work on #111 disable battery opt to allow full background mode

src/main/AndroidManifest.xml

@@ -21,6 +21,8 @@
     <uses-permission android:name="android.permission.READ_PHONE_STATE"/>
     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
 
+    <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS"/>
+
     <application  xmlns:tools="http://schemas.android.com/tools"
         android:name="org.havenapp.main.HavenApp"
         android:icon="@mipmap/ic_launcher"

src/main/java/org/havenapp/main/PreferenceManager.java

@@ -78,6 +78,7 @@ public class PreferenceManager {
 
     public static final String NOTIFICATION_TIME = "notification_time";
 
+    public static final String DISABLE_BATTERY_OPT = "config_battery_optimizations";
 
     private Context context;
 

src/main/java/org/havenapp/main/SettingsFragment.java

@@ -6,11 +6,16 @@
 
 import android.Manifest;
 import android.app.Activity;
+import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.content.pm.PackageManager;
+import android.net.Uri;
+import android.os.Build;
 import android.os.Bundle;
 import android.os.Environment;
+import android.os.PowerManager;
+import android.provider.Settings;
 import android.support.annotation.NonNull;
 import android.support.v4.app.ActivityCompat;
 import android.support.v4.content.ContextCompat;
@@ -138,6 +143,12 @@ public void onCreatePreferencesFix(Bundle bundle, String s) {
             return true;
         });
 
+        Preference prefDisableBatteryOpt = findPreference(PreferenceManager.DISABLE_BATTERY_OPT);
+        prefDisableBatteryOpt.setOnPreferenceClickListener(preference -> {
+            requestChangeBatteryOptimizations();
+            return true;
+        });
+
         checkSignalUsername();
         ((EditTextPreference) findPreference(PreferenceManager.VERIFY_SIGNAL)).setText("");
         askForPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE, 1);
@@ -431,4 +442,20 @@ public void onTimeSet(TimePickerDialog view, int hourOfDay, int minute, int seco
         int delaySeconds = second + minute * 60 + hourOfDay * 60 * 60;
         preferences.setTimerDelay(delaySeconds);
     }
+
+    private void requestChangeBatteryOptimizations ()
+    {
+        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+            Intent intent = new Intent();
+            String packageName = getActivity().getPackageName();
+            PowerManager pm = (PowerManager) getActivity().getSystemService(Context.POWER_SERVICE);
+            if (pm.isIgnoringBatteryOptimizations(packageName))
+                intent.setAction(Settings.ACTION_IGNORE_BATTERY_OPTIMIZATION_SETTINGS);
+            else {
+                intent.setAction(Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS);
+                intent.setData(Uri.parse("package:" + packageName));
+            }
+            getActivity().startActivity(intent);
+        }
+    }
 }

src/main/res/values/strings.xml

@@ -136,6 +136,8 @@
     <string name="minutes">minutes(s)</string>
     <string name="keep_watch">Keep Watch!</string>
     <string name="camera_sensitivity_tip">Select camera and use the slider to adjust motion detection sensitivity</string>
+    <string name="disable_battery_opt_title">Disable Battery Optimizations</string>
+    <string name="disable_battery_opt_summary">Allow app to run when screen is off</string>
 
 
 </resources>

src/main/res/xml/settings.xml

@@ -5,6 +5,12 @@
         android:key="config_delay_time"
         android:title="@string/timer_delay_label" />
 
+
+    <Preference
+        android:key="config_battery_optimizations"
+        android:title="@string/disable_battery_opt_title"
+        android:summary="@string/disable_battery_opt_summary"/>
+
     <PreferenceCategory android:title="@string/sensors">
 
         <ListPreference