Passing an ArrayList to another Activity but not displaying result?

Question

this is my very first question so go easy on me :) I am new to android, and I am trying to make a simple list. On the first Activity the user can enter data, which should display as a list on the second Activity.

I am using Intents to pass the data from one Activity to another, but I know I am missing something crucial in my ClassB Activity as nothing displays.

Here is my main code:

public class ClassA extends AppCompatActivity {

    EditText note;
    Button saveNoteB, goToNotesB;
    public final static String EXTRA_NOTE = "com.lisa.currys.userlistarray.note";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        saveNoteB = (Button) findViewById(R.id.saveNote);
        saveNoteB.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                    Intent i = new Intent(ClassA.this, ClassB.class);
                    note = (EditText) findViewById(R.id.note);
                    String userInput = note.getText().toString();

                    ArrayList<String> arr = new ArrayList<String>();
                    arr.add(userInput);

                    i.putStringArrayListExtra("note", arr);
                    startActivity(i);
            }
        });

and for my second activity:

public class ClassB extends AppCompatActivity {

public static android.widget.ListView displayNotes;
ArrayList<String> arr = new ArrayList<String>();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);

    arr = getIntent().getExtras().getStringArrayList(ClassA.EXTRA_NOTE);
    displayNotes = (ListView)findViewById(R.id.listView);
    Intent i = getIntent();
    arr = i.getStringArrayListExtra("note");

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(ClassB.this, android.R.layout.simple_list_item_1);
    displayNotes.setAdapter(adapter);
   }
}

Any pointers or advice would be most welcome.

Thank you.

Answer 1

In ClassA try this:

i.putStringArrayListExtra(EXTRA_NOTE, arr);

or in ClassB try this:

arr = getIntent().getExtras().getStringArrayList("note");

You have to use the same key to set and get the values.

By the way, why are you assign values to "arr" two times?

Answer 2

You are never actually adding the elements in arr to the ArrayAdapter . Use the three argument constructor for ArrayAdapter like below which will add the elements:

ArrayAdapter<String> adapter = 
    new ArrayAdapter<String>(ClassB.this, android.R.layout.simple_list_item_1, arr);

Answer 3

    Try this 

     ArrayAdapter<String> adapter = new ArrayAdapter<String>(ClassB.this, android.R.layout.simple_list_item_1);

     Above statement you are pass the context and layout in which your data
     display but you are not give the data which is store 
     in your **arr** arraylist so you not show anything.

  replace this statement to 

    ArrayAdapter<String> adapter = 
    new ArrayAdapter<String>(ClassB.this, android.R.layout.simple_list_item_1, arr);