Android:下载文件代码不工作

Question

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我的内部存储中下载的文件。下面是我的代码:

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);
    }
}

我是新的java和android开发，任何答案将非常感激，谢谢!

---

哟!我用了ff。代码来代替。这对我很有效。谢谢你的帮助!

private static String fileName = "beautiful_galaxy - tarantula.jpg";
private static String fileURL = "http://apod.nasa.gov/apod/image/0903/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

如果您正在下载文件到Sdcard，那么请确保您的Sdcard已挂载，代码将下载文件到Sdcard，如果仍然有问题请告诉我。

<>之前尝试{URL =新URL(提供任何URL);HttpURLConnection c = (HttpURLConnection) url.openConnection();c.setRequestMethod("获得");c.setDoOutput(真正的);c.connect ();String PATH = Environment.getExternalStorageDirectory()+"/下载/";日志。v(LOG_TAG， "PATH: " + PATH);File File = new File(PATH);file.mkdirs ();String fileName = "Test.mp3";文件输出文件=新文件(文件，文件名);FileOutputStream fos = new FileOutputStream(outputFile);InputStream is = c.getInputStream();Byte [] buffer = new Byte [1024];Int len1 = 0;While ((len1 = is.read(buffer)) != -1) {安全系数。Write (buffer, 0, len1);｝fos.close ();is.close ();//}} catch (IOException e) {日志。d(LOG_TAG， "Error: " + e);吐司。makeText(myApp， "error " + e.toString()， Toast.LENGTH_LONG),告诉();｝之前

祝你好运

Answer 2

他说应该用Apache HTTP客户端而不是java客户端

下面是取自教程的代码片段:

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

非常确定(就像@dmon所说的)，您不能以这种方式写入数据目录。你想:

1. 使用Environment.getDownloadCacheDirectory ()或Environment.getExternalStorageDirectory ()。看一下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，工作得很好。
3. android日志怎么说?

Answer 4

检查Manifest文件中的以下权限:

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

Answer 5

您现在将有一个NetworkOnMainThreadException。看看那只木头猫。把你的internet代码放到asynctask或线程中

Answer 6

使用以下代码下载文件:

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;
}