Switch Web Event Handler

Size: px

Start display at page:

Download "Switch Web Event Handler"

Dale Austin
5 years ago
Views:

Switch Web Event Handler Contents Introduction... 1 Use SwitchEventHandler actions... 2 Switch handler at runtime (1)... 2 Switch handler at runtime (2)... 7 Remove Event Handler... 12 Test.

1 Switch Web Event Handler Contents Introduction... 1 Use SwitchEventHandler actions... 2 Switch handler at runtime (1)... 2 Switch handler at runtime (2)... 7 Remove Event Handler Test Feedback Introduction Usually actions are assigned to events at design time. In some situations at runtime, you may want to change what to be executed for some events. Conditional execution is one way of doing it. Switching event handler is another way of doing it. This document uses a sample project to show how to switch event handler at runtime. The sample web page has a button, TEST button. Clicking the TEST button, it shows a message box. The sample web page uses another 3 buttons to switch the event handler of the TEST button. Thus, clicking one of these 3 buttons will make the TEST button function differently. At design time we assigned a message box action to the onclick event of the TEST button. This is for demo purpose only. You do not need to assign action at design time if it is not needed. Longflow Enterprises Ltd. Page 1

2 Use SwitchEventHandler actions Every web control has a SwitchEventHandler method for switching event handler at runtime. Switch handler at runtime (1) Suppose when the user clicks button Use Handler A, we want to change the TEST button s functionality to be showing a message in the text box. Right-click button Use Handler A ; choose Assign Action ; choose onclick event: Select SwitchEventHandler method of the TEST button: Longflow Enterprises Ltd. Page 2

3 Choose onclick event for eventname of the action: Click to choose an event handler: Longflow Enterprises Ltd. Page 3

Click Create new handler to create a new event

4 Click Create new handler to create a new event handler: A Method Editor appears for creating a new event handler: Actions added to this method will be executed when the TEST button is clicked because eventname is onclick. For this sample, we show a message in a text box. Longflow Enterprises Ltd. Page 4

5 We form an expression to be displayed in the text box: For this sample, we show current date time: Longflow Enterprises Ltd. Page 5

6 For this example, we just need this one action: Click OK to finish creating this SwitchEventHandler action: The action is created and assigned to button Use Handler A : Longflow Enterprises Ltd. Page 6

box. Right-click button Use Handler B ; choose Assign Action ; choose onclick

7 Switch handler at runtime (2) Suppose when the user clicks button Use Handler B, we want to change the TEST button s functionality to be adding a list item to a list box. Right-click button Use Handler B ; choose Assign Action ; choose onclick event: Choose SwitchEventHandler method of the TEST button: Longflow Enterprises Ltd. Page 7

8 Choose onclick event for eventname of the action: Click to choose an event handler: Longflow Enterprises Ltd. Page 8

You may choose a previously created event handler.

event handler: A Method Editor appears for us to add

a new list item: Use an expression to form what we

9 You may choose a previously created event handler. Here we click Create new handler to create a new event handler: A Method Editor appears for us to add actions: For this sample, we create an action to add a new list item: Use an expression to form what we want to display in the list: Longflow Enterprises Ltd. Page 9

10 For this sample, we show current date time: For this sample, we just need this one action: Longflow Enterprises Ltd. Page 10

11 Click OK to finish creating the SwitchEventHandler action: The action is created and assigned to the User Handler B button: Longflow Enterprises Ltd. Page 11

Remove Event Handler Removing event handler can be achieved by switching to an empty handler. Suppose we want to use a button to remove the TEST button s event handler.

12 Remove Event Handler Removing event handler can be achieved by switching to an empty handler. Suppose we want to use a button to remove the TEST button s event handler. Right-click a Clear button; choose Assign Action ; choose onclick event: Select SwitchEventHandler method of the TEST button: Choose onclick event for eventname of the action: Longflow Enterprises Ltd. Page 12

13 We do not need to set handler because our purpose is just removing existing handler. Click OK to finish creating this SwitchEventHandler action: The action is created and assigned to the Clear button: Longflow Enterprises Ltd. Page 13

14 Test Now we may test our programming. The sample page appears. Click the TEST button: Longflow Enterprises Ltd. Page 14

15 A message box appears. This is the action assigned at design time: Click button Use Handler A : Now clicking TEST button will show a message in the text box: Click button Use Handler B : Longflow Enterprises Ltd. Page 15

16 Now one click of the TEST button will add an item to the list box: Click button Clear Handler : Now clicking the TEST button will do nothing. Feedback Please send your feedback, comment, and suggestions to support@limnor.com. Longflow Enterprises Ltd. Page 16

Use Web Event Bubbling

Use Web Event Bubbling Contents Introduction... 1 Use event bubbling... 1 Test event bubbling... 9 Feedbacks... 11 Introduction Every element in a web page has a parent element. For example, a button s