Android TextView "append" does NOT update after each loop. How to solve this?

Question

Please answer like you'd teach an amateur. I saw a few answers but unfortunately I do not understand where to insert the code. Here's my code. How do I make this "results1" TextView update every time the for loop runs? Currently, the output displays only when the loop ends. Please remember that I am a beginner. So, clarity please.

I have a

public class MainActivity extends Activity {
    LinearLayout layout1; 
    //One text view, buttons and EditText fields 
}

Then, I have;

 private OnClickListener test = new OnClickListener() {
    @Override
    public void onClick (View V)
    {
        results1.setText("Done");
        results1.append("\n");

        try {
            for(int k=x[1];k<=x1[1];k++) {
                //Bunch of code

                BufferedReader reader = new BufferedReader(new InputStreamReader(
                        process.getInputStream()));

                int j;
                char[] buffer = new char[4096];
                StringBuffer output = new StringBuffer();
                while ((j = reader.read(buffer)) > 0)
                    output.append(buffer, 0, j);
                reader.close();

                str = output.toString();
                Log.d("1:str", str);
                results1.setTextAppearance(getApplicationContext(), 0);
                results1.setTextSize(14);
                results1.setBackgroundColor(Color.rgb(234,234,234));
                results1.setTextColor(Color.parseColor("#00BFFF"));
                results1.append(str);
                results1.append("\n");
                //results1.setTextIsSelectable(true);

            }

        } catch (ArrayIndexOutOfBoundsException e) {
            results1.append(str1);
            System.err.println("ArrayIndexOutOfBoundsException: " + e.getMessage());
        } 
    }
 }; 
 }

Answer 1

Running this sort of code in the main UI thread is not a good idea and could cause the thread to hang. You should use an AsyncTask to run your heavier processing. When you want to update the UI, you can utilize the onProgressUpdate() method.

Answer 2

Write an async class like this

public class ReadStreamTask extends AsyncTask<String,Integer,String> {

    @Override
    protected void onPreExecute() {
        // TODO Auto-generated method stub
         results1.setText("Done");
         results1.append("\n");
    }

    @Override
    protected String doInBackground(String... link) {
        // TODO Auto-generated method stub


        try {

            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    process.getInputStream()));

            int j;
            char[] buffer = new char[4096];
            StringBuffer output = new StringBuffer();
            while ((j = reader.read(buffer)) > 0)
                output.append(buffer, 0, j);
            reader.close();

           // str += output.toString();

            return output.toString();
        } catch (Exception e) {
            e.printStackTrace();
            return output.toString();
        }

    }

    @Override
    protected void onPostExecute(String result) {
        results1.setText(result);
    }
}

then call that class

new ReadStreamTask.execute();

the three parameters in asynctask (if I'm not wrong)

• 1st: use this if you want to pass a value to async class(ex String(your url)
• 2nd: a passed value to async class, usually an integer used when a progress happend to your background task. its value is used to increment a progress but is rarely used.
• 3rd: most important, is the return type of async class

Answer 3

If you want to make this "results1" TextView update every time the for loop runs, you may put the following AsyncTask as your inner class and call

[YOUR_VIEW].setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                new ReadTask().execute();
            }
});

ReadTask.java

public class ReadTask extends AsyncTask<Void, String, Void>{
        BufferedReader reader = null;
        @Override
        protected void onPreExecute() {
            results1.setText("Done");
            results1.append("\n");
            super.onPreExecute();
        }

        @Override
        protected Void doInBackground(Void... params) {
            try {
                  for(int k=x[1];k<=x1[1];k++) {
                    //Bunch of code

                    reader = new BufferedReader(new InputStreamReader(
                            process.getInputStream()));

                    int j;
                    char[] buffer = new char[4096];
                    StringBuffer output = new StringBuffer();
                    while ((j = reader.read(buffer)) > 0)
                        output.append(buffer, 0, j);
                    reader.close();

                    str = output.toString();
                    Log.d("1:str", str);
                    publishProgress(str);

                    //Sleeping for a second
                    try {
                        Thread.sleep(1000);         
                    } catch (InterruptedException e) {
                       e.printStackTrace();
                    }
                    //results1.setTextIsSelectable(true);

                }

            } catch (ArrayIndexOutOfBoundsException e) {
                results1.append(str);
                System.err.println("ArrayIndexOutOfBoundsException: " + e.getMessage());
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }  finally {
                try {

                    if (reader != null) {

                        reader.close();
                    }

                } catch (IOException ex) {

                    ex.printStackTrace();

                }
            }
            return null;
        }

        @Override
        protected void onProgressUpdate(String... values) {
            results1.setTextAppearance(getApplicationContext(), 0);
            results1.setTextSize(14);
            results1.setBackgroundColor(Color.rgb(234,234,234));
            results1.setTextColor(Color.parseColor("#00BFFF"));
            results1.append(str);
            results1.append("\n");
            super.onProgressUpdate(values);
        }

    }

Please check if this helps you.