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Mensaje de Nostalgia: j2me, Gravity Defied, 64kb

Este artículo no persigue ningún objetivo práctico: me preguntaba cómo hace unos 15 años, los desarrolladores lograron crear aplicaciones y juegos completamente funcionales para teléfonos débiles de la época.



  • En todo caso, no tengo nada que ver con este juego.

, floating-point , . "3" — fixed-point . , . , j2me Android.


, j2me — java (, 1.3), .jar PC. — . , - — API j2me .


.


, , , .


Nokia 5200, " " :


  • 2006
  • 128x160 1.8
  • 262 . ( , 6 R, G, B ).
  • - bluetooth .
  • ( , 7 )
  • microSd , , , 256 .
  • - opera mini (, , )
  • 640x480 .
  • MIDP 2.0 (wiki)
  • usb
  • -
  • , , — 100 , , floating-point . , - .

, — , 50-200 .


Write once, run everywhere


java . , . , platform- , .


, — . — . . , .jar j2me .class java. , Canvas, MIDlet javax.microedition.


, . Android : .class , .dex ( , .. dex 65 ), apk, ART.


, . , . , . , Vector synchronized. Vector , ArrayList ArrayList , .


— java . (int, boolean, ...) . Vector Object, .


, go , java 1.3. go - , java 2004 1.5 . 1.3.


j2me — .jar .class ( 1.3, 20 ), Gravity defied PC. "" java javax.microedition , . , : , java.awt.Image javax.microedition.lcdui.Image.


J2ME



javax.microedition. , - , , - , , — . javax.microedition.lcdui.


MIDlet.


startApp().
— pauseApp() startApp() . destroyApp().


, notifyPaused() notifyDestroyed() — , .
, " " resumeRequest()


, notifyPaused(), , .


, lifecycle .


, Runnable - :


Thread thread;
boolean isRunning;
boolean needToDestroy = false;

public void startApp() {
    isRunning = true;
    if (thread != null) {
        thread = new Thread(this);
        thread.start();
    }
}

public void pauseApp() {
    isRunning = false;
}

public void destroyApp(boolean unconditional) {
    needToDestroy = true;
}

, .


void run(){
    while(!needToDestroy) {
        //   
        //     - .
        while (!isRunning) {
            Thread.sleep(100);
        }
    }
    notifyDestroyed();
}

, 100 — , . , pauseApp() startApp()


Canvas


— Canvas. Canvas java.


repaint(), , . UI- paint(Graphics g). , - , Canvas — . — repaint() paint(...) .


, :
hasPointerEvents(), hasPointerMotionEvents(), hasRepeatEvents(), true. pointerDragged(int x, int y) ( ), pressed( ) released( ).
— , .



, — , . . , , . , 240360 . — — .


- , "" , . j2me - , , .., . , nokia 5800 , .


MIDlet Pascal


- , . java2me , , MIDlet pascal . j2me — , , java.


?


, , , Gravity Defied 64 .


-, .jar — zip , 122.1 kB


  • META-INF MANIFEST.MF 3.8 kB, SHA-1 MD5 . .
  • levels.mrg 5.1 kB 30 . 170 . .
  • 11 . 10.8 kB.
  • .class , 98.3 kB, 15 . — 127 , 24.3 kB. :
    • , (4 ), 127 174 .
    • — 470 .
    • 9 — 1.6 6 kB.
    • god-like :


. fernflower — , intelliJ IDEA. — , . .


IDEA — , .


: /gradlew jar, build .jar
: mkdir decompiled && java -jar fernflower.jar -ren=1 GravityDefied_java decompiled


ren , if for. , java . ren=1 field_42 method_135 — , .


2004 — , , :


  • - , . .class .
  • else, int ..
  • . "" Micro, .
  • , fixed-point , . , (int)((long)a * b >> 16)
  • , , .


— , . , , -. , .


- Netbeans, j2me SDK. , , ant. .


, Linux. gradle . — javax.microedition.*. — PC- java. . , .


watch ./gradlew run . ctrl+S .


.
19 :


  • 8 javax.microedition.rms.
  • 10 .lcdui, , , Canvas ..).
  • MIDlet — , .

, .


Micro, . - , startApp MIDlet .


:


protected void pauseApp() {
    c = true;
    if (!b) {
        this.gameToMenu();
    }
    System.gc();
}

, c isPaused.


"" :


public void a() {
    if (this.recordStore != null) {
        try {
            this.e.closeRecordStore();
            return;
        } catch (RecordStoreException var1) {
        }
    }
}

- closeMethodStore.


, intelliJ IDEA - . — , , Image.loadImage(name):


this.p = Image.createImage("/splash.png");

, p splashImage.


- — , . , … Jetbrains — , — . , , .


- . — loadImage()… null . .


: , Image:


public class Image {
    public final java.awt.Image image;

    private Image(java.at.Image image) {
        this.image = image;
    }

    public Graphics getGraphics() {
        throw new RuntimeException();
    }

    public int getWidth() {
        return image.getWidth(null);
    }

    public static Image createImage(int w, int h) {
        return new Image(new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB));
    }
    ...
}

, API , .


CanvasImpl, JPanel. Canvas.
, c :


public void paintComponent(Graphics g) {
    if (upscale == 1) {
        canvas.paint(new javax.microedition.lcdui.Graphics(g));
    } else {
        canvas.paint(new javax.microedition.lcdui.Graphics(screen.getGraphics()));
        g.drawImage(screen, 0, 0, width * upscale, height * upscale, Color.WHITE, null);
    }
}

javax.microedition.lcdui.Graphics(g) — awt.Graphics, .


, . "" , .


, , , , — . PC. ? - 64 * 64, , 1 * 1 , 240 * 320 . , , , , .


, . , , , , , .


, , j2me PC. — 2010 -, - . - - — .


!


, .


.jar . . , , . - Alert Canvas Displayable , Canvas. , .


gradle :


  • emulator , , . , , .
  • app-original, .jar
  • app-from-sources - . .


, , . "" , , .


, .


Fixed-point physics


. , 16 — . , , -32768.0 32767.999984 c 1.0 / 65536.


— .


int.


: int, , "". long. 64 32 . 16 16- int.


: . long, 16 . - , 32 — 16.


sin, cos atan2.


— 64 — 0 90 . , — . . , .




, . Canvas.hasPointerEvents() true, , . — " ", " ", " " - "" . , , .


Level format


, — 170 . ? — .


, — / .., . . 0xff, int , , — dx , dy.


for (int i = 1; i < pointsCount; ++i) {
    byte modeOrDx;
    if ((modeOrDx = var1.readByte()) == -1) {
        offsetY = 0;
        offsetX = 0;
        pointX = var1.readInt();
        pointY = var1.readInt();
    } else {
        pointX = modeOrDx;
        pointY = var1.readByte();
    }
    offsetX += pointX;
    offsetY += pointY;
    this.addPointSimple(offsetX, offsetY);
}


.



GPU full hd , (128*160 240*320). 3 - , api . , — 90-180-270 .


, — .
, 32 16 . 48*48 1091 .


, , - API 3 3 - 3-. , - .


— 2 3.



. — 100 "23" "64".


if (time10MsToStringCache[time10MsPart] == null) {
    String zeroPadding;
    if (time10MsPart >= 10) {
        zeroPadding = "";
    } else {
        zeroPadding = "0";
    }
    time10MsToStringCache[time10MsPart] = zeroPadding + time10Ms % 100L;
}

, , . , -.


No-MVP


MenuManager ( ) . - , — - , .


, - , . : Android:


  • layout . .
  • stings.txt.
  • Activity, .
  • LifecycleObserver, Adapter , Activity .
  • Adapter DataSource.
  • " ", Bundle DataSource .
  • DataSouce SQLite .

: , ? , .



, TimerOrMotoPartOrMenuElem .
, , :


  • -
  • , " "

, , , — .


, , 64 . , - , "" .



, , , , . ", " — .


:


public void init() {
    long timeToLoading = 3000L;
    Thread.yield();
    this.gameCanvas = new GameCanvas(this);
    Display.getDisplay(this).setCurrent(this.gameCanvas);
    this.gameCanvas.requestRepaint(1);

    while (!this.gameCanvas.isShown()) {
        this.goLoadingStep();
    }

    long deltaTimeMs;
    while (timeToLoading > 0L) {
        deltaTimeMs = this.goLoadingStep();
        timeToLoading -= deltaTimeMs;
    }

    this.gameCanvas.requestRepaint(2);

    for (timeToLoading = 3000L; timeToLoading > 0L; timeToLoading -= deltaTimeMs) {
        deltaTimeMs = this.goLoadingStep();
    }

    while (gameLoadingStateStage < 10) {
        this.goLoadingStep();
    }

    this.gameCanvas.requestRepaint(0);
    this.isInited = true;
}

goLoadingStep() . goLoadingStep(). goLoadingStep , .


goLoadingStep() :


private long goLoadingStep() {
    ++gameLoadingStateStage;
    this.gameCanvas.repaint();
    long startTimeMillis = System.currentTimeMillis();
    switch (gameLoadingStateStage) {
        case 1:
            this.levelLoader = new LevelLoader();
            break;
        case 2:
            this.gamePhysics = new GamePhysics(this.levelLoader);
            this.gameCanvas.init(this.gamePhysics);
            break;
        case 3:
            this.menuManager = new MenuManager(this);
            this.menuManager.initPart(1);
            break;
            .... ///   5-8
        case 9:
            this.menuManager.initPart(7);
            break;
        case 10:
            this.gameCanvas.setMenuManager(this.menuManager);
            this.gameCanvas.setViewPosition(-50, 150);
            this.setMode(1);
            break;
        default:
            --gameLoadingStateStage;

            try {
                Thread.sleep(100L);
            } catch (InterruptedException var3) {
            }
    }

    return System.currentTimeMillis() - startTimeMillis;
}

MenuManager.initPart() switch case .


, , . , .



2004 . Excitera Mobile Awards 2004 (EMA04) best-in-show. Codebrew Software :


  • Tors Björn Henrik Johansson — system/game logic/interface, testing, levels design
  • Set Elis Norman — graphics/physics/mathematics/system/tools programming, levels design
  • Per David Jacobsson — physics programming, game graphics, levels design

Además, hay un puerto de este juego para Android hecho por nuestros compatriotas, pero solo usa un código descompilado.


Dado que no ha habido quejas sobre ese código durante cinco años, creo que mi intento de descompilar la aplicación original y entender que no hará ningún daño. Ahora el juego es de interés histórico y le permite echar un vistazo más de cerca a la era de los teléfonos inteligentes pequeños que podrían.

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