Android 下载文件及写入SD卡

Android 下载文件及写入SD卡,实例代码

<?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="下载文本文件"
    />

<Button
    android:id="@+id/downloadMp3"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="下载MP3文件"
    />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.learning.example"
      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="8" />

<!-- 访问网络和操作SD卡 加入的两个权限配置-->
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
</manifest>

package com.learning.example.util;

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本当中的内容
     * 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 {
            url = new URL(urlStr);
            HttpURLConnection urlConn = (HttpURLConnection)url.openConnection();
            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) {
                e.printStackTrace();
            }
        }
        return sb.toString();
    }

    /**
     *
     * @param urlStr
     * @param path
     * @param fileName
     * @return
     *      -1:文件下载出错
     *       0:文件下载成功
     *       1: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 (IOException e) {
                e.printStackTrace();
            }
        }
        return 0;
    }

    /**
     * 根据URL得到输入流
     * @param urlStr
     * @return
     */
    public InputStream getInputStreamFromURL(String urlStr) {
        HttpURLConnection urlConn = null;
        InputStream inputStream = null;
        try {
            url = new URL(urlStr);
            urlConn = (HttpURLConnection)url.openConnection();
            inputStream = urlConn.getInputStream();

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return inputStream;
    }
}

package com.learning.example.util;

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;

    private int FILESIZE = 4 * 1024;

    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
     * @param fileName
     * @return
     * @throws 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
     * @return
     */
    public File createSDDir(String dirName){
        File dir = new File(SDPATH + dirName);
        dir.mkdir();
        return dir;
    }

    /**
     * 判断SD卡上的文件夹是否存在
     * @param fileName
     * @return
     */
    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
     * @param path
     * @param fileName
     * @param input
     * @return
     */
    public File write2SDFromInput(String path,String fileName,InputStream input){
        File file = null;
        OutputStream output = null;
        try {
            createSDDir(path);
            file = createSDFile(path + fileName);
            output = new FileOutputStream(file);
                            byte[] buffer = new byte[FILESIZE];

            /*真机测试，这段可能有问题，请采用下面网友提供的
                            while((input.read(buffer)) != -1){
                output.write(buffer);
            }
                            */

                           /* 网友提供 begin */
                           int length;
                           while((length=(input.read(buffer))) >0){
                                 output.write(buffer,0,length);
                           }
                           /* 网友提供 end */

            output.flush();
        }
        catch (Exception e) {
            e.printStackTrace();
        }
        finally{
            try {
                output.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return file;
    }

}

package com.learning.example;

import com.learning.example.util.HttpDownloader;

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

public class Download extends Activity {
    private Button downlaodTxtButton ;
    private Button downlaodMP3Button ;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        downlaodTxtButton = (Button)findViewById(R.id.downloadTxt);
        downlaodTxtButton.setOnClickListener(new DownloadTxtListener());

        downlaodMP3Button = (Button)findViewById(R.id.downloadMp3);
        downlaodMP3Button.setOnClickListener(new DownloadMP3Listener());
    }

    class DownloadTxtListener implements OnClickListener{

        @Override
        public void onClick(View v) {
            HttpDownloader downloader = new HttpDownloader();
            String lrc = downloader.download("http://172.16.11.9:8080/test/1.lrc");
            System.out.println(lrc);
        }

    }

    class DownloadMP3Listener implements OnClickListener{

        @Override
        public void onClick(View v) {
            HttpDownloader downloader = new HttpDownloader();
            int result = downloader.downFile("http://172.16.11.9:8080/test/1.mp3", "voa/", "1.map3");
            System.out.println(result);
        }

    }
}

Notice:访问网络和操作SD卡 记得加入的两个权限配置

<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>