Ako vytvoriť mobilnú aplikáciu pre rôzne platformy v Jave

Vedeli ste, že pomocou Java môžete vytvárať mobilné aplikácie pre rôzne platformy? Áno, štipnite sa do seba, čítate to správne prvýkrát! Naučím vás základy, ako využiť svoje súčasné znalosti jazyka Java na vytváranie výkonných aplikácií pre Android a iOS v 12 jednoduchých krokoch. Všetko to urobíme pomocou JavaFX ako sady nástrojov GUI.

Najskôr však nejaké ďalšie popredia. Budete musieť splniť následné požiadavky, aby bolo možné vytvoriť aplikáciu pre oba systémy Android a iOS. Ak však nechcete vytvárať aplikáciu pre iOS, môžete sa bez problémov vyvíjať na akomkoľvek x64 bitovom stroji, ktorý podporuje Java SE 8. Tento projekt bude Git repozitár postavený s gradle. Ale nemusíte vytvárať úložisko Git.

Toto sú požiadavky :

  • JVM v súlade s JDK 1.8
  • Nástroje príkazového riadku pre Android (SDK v.27)
  • XCode 9.2
  • Gradle 4.2
  • Veľké úložisko súborov Git (v.2.5.0) (zbytočné, ak nechcete vytvoriť úložisko git)
  • Najlepšie aspoň 4G RAM

Netrpezlivý? Chcete vidieť konečný výsledok? Nižšie si pozrite dokončený projekt.

afinlay5 / OnyxFx

Úložisko zdrojových kódov Gradle pre OnyxFx, multiplatformové (Android / iOS / Linux / macOS / Windows) vykresľovanie aplikácií JavaFX ... github.com

Moje vývojové prostredie bude Fedora Linux 28 a macOS High Sierra. Teraz, keď to máme z cesty, sa do toho pustíme.

1) Vytvorte priečinok na umiestnenie projektu

Hostil som svoj projekt OnyxFx nasledovne: „ / home / adriandavid / Projects / OnyxFx“. Projekt môžete, samozrejme, slobodne usporiadať, kdekoľvek chcete.

2) Inicializujte gradle, Git, nastavte JAVA_HOME

Otvorte terminál v koreňovom adresári projektu. Ak je gradle správne nakonfigurovaný, mali by ste niečo také vidieť po vykonaní nasledujúceho príkazu:

gradle -v

Musíte sa ubezpečiť, že v gradle je uvedená vaša inštalácia Java Development Kit (JDK) 8 vedľa časti s názvom „JVM“.

Existuje mnoho spôsobov, ako to dosiahnuť, najjednoduchším spôsobom je zabezpečiť, aby bola vaša environmentálna premenná JAVA_HOME správne nastavená.

V závislosti od vášho prostredia existuje veľa spôsobov, ako to urobiť. Jedným zo spôsobov, ako to urobiť vo väčšine prostredí * nix, je nastavenie premennej v súbore /home//.b ash rc alebo / etc / pro . Pozrite si príručku k svojmu operačnému systému, aby ste sa ubezpečili, že vaša environmentálna premenná JAVA_HOME je nastavená správne.

Nasledujúce riadky môžete zahrnúť na koniec súboru .bashrc alebo profilu, aby ste sa ubezpečili, že je JAVA_HOME nastavený správne.

JAVA_HOME=/home/adriandavid/java/oracle_jdk1.8.0_181/export JAVA_HOME

Poznámka: Tu si môžete nainštalovať Oracle JDK 8.

Potom spustením jedného z nasledujúcich príkazov skontrolujte, či shell odráža vyššie uvedené zmeny:

source ~/.bashrcsource /etc/profile

Zadajte nasledujúci príkaz a overte, či je premenná správne nastavená:

echo $JAVA_HOME

Ak stále máte ťažkosti alebo používate systém Microsoft Windows, prečítajte si tu.

Najskôr spustite git initv koreňovom adresári projektu inicializáciu úložiska Git. Poznámka: ak nechcete hostovať úložisko git, môžete tento krok preskočiť.

Po druhé, spustite gradle initv koreňovom adresári projektu inicializáciu úložiska gradle. Tento krok je povinný.

Poznámka: Všimnete si, že môj príklad sa javí mierne odlišne. Je to preto, že už mám gradle a Git inicializované v mojom miestnom prostredí.

3) Získajte groovy! Upravte gradle.build a

Dúfajme, že Zem, vietor a oheň vám pomôžu dostať sa do rytmu! Zapnite svoj obľúbený textový editor, upravte súbor build.gradle umiestnený v koreňovom adresári projektu a nahraďte obsah obsahom nasledujúceho prehľadu GitHub.

Tieto nastavenia build.gradle konfigurujú náš projekt gradle tak, aby používal doplnok javafxmobile , ktorý je pracovným koňom nášho projektu. Viac informácií o doplnku sa dozviete tu a tu. Doplnok javafxmobile okrem iného automatizuje proces sťahovania (z Maven Central alebo jcenter) a pridávania SDK pre iOS a Android do triedy súborov vašej aplikácie.

Ak ste oboznámení s gradle, maven alebo ant, super - pravdepodobne máte predstavu o tom, čo sa deje. Ak nie ste oboznámení s gradle, nerobte si z toho starosti . Všetko, čo musíte pochopiť, je, že gradle je nástroj na vytváranie, ktorý sa používa na automatizáciu mnohých úloh spojených s vytváraním aplikácií, ako sú napríklad: chytenie závislostí, organizácia projektu atď.

Všimnite si, že sa zameriavame na Android 7.1 Nougat (API verzie 25) a iOS 11 (kde sa to čoskoro stane, uvidíme). Tieto hodnoty môžete upraviť, ako uznáte za vhodné. Upozorňujeme však, že v prípade systému Android musíte zabezpečiť, aby sa verzia API zhodovala s verziou SDK, ktorú ste stiahli (viac o tom neskôr).

Nakoniec v tomto tutoriále nebudem demonštrovať produkciu podpísaných spustiteľných súborov. Z tohto dôvodu je iOSSkipSigning nastavený na hodnotu true a nevyužívame úlohu releaseAndroid gradle. Môžete však poskytnúť príslušné ubytovanie na vytvorenie podpísaných aplikácií.

4) Vytvorte nový súbor s názvom gradle.properties a nakonfigurujte ho

Vytvorte nový súbor v koreňovom adresári projektu s názvom gradle.propertiesa do súboru pridajte nasledujúci obsah.

robovm.device.name=iPhone-7robovm.sdk.version=11.0org.gradle.jvmargs=-Xms4g -Xmx8g

These settings tell the javafxports plugin to use an iPhone-7 as the on-board emulator, to target iOS 11, and to pass the Xms and Xmx flags to the JVM, which specifies both the initial memory pool to 4GB and the maximum heap memory pool to 8GB. This will be necessary for the compilation of the openJDK and the development of the iOS build.

5) Install Homebrew (iOS only)

If you do not have a Mac and are not intending to produce an iOS build, feel free to skip this step.

Open the terminal in macOS and paste the following command.

/usr/bin/ruby -e "$(curl -fsSL //raw.githubusercontent.com/Homebrew/install/master/install)"

6) Install the USB Multiplexing Socket (iOS only)

Only move on to this step if Homebrew has successfully installed. If you do not have a Mac and are not intending to produce an iOS build, feel free to skip this step.

Open the terminal in macOS and paste the following command.

brew install usbmuxd

7) Grab the Android Command Line Tools

Grab Android Command Line Tools for your platform here. After the download has finished, unzip the folder and paste the contents in the directory of your choice. For me, this was /home//Android.

8) Set Android_HOME, Grab necessary Android packages

As with Java, gradle needs to know where to look to find the Android Command Line Tools. There are a few ways to do this. However, in the spirit of simplicity and consistency, we will set the ANDROID_HOME environmental variable in this tutorial. Add the following variable in the same way that we did it for JAVA_HOME. For example:

ANDROID_HOME=/home/adriandavid/Android/ export ANDROID_HOME

Remember to reload the shell by adding source le> as we did for JAVA_HOME.

Now, grab the tools necessary to build the Android build. Execute the following command:

# *.nix./sdkmanager "platform-tools" "build-tools;25.0.3" "platforms;android-25" "extras;android;m2repository" "extras;google;m2repository"
or
#Windowssdkmanager "platform-tools" "build-tools;25.0.3" "platforms;android-25" "extras;android;m2repository" "extras;google;m2repository"

Take careful notice that the SDK and API version we have specified in gradle.build correspond to the version we have specified in this command. Namely, “25”. Should this be misaligned, the build will not succeed.

9) Create the application’s directory structure

To automate the process of creating these directories, execute the following shell script.

Bourne-Again Shell / Korn Shell:

Windows Shell (cmd):

Save the file as mkpdir.bat or mkpdir.sh and execute the file from the project’s root directory as root (or Administrator).

# *.nixchmod +x mkdir.sh-sh ./mkpdir.sh
# Windowsmkpdir

Notice that we created directories for embedded and desktop. We will produce a desktop build, because it takes no additional work to do so. However, we will not produce any builds for embedded devices.

10) Create your JavaFX Application!

Navigate to /src//java and begin developing your JavaFx application! Application resources are stored in /src//resources.

You can start with a simple Hello World application or look at the source code that I have put together here. OnyxFx is an application I made, following these instructions, that makes REST calls over HTTP to the OnyxFxAPI. The API, in turn, is a web scraper that will return the statistical data (points per game, rebounds per game, assists per game) for the NBA® player and season the client specifies. It returns the data as JSON, which is then parsed and displayed to the screen of the mobile app. Feel free to edit it!

Keep in mind that although you can share source code, you should include custom edits in each copy of the source, should you want to make device specific changes.

Also note that the underlying compiler (MobiDevelop’s fork of RoboVM) does not fully support all Java 8 APIs. If you look very closely at my source code, you will notice that in the iOS version of the source code, I have removed unsupported API such as java.util.function.BiConsumer and java.util.Map.replace().

11) Create a RAM disk for iOS builds (iOS only)

The compilation process for iOS is very resource-heavy, as the plugin will compile the entire openJDK and other libraries twice to create a fat JAR that it will use to build your application. Therefore, you should preemptively create a RAM disk to accommodate for the memory requirements.

This step, however, is subject to your judgement of your machine’s capabilities. For context, the macOS machine that I used to compile my iOS app has 4GB of DDR2 RAM. I decided to make an 8GB RAM disk. To do so, execute the following command in the terminal.

SIZE=8192 ; diskutil erasevolume HFS+ ‘RoboVM RAM Disk’ `hdiutil attach -nomount ram://$((SIZE * 8192))`

12) Build and Run your application!

To build your application, execute the gradle wrapper in the root directory from the terminal as follows.

./gradlew clean build

This will produce a desktop application packaged as a JAR with scripts to run the application provided in /build/distributions/ ar> ; and /build/distributions/ Name.zip>. Should you unzip the directories, you will notice the following structure:

Notice that in /bin there are scripts to execute the application. These scripts rely on preserving the current folder structure. Also notice that is not necessary for you to have tree installed. It is used here simply for illustrative purposes.

There is, additionally, a standalone JAR that you can use to execute the application on any desktop environment supporting JavaFX 8. To run the application, execute one of the following:

# Navigate to /build/distributions//
#On *.nixcd bin./
#On Windowscd bin
#Platform agnosticjava -jar OnyxFxMobile.jar (or double click, if jvm is configured to run .jar files)
Note: If the executable providing "java" is not the same vendor and/or version of the Java 8 JDK with which you built this application, the jar may not run. JavaFX 8 builds between the openJDK & Oracle JDK are incompatible.
Otherwise: /location/to/java8/bin/java -jar 

View this project’s gradle tasks

You can view this project’s gradle tasks by running the following in the project’s root directory.

./gradlew tasks

To Compile, Run on Desktop

The following command will run your project in the host environment.

./gradlew jar./gradlew run

You will find a standalone jar in build/libs/ t;.jar .

To Compile, Run on Android

./android #Generates a debug Android apk containing the JavaFX application.
./androidInstall #Launch the application on a connected android device.
./androidRelease #Generates a release Android apk containing the JavaFX application.
Note: You will need to configure a valid signingConfig when releasing an APK (javafxports).

You will find two APKs in build/javafxports/android.

The first will be named t;.apk.

The second will be named -unaligned.apk.

To Compile, Run on iOS

./createIpa - Generates an iOS ipa containing the JavaFX app.
./launchIOSDevice - Launches app on a connected ios device.
./launchIPadSimulator - Launches app on an iPad simulator.
./launchIPhoneSimulator - Launches app on an iPhone simulator.

You will find three executables in build/javafxports/ios.

The first will be named t;.ipa.

The second will be named ame>.dSYM.

The third will be named <AppName>.app.

Some screenshots of my sample app

On Desktop

On Android

On iPhone

On iPad

Splash Screen

My Closing Thoughts

javafxports is a promising project that aims to bring JavaFX and the Java SE platform onto mobile and other devices. In a way, the tool parallels Xamarin in its efforts. However, the project has a lot of work left to be done.

For a start, the plugin currently does not fully support Java 8. On Android, it uses retrolambda to handle Java 8 Lambda Expressions & Method References. It technically is up to Java 6. Additional dependencies make it such that you can use Java 8. However, the process is straightforward, the builds work as expected, and the compilation time is not too long.

On iOS, however, the builds are extremely memory-intensive and the compilation process takes a very long time. The following is a snippet of the log for ./gradlew createIpa task.

:createIpa (Thread[Task worker for ‘:’,5,main]) completed. Took 1 hrs 46 mins 40.198 secs.

In total, the process consumed about over 6GB of RAM on my machine. This is hardly ideal. However, the future is promising. A company called Gluon has developed a high performance, fully modular custom JVM fully supporting Java 9, that you can read more about here.

This article is originally published on the blog section of my homepage, here.

Resources to explore:

  • JavaFxMobile Plugin Git Repo: //github.com/javafxports/javafxmobile-plugin
  • JavaFxPorts Documentation: //docs.gluonhq.com/javafxports/#_how_it_works
  • JavaFxPorts Homepage: //javafxports.org/
  • Gluon Documentation: //gluonhq.com/developers/documentation/
  • Google Groups Page for JavaFxPorts: //groups.google.com/forum/#!forum/javafxports
  • StackOverflow Page for JavaFxPorts: //stackoverflow.com/questions/tagged/javafxports
  • Gluon Mobile Pricing/License Options: //gluonhq.com/products/mobile/buy/