Add support for Android API >= 31

.gitignore

@@ -30,3 +30,6 @@ node_modules/
 
 # Vim swap
 *.sw?
+
+# Android Studio files
+.idea/

src/android/PhoneCallTrap.java

@@ -1,38 +1,125 @@
 package io.gvox.phonecalltrap;
 
+import android.Manifest;
+import androidx.annotation.RequiresApi;
+import android.os.Build;
+import android.content.pm.PackageManager;
 import org.apache.cordova.CordovaPlugin;
 import org.apache.cordova.CallbackContext;
 import org.apache.cordova.PluginResult;
 import android.content.Context;
 import android.telephony.PhoneStateListener;
 import android.telephony.TelephonyManager;
+import android.telephony.TelephonyCallback;
 
 import org.json.JSONException;
 import org.json.JSONArray;
 
 
 public class PhoneCallTrap extends CordovaPlugin {
 
+    OldCallStateListener oldListener;
     CallStateListener listener;
+    CallbackContext callbackContext;
+    boolean listenerSet = false;
 
+    @Override
     public boolean execute(String action, JSONArray args, CallbackContext callbackContext) throws JSONException {
         prepareListener();
+        this.callbackContext = callbackContext;
 
-        listener.setCallbackContext(callbackContext);
+        if (listenerSet) {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+                listener.setCallbackContext(callbackContext);
+            } else {
+                oldListener.setCallbackContext(callbackContext);
+            }
+        }
 
         return true;
     }
 
+    @Override
+    public void onRequestPermissionResult(int requestCode, String[] permissions, int[] grantResults) throws JSONException {
+        for (int r:grantResults) {
+            if(r == PackageManager.PERMISSION_DENIED) {
+                callbackContext.sendPluginResult(new PluginResult(PluginResult.Status.ERROR, 1));
+                return;
+            }
+        }
+        registerListener();
+    }
+
+    private void registerListener() {
+        TelephonyManager TelephonyMgr = (TelephonyManager) cordova.getActivity().getSystemService(Context.TELEPHONY_SERVICE);
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+            TelephonyMgr.registerTelephonyCallback(cordova.getThreadPool(), listener);
+            if (!listenerSet) {
+                listener.setCallbackContext(callbackContext);
+            }
+            listenerSet = true;
+        }
+    }
+
     private void prepareListener() {
-        if (listener == null) {
-            listener = new CallStateListener();
-            TelephonyManager TelephonyMgr = (TelephonyManager) cordova.getActivity().getSystemService(Context.TELEPHONY_SERVICE);
-            TelephonyMgr.listen(listener, PhoneStateListener.LISTEN_CALL_STATE);
+        if (!listenerSet) {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+                listener = new CallStateListener();
+                boolean hasPhoneStatePermission = cordova.hasPermission(Manifest.permission.READ_PHONE_STATE);
+                if (!hasPhoneStatePermission) {
+                    cordova.requestPermissions(this, 0, new String[]{
+                        Manifest.permission.READ_PHONE_STATE
+                    });
+                } else {
+                    registerListener();
+                }
+            } else {
+                TelephonyManager TelephonyMgr = (TelephonyManager) cordova.getActivity().getSystemService(Context.TELEPHONY_SERVICE);
+                oldListener = new OldCallStateListener();
+                TelephonyMgr.listen(oldListener, PhoneStateListener.LISTEN_CALL_STATE);
+                listenerSet = true;
+            }
+        }
+    }
+}
+
+@RequiresApi(api = Build.VERSION_CODES.S)
+class CallStateListener extends TelephonyCallback implements TelephonyCallback.CallStateListener {
+    private CallbackContext callbackContext;
+
+    public void setCallbackContext(CallbackContext callbackContext) {
+        this.callbackContext = callbackContext;
+    }
+
+    @Override
+    public void onCallStateChanged(int state) {
+
+        if (callbackContext == null) return;
+
+        String msg = "";
+
+        switch (state) {
+            case TelephonyManager.CALL_STATE_IDLE:
+            msg = "IDLE";
+            break;
+
+            case TelephonyManager.CALL_STATE_OFFHOOK:
+            msg = "OFFHOOK";
+            break;
+
+            case TelephonyManager.CALL_STATE_RINGING:
+            msg = "RINGING";
+            break;
         }
+
+        PluginResult result = new PluginResult(PluginResult.Status.OK, msg);
+        result.setKeepCallback(true);
+
+        callbackContext.sendPluginResult(result);
     }
 }
 
-class CallStateListener extends PhoneStateListener {
+class OldCallStateListener extends PhoneStateListener {
 
     private CallbackContext callbackContext;