show a Rate us button to returning users

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

@@ -0,0 +1,26 @@
+package com.simplemobiletools.flashlight;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+
+import com.simplemobiletools.flashlight.activities.Constants;
+
+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/flashlight/activities/AboutActivity.java

@@ -1,5 +1,6 @@
 package com.simplemobiletools.flashlight.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.flashlight.BuildConfig;
+import com.simplemobiletools.flashlight.Config;
 import com.simplemobiletools.flashlight.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;
 
@@ -35,6 +39,7 @@ public class AboutActivity extends AppCompatActivity {
         setupEmail();
         setupVersion();
         setupCopyright();
+        setupRateUs();
     }
 
     private void setupEmail() {
@@ -57,6 +62,22 @@ 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/flashlight/activities/Constants.java

@@ -0,0 +1,7 @@
+package com.simplemobiletools.flashlight.activities;
+
+public class Constants {
+    // shared preferences
+    public static final String PREFS_KEY = "Flashlight";
+    public static final String IS_FIRST_RUN = "is_first_run";
+}

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

@@ -10,6 +10,7 @@ import android.view.WindowManager;
 import android.widget.ImageView;
 
 import com.simplemobiletools.flashlight.BusProvider;
+import com.simplemobiletools.flashlight.Config;
 import com.simplemobiletools.flashlight.Events;
 import com.simplemobiletools.flashlight.MyCameraImpl;
 import com.simplemobiletools.flashlight.R;
@@ -90,8 +91,11 @@ public class MainActivity extends AppCompatActivity {
     @Override
     protected void onDestroy() {
         super.onDestroy();
-        mCameraImpl.releaseCamera();
-        mCameraImpl = null;
+        Config.newInstance(getApplicationContext()).setIsFirstRun(false);
+        if (mCameraImpl != null) {
+            mCameraImpl.releaseCamera();
+            mCameraImpl = null;
+        }
     }
 
     @Subscribe