在Android中找不到文件错误？

Question

I am trying to download pdf file and save on android at some location .But I am getting this error why ? java.io.FileNotFoundException: http://www.pdf995.com/samples/pdf.pdf I am checking my code on emulator.can you please tell me why this error coming because when I hit this url on browser http://www.pdf995.com/samples/pdf.pdf it give pdf to us .But here it is not giving to use,

code:

package com.example.downloadfile;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;



public class MainActivity extends Activity {
    int totalSize = 0;
     int downloadedSize = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button b = (Button) findViewById(R.id.b1);
        b.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                 //showProgress(dwnload_file_path);

                    new Thread(new Runnable() {
                        public void run() {
                             downloadFile();
                        }
                      }).start();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
      void downloadFile(){

            try {
                URL url = new URL("http://www.pdf995.com/samples/pdf.pdf");
                HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

                urlConnection.setRequestMethod("GET");
                urlConnection.setDoOutput(true);

                //connect
                urlConnection.connect();

                //set the path where we want to save the file           
                File SDCardRoot = Environment.getExternalStorageDirectory(); 
                //create a new file, to save the <span id="IL_AD12" class="IL_AD">downloaded</span> file 
                File file = new File(SDCardRoot,"aaa.pdf");

                FileOutputStream fileOutput = new FileOutputStream(file);

                //Stream used for reading the data from the internet
                InputStream inputStream = urlConnection.getInputStream();

                //this is the total size of the file which we are <span id="IL_AD9" class="IL_AD">downloading</span>
                totalSize = urlConnection.getContentLength();



                //create a buffer...
                byte[] buffer = new byte[1024];
                int bufferLength = 0;

                while ( (bufferLength = inputStream.read(buffer)) > 0 ) {
                    fileOutput.write(buffer, 0, bufferLength);
                    downloadedSize += bufferLength;
                    // update the progressbar //
                    runOnUiThread(new Runnable() {
                        public void run() {
                            float per = ((float)downloadedSize/totalSize) * 100;
                            //cur_val.setText("Downloaded " + downloadedSize + "KB / " + totalSize + "KB (" + (int)per + "%)" );
                        }
                    });
                }
                //close the output stream when complete //
                fileOutput.close();
                runOnUiThread(new Runnable() {
                    public void run() {
                        // pb.dismiss(); // if you want close it..
                    }
                });         

            } catch (final MalformedURLException e) {
               // showError("Error : MalformedURLException " + e);        
                e.printStackTrace();
            } catch (final IOException e) {
                //showError("Error : IOException " + e);          
                e.printStackTrace();
            }
            catch (final Exception e) {
                //showError("Error : Please <span id="IL_AD4" class="IL_AD">check your</span> internet connection " + e);
            }       
        }

}

Answer 1

Calling openConnection() is enough to access the input stream later. Looks like the second call to connect() is what's causing the problem. Just strip that part from your code and it will work fine:

URL url = new URL("http://www.pdf995.com/samples/pdf.pdf");
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

//set the path where we want to save the file           
File SDCardRoot = Environment.getExternalStorageDirectory(); 
...

As an aside, if you want to show progress during the download, I'd suggest using an AsyncTask instead. It's tailor-made for uses like this.