How to get past information while converting speech to text in android?

As i am developing an android app and wants to convert speech into text, i am using built-in Google speech input activity to convert voice into text. I need past information but it continuously get cleared i got only current response. How need to handle same as google voice keyboard. As i talk it included to current String instep of clear.

MainActivity .java

public class MainActivity extends AppCompatActivity
  {
     private EditText txtSpeechInput;
     private ImageButton btnSpeak;
     private final int REQ_CODE_SPEECH_INPUT = 100;

 @Override
  protected void onCreate(Bundle savedInstanceState)
   {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      txtSpeechInput =  findViewById(R.id.txtSpeechInput);
      btnSpeak = (ImageButton) findViewById(R.id.btnSpeak);
    btnSpeak.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            promptSpeechInput();
        }
    });
   private void promptSpeechInput()
      {
    Intent intent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
    intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL,
            RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
    intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE, Locale.getDefault());
    intent.putExtra(RecognizerIntent.EXTRA_PROMPT,
            getString(R.string.speech_prompt));
    intent.putExtra(RecognizerIntent.EXTRA_SPEECH_INPUT_MINIMUM_LENGTH_MILLIS, 20000000);

  try
    {
        startActivityForResult(intent, REQ_CODE_SPEECH_INPUT);
    }
    catch (ActivityNotFoundException a)
    {
        Toast.makeText(getApplicationContext(),
                getString(R.string.speech_not_supported),
                Toast.LENGTH_SHORT).show();
    }
}
    protected void onActivityResult(int requestCode, int resultCode, Intent data)
{
    super.onActivityResult(requestCode, resultCode, data);

    switch (requestCode)
    {
        case REQ_CODE_SPEECH_INPUT:
        {
            if (resultCode == RESULT_OK && null != data)
            {

              final ArrayList<String> result= data
                        .getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS);


                txtSpeechInput.setText(result.get(0));
            }
            break;
        }

    }
}

If you only want to save one previously detected String, for this to achieve, you need to make a global String variable and store the value in that variable from results list.(Save the same String as you are setting on text view). But if you want to save all the strings, you need to make global String Arraylist and add all those string in that array list. Below is the code for that.

private EditText txtSpeechInput;
private ImageButton btnSpeak;
private final int REQ_CODE_SPEECH_INPUT = 100;
private List<String> previousStringList;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    previousStringList = new ArrayList<>();

    txtSpeechInput = findViewById(R.id.txtSpeechInput);
    btnSpeak = (ImageButton) findViewById(R.id.btnSpeak);
    btnSpeak.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            promptSpeechInput();
        }
    });
}

private void promptSpeechInput() {
    Intent intent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
    intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL,
            RecognizerIntent.LANGUAGE_MODEL_FREE_FORM);
    intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE, Locale.getDefault());
    intent.putExtra(RecognizerIntent.EXTRA_PROMPT,
            getString(R.string.speech_prompt));
    intent.putExtra(RecognizerIntent.EXTRA_SPEECH_INPUT_MINIMUM_LENGTH_MILLIS, 20000000);

    try {
        startActivityForResult(intent, REQ_CODE_SPEECH_INPUT);
    } catch (ActivityNotFoundException a) {
        Toast.makeText(getApplicationContext(),
                getString(R.string.speech_not_supported),
                Toast.LENGTH_SHORT).show();
    }
}

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    switch (requestCode) {
        case REQ_CODE_SPEECH_INPUT: {
            if (resultCode == RESULT_OK && null != data) {

                final ArrayList<String> result = data
                        .getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS);


                txtSpeechInput.setText(result.get(0));
                if (result.get(0) != null) {
                    previousStringList.add(result.get(0));
                }
            }
            break;
        }

    }
}

Hope that helps you.If you don't understand anything feel free to ask. If you don't want to save same String twice(already saved string), just replace below conditional line of code..

if (result.get(0) != null && !previousStringList.contains(result.get(0))) {
    previousStringList.add(result.get(0));
   }