Hello all,

First of all, I apologize if this thread is not in the right place, and ask the moderators to kindly re-direct it appropriately.

With the advent of Qt 5.2 beta, we have access to QtAndroidExtras, which is very nice. I want to use this to invoke Android's text to speech functionality, and it appears that the class for doing this is android.speech.tts.TextToSpeech.

On the Qt side, I have this:

Qt Code: 
  1. void TTSClient::speak(const QString &msg) {
  2.     QAndroidJniObject myTtsObj("org.qtproject.qt5.android.bindings.MyTextToSpeech");
  3.     if (myTtsObj.isValid())
  4.         myTtsObj.callMethod<void>("speak", "(Ljava/lang/String;)V", QAndroidJniObject::fromString(msg).object<jstring>());
  5.     else
  6.         qDebug() << "TTSClient::speak() - Failed: invalid QAndroidJniObject!";
  7. }
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While on the Java side, I have this:

Qt Code: 
  1. package org.qtproject.qt5.android.bindings;
  2.  
  3. import android.speech.tts.TextToSpeech;
  4. import android.speech.tts.TextToSpeech.OnInitListener;
  5.  
  6. public class MyTextToSpeech implements OnInitListener {
  7.  
  8.     private TextToSpeech tts;
  9.  
  10.     public MyTextToSpeech() {
  11.         // tts = new TextToSpeech(<something that is-a android.content.Context>, this);
  12.     }
  13.  
  14.     @Override
  15.     public void onInit(int status) {
  16.         System.out.println("MyTextToSpeech.onInit() - Got status: " + status);
  17.     }
  18.  
  19.     @Override
  20.     public void finalize() throws Throwable {
  21.         if (tts != null) {
  22.             tts.stop();
  23.             tts.shutdown();
  24.         }
  25.         super.finalize();
  26.     }
  27.  
  28.     public void speak(String msg) {
  29.         System.out.println("MyTextToSpeech.speak() - " + msg);
  30.         // rest to be implemented once TextToSpeech constructor is sorted out!
  31.     }
  32. }
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My Java class has-a TextToSpeech. The TextToSpeech class does not expose a default constructor, and at minimum requires two things: a Context, and an OnInitListener. The second part is easy. The first is giving me a terrible headache! At first I thought I could simply pass in an instance of android.app.Application, which is-a Context. So, I altered my Java constructor accordingly, and created an Application in Qt:

Qt Code: 
  1. QAndroidJniEnvironment jniEnv;
  2. jclass appClass = jniEnv->FindClass("android/app/Application");
  3. jmethodID appCtor = jniEnv->GetMethodID(appClass, "<init>", "()V");
  4. jobject appObj = jniEnv->NewObject(appClass, appCtor);
  5. QAndroidJniObject myTtsObj("org.qtproject.qt5.android.bindings.MyTextToSpeech", "(Landroid/app/Application;)V", appObj);
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But the MyTextToSpeechClass constructor call would seemingly hang when it tried to initialize the TextToSpeech member, and on any subsequent attempt to call TTSClient::speak() would crash with a NullPointerException:

Qt Code: 
  1. E/AndroidRuntime(11258): FATAL EXCEPTION: Thread-579
  2. E/AndroidRuntime(11258): java.lang.NullPointerException
  3. E/AndroidRuntime(11258): 	at android.content.ContextWrapper.getPackageName(ContextWrapper.java:135)
  4. E/AndroidRuntime(11258): 	at android.speech.tts.TextToSpeech.<init>(TextToSpeech.java:606)
  5. E/AndroidRuntime(11258): 	at android.speech.tts.TextToSpeech.<init>(TextToSpeech.java:582)
  6. E/AndroidRuntime(11258): 	at android.speech.tts.TextToSpeech.<init>(TextToSpeech.java:567)
  7. E/AndroidRuntime(11258): 	at org.qtproject.qt5.android.bindings.MyTextToSpeech.<init>(MyTextToSpeech.java:13)
  8. E/AndroidRuntime(11258): 	at dalvik.system.NativeStart.run(Native Method)
  9. I/Process (11258): Sending signal. PID: 11258 SIG: 9
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Then I thought to try using an instance of QtApplication (which is placed by Qt in android\src\org\qtproject\qt5\android\bindings) but this crashed without even having the decency to say much about it:

Qt Code: 
  1. F/libc    (13574): Fatal signal 11 (SIGSEGV) at 0x0000002c (code=1), thread 13589 (.MyProjectName)
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Finally, I thought to make my Java class extend android.app.Activity, which is-a Context as well. But, this crashed too:

Qt Code: 
  1. W/dalvikvm(11794): threadid=12: thread exiting with uncaught exception (group=0x416aa700)
  2. E/AndroidRuntime(11794): FATAL EXCEPTION: Thread-583
  3. E/AndroidRuntime(11794): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
  4. E/AndroidRuntime(11794): 	at android.os.Handler.<init>(Handler.java:197)
  5. E/AndroidRuntime(11794): 	at android.os.Handler.<init>(Handler.java:111)
  6. E/AndroidRuntime(11794): 	at android.app.Activity.<init>(Activity.java:759)
  7. E/AndroidRuntime(11794): 	at org.qtproject.qt5.android.bindings.MyTextToSpeech.<init>(MyTextToSpeech.java:11)
  8. E/AndroidRuntime(11794): 	at dalvik.system.NativeStart.run(Native Method)
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I guess my over-arching question is: how do I supply the requisite Context to my TextToSpeech member variable?

Any guidance is very appreciated. I think I must be missing some crucial concepts.

Thank you for your time.