Custom UI Class Example: Choose Random Input Rasters

This example displays a UI dialog with a button for users to randomly select an input raster from files that are currently open in ENVI. The dialog is created using a simple IDL widget. This is an example of custom UI functionality that can be added to a workflow step.

Follow these steps to run the example:

1. Copy and paste the code below into the IDL Editor. Save the file as pickrandomraster_ui__define.pro.
2. Compile pickrandomraster_ui__define.pro.
3. Start ENVI.
4. From the ENVI menu bar, select File > Open.
5. Navigate to the ENVIxx\data\time_series folder of your ENVI installation path and use Ctrl-click to select all of the AirTemp*.dat files. Click Open.
6. Type the following in the IDL command line:

   IDL> e = ENVI()

   IDL> outputUI = Obj_New('PickRandomRaster_UI')

   IDL> raster = e.UI.CreateFromDialog(outputUI)

7. In the dialog that appears, click the Pick a Random Raster button. ENVI selects a random raster from the opened files and displays it in the dialog.

Code Example

PRO PickRandomRaster_UI_EventHandler, sEvent

COMPILE_OPT IDL2, HIDDEN

 

Widget_Control, sEvent.id, GET_UVALUE=self

self.HandleEvent, sEvent

END

 

;-----------------------------------------------------

FUNCTION PickRandomRaster_UI::Init, _REF_EXTRA=refExtra

COMPILE_OPT IDL2, HIDDEN

 

self.oRaster = ENVIRaster_UI()

return, self.ENVIParameterUI::Init(_EXTRA=refExtra)

END

 

;-----------------------------------------------------

PRO PickRandomRaster_UI::Cleanup

COMPILE_OPT IDL2, HIDDEN

 

IF (Obj_Valid(self.oRaster)) THEN BEGIN

  Obj_Destroy, self.oRaster

ENDIF

 

self.ENVIParameterUI::Cleanup

END

;-----------------------------------------------------

; Populate the UI with parameters based on the

; supplied value

PRO PickRandomRaster_UI::SetValue, value

COMPILE_OPT IDL2, HIDDEN

 

self.oRaster.SetValue, value

END

 

;-----------------------------------------------------

; Return the parameter value defined by the user and

; stored by the UI

FUNCTION PickRandomRaster_UI::GetValue, ERROR=error

COMPILE_OPT IDL2, HIDDEN

 

return, self.oRaster.GetValue(ERROR=error)

END

 

;-----------------------------------------------------

PRO PickRandomRaster_UI::HandleEvent, sEvent

COMPILE_OPT IDL2, HIDDEN

CASE Widget_Info(sEvent.id, /UNAME) OF

'randomize': BEGIN

  rasters = envi.data.Get(/RASTER)

  value = !null

  IF (N_Elements(rasters) ne 0) THEN BEGIN

    pos = Sort(Randomu(seed, N_Elements(rasters)))

    value = rasters[pos[0]]

  ENDIF

  self.SetValue, value

  END

  ELSE:

ENDCASE

END

 

;----------------------------------------------------

; Build and display the UI

PRO PickRandomRaster_UI::BuildUI, wBase, xSize

COMPILE_OPT IDL2, HIDDEN

 

wColumn = WIDGET_BASE(wBase, /COLUMN)

self.oRaster.BuildUI, wColumn, xSize

wRow = WIDGET_BASE(wColumn, /ROW)

!null = WIDGET_BUTTON(wRow, $

  VALUE='Pick a Random Raster', $

  UVALUE=self, $

  UNAME='randomize', $

EVENT_PRO='PickRandomRaster_UI_EventHandler')

END

 

; ----------------------------------------------------

PRO PickRandomRaster_UI__Define

COMPILE_OPT IDL2, HIDDEN

 

!null = {PickRandomRaster_UI, $

  inherits ENVIParameterUI, $

  oRaster: Obj_New() $

  }

END

See Also

Customize Workflows