Android：下载文件代码不起作用

我正在尝试从URL下载文件。 我的代码没有返回错误，但我看不到我应该在内部存储中下载的文件。 这是我的代码：

package com.example.downloadfile; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.net.HttpURLConnection; import java.net.URL; import android.app.Activity; import android.os.Bundle; import android.os.Environment; import android.util.Log; import android.widget.TextView; public class DownloadFile extends Activity { private static String fileName = "al.jpg"; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); TextView tv = new TextView(this); tv.setText("This is download file program... "); try { URL url = new URL("http://www.fullissue.com/wp-content/uploads/2010/12/Adam-Lambert.jpg"); HttpURLConnection c = (HttpURLConnection) url.openConnection(); c.setRequestMethod("GET"); c.setDoOutput(true); c.connect(); String PATH = Environment.getDataDirectory() + "/"; tv.append("\nPath > " + PATH); Log.v("log_tag", "PATH: " + PATH); File file = new File(PATH); file.mkdirs(); File outputFile = new File(file, fileName); FileOutputStream fos = new FileOutputStream(outputFile); InputStream is = c.getInputStream(); byte[] buffer = new byte[1024]; int len1 = 0; while ((len1 = is.read(buffer)) != -1) { fos.write(buffer, 0, len1); } fos.close(); is.close(); } catch (IOException e) { Log.d("log_tag", "Error: " + e); } Log.v("log_tag", "Check: "); tv.append("\nAnother append!"); this.setContentView(tv); } } 

我是java和android dev的新手，任何答案都会非常感谢，谢谢！

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呦！ 我使用了ff。 代码而不是。 这对我有用。 感谢你的帮助！

 private static String fileName = "beautiful_galaxy - tarantula.jpg"; private static String fileURL = "http://sofzh.miximages.com/java/tarantula2_hst_big.jpg"; try { File root = Environment.getExternalStorageDirectory(); URL u = new URL(fileURL); HttpURLConnection c = (HttpURLConnection) u.openConnection(); c.setRequestMethod("GET"); c.setDoOutput(true); c.connect(); int lenghtOfFile = c.getContentLength(); FileOutputStream f = new FileOutputStream(new File(root + "/download/", fileName)); InputStream in = c.getInputStream(); byte[] buffer = new byte[1024]; int len1 = 0; long total = 0; while ((len1 = in.read(buffer)) > 0) { total += len1; //total = total + len1 //publishProgress("" + (int)((total*100)/lenghtOfFile)); f.write(buffer, 0, len1); } f.close(); } catch (Exception e) { Log.d("Downloader", e.getMessage()); } 

Answer 1

如果你正在下载文件到Sdcard然后确保你的SD卡已经安装，代码将下载文件到SD卡，如果仍然有问题让我知道。

尝试{
             URL url =新URL（提供任何URL）;
             HttpURLConnection c =（HttpURLConnection）url.openConnection（）;
             c.setRequestMethod（ “GET”）;
             c.setDoOutput（真）;
             c.connect（）;

             String PATH = Environment.getExternalStorageDirectory（）
                     +“/ download /”;
             Log.v（LOG_TAG，“PATH：”+ PATH）;
            文件文件=新文件（PATH）;
             file.mkdirs（）;

             String fileName =“Test.mp3”;


            文件outputFile = new File（file，fileName）;
             FileOutputStream fos = new FileOutputStream（outputFile）;

             InputStream = c.getInputStream（）;

             byte [] buffer = new byte [1024];
             int len1 = 0;
             while（（len1 = is.read（buffer））！= -1）{

                 fos.write（buffer，0，len1）;

             }
             fos.close（）;
             is.close（）;

             //}
         } catch（IOException e）{
             Log.d（LOG_TAG，“错误：”+ e）;
             Toast.makeText（myApp，“error”+ e.toString（），Toast.LENGTH_LONG）
                     。节目（）;

         }

祝你好运:)

Answer 2

我看到了这个话题 ，那个人说你应该使用Apache HTTP客户端而不是java 客户端

以下是教程中的代码片段：

 HttpClient httpclient = new DefaultHttpClient(); HttpGet httpget = new HttpGet("http://localhost/"); HttpResponse response = httpclient.execute(httpget); HttpEntity entity = response.getEntity(); if (entity != null) { InputStream instream = entity.getContent(); int l; byte[] tmp = new byte[2048]; while ((l = instream.read(tmp)) != -1) { } } 

Answer 3

非常肯定（就像@dmon所说的那样）你不能以这种方式写入数据目录。 你想要：

1. 使用Environment.getDownloadCacheDirectory ()或Environment.getExternalStorageDirectory () 。 查看http://developer.android.com/reference/android/os/Environment.html#getDataDirectory%28%29的javadoc。
2. 使用URLConnection（）很好：这是标准的java，并且工作得很好。
3. android日志说什么？

Answer 4

检查Manifest文件中的以下权限：

Answer 5

您现在将拥有NetworkOnMainThreadException。 看看日志猫。 将您的互联网代码放在asynctask或线程中。

Answer 6

要下载文件，我使用以下代码：

 public boolean DownloadFile(String url, File outputFile) { try { URL u = new URL(url); URLConnection conn = u.openConnection(); int contentLength = conn.getContentLength(); DataInputStream stream = new DataInputStream(u.openStream()); byte[] buffer = new byte[contentLength]; stream.readFully(buffer); stream.close(); DataOutputStream fos = new DataOutputStream(new FileOutputStream(outputFile)); fos.write(buffer); fos.flush(); fos.close(); } catch(FileNotFoundException e) { return false; } catch (IOException e) { return false; } return true; }