Grids with Multiple Selection for Native Mobile Applications

GeneXus lets you define that a Grid has multiple selecction, and then lets you scan all the selected items in the Grid with the for each selected line command. The code to execute an action on all selected items will look as follows.

for each selected line [in <GridName>]
     <action or set of actions to execute for each item>
endfor

Adding multiple selections

To further explain the use of multiple selection actions, suppose that you have a set of customers and you want to apply a tax of 25% for some of them depending on their total amount.

Step 1 - Setting the UI behavior

Previously, create a Customer Transaction object as follows and apply the WorkWithDevices pattern.

In the Grid control from the List section of WorkWithDevicesCustomer, set the following properties:

• Default Action property = <default>
  In this case, the end-user is able to see the Detail section of the WorkWithDevicesCustomer when tapping in a register.
   
• Enable Multiple Selection property = True
  For allowing multiple selections over the Customer grid in the List Node.
   
• Show Selector property = Always
  It sets the user interface behavior for multiple item selections as always show its selector.

Step 2 - Creating the action

Create a new action called "Add tax" (right-click on the Application Bar > Insert Button).

This action will perform an ApplyTax procedure for updating the CustomerAmount by adding interest of 25% on the selected items. In this procedure, you have to write the following code:

for each
     CustomerAmount = CustomerAmount * 1.25
endfor

The procedure must have a Parm rule as it is shown below for automatically filtering the items in the for each command.

Parm(in:CustomerId);

3. Writing the action execution code

Finally, you have to write the section code associated with the action 'Add tax' on the Event section as follows.

Event 'Add tax'
     Composite
          For each selected line in Grid1
               ApplyTax(CustomerId)
          Endfor
          Refresh
     EndComposite
EndEvent

Note:

• For SDT or BC collection based Grids, the way to access to each item is by the CurrentItem runtime property.
  For example:

For each selected line in Grid1
    ApplyTax(&Customer.CurrentItem.CustomerId)
Endfor

where &Customer is a variable based on an SDT or BC item.

Application runtime behavior

1. You have to select the items that you would like to update. Every item can be selected by tapping on the left check-box.

2. Once you finish the selection, tap on "Add tax" action for executing the action to apply the 25% tax interest.

3. After the refresh of the device, you can see the total amount has changed correctly.

Notes

• If you have an action with several for each selected line over different Grids, the behavior of the User Interface is the platform default.
• An attribute used in a for each selected line command must be present in the grid on the form to work correctly.
• In the for each selected line in <grid> command, the grid's name is optional when you have only one grid in the SD Panel or WorkWithDevices object.
• If the grid row theme class has highlighted background color, this color will be used to mark the selected items.
• For Android devices, the selection user interface may depend on the operating system version.