AsyncTask Execution Debugging

Question

I have used ASyncTask before and have not faced any problems. I don't understand why this code is not working. I have to access an ftp server to download a text file that i set to a TextView. The code within the ASyncTask works fine. I have checked it. For some reason I am getting a problem when I call the new thread 'new GetStory().execute'. Any help would be great.

package com.amazingstories;

import it.sauronsoftware.ftp4j.FTPAbortedException;
import it.sauronsoftware.ftp4j.FTPClient;
import it.sauronsoftware.ftp4j.FTPDataTransferException;
import it.sauronsoftware.ftp4j.FTPDataTransferListener;
import it.sauronsoftware.ftp4j.FTPException;
import it.sauronsoftware.ftp4j.FTPIllegalReplyException;

import java.io.File;
import java.io.IOException;

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.view.Window;
import android.view.WindowManager;
import android.widget.TextView;
import android.widget.Toast;

public class DisplayStory extends Activity {

    String path;
    TextView story;
    FTPClient ftp = new FTPClient();
    File file;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        path = getIntent().getExtras().getString("path");
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        setContentView(R.layout.displaystory);
        story = (TextView) findViewById(R.id.tvStory);
        story.setText(path);
        file = new File(
                Environment
                        .getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS),
                "temp.txt");    
        new GetStory().execute();
//      try{
//      new GetStory().execute();
//      }catch(Exception e){
//          Toast.makeText(getApplicationContext(), e.toString(),
//                  Toast.LENGTH_SHORT).show();
//          
//      }
    }   

    public class GetStory extends AsyncTask<Void, Integer, Void> {

        @Override
        protected Void doInBackground(Void... params) {
            // TODO Auto-generated method stub
            Toast.makeText(getApplicationContext(), "Try",
                    Toast.LENGTH_SHORT).show();
            try {
                Toast.makeText(getApplicationContext(), "Try",
                        Toast.LENGTH_SHORT).show();

                if (!ftp.isConnected()) {

                    ftp.connect(".....");
                    Toast.makeText(getApplicationContext(),
                            "connected to server", Toast.LENGTH_SHORT).show();
                    ftp.login("....", ".....");
                }
                Toast.makeText(getApplicationContext(), "FTP Connected",
                        Toast.LENGTH_SHORT).show();
                ftp.changeDirectoryUp();
                ftp.download(path, file, new FTPDataTransferListener() {

                    //ProgressDialog dialog;

                    @Override
                    public void aborted() {
                        // TODO Auto-generated method stub
                    //  dialog.dismiss();
                        story.setText("Transfer Aborted");
                    }

                    @Override
                    public void completed() {
                        // TODO Auto-generated method stub
                        //dialog.dismiss();
                    }

                    @Override
                    public void failed() {
                        // TODO Auto-generated method stub
                        //dialog.dismiss();
                        story.setText("Transfer Failed");
                    }

                    @Override
                    public void started() {
                        // TODO Auto-generated method stub
                        //dialog = ProgressDialog.show(DisplayStory.this, "",
                            //  "Loading. Please wait...", true);
                    }

                    @Override
                    public void transferred(int arg0) {
                        // TODO Auto-generated method stub

                    }

                });
                // tv.setText(test.toString());
                Toast.makeText(getApplicationContext(), "Done",
                        Toast.LENGTH_SHORT).show();
            } catch (FTPException e) {
                Toast.makeText(getApplicationContext(),
                        "Exception Caught " + e, Toast.LENGTH_LONG).show();
            } catch (IllegalStateException e) {
                // TODO Auto-generated catch block
                Toast.makeText(getApplicationContext(),
                        "Exception Caught " + e, Toast.LENGTH_LONG).show();
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                Toast.makeText(getApplicationContext(),
                        "Exception Caught " + e, Toast.LENGTH_LONG).show();
                e.printStackTrace();
            } catch (FTPIllegalReplyException e) {
                // TODO Auto-generated catch block
                Toast.makeText(getApplicationContext(),
                        "Exception Caught " + e, Toast.LENGTH_LONG).show();
                e.printStackTrace();
            } catch (FTPDataTransferException e) {
                // TODO Auto-generated catch block
                Toast.makeText(getApplicationContext(),
                        "Exception Caught " + e, Toast.LENGTH_LONG).show();
                e.printStackTrace();
            } catch (FTPAbortedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } finally {
                try {
                    ftp.logout();
                } catch (IllegalStateException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (FTPIllegalReplyException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (FTPException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
            getFileData get = new getFileData();
            try {
                story.setText(get.getData(file));
                Toast.makeText(getApplicationContext(), "Set TextView",
                        Toast.LENGTH_SHORT).show();
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            file.delete();

        }

    }
}

Answer 1

   @Override
        protected Void doInBackground(Void... params) {
            // TODO Auto-generated method stub
            Toast.makeText(getApplicationContext(), "Try",
                    Toast.LENGTH_SHORT).show();

You are not allowed to call Toast inside doInBackground. doInBackground method runs in non-ui thread so you can not manipulate or sidplay Toast on UI.It must be done in onPreExecute or in onPostExceute.

Answer 2

The methods onPreExecute(), onPostExecute(), and onProgressUpdate() are the only methods during an AsyncTask execution that are called on the main (UI) thread, and therefore are the only places you can directly make calls to UI methods (like TextView.setText() and Toast.makeText()).

Your program is likely crashing because you cannot create a Toast from a thread where "a Looper has not been prepared", which is what happends when you do so from doInBackground(); this causes an exception and a crash.