display a Rate us button to returning users

app/src/main/java/com/simplemobiletools/calculator/Config.java

@@ -0,0 +1,24 @@
+package com.simplemobiletools.calculator;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+
+public class Config {
+    private SharedPreferences mPrefs;
+
+    public static Config newInstance(Context context) {
+        return new Config(context);
+    }
+
+    public Config(Context context) {
+        mPrefs = context.getSharedPreferences(Constants.PREFS_KEY, Context.MODE_PRIVATE);
+    }
+
+    public boolean getIsFirstRun() {
+        return mPrefs.getBoolean(Constants.IS_FIRST_RUN, true);
+    }
+
+    public void setIsFirstRun(boolean firstRun) {
+        mPrefs.edit().putBoolean(Constants.IS_FIRST_RUN, firstRun).apply();
+    }
+}

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

@@ -28,4 +28,8 @@ public class Constants {
     public static final String PREFS = "prefs";
     public static final String WIDGET_BG_COLOR = "widget_bg_color";
     public static final String WIDGET_TEXT_COLOR = "widget_text_color";
+
+    // shared preferences
+    public static final String PREFS_KEY = "Calculator";
+    public static final String IS_FIRST_RUN = "is_first_run";
 }

app/src/main/java/com/simplemobiletools/calculator/activities/AboutActivity.java

@@ -1,5 +1,6 @@
 package com.simplemobiletools.calculator.activities;
 
+import android.content.ActivityNotFoundException;
 import android.content.Intent;
 import android.content.res.Resources;
 import android.net.Uri;
@@ -7,9 +8,11 @@ import android.os.Bundle;
 import android.support.v7.app.AppCompatActivity;
 import android.text.Html;
 import android.text.method.LinkMovementMethod;
+import android.view.View;
 import android.widget.TextView;
 
 import com.simplemobiletools.calculator.BuildConfig;
+import com.simplemobiletools.calculator.Config;
 import com.simplemobiletools.calculator.R;
 
 import java.util.Calendar;
@@ -22,6 +25,7 @@ public class AboutActivity extends AppCompatActivity {
     @BindView(R.id.about_copyright) TextView mCopyright;
     @BindView(R.id.about_version) TextView mVersion;
     @BindView(R.id.about_email) TextView mEmailTV;
+    @BindView(R.id.about_rate_us) View mRateUs;
     private static Resources mRes;
 
     @Override
@@ -34,6 +38,7 @@ public class AboutActivity extends AppCompatActivity {
         setupEmail();
         setupVersion();
         setupCopyright();
+        setupRateUs();
     }
 
     private void setupEmail() {
@@ -56,6 +61,22 @@ public class AboutActivity extends AppCompatActivity {
         mCopyright.setText(copyrightText);
     }
 
+    private void setupRateUs() {
+        if (Config.newInstance(getApplicationContext()).getIsFirstRun()) {
+            mRateUs.setVisibility(View.GONE);
+        }
+    }
+
+    @OnClick(R.id.about_rate_us)
+    public void rateUsClicked() {
+        final Uri uri = Uri.parse("market://details?id=" + getPackageName());
+        try {
+            startActivity(new Intent(Intent.ACTION_VIEW, uri));
+        } catch (ActivityNotFoundException ignored) {
+            startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("http://play.google.com/store/apps/details?id=" + getPackageName())));
+        }
+    }
+
     @OnClick(R.id.about_license)
     public void licenseClicked() {
         final Intent intent = new Intent(getApplicationContext(), LicenseActivity.class);

app/src/main/java/com/simplemobiletools/calculator/activities/MainActivity.java

@@ -13,6 +13,7 @@ import android.widget.TextView;
 
 import com.simplemobiletools.calculator.Calculator;
 import com.simplemobiletools.calculator.CalculatorImpl;
+import com.simplemobiletools.calculator.Config;
 import com.simplemobiletools.calculator.Constants;
 import com.simplemobiletools.calculator.Formatter;
 import com.simplemobiletools.calculator.R;
@@ -42,6 +43,12 @@ public class MainActivity extends AppCompatActivity implements Calculator {
         AutofitHelper.create(mFormula);
     }
 
+    @Override
+    protected void onDestroy() {
+        super.onDestroy();
+        Config.newInstance(getApplicationContext()).setIsFirstRun(false);
+    }
+
     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         getMenuInflater().inflate(R.menu.menu, menu);

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

@@ -29,11 +29,21 @@
         android:text="@string/email"/>
 
     <TextView
-        android:id="@+id/about_license"
+        android:id="@+id/about_rate_us"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_below="@+id/about_email"
         android:layout_marginTop="@dimen/activity_margin"
+        android:paddingTop="@dimen/activity_margin"
+        android:text="@string/rate_us_underlined"
+        android:textColor="@color/colorPrimary"/>
+
+    <TextView
+        android:id="@+id/about_license"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_below="@+id/about_rate_us"
+        android:layout_marginTop="@dimen/activity_margin"
         android:paddingBottom="@dimen/activity_margin"
         android:paddingTop="@dimen/activity_margin"
         android:text="@string/third_party_licences_underlined"

app/src/main/res/values/strings.xml

@@ -8,6 +8,7 @@
     <string name="email_label">Send your feedback or suggestions at:</string>
     <string name="email">hello@simplemobiletools.com</string>
     <string name="third_party_licences_underlined"><u>Third party licences</u></string>
+    <string name="rate_us_underlined"><u>Rate us in the Play Store</u></string>
     <string name="follow_us">Follow us at:</string>
     <string name="version">v %1$s</string>
     <string name="copyright">Copyright © Simple Mobile Tools %1$d</string>