basic widget functionality + misc cleanup

app/src/main/java/calendar/simplemobiletools/com/CalendarImpl.java

@@ -15,15 +15,14 @@ public class CalendarImpl {
     private final String today;
     private DateTime targetDate;
 
-    public CalendarImpl(Calendar callback, DateTime targetDate) {
+    public CalendarImpl(Calendar callback) {
         this.callback = callback;
-        this.targetDate = targetDate;
         today = new DateTime().toString(DATE_PATTERN);
     }
 
-    public void updateCalendar(DateTime targetDateTime) {
-        this.targetDate = targetDateTime;
-        getDays(targetDateTime);
+    public void updateCalendar(DateTime targetDate) {
+        this.targetDate = targetDate;
+        getDays(targetDate);
         getMonthName();
     }
 

app/src/main/java/calendar/simplemobiletools/com/MainActivity.java

@@ -46,9 +46,8 @@ public class MainActivity extends AppCompatActivity implements MyDatePickerDialo
         dayTextSize /= getResources().getDisplayMetrics().density;
         todayTextSize /= getResources().getDisplayMetrics().density;
 
-        DateTime now = new DateTime();
-        calendar = new CalendarImpl(this, now);
-        calendar.updateCalendar(now);
+        calendar = new CalendarImpl(this);
+        calendar.updateCalendar(new DateTime());
 
         setupLabelSizes();
     }

app/src/main/java/calendar/simplemobiletools/com/MyWidgetProvider.java

@@ -1,13 +1,88 @@
 package calendar.simplemobiletools.com;
 
+import android.app.PendingIntent;
 import android.appwidget.AppWidgetManager;
 import android.appwidget.AppWidgetProvider;
+import android.content.ComponentName;
 import android.content.Context;
+import android.content.Intent;
+import android.graphics.Color;
+import android.widget.RemoteViews;
 
-public class MyWidgetProvider extends AppWidgetProvider {
+import org.joda.time.DateTime;
+
+import java.util.List;
+
+public class MyWidgetProvider extends AppWidgetProvider implements Calendar {
+    private static final String PREV = "prev";
+    private static final String NEXT = "next";
+    private static RemoteViews remoteViews;
+    private static int[] widgetIds;
+    private static AppWidgetManager widgetManager;
+    private static Intent intent;
+    private static Context cxt;
+    private static CalendarImpl calendar;
 
     @Override
     public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
+        initVariables(context);
+    }
+
+    private void initVariables(Context context) {
+        cxt = context;
+        final ComponentName component = new ComponentName(cxt, MyWidgetProvider.class);
+        widgetManager = AppWidgetManager.getInstance(cxt);
+        widgetIds = widgetManager.getAppWidgetIds(component);
+
+        remoteViews = new RemoteViews(cxt.getPackageName(), R.layout.activity_main);
+        remoteViews.setInt(R.id.table_month, "setTextColor", Color.WHITE);
+
+        intent = new Intent(cxt, MyWidgetProvider.class);
+        setupButtons();
+
+        calendar = new CalendarImpl(this);
+        calendar.updateCalendar(new DateTime());
+
+        widgetManager.updateAppWidget(widgetIds, remoteViews);
+    }
+
+    private void setupIntent(String action, int id) {
+        intent.setAction(action);
+        final PendingIntent pendingIntent = PendingIntent.getBroadcast(cxt, 0, intent, 0);
+        remoteViews.setOnClickPendingIntent(id, pendingIntent);
+    }
+
+    private void setupButtons() {
+        setupIntent(PREV, R.id.left_arrow);
+        setupIntent(NEXT, R.id.right_arrow);
+    }
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        if (remoteViews == null || widgetManager == null || widgetIds == null || calendar == null)
+            initVariables(context);
+
+        final String action = intent.getAction();
+        switch (action) {
+            case PREV:
+                calendar.getPrevMonth();
+                break;
+            case NEXT:
+                calendar.getNextMonth();
+                break;
+            default:
+                super.onReceive(context, intent);
+        }
+    }
+
+    @Override
+    public void updateDays(List<Day> days) {
 
     }
+
+    @Override
+    public void updateMonth(String month) {
+        remoteViews.setTextViewText(R.id.table_month, month);
+        widgetManager.updateAppWidget(widgetIds, remoteViews);
+    }
 }

app/src/main/res/layout/activity_main.xml

@@ -28,7 +28,7 @@
         android:paddingBottom="@dimen/activity_margin"
         android:paddingTop="@dimen/activity_margin"
         android:textColor="@color/darkGrey"
-        android:textSize="24sp"/>
+        android:textSize="22sp"/>
 
     <ImageView
         android:id="@+id/right_arrow"