add a widget

app/src/main/AndroidManifest.xml

@@ -18,5 +18,18 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+
+        <receiver
+            android:name=".MyWidgetProvider"
+            android:icon="@mipmap/ic_launcher"
+            android:label="Simple Notes">
+            <intent-filter>
+                <action android:name="android.appwidget.action.APPWIDGET_UPDATE"/>
+            </intent-filter>
+
+            <meta-data
+                android:name="android.appwidget.provider"
+                android:resource="@xml/widget_info"/>
+        </receiver>
     </application>
 </manifest>

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

@@ -1,6 +1,9 @@
 package notes.simplemobiletools.com;
 
+import android.appwidget.AppWidgetManager;
+import android.content.ComponentName;
 import android.content.Context;
+import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.Bundle;
 import android.support.v7.app.AppCompatActivity;
@@ -47,12 +50,25 @@ public class MainActivity extends AppCompatActivity {
     private void saveText() {
         final String text = notesView.getText().toString().trim();
         prefs.edit().putString(Constants.TEXT, text).apply();
+
         Toast.makeText(this, "Text saved", Toast.LENGTH_SHORT).show();
         hideKeyboard();
+        updateWidget();
     }
 
     private void hideKeyboard() {
         final InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
         imm.hideSoftInputFromWindow(notesView.getWindowToken(), 0);
     }
+
+    private void updateWidget() {
+        final Context context = getApplicationContext();
+        final AppWidgetManager widgetManager = AppWidgetManager.getInstance(context);
+        int[] ids = widgetManager.getAppWidgetIds(new ComponentName(context, MyWidgetProvider.class));
+
+        final Intent intent = new Intent(this, MyWidgetProvider.class);
+        intent.setAction(AppWidgetManager.ACTION_APPWIDGET_UPDATE);
+        intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_IDS, ids);
+        sendBroadcast(intent);
+    }
 }

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

@@ -0,0 +1,27 @@
+package notes.simplemobiletools.com;
+
+import android.appwidget.AppWidgetManager;
+import android.appwidget.AppWidgetProvider;
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.widget.RemoteViews;
+
+public class MyWidgetProvider extends AppWidgetProvider {
+    private static SharedPreferences prefs;
+
+    @Override
+    public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
+        prefs = context.getSharedPreferences(Constants.PREFS, Context.MODE_PRIVATE);
+        for (int widgetId : appWidgetIds) {
+            updateWidget(context, appWidgetManager, widgetId);
+        }
+        super.onUpdate(context, appWidgetManager, appWidgetIds);
+    }
+
+    private void updateWidget(Context context, AppWidgetManager widgetManager, int widgetId) {
+        final String text = prefs.getString(Constants.TEXT, "");
+        final RemoteViews remoteViews = new RemoteViews(context.getPackageName(), R.layout.widget);
+        remoteViews.setTextViewText(R.id.notesView, text);
+        widgetManager.updateAppWidget(widgetId, remoteViews);
+    }
+}

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

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<RelativeLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <TextView
+        android:id="@+id/notesView"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:background="@null"
+        android:gravity="top"
+        android:textSize="18sp"/>
+</RelativeLayout>

app/src/main/res/xml/widget_info.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
+                    android:initialLayout="@layout/widget"
+                    android:minHeight="110dp"
+                    android:minWidth="110dp">
+</appwidget-provider>