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安卓可以下载文件

运维开发网 https://www.qedev.com 2022-05-15 16:51 出处:网络
这篇文章主要为大家详细介绍了android实现文件下载功能,android在网络上下载文件,具有一定的参考价值,感兴趣的小伙伴们可以参考一下

这篇文章主要为大家详细介绍了android实现文件下载功能,android在网络上下载文件,具有一定的参考价值,感兴趣的小伙伴们可以参考一下

下载android上的文件供你参考。具体情况如下

步骤:

1.使用HTTP协议下载文件

-创建一个HttpURLConnection对象:HttpURLConnection URL conn =(HttpURLConnection)URL . open connection();
-获取InputStream对象:URL conn . getinputstream()
-访问网络的权限:Android . Permission . internet

2.将下载的文件写入SDCARD
-获取设备当前SD卡的目录:environment . getexternalmanaged Directory()
-访问SD卡:Android . permission . write _ external _ storage

代码:

activity_main.xml

lt;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" gt; lt;Button android:id="@+id/btn_txt" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="download lrc" /gt; lt;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" /gt; lt;/RelativeLayoutgt;

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---gt;"); } } //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---gt;"); } } //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); } } }

工具类别:

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; } }


如果下载不到,请先关闭windows防火墙。


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