Android - Adding item to ListView from another Activity

Question

First of all, I've searched on many other posts and still not found a fix for it.

MainActivity contains a ListView and an ImageButton that takes to AddActivity . This AddActivity has got a EditText ( nameAddInput ) and a Button ( addButton ).

Despite clicking this Button , the ListView in MainActivity remains empty... Don't understand why...

Here is the the code of MainActivity :

public class MainActivity extends AppCompatActivity {

static final int PICK_CONTACT_REQUEST = 0;

private ListView list;
private ArrayAdapter<String> adapter;
private ArrayList<String> arrayList;


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

    list = (ListView) findViewById(R.id.itemsList);
    arrayList = new ArrayList<>();
    adapter = new ArrayAdapter<>(this, R.layout.listview_style1, android.R.id.text1, arrayList);
}

public void onClickAddButton(View view) {
    Intent i = new Intent(MainActivity.this, AddActivity.class);
    startActivityForResult(i, 2);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == PICK_CONTACT_REQUEST) {
        if (resultCode == RESULT_OK) {
            addNewItem();
        }
    }
}

public void addNewItem() {
    Bundle addNameInfo = getIntent().getExtras();
    if(addNameInfo == null)
        return;
    String nameInput = addNameInfo.getString("nameInput");
    arrayList.add(nameInput);
    list.setAdapter(adapter);
    adapter.notifyDataSetChanged();
}

}

In xml file of MainActivity in the ImageButton: android:onClick="onClickAddButton"

The code of AddActivity :

public class AddActivity extends AppCompatActivity {

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

public void backToMain(View view) {
    Intent i = new Intent();
    EditText nameAddInput = (EditText) findViewById(R.id.nameAddInput);
    String userNameText = nameAddInput.getText().toString();
    i.putExtra("nameInput", userNameText);
    setResult(RESULT_OK, i);
    finish();
}

}

In xml file of AddActivity in the Button: android:onClick="backToMain"

Hope someone can help!! Thank you in advance!!

Answer 1

getIntent() returns you the intent that launched MainActivity, not the one you set in backInMain

Try the "data" variable passed to you in onActivityResult?

Also change to

startActivityForResult(i, PICK_CONTACT_REQUEST);

I'd also suggest you rename that variable 😉

Answer 2

只需在onCreate中设置适配器，然后在addNewItem方法中调用notifyDataSetChanged即可。

Answer 3

the resulting value is returned in the Intent data -Parameter of the onActivityResult function, not in the intent-member of the mainActivity.

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent    data) {
    if (requestCode == PICK_CONTACT_REQUEST) {
        if (resultCode == RESULT_OK) {
            addNewItem(data.getExtras().getString("nameInput");
       }
   }
}
...
public void addNewItem(String newItem)
...