modules/midp-lcdui/src/main/java/cc/squirreljme/runtime/lcdui/scritchui/ObjectTracker.java

   1 // -*- Mode: Java; indent-tabs-mode: t; tab-width: 4 -*-
   2 // ---------------------------------------------------------------------------
   3 // Multi-Phasic Applications: SquirrelJME
   4 //     Copyright (C) Stephanie Gawroriski <xer@multiphasicapps.net>
   5 // ---------------------------------------------------------------------------
   6 // SquirrelJME is under the Mozilla Public License Version 2.0.
   7 // See license.mkd for licensing and copyright information.
   8 // ---------------------------------------------------------------------------
   9
  10 package cc.squirreljme.runtime.lcdui.scritchui;
  11
  12 import cc.squirreljme.jvm.mle.scritchui.ScritchEventLoopInterface;
  13 import cc.squirreljme.runtime.cldc.annotation.SquirrelJMEVendorApi;
  14
  15 /**
  16  * This keeps track of an object string, if it changes then an update to
  17  * a signal end is emitted.
  18  *
  19  * The listener that is called is always in the event loop.
  20  *
  21  * @param <T> The object type.
  22  * @param <L> The listener type to use.
  23  * @since 2024/07/18
  24  */
  25 @SquirrelJMEVendorApi
  26 public abstract class ObjectTracker<T, L>
  27 {
  28         /** The event loop used. */
  29         @SquirrelJMEVendorApi
  30         protected final ScritchEventLoopInterface loop;
  31
  32         /** The current value. */
  33         @SquirrelJMEVendorApi
  34         volatile T _value;
  35
  36         /** The currently attached listener. */
  37         @SquirrelJMEVendorApi
  38         volatile L _listener;
  39
  40         /**
  41          * Initializes the object tracker with the given initial text.
  42          *
  43          * @param __loop The event loop interface.
  44          * @param __init The initial value to use.
  45          * @throws NullPointerException On null arguments.
  46          * @since 2024/07/20
  47          */
  48         @SquirrelJMEVendorApi
  49         public ObjectTracker(ScritchEventLoopInterface __loop, T __init)
  50                 throws NullPointerException
  51         {
  52                 if (__loop == null)
  53                         throw new NullPointerException("NARG");
  54
  55                 this.loop = __loop;
  56                 this._value = __init;
  57         }
  58
  59         /**
  60          * Executes the given listener.
  61          *
  62          * @param __listener The listener to execute.
  63          * @param __value The value being set.
  64          * @throws NullPointerException If no listener was specified.
  65          * @since 2024/07/20
  66          */
  67         @SquirrelJMEVendorApi
  68         protected abstract void exec(L __listener, T __value)
  69                 throws NullPointerException;
  70
  71         /**
  72          * Connects to the given listener.
  73          *
  74          * @param __listener The listener to connect to.
  75          * @throws NullPointerException On null arguments.
  76          * @since 2024/07/18
  77          */
  78         @SquirrelJMEVendorApi
  79         public final void connect(L __listener)
  80                 throws NullPointerException
  81         {
  82                 if (__listener == null)
  83                         throw new NullPointerException("NARG");
  84
  85                 synchronized (this)
  86                 {
  87                         this._listener = __listener;
  88                 }
  89
  90                 // Since we connected a listener, we want to make sure it has the
  91                 // most up-to-date information
  92                 this.loop.loopExecute(new __ExecObjectTracker__<T, L>(this));
  93         }
  94
  95         /**
  96          * Gets the current text.
  97          *
  98          * @return The current text.
  99          * @since 2024/07/18
 100          */
 101         @SquirrelJMEVendorApi
 102         public final T get()
 103         {
 104                 synchronized (this)
 105                 {
 106                         return this._value;
 107                 }
 108         }
 109
 110         /**
 111          * Sets the given text.
 112          *
 113          * @param __t The text to set.
 114          * @since 2024/07/18
 115          */
 116         @SquirrelJMEVendorApi
 117         public final void set(T __t)
 118         {
 119                 L listener;
 120                 synchronized (this)
 121                 {
 122                         this._value = __t;
 123                         listener = this._listener;
 124                 }
 125
 126                 // Inform listener of the change?
 127                 if (listener != null)
 128                         this.loop.loopExecute(new __ExecObjectTracker__<T, L>(
 129                                 this));
 130         }
 131 }