■ サンプル

import android.speech.tts.TextToSpeech;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;

import java.util.Locale;

public class MainActivity extends AppCompatActivity implements TextToSpeech.OnInitListener {
    private TextToSpeech tts;

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

        // TextToSpeechオブジェクトの生成
        tts = new TextToSpeech(this, this);
    }


    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (null != tts) {
            // TextToSpeechのリソースを解放する
            tts.shutdown();
        }
    }

    @Override
    public void onInit(int status) {
        if (TextToSpeech.SUCCESS == status) {
            Locale locale = Locale.ENGLISH;
            if (tts.isLanguageAvailable(locale) >= TextToSpeech.LANG_AVAILABLE) {
                tts.setLanguage(locale);
            } else {
                Log.d("", "Error SetLocale");
            }
        } else {
            Log.d("", "Error Init");
        }
    }

    protected  void onClickButton(View view) {
        try {
            String value = ((EditText)findViewById(R.id.inputEditText)).getText().toString();
            this.speechText(value);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        Toast.makeText(this, "Done!!", Toast.LENGTH_LONG).show();
    }

    private void speechText(String value) {
        if (0 < value.length()) {
            if (tts.isSpeaking()) {
                // 読み上げ中なら止める
                tts.stop();
            }

            // 読み上げ開始
            tts.speak(value, TextToSpeech.QUEUE_FLUSH, null);
        }
    }
}

参考文献