GPS service for android and suggested changes in Necessitas.
Frameworks
frameworks at qlands.com
Thu Jun 2 14:10:15 CEST 2011
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.
>
>
>
More information about the Necessitas-devel
mailing list