I need help converting a string to an integer - android-studio

Question

Good day,
I have an array adapter in Activity1 in my AndroidStudio project. I would like to transfer two specific items from the ArrayAdapter (in positions 1 and 2) to Activity2 with an intent. (the ArrayAdapter is connected to an editTextNumber) That works well if I then display the two items in a TextView. But if I want to convert the items to an int, the app always crashes. I can somehow just convert "message1" into an int. Why is that so?
Thank you for your help
(Activity 1):
[...]
#Override
protected void onCreate(Bundle savedInstanceState) {
ArrayAdapter adapterzeit = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, zeit1);
Intent intent = new Intent(this, Activity2.class);
start.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
intent.putExtra("EXTRA_MESSAGE1", adapterzeit.getItem(1).toString());
intent.putExtra("EXTRA_MESSAGE2", adapterzeit.getItem(3).toString());
startActivity(intent);
}
});
}
(Activity 2):
[...]
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_timer);
Intent intent = getIntent();
String message1 = intent.getStringExtra("EXTRA_MESSAGE1");
String message2 = intent.getStringExtra("EXTRA_MESSAGE2");
int numberInt = Integer.parseInt(message1);
int number2 = Integer.parseInt(message2);
}
}

Answer 1

You add the extra to the Intent like this:
intent.putExtra("EXTRA_MESSAGE1", adapterzeit.getItem(1).toString());
and then you try to extract it from the Intent like this:
String message1 = intent.getStringExtra("EXTRA_MESSAGE");
You are using different String values for the keys! EXTRA_MESSAGE != EXTRA_MESSAGE1
This is one reason why you should always use constant definitions for these kinds of things, then you wouldn't have this problem. For example, in Activity1:
public static final String EXTRA_MESSAGE1 = "EXTRA_MESSAGE1";
intent.putExtra(EXTRA_MESSAGE1, adapterzeit.getItem(1).toString());
and then in Activity2:
String message1 = intent.getStringExtra(Activity1.EXTRA_MESSAGE1);