Sådan oprettes en mobilplatform på tværs af platforme i Java

Vidste du, at du kan bruge Java til at oprette mobilapps på tværs af platforme? Ja, klem dig selv, du læste det rigtigt første gang! Jeg lærer dig det grundlæggende om, hvordan du bruger din eksisterende Java-viden til at oprette performante apps på Android og iOS i 12 nemme trin. Vi gør alt dette ved hjælp af JavaFX som GUI-værktøjssæt.

Men først lidt mere forgrund. Du bliver nødt til at opfylde de efterfølgende krav for at kunne oprette en applikation til både Android og iOS. Men hvis du ikke ønsker at opbygge en iOS-applikation, er du velkommen til at udvikle på enhver x64-bitmaskine, der understøtter Java SE 8. Dette projekt vil være et Git-arkiv bygget med gradle. Men du behøver ikke oprette et Git-arkiv.

Følgende er kravene :

  • En JDK 1.8-kompatibel JVM
  • Android Command Line Tools (SDK v.27)
  • XCode 9.2
  • Gradering 4.2
  • Git Large File Storage (v.2.5.0) (unødvendigt, hvis du ikke vil oprette et git-arkiv)
  • Fortrinsvis mindst 4G RAM

Utålmodig? Vil du se et slutresultat? Tjek det afsluttede projekt nedenfor.

afinlay5 / OnyxFx

Gradle kildekodebaseret til OnyxFx, en cross-platform (Android / iOS / Linux / macOS / Windows) JavaFX app-gengivelse ... github.com

Mit udviklingsmiljø vil være Fedora Linux 28 og macOS High Sierra. Nu hvor vi har fået det ud af vejen, lad os grave ind.

1) Opret en mappe til projektets projekt

Jeg var vært for mit projekt, OnyxFx, som følger: “ / home / adriandavid / Projects / OnyxFx”. Du er selvfølgelig fri til at være vært for projektet, uanset hvor du vil.

2) Initialiser graduer, Git, indstil JAVA_HOME

Åbn en terminal i roden til projektmappen. Hvis gradle er korrekt konfigureret, skal du se noget lignende efter at have udført følgende kommando:

gradle -v

Du skal sørge for, at gradle viser din Java Development Kit (JDK) 8-installation ved siden af ​​sektionen mærket "JVM".

Mens der er mange måder at gøre dette på, er den mest enkle måde at sikre, at din JAVA_HOME miljøvariabel er korrekt indstillet.

Afhængigt af dit miljø er der mange måder at gøre dette på. En måde at gøre dette på i de fleste * nix-miljøer er at indstille variablen i /home//.b ash rc eller / etc / pro- fil. Se manualen til dit operativsystem for at sikre, at din JAVA_HOME miljøvariabel er indstillet korrekt.

Du kan inkludere følgende linjer i slutningen af ​​enten .bashrc eller profil for at sikre, at JAVA_HOME er indstillet korrekt.

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

Bemærk: Du kan installere Oracle's JDK 8 her.

Sørg derefter for, at skallen reflekterer ovenstående ændringer ved at køre en af ​​følgende kommandoer:

source ~/.bashrcsource /etc/profile

Indtast følgende kommando for at kontrollere, at variablen er korrekt indstillet:

echo $JAVA_HOME

Hvis du stadig har problemer, eller du bruger Microsoft Windows, kan du se her.

Kør først git initi projektets rodkatalog for at initialisere Git-arkivet. Bemærk: Hvis du ikke ønsker at være vært for et git-arkiv, kan du springe dette trin over.

For det andet skal du køre gradle initi projektets rodmappe for at initialisere gradle-arkivet. Dette trin er påkrævet.

Bemærk: Du vil bemærke, at mit eksempel ser lidt anderledes ud. Dette skyldes, at jeg allerede har gradueret og Git initialiseret på mit lokale miljø.

3) Bliv groovy! Rediger gradle.build og

Forhåbentlig kan jord, vind og ild hjælpe dig med at blive groovy! Tænd din yndlings teksteditor, og rediger din build.gradle, der er placeret i dit projekts rodmappe, og udskift indholdet med indholdet af følgende GitHub-kerne.

Disse build.gradle-indstillinger konfigurerer vores gradle-projekt til at bruge javafxmobile- pluginet, som er arbejdshesten i vores projekt. Du kan lære mere om pluginet her og her. Blandt mange ting automatiserer javafxmobile-pluginet processen med at downloade (fra Maven Central eller jcenter) og tilføje iOS og Android SDK'er til din applikations klassesti.

Hvis du er fortrolig med gradle, maven eller myre, fantastisk - har du sandsynligvis en idé om, hvad der foregår. Hvis du ikke er fortrolig med gradle, skal du ikke bekymre dig om det . Alt hvad du behøver at forstå er, at gradle er et buildværktøj, der bruges til at automatisere mange opgaver, der er involveret i at opbygge apps, såsom: grabbing afhængigheder, projektorganisation osv.

Bemærk, at vi målretter mod Android 7.1 Nougat (API version 25) og iOS 11 (vi vil se, hvor dette sker inden længe). Du kan justere disse værdier, som du finder passende. Bemærk dog, at i tilfælde af Android skal du sikre dig, at API-versionen matcher den version af SDK, du har downloadet (mere om dette senere).

Endelig vil jeg ikke demonstrere produktionen af ​​underskrevne eksekverbare filer i denne vejledning. Af denne grund er iOSSkipSigning indstillet til sandt, og vi gør ikke brug af releaseAndroid gradle-opgaven. Du kan dog tilbyde de relevante boliger til at producere underskrevne apps.

4) Opret en ny fil kaldet gradle.properties og konfigurer den

Opret en ny fil i projektets rodmappe, der kaldes, gradle.propertiesog tilføj følgende indhold til filen.

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/