gr.zeus.ui

## Class SingleAppInstance

- java.lang.Object
- - gr.zeus.ui.SingleAppInstance

-     public final class SingleAppInstance
      extends java.lang.Object

  This helper component provides a simple solution to the multiple applications instances problem. Just invoke `onInit()` at your application's startup and `onExit()` at your application's shutdown and that's all there is to it. `SingleAppInstance` creates and locks a file within the startup directory so if anyone is to execute your application again the second `onInit()` call fails with a message. The `onExit()` method unlocks and deletes the file. If `m_reportPopup` is true, a popup window is displayed for the user to take action, else the user is informed via `stderr`. If you wish to change the look and feel of the popup window invoke `SingleAppInstance` after setting the look and feel inside your application. If you wish to translate the messages for this component create a new property file for your locale and place it inside `/gr/zeus/` where the default "singleappinstance.properties" resides.

  Since:
    1.05
  Author:
    Gregory Kotsaftis

- - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static SingleAppInstance` | `getInstance()` This method returns the single instance of this class.
    `static SingleAppInstance` | `getInstance(java.lang.String filename)` This method returns the single instance of this class.
    `boolean` | `getReportPopup()` Gets whether to report via a popup or via `stderr`.
    `void` | `onExit()` Release the file lock and delete the file.
    `void` | `onInit()` Creates a file and obtains a lock.
    `void` | `setReportPopup(boolean f)` Sets whether to report via a popup or via `stderr`.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Method Detail

    - #### getInstance

          public static SingleAppInstance getInstance()

      This method returns the single instance of this class.

      Returns:
        The single instance of this class.

    - #### getInstance

          public static SingleAppInstance getInstance(java.lang.String filename)

      This method returns the single instance of this class. Uses the filename parameter instead of default filename.

      Parameters:
        `filename` - The filename to create and lock, should be unique and within current folder.

      Returns:
        The single instance of this class.

    - #### onInit

          public void onInit()

      Creates a file and obtains a lock. If the file exists or there is any error creating it this method invokes `System.exit()`. Should be invoked ONCE inside `main()` in your application.

    - #### onExit

          public void onExit()

      Release the file lock and delete the file. Should be invoked ONCE just before calling `System.exit()` on your application.

    - #### getReportPopup

          public boolean getReportPopup()

      Gets whether to report via a popup or via `stderr`.

      Returns:
        If `true`, a popup window is displayed, else the user is informed via `stderr`.

    - #### setReportPopup

          public void setReportPopup(boolean f)

      Sets whether to report via a popup or via `stderr`.

      Parameters:
        `f` - If `true`, via a popup window, else via `stderr`.