Added TTS

app/src/main/java/eu/faircode/email/TTSHelper.java

@@ -0,0 +1,44 @@
+package eu.faircode.email;
+
+import android.content.Context;
+import android.speech.tts.TextToSpeech;
+
+import java.util.Locale;
+
+public class TTSHelper {
+    private static boolean initialized;
+    private static TextToSpeech instance;
+
+    static void speak(Context context, final String utteranceId, final String text, final String language) {
+        // https://developer.android.com/reference/android/speech/tts/TextToSpeech
+        // https://android-developers.googleblog.com/2009/09/introduction-to-text-to-speech-in.html
+
+        final Runnable speak = new Runnable() {
+            @Override
+            public void run() {
+                if (language != null) {
+                    Locale loc = new Locale(language);
+                    if (instance.setLanguage(loc) < 0)
+                        EntityLog.log(context, "TTS unavailable language=" + loc);
+                }
+
+                instance.speak(text, TextToSpeech.QUEUE_ADD, null, utteranceId);
+            }
+        };
+
+        if (initialized) {
+            speak.run();
+            return;
+        }
+
+        instance = new TextToSpeech(context, new TextToSpeech.OnInitListener() {
+            @Override
+            public void onInit(int status) {
+                initialized = (status == TextToSpeech.SUCCESS);
+                Log.i("TTS status=" + status + " ok=" + initialized);
+                if (initialized)
+                    speak.run();
+            }
+        });
+    }
+}