add the Save functionality

app/src/main/AndroidManifest.xml

@@ -19,5 +19,4 @@
             </intent-filter>
         </activity>
     </application>
-
 </manifest>

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

@@ -0,0 +1,6 @@
+package notes.simplemobiletools.com;
+
+public class Constants {
+    public static final String PREFS = "prefs";
+    public static final String TEXT = "text";
+}

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

@@ -1,13 +1,58 @@
 package notes.simplemobiletools.com;
 
+import android.content.Context;
+import android.content.SharedPreferences;
 import android.os.Bundle;
 import android.support.v7.app.AppCompatActivity;
+import android.view.Menu;
+import android.view.MenuInflater;
+import android.view.MenuItem;
+import android.view.inputmethod.InputMethodManager;
+import android.widget.EditText;
+import android.widget.Toast;
 
 public class MainActivity extends AppCompatActivity {
+    private SharedPreferences prefs;
+    private EditText notesView;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
+
+        prefs = getSharedPreferences(Constants.PREFS, Context.MODE_PRIVATE);
+        final String text = prefs.getString(Constants.TEXT, "");
+        notesView = (EditText) findViewById(R.id.notesView);
+        notesView.setText(text);
+    }
+
+    @Override
+    public boolean onCreateOptionsMenu(Menu menu) {
+        MenuInflater inflater = getMenuInflater();
+        inflater.inflate(R.menu.menu, menu);
+        return true;
+    }
+
+    @Override
+    public boolean onOptionsItemSelected(MenuItem item) {
+        switch (item.getItemId()) {
+            case R.id.save:
+                saveText();
+                return true;
+            default:
+                return super.onOptionsItemSelected(item);
+        }
+    }
+
+    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();
+    }
+
+    private void hideKeyboard() {
+        final InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
+        imm.hideSoftInputFromWindow(notesView.getWindowToken(), 0);
     }
 }

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

@@ -6,6 +6,7 @@
     android:padding="@dimen/activity_margin">
 
     <EditText
+        android:id="@+id/notesView"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:background="@null"

app/src/main/res/menu/menu.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+      xmlns:app="http://schemas.android.com/apk/res-auto">
+    <item
+        android:id="@+id/save"
+        android:icon="@mipmap/check"
+        android:title="Save"
+        app:showAsAction="always"/>
+</menu>