Kako izraditi mobilnu aplikaciju za više platformi na Javi

Jeste li znali da Javu možete koristiti za izradu mobilnih aplikacija s više platformi? Da, uštipnite se, dobro ste pročitali prvi put! Naučit ću vas osnovama kako pomoću postojećeg Java znanja stvoriti učinkovite aplikacije na Androidu i iOS-u u 12 jednostavnih koraka. Sve ćemo to raditi pomoću JavaFX-a kao GUI alata.

Ali prvo, još malo u prvi plan. Morat ćete ispuniti naknadne zahtjeve kako bi mogao izgraditi zahtjev za obje Android i iOS. Međutim, ako ne želite graditi iOS aplikaciju, možete se slobodno razvijati na bilo kojem x64 bitnom stroju koji podržava Java SE 8. Ovaj će projekt biti Git spremište izgrađeno s gradle. Ali ne trebate stvoriti Git spremište.

Slijede zahtjevi :

  • JVK usklađen s JDK 1.8
  • Alati za naredbene retke Androida (SDK v.27)
  • XCode 9.2
  • Gradle 4.2
  • Git Storage File File (v.2.5.0) (nepotrebno ako ne želite stvoriti git spremište)
  • Po mogućnosti barem 4G RAM-a

Nestrpljiv? Želite li vidjeti krajnji rezultat? U nastavku pogledajte dovršeni projekt.

afinlay5 / OniksFx

Gradle spremište izvornog koda za OnyxFx, cross-platform (Android / iOS / Linux / macOS / Windows) JavaFX prikaz aplikacije ... github.com

Moje razvojno okruženje bit će Fedora Linux 28 i macOS High Sierra. Sad kad smo to uklonili s puta, krenimo.

1) Stvorite mapu za smještaj projekta

Bio sam domaćin svog projekta OnyxFx, kako slijedi: “ / home / adriandavid / Projects / OnyxFx”. Možete, naravno, biti domaćin projekta gdje god želite.

2) Inicijalizirajte gradle, Git, postavite JAVA_HOME

Otvorite terminal u korijenu direktorija projekta. Ako je gradle pravilno konfiguriran, trebali biste vidjeti nešto slično nakon izvršavanja sljedeće naredbe:

gradle -v

Morate biti sigurni da gradle navodi vašu instalaciju Java Development Kit (JDK) 8 u blizini odjeljka s oznakom "JVM".

Iako postoji mnogo načina za to, najjednostavniji način je osigurati da je vaša varijabla okoliša JAVA_HOME pravilno postavljena.

Ovisno o vašem okruženju, postoji mnogo načina kako to učiniti. Jedan od načina da se to učini u većini * nix okruženja je postavljanje varijable u datoteku /home//.b ash rc ili / etc / pro . Pogledajte priručnik za svoj operativni sustav kako biste bili sigurni da je vaša varijabla okoliša JAVA_HOME ispravno postavljena.

Možete uključiti sljedeće retke na kraj .bashrc ili profila kako biste bili sigurni da je JAVA_HOME ispravno postavljen.

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

Napomena: Ovdje možete instalirati Oracleov JDK 8.

Zatim se pobrinite da ljuska odražava gore navedene promjene pokretanjem jedne od sljedećih naredbi:

source ~/.bashrcsource /etc/profile

Unesite sljedeću naredbu da biste provjerili je li varijabla ispravno postavljena:

echo $JAVA_HOME

Ako i dalje imate poteškoća ili koristite Microsoft Windows, pogledajte ovdje.

Prvo pokrenite git initu osnovnom direktoriju projekta da biste inicijalizirali Git spremište. Napomena: ako ne želite ugostiti git spremište, možete preskočiti ovaj korak.

Drugo, pokrenite gradle initu korijenskom direktoriju projekta da biste inicijalizirali spremište gradle. Ovaj korak je obavezan.

Napomena: Primijetit ćete da se moj primjer čini malo drugačijim. To je zato što gradle i Git već imam inicijalizirane u svom lokalnom okruženju.

3) Postanite groovy! Uredi gradle.build i

Nadamo se da vam Zemlja, Vjetar i Vatra mogu pomoći da postanete žustri! Uključite svoj omiljeni uređivač teksta i uredite svoj build.gradle koji se nalazi u korijenskom direktoriju vašeg projekta i zamijenite sadržaj sadržajem sljedećeg GitHub-ovog testa.

Ove postavke build.gradle konfiguriraju naš gradle projekt da koristi dodatak javafxmobile , koji je radni konj našeg projekta. Više o dodatku možete saznati ovdje i ovdje. Između ostalog, dodatak javafxmobile automatizira postupak preuzimanja (s Maven Central ili jcenter) i dodavanja iOS i Android SDK-ova na put predavanja vaše aplikacije.

Ako ste upoznati s gradleom, mavenom ili mravom, sjajno - vjerojatno imate predodžbu o tome što se događa. Ako gradle niste upoznati, ne brinite zbog toga . Sve što trebate razumjeti je da je gradle alat za izgradnju koji se koristi za automatizaciju mnogih zadataka koji su uključeni u izgradnju aplikacija kao što su: hvatanje ovisnosti, organizacija projekta i tako dalje.

Primijetite da ciljamo Android 7.1 Nougat (API verzija 25) i iOS 11 (uskoro ćemo vidjeti gdje se to radi). Možete prilagoditi ove vrijednosti kako vam odgovara. Međutim, imajte na umu da u slučaju Android-a morate osigurati da se inačica API-ja podudara s verzijom SDK-a koju ste preuzeli (o tome kasnije).

Na kraju, u ovom uputstvu neću pokazati proizvodnju potpisanih izvršnih datoteka. Iz tog je razloga iOSSkipSigning postavljen na true i ne koristimo zadatak releaseAndroid gradle. Međutim, možete pružiti odgovarajući smještaj za izradu potpisanih aplikacija.

4) Napravite novu datoteku pod nazivom gradle.properties i konfigurirajte je

Stvorite novu datoteku u nazvanom korijenskom direktoriju projekta gradle.propertiesi dodajte joj sljedeći sadržaj.

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/