get Activity object while in View context

问题

This is a followup to this post:

findViewById in a subclassed SurfaceView throwing RuntimeException

Based on Romain Guy's feedback (which I'll accept shortly as it is a solution), I'd like to obtain the calling Activity from within the View, so that I can use it to obtain the desired TextView resource.

I don't see any methods in View that return Activity. What is the proper way to do this? Or is there a better alternative for working with TextViews from within another View context.

Basically, I am calling setContentView(R.layout.xxx) in onCreate() (as usual), so I don't really have a way to pass in references to additional TextViews unless I awkwardly retrieve the View after setContentView and then make calls on it.

回答1:

An Activity is a Context, but there is no guarantee that the Context used by a View is always an Activity. Getting the views from onCreate() to do some setup is perfectly valid and is how Android applications are usually written. You could do something like this for instance:

setContentView(...);
MySurfaceView v = findViewById(R.id.theusrface);
TextView t = findViewById(R.id.thecontent);
v.setContent(v);

The logic should not go in your Views.

回答2:

If you already know the Activity class your View is in, i.e. MyActivity, you can use the static member MyActivity.this from inside your View and its listeners, as in the following example:

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit?")
       .setCancelable(false)
       .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
                MyActivity.this.finish();
           }
       })
       .setNegativeButton("No", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
                dialog.cancel();
           }
       });
AlertDialog alert = builder.create();

which I've found in this Android tutorial:

http://developer.android.com/guide/topics/ui/dialogs.html

It worked wonders for me.

PJ_Finnegan

来源：https://stackoverflow.com/questions/3901590/get-activity-object-while-in-view-context