GPS service for android and suggested changes in Necessitas.
BogDan
bog_dan_ro at yahoo.com
Thu Jun 2 15:00:57 CEST 2011
Great !
Please let me know when you have something.
Cheers,
BogDan.
>________________________________
>From: Frameworks <frameworks at qlands.com>
>To:
>Cc: "necessitas-devel at kde.org" <necessitas-devel at kde.org>
>Sent: Thursday, June 2, 2011 8:10 PM
>Subject: Re: GPS service for android and suggested changes in Necessitas.
>
>Hi,
>
>No problem.
>
>I am working on the GPS mobility plug-in (giving that there is a way of
>having the JObject of the current activity running the QT application).
>
>Cheers,
>Carlos.
>
>On 06/01/2011 09:53 PM, BogDan wrote:
>> Hi,
>>
>>
>> Please accept my apologize for slow replay.
>>
>>
>>> ________________________________
>>> From: "frameworks at qlands.com"<frameworks at qlands.com>
>>> To: necessitas-devel at kde.org
>>> Sent: Sunday, May 29, 2011 10:58 AM
>>> Subject: GPS service for android and suggested changes in Necessitas.
>>>
>>>
>>>
>>> Hi,
>>>
>>>
>>>
>>> First of all. Thanks for the brilliant work!.... Running QT in Android is just mind-blowing!
>>>
>>>
>>> I just joined the list of developers to contribute to the project. Just after I got a copy of Necessitas 0.1 I had to see how to make the GPS work. I wanted to implement it as most as possible with JNI and with the minimum of java code.
>>>
>> Great, we have something in common :)
>>
>>
>>
>>> From a GPS example written in Java (http://hejp.co.uk/android/android-gps-example/) I got that the main challenges were:
>>> 1- To implement the LocationListener interface
>>> 2- To connect to the location manager by Activity.getSystemService(service)
>>> 3- To request the locations using the Listener by LocationManager.requestLocationUpdates(gps provider, double, float, listener,looper)
>>>
>>> This main challenges arose from two main constraints:
>>> 1- The LocationListener is an interface so needs to be implemented in a class in a very basic way. Thus I had to include such implementation as part of the industrius java classes: QtGPSListener.java with the following implementation:
>>>
>>> package eu.licentia.necessitas.industrius;
>>> import android.location.Location;
>>> import android.location.LocationListener;
>>> import android.location.LocationProvider;
>>> import android.os.Bundle;
>>>
>>> public class QtGPSListener implements LocationListener {
>>>
>>> public void onLocationChanged(Location location)
>>> {
>>> // Here we get the location data and create a result
>>> // string (A really basic way of passing data). We called sndonLocationChanged that is
>>> // in fact connected to the qt application by JNI's registeNatives
>>> String accuracy;
>>> accuracy = String.valueOf(location.getAccuracy());
>>>
>>> String altitude;
>>> altitude = String.valueOf(location.getAltitude());
>>>
>>> String latitude;
>>> latitude = String.valueOf(location.getLatitude());
>>>
>>> String longitude;
>>> longitude = String.valueOf(location.getLongitude());
>>>
>>> String res;
>>>
>>> res = "|AC:" + accuracy;
>>> res = res + "|AL:" + altitude;
>>> res = res + "|LA:" + latitude;
>>> res = res + "|LO:" + longitude + "|";
>>>
>>> sndonLocationChanged(res);
>>> }
>>>
>>>
>>> public void onProviderDisabled(String provider)
>>> {
>>> String res;
>>> res = "Provider " + provider + " is disabled";
>>> sndonProviderDisabled(res);
>>> }
>>>
>>>
>>> public void onProviderEnabled(String provider)
>>> {
>>> String res;
>>> res = "Provider " + provider + " is enabled";
>>> sndonProviderEnabled(res);
>>> }
>>>
>>>
>>> public void onStatusChanged(String provider, int status, Bundle extras)
>>> {
>>> switch (status) {
>>> case LocationProvider.OUT_OF_SERVICE:
>>> sndonStatusChanged("Status Changed: Out of Service");
>>>
>>> break;
>>> case LocationProvider.TEMPORARILY_UNAVAILABLE:
>>> sndonStatusChanged("Status Changed: Temporarily Unavailable");
>>>
>>> break;
>>> case LocationProvider.AVAILABLE:
>>> sndonStatusChanged("Status Changed: Available");
>>>
>>> break;
>>> }
>>>
>>> }
>>> // List of methods that will be linked in the qt application
>>> // using JNI's registerNatives
>>> public static native void sndonLocationChanged(String currLocation);
>>> public static native void sndonProviderDisabled(String message);
>>> public static native void sndonProviderEnabled(String message);
>>> public static native void sndonStatusChanged(String message);
>>>
>>> }
>>>
>>> 2- I had to use the activity running the qt application so I can use getSystemService(String). I though there were some Android API to get an instance to the current activity running (so I can use JNI to get it) but it seems that there is none.
>>>
>> Actually it is, QtApplication.mainActivity()
>>
>>
>>
>>> So the only alternative that I had was to pass the activity from QtApplication.java to qtmain_android.cpp. For this I made the following changes:
>>>
>>> 2.1 - In QtApplication.java: FROM: public static native void startQtApp(String params,String env) TO: public static native void startQtApp(String params,String env,Object currAct)
>>> 2.2 - In qtmain_android.cpp: FROM: static jboolean startQtApp(JNIEnv* env, jobject /*object*/, jstring paramsString, jstring environmentString) TO: tatic jboolean startQtApp(JNIEnv* env, jobject /*object*/, jstring paramsString, jstring environmentString,jobject currAct)
>>> 2.3 - In qtmain_android.cpp: I created a jobject currActivity = NULL that I can extern in my sample application. Plus assigning it a global reference of the current activity: currActivity = env->NewGlobalRef(currAct). This to use it in JNI thread of execution
>>>
>>>
>> Hmm :)
>>
>>
>>
>>> With this changes I create a QT GPS class with JNI code that access the GPS. I just need to pass it the JavaVM that I extern from qtmain_android.cpp and currActivity.
>>>
>>>
>>> I can see that in 0.2 necessitas include QtLocation.java (which implements the GPS). Although it is fine, I reckon it is better to implement much of that code in the c++ side with JNI and only have the minimum java code just for implementing interfaces for example.
>>>
>>>
>> Agree with you !
>>
>>
>>
>>> This is an snapshot of the QT GPS class where it connects to the service
>>>
>>>
>>>
>> [...]
>>
>>
>>> To conclude. A JNI implementation of the Android GPS service with very basic java code will require to have a Jobject pointing to the current activity running the QT application.
>>>
>> Please call QtApplication.mainActivity() to get it !
>>
>>
>>
>>> This I reckon would make a Mobility plugin less dependent on external java coding.
>>>
>> It will be great, because the java part can't be updated, by Ministro service !
>>
>>
>>
>>> But where it would be the best place to implement this change? I made it on qtmain_android.cpp and qtApplication.java but for a Mobility plugin this might not be the case.
>>>
>>>
>> Please change current Mobility implementation ! You'll get Java_vm pointer when the plugin is loaded by application and QtApplication.mainActivity() is a static function which can be used to get current activity.
>>
>>
>>
>>> I register myself on gitorious. For contributing do I need to work on a clone of master?
>>>
>>>
>> Please clone http://qt.gitorious.org/~taipan/qt-mobility/android-qt-mobility and use testing branch !
>>
>>
>>
>>>
>>> Thanks a lot for the brilliant work!
>>>
>>>
>>>
>>>
>> Thanks,
>>
>> I'm looking forward to hearing from you
>>
>> Cheers,
>> BogDan.
>>
>>
>> Again, sorry for slow replay.
>>
>>
>>
>
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