Android下载文本文件和mp3文件

布局文件main.xml

main.xml 
 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:layout_width="fill_parent"
 4     android:layout_height="fill_parent"
 5     android:orientation="vertical" >
 6 
 7     <Button 
 8         android:id="@+id/downloadTxt"
 9         android:layout_width="fill_parent"
10         android:layout_height="wrap_content"
11         android:text="Download text"/>
12     <Button 
13         android:id="@+id/downloadMp3"
14         android:layout_width="fill_parent"
15         android:layout_height="wrap_content"
16         android:text="Download MP3"/>
17 </LinearLayout>

Activity文件DownloadFileToSDKCardActivity.java

DownloadFileToSDKCardActivity.java 
 1 package paul.Activity;
 2 
 3 import paul.utils.HttpDownloadUtil;
 4 import android.app.Activity;
 5 import android.os.Bundle;
 6 import android.view.View;
 7 import android.view.View.OnClickListener;
 8 import android.widget.Button;
 9 
10 //创建一个HttpURLConnection对象
11 //HttpURLConnection urlConn=(HttpURLConnection)url.openConnection();
12 //获取一个InputStream对象
13 //InputStream is=urlConn.getInputStream();
14 //访问网络权限
15 //android.permission.INTERNET
16 //得到当前设备SD卡的目录
17 //Environment.getExternalStorageDirectory()
18 //访问SD卡的权限
19 //android.permission.WEITE_EXTERNAL_STORAGE
20 public class DownloadFileToSDKCardActivity extends Activity {
21     /** Called when the activity is first created. */
22     HttpDownloadUtil httpDownloadUtil;
23     private Button downloadTxt;
24     private Button downloadMp3;
25     public DownloadFileToSDKCardActivity(){
26         httpDownloadUtil=new HttpDownloadUtil();
27     }
28     @Override
29     public void onCreate(Bundle savedInstanceState) {
30         super.onCreate(savedInstanceState);
31         setContentView(R.layout.main);
32         downloadTxt=(Button) this.findViewById(R.id.downloadTxt);
33         downloadTxt.setOnClickListener(new DownloadTxt());
34         downloadMp3=(Button) this.findViewById(R.id.downloadMp3);
35         downloadMp3.setOnClickListener(new DownloadMp3());
36     }
37     
38     
39     class DownloadTxt implements OnClickListener{
40 
41         @Override
42         public void onClick(View arg0) {
43             String url="http://www.baidu.com";
44             System.out.println(httpDownloadUtil.downFile(url));
45         }
46         
47     }
48     
49     class DownloadMp3 implements OnClickListener{
50 
51         @Override
52         public void onClick(View arg0) {
53             String url="http://media.ringring.vn/ringtone/realtone/0/0/161/165346.mp3";
54             //int index=url.lastIndexOf("/");
55 //String fileName=url.substring(index+1);
56             int result=httpDownloadUtil.downFile(url, "music", "aa.mp3");
57             System.out.println(result);
58         }
59         
60     }
61 }

文件下载类HttpDownloadUtil.java

HttpDownloadUtil.java 
 1 package paul.utils;
 2 
 3 import java.io.BufferedReader;
 4 import java.io.File;
 5 import java.io.IOException;
 6 import java.io.InputStream;
 7 import java.io.InputStreamReader;
 8 import java.net.HttpURLConnection;
 9 import java.net.MalformedURLException;
10 import java.net.URL;
11 
12 public class HttpDownloadUtil {
13     
14     /**
15      * 根据URL下载文件，前提是这个文件当中的内容是文本，函数返回值是文件当中的文本内容
16      * @param urlstr
17      * @return
18 */
19     public String downFile(String urlstr){
20         StringBuffer sb=new StringBuffer();
21         BufferedReader buffer=null;
22         URL url=null;
23         String line=null;
24         try {
25             //创建一个URL对象
26             url=new URL(urlstr);
27             //根据URL对象创建一个Http连接
28             HttpURLConnection urlConn=(HttpURLConnection) url.openConnection();
29             //使用IO读取下载的文件数据
30             buffer=new BufferedReader(new InputStreamReader(urlConn.getInputStream()));
31             while((line=buffer.readLine())!=null){
32                 sb.append(line);
33             }
34         } catch (MalformedURLException e) {
35             // TODO Auto-generated catch block
36             e.printStackTrace();
37         } catch (IOException e) {
38             // TODO Auto-generated catch block
39             e.printStackTrace();
40         }finally{
41             try {
42                 buffer.close();
43             } catch (IOException e) {
44                 e.printStackTrace();
45             }
46         }
47         return sb.toString();
48     }
49     
50     /**
51      * 该函数返回整形    -1：代表下载文件错误0 ：下载文件成功1：文件已经存在 
52      * @param urlstr
53      * @param path
54      * @param fileName
55      * @return
56 */
57     public int downFile(String urlstr,String path,String fileName){
58         InputStream inputStream=null;
59         FileUtils fileUtils=new FileUtils();
60         
61         if(fileUtils.isFileExist(path+fileName)){
62             return 1;
63         }else{
64             inputStream=getInputStreamFormUrl(urlstr);
65             File resultFile=fileUtils.writeToSDfromInput(path, fileName, inputStream);
66             if(resultFile==null){
67                 return -1;
68             }
69         }
70         return 0;
71     }
72     
73     /**
74      * 根据URL得到输入流
75      * @param urlstr
76      * @return
77 */
78     public InputStream getInputStreamFormUrl(String urlstr){
79         InputStream inputStream=null;
80         try {
81             URL url=new URL(urlstr);
82             HttpURLConnection urlConn=(HttpURLConnection) url.openConnection();
83             inputStream=urlConn.getInputStream();
84         } catch (MalformedURLException e) {
85             e.printStackTrace();
86         } catch (IOException e) {
87             e.printStackTrace();
88         }
89         return inputStream;
90     }
91 }

保存文件到SD卡通用工具类FileUtils.java

FileUtils.java 
 1 package paul.utils;
 2 
 3 import java.io.File;
 4 import java.io.FileNotFoundException;
 5 import java.io.FileOutputStream;
 6 import java.io.IOException;
 7 import java.io.InputStream;
 8 import java.io.OutputStream;
 9 
10 import android.os.Environment;
11 
12 public class FileUtils {
13     private String SDPath;
14     
15     public FileUtils(){
16         //得到当前外部存储设备的目录
17         SDPath=Environment.getExternalStorageDirectory().getAbsolutePath()+"/";
18     }
19     
20     /**
21      * 在SD卡上创建文件
22      * @param fileName
23      * @return
24 */
25     public File createSDFile(String fileName){
26         File file=new File(SDPath+fileName);
27         try {
28             file.createNewFile();
29         } catch (IOException e) {
30             e.printStackTrace();
31         }
32         return file;
33     }
34     
35     /**
36      * 在SD卡上创建目录
37      * @param dirName
38      * @return
39 */
40     public File createSDDir(String dirName){
41         File file=new File(SDPath+dirName);
42         file.mkdir();
43         return file;
44     }
45     
46     /**
47      * 判断SD卡上文件是否存在
48      * @param fileName
49      * @return
50 */
51     public boolean isFileExist(String fileName){
52         File file=new File(SDPath+fileName);
53         return file.exists();
54     }
55     /**
56      * 将一个inputStream里面的数据写到SD卡中
57      * @param path
58      * @param fileName
59      * @param inputStream
60      * @return
61 */
62     public File writeToSDfromInput(String path,String fileName,InputStream inputStream){
63         //createSDDir(path);
64         File file=createSDFile(path+fileName);
65         OutputStream outStream=null;
66         try {
67             outStream=new FileOutputStream(file);
68             byte[] buffer=new byte[4*1024];
69             while(inputStream.read(buffer)!=-1){
70                 outStream.write(buffer);
71             }
72             outStream.flush();
73         } catch (FileNotFoundException e) {
74             e.printStackTrace();
75         } catch (IOException e) {
76             e.printStackTrace();
77         }finally{
78             try {
79                 outStream.close();
80             } catch (IOException e) {
81                 e.printStackTrace();
82             }
83         }
84         return file;
85     }
86 }

AndroidManifest.xml

AndroidManifest.xml 
 1 <?xml version="1.0" encoding="utf-8"?>
 2 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
 3     package="paul.Activity"
 4     android:versionCode="1"
 5     android:versionName="1.0" >
 6 
 7     <uses-sdk android:minSdkVersion="10" />
 8     <uses-permission android:name="android.permission.INTERNET" />
 9     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
10     <application
11         android:icon="@drawable/ic_launcher"
12         android:label="@string/app_name" >
13         <activity
14             android:name=".DownloadFileToSDKCardActivity"
15             android:label="@string/app_name" >
16             <intent-filter>
17                 <action android:name="android.intent.action.MAIN" />
18 
19                 <category android:name="android.intent.category.LAUNCHER" />
20             </intent-filter>
21         </activity>
22     </application>
23 </manifest>
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原文地址：https://www.cnblogs.com/Laupaul/p/2348293.html