Download Microsoft Edge More info. Contents Exit focus mode. Install and setup Xamarin. Is this page helpful? Please rate your experience Yes No. Any additional feedback? In this article. The Code Button Click page demonstrates how to create a page that is functionally equivalent to the Basic Button Click page but entirely in C :.
Everything is done in the class's constructor. Because the Clicked handler is only one statement long, it can be attached to the event very simply:. Of course, you can also define the event handler as a separate method just like the OnButtonClick method in Basic Button Click and attach that method to the event:.
Sometimes an application is in a particular state where a particular Button click is not a valid operation. In those cases, the Button should be disabled by setting its IsEnabled property to false. The classic example is an Entry control for a filename accompanied by a file-open Button : The Button should be enabled only if some text has been typed into the Entry. You can use a DataTrigger for this task, as shown in the Data Triggers article.
It is possible for an application to respond to Button taps without handling the Clicked event. The Button implements an alternative notification mechanism called the command or commanding interface. This consists of two properties:.
Commanding is described in greater detail in the article The Command Interface but the Basic Button Command page in the ButtonDemos sample shows the basic approach. The two ICommand properties are initialized in the class's constructor with two objects of type Command.
The Command constructors include a little function called the execute constructor argument that either doubles or halves the Number property.
The BasicButtonCommand. As the two Button elements are tapped, the commands are executed, and the number changes value:. The advantage of this approach over Clicked handlers is that all the logic involving the functionality of this page is located in the viewmodel rather than the code-behind file, achieving a better separation of the user interface from the business logic.
It is also possible for the Command objects to control the enabling and disabling of the Button elements. For example, suppose you want to limit the range of number values between 2 10 and 2 — You can add another function to the constructor called the canExecute argument that returns true if the Button should be enabled.
Here's the modification to the CommandDemoViewModel constructor:. The calls to the ChangeCanExecute method of Command are necessary so that the Command method can call the canExecute method and determine whether the Button should be disabled or not. With this code change, as the number reaches the limit, the Button is disabled:. It is possible for two or more Button elements to be bound to the same ICommand property. The Button elements can be distinguished using the CommandParameter property of Button.
The CommandParameter object is then passed as an argument to the execute and canExecute methods. This technique is shown in detail in the Basic Commanding section of the Command Interface article. The ButtonDemos sample also uses this technique in its MainPage class. The MainPage. Each Button has its Command property bound to a property named NavigateCommand , and the CommandParameter is set to a Type object corresponding to one of the page classes in the project.
That NavigateCommand property is of type ICommand and is defined in the code-behind file:. This means that the execute method has an argument of type Type that corresponds to this CommandParameter object. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Create button with click event Xamarin Android Ask Question. Asked 2 years, 7 months ago. Active 2 years, 7 months ago. Viewed 2k times. I have the following item. Inflate Resource. Improve this question. Forms buttons use the default padding and shadow values of Android buttons. UseDefaultPadding and Button. UseDefaultShadow attached properties to boolean values:. The Button. SetUseDefaultPadding and Button.
SetUseDefaultShadow methods, in the Xamarin.
0コメント