Android Starter Code: https://medium.com/@aviparshan/android-starter-code-e58f1b94685d

About

package com.aviparshan.flashlight;


import android.app.Dialog;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.DialogFragment;
import android.support.v7.app.AppCompatActivity;

import com.afollestad.materialdialogs.MaterialDialog;

public class AboutDialog extends DialogFragment {

    public static void show(AppCompatActivity context) {
        AboutDialog dialog = new AboutDialog();
        dialog.show(context.getSupportFragmentManager(), "[ABOUT_DIALOG]");
    }

    @NonNull
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        return new MaterialDialog.Builder(getActivity())
                .title(R.string.about)
                .positiveText(R.string.dismiss)
                .content(R.string.about_body, true)
                .contentLineSpacing(1.6f)
                .build();
    }
}

ComposeEmail

 public void composeEmail() {
 
 //Used in CPU Info app I made: https://play.google.com/store/apps/details?id=com.aviparshan.appinfo
        String PhoneModel = android.os.Build.MODEL;
        String AndroidVersion = android.os.Build.VERSION.RELEASE;
        int API = Build.VERSION.SDK_INT;
        String Language = Locale.getDefault().getISO3Language();
        int versionCode = BuildConfig.VERSION_CODE;
        String versionName = BuildConfig.VERSION_NAME;

        Intent intent = new Intent(Intent.ACTION_SENDTO);
        intent.setData(Uri.parse("mailto:"));
        intent.putExtra(Intent.EXTRA_EMAIL, new String[]{"[email protected]"});
        intent.putExtra(Intent.EXTRA_SUBJECT, getString(R.string.app_name));
        intent.putExtra(Intent.EXTRA_TEXT, "App Information \n" +
                "Phone Model: " + PhoneModel + "\nAndroid Version: " + AndroidVersion + "\nAPI Level: " + API + "\nVersion Code: " + versionCode + "\nVersion Name: " + versionName + "\nLanguage: "+ Language);
        try {
            //startActivity(Intent.createChooser(intent, "Send mail..."));
            startActivity(intent);
        } catch (android.content.ActivityNotFoundException ex) {
            Toast.makeText(MainActivity.this, R.string.rate_error, Toast.LENGTH_SHORT).show();
        }
    }

Gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.2"
    defaultConfig {
        applicationId "com.aviparshan.flashlight"
        minSdkVersion 17
        targetSdkVersion 25
        versionCode 1
        versionName "1.0.0"
        resConfig("en")

    }

    signingConfigs {
        release
        Key {
            keyAlias 'Key'
            keyPassword 'Pass'
            storeFile file('C:/Users/keystore.jks')
            storePassword 'Pass2'
        }
    }
    
    buildTypes {
        debug {
            minifyEnabled false
        }
        release {
            minifyEnabled true
            shrinkResources true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile 'com.android.support:appcompat-v7:25.2.0'
    compile 'com.android.support:design:25.2.0'
    compile 'com.afollestad.material-dialogs:core:0.9.3.0'


}
def Properties props = new Properties()
def propFile = new File('signing.properties')
if (propFile.canRead()) {
    props.load(new FileInputStream(propFile))

    if (props != null && props.containsKey('STORE_FILE') && props.containsKey('STORE_PASSWORD') &&
            props.containsKey('KEY_ALIAS') && props.containsKey('KEY_PASSWORD')) {
        android.signingConfigs.release.storeFile = file(props['STORE_FILE'])
        android.signingConfigs.release.storePassword = props['STORE_PASSWORD']
        android.signingConfigs.release.keyAlias = props['KEY_ALIAS']
        android.signingConfigs.release.keyPassword = props['KEY_PASSWORD']
    } else {
        println 'signing.properties found but some entries are missing'
        android.buildTypes.release.signingConfig = null
    }
} else {
    println 'signing.properties not found'
    android.buildTypes.release.signingConfig = null
}

Overflow Java

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.about:
                AboutDialog.show(this);
                return true;
            case R.id.feedback:
                composeEmail();
                return true;
            case R.id.rate:
                goToMyApp(this);
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

Overflow xml

<?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/about"
        android:title="@string/about"
        app:showAsAction="never"/>
    <item
        android:id="@+id/feedback"
        android:title="@string/feedback"
        app:showAsAction="never"
        />
    <item
        android:id="@+id/rate"
        android:title="@string/rate_app"
        app:showAsAction="ifRoom"
        android:icon="@drawable/ic_star_black_24dp" />
</menu>

Rate My App

public void goToMyApp(Context context) {
        try {
            startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse("http://play.google.com/store/apps/details?id=" + getPackageName())));
        } catch (ActivityNotFoundException e1) {
            Toast.makeText(this, R.string.rate_error, Toast.LENGTH_SHORT).show();
        }
    }

Strings

<!-- About -->
    <string name="about">About</string>
     <string name="about_body"><![CDATA[
         <b>Avi Parshan</b> created this app, Check his website and social media:<br/>
        <a href=\'http://aviparshan.com\'>Website</a>&nbsp;&nbsp;
        <a href=\'https://twitter.com/aviinfinity\'>Twitter</a>&nbsp;&nbsp;
        <a href=\'https://www.youtube.com/channel/UCYzocrbgFApPAGhq7PAw9Gw\'>YouTube</a>&nbsp;&nbsp;
        <a href=\'https://www.linkedin.com/in/aviparshan\'>LinkedIn</a>&nbsp;&nbsp;
        <a href=\'https://www.facebook.com/appdeomcracy\'>Facebook</a>
    ]]></string>
    <string name="dismiss">Dismiss</string>
    <string name="feedback">Contact Me</string>
    <string name="rate_app">Rate App</string>