How can I start an Activity from a non-Activity cl

问题:

I have a map view activity that shows a few OverlayItems. In the onTap method of an overlay, I want to trigger a new activity that shows this overlay photo as a fullscreen, for example.

When I do this inside my overlay class:

Intent intent = new Intent();
intent.setClass(getApplicationContext, FullscreenView.class);
startActivity(intent);

.. it can't find an application context, as I am not in the scope of an activity.

When I add a method to my main activity, let's say startFullscreen:

public static void startFullscreen() {
    if (sCurrentPhoto != null) {
        Intent intent = new Intent();
        intent.setClass(getApplicationContext(), FullscreenView.class);
        startActivity(intent);          
    }
}

I can not call getApplicationContext() and startActivity(), because I am in a static context. I need the static method however to call it in the Overlay class like MainView.startFullscreen().

Put simply: How can I start an Activity from a non-Activity class?

回答1:

Your onTap override receives the MapView from which you can obtain the Context:

@Override
public boolean onTap(GeoPoint p, MapView mapView)
{
    // ...

    Intent intent = new Intent();
    intent.setClass(mapView.getContext(), FullscreenView.class);
    startActivity(intent);

    // ...
}

回答2:

Once you have obtained the context in your onTap() you can also do:

Intent myIntent = new Intent(mContext, theNewActivity.class);
mContext.startActivity(myIntent);

回答3:

I don't know if this is good practice or not, but casting a Context object to an Activity object compiles fine.

Try this: ((Activity) mContext).startActivity(...)

回答4:

You can define a context for your application say ExampleContext which will hold the context of your application and then use it to instantiate an activity like this:

var intent = new Intent(Application.ApplicationContext, typeof(Activity2));
intent.AddFlags(ActivityFlags.NewTask);
Application.ApplicationContext.StartActivity(intent);

Please bear in mind that this code is written in C# as I use MonoDroid, but I believe it is very similar to Java. For how to create an ApplicationContext look at this thread

This is how I made my Application Class

    [Application]
    public class Application : Android.App.Application, IApplication
    {
        public Application(IntPtr handle, JniHandleOwnership transfer) : base(handle, transfer)
        {

        }
        public object MyObject { get; set; }
    }