Class Cancellable.Builder<B extends Cancellable.Builder<B>>

java.lang.Object
org.javagi.gobject.Builder<B>
org.gnome.gobject.GObject.Builder<B>
org.gnome.gio.Cancellable.Builder<B>
Type Parameters:
B - the type of the Builder that is returned
All Implemented Interfaces:
BuilderInterface
Enclosing class:
Cancellable
public static class Cancellable.Builder<B extends Cancellable.Builder<B>> extends GObject.Builder<B>
Inner class implementing a builder pattern to construct a GObject with properties.

  • Constructor Details

    • Builder

      protected Builder()
      Default constructor for a Builder object.

  • Method Details

    • build

      public Cancellable build()
      Finish building the Cancellable object. This will call GObject.withProperties(Type, String[], Value[]) to create a new GObject instance, which is then cast to Cancellable.
      Overrides:
      build in class GObject.Builder<B extends Cancellable.Builder<B>>
      Returns:
      a new instance of Cancellable with the properties that were set in the Builder object.

    • onCancelled

      public B onCancelled(Cancellable.CancelledCallback handler)

      Emitted when the operation has been cancelled.

      Can be used by implementations of cancellable operations. If the operation is cancelled from another thread, the signal will be emitted in the thread that cancelled the operation, not the thread that is running the operation.

      Note that disconnecting from this signal (or any signal) in a multi-threaded program is prone to race conditions. For instance it is possible that a signal handler may be invoked even after a call to g_signal_handler_disconnect() for that handler has already returned.

      There is also a problem when cancellation happens right before connecting to the signal. If this happens the signal will unexpectedly not be emitted, and checking before connecting to the signal leaves a race condition where this is still happening.

      In order to make it safe and easy to connect handlers there are two helper functions: g_cancellable_connect() and g_cancellable_disconnect() which protect against problems like this.

      An example of how to us this:

          // Make sure we don't do unnecessary work if already cancelled
    if (g_cancellable_set_error_if_cancelled (cancellable, error))
      return;

    // Set up all the data needed to be able to handle cancellation
    // of the operation
    my_data = my_data_new (...);

    id = 0;
    if (cancellable)
      id = g_cancellable_connect (cancellable,
    			      G_CALLBACK (cancelled_handler)
    			      data, NULL);

    // cancellable operation here...

    g_cancellable_disconnect (cancellable, id);

    // cancelled_handler is never called after this, it is now safe
    // to free the data
    my_data_free (my_data);

      Note that the cancelled signal is emitted in the thread that the user cancelled from, which may be the main thread. So, the cancellable signal should not do something that can block.

      Parameters:
      handler - the signal handler
      Returns:
      the Builder instance is returned, to allow method chaining
      See Also: