RxJava Android example of .withLatestFrom usage

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.tehmou.book.chapter7coffeebreak.MainActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Title"/>
    <EditText
        android:id="@+id/title_edit_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Message"/>
    <EditText
        android:id="@+id/message_edit_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/action_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Show Alert"/>
</LinearLayout>

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.2"
    defaultConfig {
        applicationId "com.tehmou.book.chapter7coffeebreak"
        minSdkVersion 15
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

        jackOptions {
            enabled true
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.1.0'
    testCompile 'junit:junit:4.12'

    // RxJava
    compile 'io.reactivex:rxjava:1.1.3'
    compile 'io.reactivex:rxandroid:1.1.0'

    // RxBinding wrappers
    compile 'com.jakewharton.rxbinding:rxbinding:0.3.0'
}

MainActivity.java

package com.tehmou.book.chapter7coffeebreak;

import android.support.v4.util.Pair;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

import com.jakewharton.rxbinding.view.RxView;
import com.jakewharton.rxbinding.widget.RxTextView;

import rx.Observable;
import rx.android.schedulers.AndroidSchedulers;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final Observable<String> titleObservable =
                RxTextView
                        .textChanges((TextView) findViewById(R.id.title_edit_text))
                        .map(Object::toString);

        final Observable<String> messageObservable =
                RxTextView
                        .textChanges((TextView) findViewById(R.id.message_edit_text))
                        .map(Object::toString);

        final Observable<Void> clickEvents =
                RxView.clicks(findViewById(R.id.action_button));

        final Observable<Pair<String, String>> dialogContentsObservable =
                Observable.combineLatest(titleObservable, messageObservable, Pair::new);


        final Observable<Pair<String, String>> showDialogEventObservable =
                clickEvents.withLatestFrom(dialogContentsObservable,
                        (ignore, dialogContents) -> dialogContents);

        showDialogEventObservable
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(dialogContents ->
                        new AlertDialog.Builder(this)
                                .setTitle(dialogContents.first)
                                .setMessage(dialogContents.second)
                                .show()
                );

    }
}