How to send (from Native code) a android.content.Context parameter to a Java fct (via JNI)

I am developping an application for my android phone, and I am trying to enable the Wifi hotspot. I am using Qt 5.4.1 so I developp in C++. As there is not any function to do this in the NDK, I am using JNI to call Java Methods.

My java code is (thanks to Ashish Sahu's answer in stackoverflow thread) :

package; import android.content.*; import*; import java.lang.reflect.*; //Class that handles Wifi Hotspot (access point) configuration public class ApManager { //Is Wifi hotspot on or off ? public static boolean isApOn(Context context) { WifiManager wifimanager = (WifiManager) context.getSystemService(context.WIFI_SERVICE); try { Method method = wifimanager.getClass().getDeclaredMethod("isWifiApEnabled"); method.setAccessible(true); return (Boolean) method.invoke(wifimanager); } catch (Throwable ignored) {} return false; } //Turn Wifi hotspot on or off public static boolean configApState(Context context, boolean b) { WifiManager wifimanager = (WifiManager) context.getSystemService(context.WIFI_SERVICE); WifiConfiguration wificonfiguration = null; try { //if Wifi is on, turn it off if(isApOn(context)) { wifimanager.setWifiEnabled(false); } Method method = wifimanager.getClass().getMethod("setWifiApEnabled", WifiConfiguration.class, boolean.class); method.invoke(wifimanager, wificonfiguration, b); return true; } catch(Exception e) { e.printStackTrace(); } return false; } }

C++ code sample :

setWifiApEnabled(QAndroidJniObject context, bool b) { return QAndroidJniObject::callStaticMethod<jboolean>("org/app/test/ApManager" , "configApState" , "(Ljava/lang/Object;Z)Z" //Or (Landroid/content/Context;Z)Z ??? , context.object<jobject>() , b); }

But now I have a problem ; how to get the parameter context to pass to the function setWifiApEnabled(context, b) when I call it ?

I am a little lost, I read some threads about this problem (like this one) but I do not totally understand what the people who answered meant.

Could you help me with this ?

EDIT : I found on this stackoverflow thread a way to get the context :

interface = QApplication::platformNativeInterface(); activiti = (jobject)interface->nativeResourceForIntegration("QtActivity"); at = new QAndroidJniObject(activiti); appctx = at->callObjectMethod("getApplicationContext", "()Landroid/content/Context;"); if(appctx.isValid()) qDebug() << "I am valid !"; else qDebug() << "I ain't valid !";

appctx is valid, but the Wifi hotspot doesn't get enabled and I cannot get its state.

EDIT 2 : : I successfully managed to enable the Wifi hotspot in java, using Android Studio. The code is the following : :

public class WifiApManager { private WifiManager wifiMan; protected Method setWifiApEnabledMethod, isWifiApEnabledMethod; protected final static int MAX_ITER = 10; public WifiApManager(WifiManager wifiMan) { this.wifiMan = wifiMan; getHiddenMethods(); } private void getHiddenMethods() { try { setWifiApEnabledMethod = wifiMan.getClass().getMethod("setWifiApEnabled", WifiConfiguration.class, boolean.class); isWifiApEnabledMethod = wifiMan.getClass().getMethod("isWifiApEnabled"); } catch (NoSuchMethodException e) { e.printStackTrace(); } } public boolean isWifiApEnabled() { try { return (Boolean)isWifiApEnabledMethod.invoke(wifiMan); } catch (Exception e) { return false; } } public boolean isWifiEnabled() { return wifiMan.isWifiEnabled(); } public boolean setWifiApEnabled(WifiConfiguration conf, boolean enabled) { try { return (Boolean) setWifiApEnabledMethod.invoke(wifiMan, conf, true); } catch (Exception e) { return false; } } public boolean toggleWifi(String ssid) { // WifiConfiguration creation: WifiConfiguration conf = new WifiConfiguration(); conf.SSID = ssid; conf.allowedAuthAlgorithms.set(WifiConfiguration.AuthAlgorithm.OPEN); // If AP Wifi is enabled, disables it and returns: if(isWifiApEnabled()) { //setWifiApEnabled(null, false); Won't work, see two further lines wifiMan.setWifiEnabled(true); wifiMan.setWifiEnabled(false); int maxIter = MAX_ITER; while (isWifiApEnabled() && maxIter-- >= 0) { try {Thread.sleep(500);} catch (Exception e) {} } return isWifiApEnabled(); } // If standard Wifi is enabled, disables it: if (isWifiEnabled()) { if (wifiMan.setWifiEnabled(false)) { int maxIter = MAX_ITER; while (wifiMan.isWifiEnabled() && maxIter-- >= 0) { try {Thread.sleep(500);} catch (Exception e) {} } } if (isWifiEnabled()) { return false; } } // Enables AP Wifi try { if (! setWifiApEnabled(conf, true)) { System.out.println("setWifiApEnabledMethod failed."); return false; } int maxIter = MAX_ITER; while (! isWifiApEnabled() && maxIter-- > 0) { try {Thread.sleep(500);} catch (Exception e) {} } } catch(Exception e) { e.printStackTrace(); return false; } return true; } }

Main class :

public class AndroidMenusActivity extends Activity implements OnClickListener { private WifiApManager wifiMan; private ToggleButton wifiButton; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); wifiMan = new WifiApManager((WifiManager) this.getSystemService(Context.WIFI_SERVICE)); setContentView(R.layout.activity_android_menus); makeUI(); } private void makeUI() { LinearLayout subLayout = (LinearLayout) findViewById(; wifiButton = new ToggleButton(this); wifiButton.setTextOn("Disable Wifi"); wifiButton.setTextOff("Enable AP Wifi"); wifiButton.setChecked(wifiMan.isWifiApEnabled()); wifiButton.setOnClickListener(this); subLayout.addView(wifiButton); } @Override public void onClick(View sender) { if (!wifiButton.equals(sender)) return; AsyncTask<Object, Void, Boolean> task = new AsyncTask<Object, Void, Boolean>() { private ToggleButton bt; private WifiApManager wm; @Override protected Boolean doInBackground(Object... args) { bt = (ToggleButton) args[0]; wm = (WifiApManager) args[1]; return wm.toggleWifi(""); } @Override protected void onPostExecute (Boolean result) { bt.setChecked(result.booleanValue()); bt.setEnabled(true); } }; wifiButton.setEnabled(false); task.execute(wifiButton, wifiMan); } }

But I cannot find a way to do the same in C++, any help ?

Category:java Time:2018-11-03 Views:1
Tags: java jni android

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