This is the code
    public class MainActivity extends Activity {
    protected static final int RESULT_SPEECH = 1;
    private ImageButton btnSpeak;
    private TextView txtText;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        txtText = (TextView) findViewById(R.id.txtText);
        btnSpeak = (ImageButton) findViewById(R.id.btnSpeak);
        btnSpeak.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(
                        RecognizerIntent.ACTION_RECOGNIZE_SPEECH);
                intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL, "en-US");
                try {
                    startActivityForResult(intent, RESULT_SPEECH);
                    txtText.setText("");
                } catch (ActivityNotFoundException a) {
                    Toast t = Toast.makeText(getApplicationContext(),
                            "Opps! Your device doesn't support Speech to Text",
                            Toast.LENGTH_SHORT);
                    t.show();
                }
            }
        });
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        switch (requestCode) {
        case RESULT_SPEECH: {
            if (resultCode == RESULT_OK && null != data) {
                ArrayList<String> text = data
                        .getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS);
                txtText.setText(text.get(0));
            }
            break;
        }
        }
    }
}