android实现文件下载功能 android实现文件下载功能
dgdisme 人气:0android 在网络上下载文件,供大家参考,具体内容如下
步骤 :
1.使用HTTP协议下载文件
- 创建一个HttpURLConnection对象 : HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
- 获取一个InputStream对象 : urlConn.getInputStream()
- 访问网络的权限 : android.permission.INTERNET
2.将下载的文件写入SDCARD
- 得到当前设备SD卡的目录 : Environment.getExternalStrageDirectory()
- 访问SD卡的权限 : android.permission.WRITE_EXTERNAL_STORAGE
代码 :
activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context=".MainActivity" > <Button android:id="@+id/btn_txt" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="download lrc" /> <Button android:id="@+id/btn_mp3" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_below="@id/btn_txt" android:text="download mp3" /> </RelativeLayout>
MainActivity.java
package com.chay.download; import com.chay.utils.HttpDownloader; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; public class MainActivity extends Activity { String urlStr_txt = "http://192.168.56.1:8080/mp3/wan.lrc"; String urlStr_mp3 = "http://192.168.56.1:8080/mp3/wan.mp3"; String path = "mp3/"; String fileName = "wan.mp3"; private Button downloadTxtButton; private Button downloadMp3Button; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); downloadTxtButton = (Button) findViewById(R.id.btn_txt); downloadTxtButton.setOnClickListener(new DownloadTxtListener()); downloadMp3Button = (Button) findViewById(R.id.btn_mp3); downloadMp3Button.setOnClickListener(new DownloadMp3Listener()); } //下载歌词文件按钮监听器 class DownloadTxtListener implements OnClickListener { @Override public void onClick(View v) { Thread t = new DownloadTxtThread(); t.start(); System.out.println("txt--->"); } } //下载歌词文件线程 class DownloadTxtThread extends Thread{ @Override public void run() { HttpDownloader httpDownloader = new HttpDownloader(); String lrc = httpDownloader.download(urlStr_txt); System.out.println(lrc); } } //下载MP3文件按钮监听器 class DownloadMp3Listener implements OnClickListener { @Override public void onClick(View v) { Thread h = new DownMp3Thread(); h.start(); System.out.println("mp3--->"); } } //下载MP3文件线程 class DownMp3Thread extends Thread{ @Override public void run() { HttpDownloader httpDownloader = new HttpDownloader(); int result = httpDownloader.downFile(urlStr_mp3, path, fileName); System.out.println(result); } } }
工具类:
HttpDownloader.java
package com.chay.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 com.chay.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; } }
如果不能下载,请先将windows防火墙关闭。
加载全部内容