Question

I found a snippet online for showing a download’s progress. The error I’m getting is android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. My goal is to have the phone download a file and then when completed, switch to the chaptermenu intent

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.content.Intent;
import android.os.Bundle;
import android.os.Environment;
import android.widget.TextView;

public class CheckDownload extends Activity {

/** Called when the activity is first created. */
@Override
protected void onCreate(Bundle SavedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(SavedInstanceState);
    setContentView(R.layout.downloadscreen);
    Thread timer = new Thread() {
        public void run() {
            try {
                // set the download URL, a url that points to a file on the
                // internet
                // this is the file to be downloaded
                URL url = new URL(
                        "http://www.android.com/media/wallpaper/gif/android_logo.gif");

                // create the new connection
                HttpURLConnection urlConnection = (HttpURLConnection) url
                        .openConnection();

                // set up some things on the connection
                urlConnection.setRequestMethod("GET");
                urlConnection.setDoOutput(true);

                // and connect!
                urlConnection.connect();

                // set the path where we want to save the file
                // in this case, going to save it on the root directory of
                // the
                // sd card.
                File SDCardRoot = Environment.getExternalStorageDirectory();
                // create a new file, specifying the path, and the filename
                // which we want to save the file as.
                File file = new File(SDCardRoot, "android_logo.gif");

                // this will be used to write the downloaded data into the
                // file we created
                FileOutputStream fileOutput = new FileOutputStream(file);

                // this will be used in reading the data from the internet
                InputStream inputStream = urlConnection.getInputStream();

                // this is the total size of the file
                int totalSize = urlConnection.getContentLength();
                // variable to store total downloaded bytes
                int downloadedSize = 0;

                // create a buffer...
                byte[] buffer = new byte[1024];
                int bufferLength = 0; // used to store a temporary size of
                                        // the buffer

                // now, read through the input buffer and write the contents
                // to the file
                while ((bufferLength = inputStream.read(buffer)) > 0) {
                    // add the data in the buffer to the file in the file
                    // output stream (the file on the sd card
                    fileOutput.write(buffer, 0, bufferLength);
                    // add up the size so we know how much is downloaded
                    downloadedSize += bufferLength;
                    // this is where you would do something to report the
                    // prgress, like this maybe
                    updateProgress(downloadedSize, totalSize);

                }
                // close the output stream when done
                fileOutput.close();

                // catch some possible errors...
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                Intent chapterMenuIntentObject = new Intent(
                        "com.blah.blah.CHAPTERMENU");
                startActivity(chapterMenuIntentObject);
            }
        }

    };
    timer.start();
}

public void updateProgress(int downloadedSize, int totalSize) {
    int percentage = downloadedSize / totalSize * 100;
    String stringy = "Download Progress: " + percentage + "%";
    TextView textytext = (TextView) findViewById(R.id.downloadscreentextview);
    textytext.setText(stringy);
}

@Override
protected void onPause() {
    // TODO Auto-generated method stub
    super.onPause();
    finish();
}

}

Answer 1

You are trying to update the progress from worker(or background thread) where it doesnot get reference to your views. It has to be done on UI thread.
Try using AsynTask , makes life easier with threads.
http://developer.android.com/reference/android/os/AsyncTask.html

or

if you want to stick with normal threads,
Check this code,
http://huuah.com/android-progress-bar-and-thread-updating/
You might have to use messageHandler to send message to progressbar, and then update.