           inputStream.close();
        }
    }

}

androidmainfest.xml

main.xml

<?xml version= "1.0" encoding ="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation= "vertical"
    android:layout_width= "fill_parent"
    android:layout_height= "fill_parent"
    >
    
    <Button 
        android:id="@+id/downloadTxt"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="downloadtxt"
        />
    
     <Button 
        android:id="@+id/downloadMp3"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="downloadMP3"
        />
</LinearLayout>