Package org.eclipse.e4.core.commands

Interface EHandlerService

All Known Implementing Classes:
HandlerServiceImpl
public interface EHandlerService
This service enables actions on handlers. A handler is an object which has methods that are annotated with @CanExecute (optional) and @Execute. A handler is associated with a Command which is an abstract notion of a user action like "copy" and "paste".

Many handlers may be associated with a command (e.g. "copy") because each handler typically only handles the command when in a specific context.

An example of different contexts, is the use of the "copy" command in a text editor versus in a table. In every case the command is the same, but the code executed is very different.

You should not implement this interface, an implementation is provided by Eclipse.

It is usually not needed to use this service in your programs because handler activation is done by Eclipse using binding contexts that are evaluated when a part is made active. Execution is done by Eclipse when a user presses a button or uses a context menu. However, in some cases it may be needed to programmatically manipulate handler activation, or execute the handler that is active for a give command.

Example usage: 

 
 @inject  ECommandService cs;
 @inject  EHandlerService hs;

 Command command = cs.getCommand(commandId);
 if (command.isDefined()) {
        Map<String Object> parameters = new HashMap<String, Object>();
        parameters.put("parm1", "hello, world");
        ParameterizedCommand parmCmd = cs.createCommand(commandId, parameters);
        if (hs.canExecute(parmCmd)) {
                hs.executeHandler(parmCmd);
        }
        else {logger.error("Cannot execute command");}
 }
 else {logger.error("Command is not defined");}
Since:
1.0
See Also:
Restriction:
This interface is not intended to be implemented by clients.
Restriction:
This interface is not intended to be extended by clients.

  • Method Details

    • activateHandler

      void activateHandler(String commandId, Object handler)
      Makes the passed handler active for the command with the passed commandId.
      Parameters:
      commandId - Must not be null
      handler - Must not be null

    • deactivateHandler

      void deactivateHandler(String commandId, Object handler)
      Deactivates the passed handler from the command with the passed id.
      Parameters:
      commandId - Must not be null
      handler - Must not be null

    • executeHandler

      Object executeHandler(ParameterizedCommand command)
      Executes the active handler of the passed command.
      Parameters:
      command - Must not be null
      Returns:
      the return value of the handler, could be null

    • canExecute

      boolean canExecute(ParameterizedCommand command)
      Tests if the active handler associated with the passed command can be executed.
      Parameters:
      command - Must not be null
      Returns:
      true of the handler can be executed, false if it cannot be executed or if no handler is active for the passed command.

    • executeHandler

      Object executeHandler(ParameterizedCommand command, IEclipseContext staticContext)
      Execute a handler for the command.
      Parameters:
      command - Must not be null
      staticContext - Must not be null. You must dispose your context when you are done.
      Returns:
      the command return value.

    • canExecute

      boolean canExecute(ParameterizedCommand command, IEclipseContext staticContext)
      Check if a command can be executed.
      Parameters:
      command - Must not be null.
      staticContext - Must not be null. You must dispose your context when you are done.
      Returns:
      true if the command can be executed.