Android/java: Change View From Another Class?

There are two classes. MainActivity, in which i set the view, and ClassX from which i want to update a view in MainActivity. ClassX is an AsyncTask called from MainActivity, if tha

Solution 1:

If you are using an AsyncTask you need to set the value in either onProgressUpdate or in onPostExecute.

You really should read the documentation for AsyncTasks

You CANNOT update the UI from the doInBackground method as it is not run in the UI thread and will give you an exception.

Also, you should post the exception you are getting when the application crashes so we have a better idea what the problem is. But I'd guess you are trying to update the text from the wrong thread.

Solution 2:

I've done this plenty in the app im working on, its sort of an MDI type app on the android tablet.

To do what you're asking....

in MainActivity have

public static void setText(String txt){
  ((TextView)findViewById(R.id.mainTextLog)).setText(txt);
}

then in the child (or calling class) call it like...

MainActivity.setText("myTextToShow");

That's it... im using android api level 12... If i remember correcty it worked in api level 7 as well though.

Hope this helps...

Solution 3:

One possibility is that: when you call setLogText in another Class X. The MainActivity may not be existing anymore, which makes the logger a null reference?