Interaction between activities

Question

I start an activity from the main one using a Intent:

Intent i = new Intent(getApplicationContext(), InfoChiamata.class); i.putExtra("codice_cliente", codice_cliente[tv_clicked_id]); i.putExtra("descrizione_chiamata", descrizione_chiamata[tv_clicked_id]); startActivity(i);

How can I edit the main activity ui from the activity started whit Intent? How can I know when i return back from the second activity to the main one? I tried to Override the onResume and onStart method but the application doesn't even start. I tryed to override onRestart method when it get called the application crash.

@Override protected void onRestart() { if(call_back == 1) Toast.makeText(getApplicationContext(), "asd", Toast.LENGTH_LONG).show(); }

call_back variable is set to 1 from the secondary activity, when it is launched.

Thanks, Mattia

L7ColWinters · Accepted Answer · 2012-02-13 16:07:10Z

try startActivityForResult instead which gives you a callback to your first activity. also don't use the application context, unless absolutely necessary, use the activity context instead. Also when you call certain methods from the activity class and override them like onRestart or onStop or onResume you have to do super.onResume() inside the method first, making sure that the app life cycle is not broken.

Thanks, now it works! Do you also know how to solve the first problem? I create a static method in main activity that edit his view, that it's the sam ethat i call from the secondary activity to edit main activity ui, but when i call i from secondary activity it shows in secondary activity the the piece of the view that has been update in main activity. Why? Thanks!

coder · Accepted Answer · 2012-02-13 16:12:16Z

Try starting your new Activity with

startActivityForResult(i, 1);

Then, in your main activity, use this code to catch when the user leaves the second activity and returns to the first one:

@Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); //your request code will be 1 since you started the //activity with result 1. Your result code will be detemined //by if the activity ended properly. }

Mel Stanley · Accepted Answer · 2012-02-13 16:15:15Z

It sounds like maybe you want to use startActivityForResult(Context, Intent) to call your second activity. When you do this, your second activity can return a value to the activity that called it, and you can decide what to do from there. When the second activity is finished your first activity will receive a callback. This tells your first activity that the second one is finished and it is passed the result of what happened in the second activity.

It is explained in the Android docs here: http://developer.android.com/reference/android/app/Activity.html#startActivityForResult(android.content.Intent,%20int)

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