Xamarin Community Toolkit AsyncCommand

  • Artikel

Ermöglicht die sichere Verwendung des Task Typs mit einer ICommand.

Syntax

AsyncCommand<TExecute, TCanExecute> : IAsyncCommand<TExecute, TCanExecute>

public AsyncCommand(
    Func<TExecute, Task> execute,
    Func<TCanExecute, bool> canExecute = null,
    Action<Exception> onException = null,
    bool continueOnCapturedContext = false,
    bool allowsMultipleExecutions = true)

AsyncCommand<T> : IAsyncCommand<T>

public AsyncCommand(
    Func<T, Task> execute,
    Func<object, bool> canExecute = null,
    Action<Exception> onException = null,
    bool continueOnCapturedContext = false,
    bool allowsMultipleExecutions = true)

public AsyncCommand(
    Func<T, Task> execute,
    Func<bool> canExecute,
    Action<Exception> onException = null,
    bool continueOnCapturedContext = false,
    bool allowsMultipleExecutions = true)
    : this(execute, _ => canExecute(), onException, continueOnCapturedContext, allowsMultipleExecutions)

AsyncCommand : IAsyncCommand

public AsyncCommand(
    Func<Task> execute,
    Func<object, bool> canExecute = null,
    Action<Exception> onException = null,
    bool continueOnCapturedContext = false,
    bool allowsMultipleExecutions = true)

public AsyncCommand(
    Func<Task> execute,
    Func<bool> canExecute,
    Action<Exception> onException = null,
    bool continueOnCapturedContext = false,
    bool allowsMultipleExecutions = true)
    : this(execute, _ => canExecute(), onException, continueOnCapturedContext, allowsMultipleExecutions)

IAsyncCommand<TExecute, TCanExecute>

interface IAsyncCommand<TExecute, TCanExecute> : IAsyncCommand<TExecute>

IAsyncCommand<T>

interface IAsyncCommand<T> : ICommand

IAsyncCommand

interface IAsyncCommand : ICommand

Methoden

Methoden Rückgabetyp BESCHREIBUNG
ExecuteAsync() Aufgabe Führt den Befehl als Aufgabe aus.
ExecuteAsync(T) Aufgabe Führt den Befehl als Aufgabe aus.
ExecuteAsync(TExecute) Aufgabe Führt den Befehl als Aufgabe aus.

Beispiele

AsyncCommand

class MyViewModel
{
    bool _isBusy;

    public MyViewModel()
    {
        ButtonCommand = new AsyncCommand(() => ExecuteButtonCommand(), _ => !IsBusy);
    }

    public IAsyncCommand ButtonCommand { get; }

    public bool IsBusy
    {
        get => _isBusy;
        set
        {
            if(_isBusy != value)
            {
                _isBusy = value;
                ButtonCommand.RaiseCanExecuteChanged();
            }
        }
    }    

    async Task ExecuteButtonCommand()
    {
        // ...
    }
}

AsyncCommand<T>

class MyViewModel
{
    bool _isBusy;

    public MyViewModel()
    {
        ButtonCommand = new AsyncCommand<int>(buttonClicks => ExecuteButtonCommand(buttonClicks), _ => !IsBusy);
    }

    public IAsyncCommand<int> ButtonCommand { get; }

    public bool IsBusy
    {
        get => _isBusy;
        set
        {
            if(_isBusy != value)
            {
                _isBusy = value;
                ButtonCommand.RaiseCanExecuteChanged();
            }
        }
    }   
    

    async Task ExecuteButtonCommand(int buttonClicks)
    {
        // ...
    }
}

AsyncCommand<TExecute, TCanExecute>

class MyViewModel
{
    public MyViewModel()
    {
        ButtonCommand = new AsyncCommand<int, bool>(buttonClicks => ExecuteButtonCommand(buttonClicks), isBusy => !isBusy);
    }

    public IAsyncCommand<int, bool> ButtonCommand { get; } 
    

    async Task ExecuteButtonCommand(int buttonClicks)
    {
        // ...
    }
}

Beispielprojekt

AboutViewModel.

Dieses Element wird in der Beispiel-App des Xamarin-Community-Toolkits angezeigt.

API