从上一个活动获取文本并将其添加到另一个活动列表视图

Question

How do I add items to a list dynamically when button is clicked? The text is added to the listView . At the moment it only adds one item to the list view, and when you try to add another it just changes the already added item in the list.

Here is my code:

This is the button on click for activity A that gets the text:

schedule.setOnClickListener(new OnClickListener() {

         public void onClick(View view) {

             AddSchedule();

             Intent i = new Intent(ScheduleActivity.this, MainActivity.class);
             String str = event_name.getText().toString();
             i.putExtra("myExtra", str);
             startActivity(i);

         }

     });

Then in activity B it gets the text from activity B but only adds the

Final ListView listView = (ListView) findViewById(R.id.listView); adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, list); listView.setAdapter(adapter);

    Intent i = getIntent();
    if (i.hasExtra("myExtra")) {
        list.add(i.getStringExtra("myExtra"));
        adapter.notifyDataSetChanged();
    }

Answer 1

You only see one item in the new activty's list, since that Activity is created each time via startActivity(Intent) (I suppose). So each time open Activity B, it's a new instance. The arraylist is empty.

You need to keep track of the items clicked in Activity A and send the whole list to Activity B, every time. Activity B should get the complete list in the intent and create the gui-list.

Make your class implement Parcelable or Serializable (slower).

Answer 2

Inside activity B you should include the following:

@Override
public void onSaveInstanceState(Bundle out){
    super.onSaveInstanceState(out);
    out.putStringArrayList(key, list);
}

"key" is a final String you have defined in Activity's B member variables.

This will make sure your list is saved before being destroyed (For more, read about Activity Lifecycle . Now, you also need to restore in whenever the activity is created. You can do that in onCreateView like so:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    //restore the contents of your list
    if (savedInstanceState!=null)
        list=savedInstanceState.getStringArrayList(key);

    /* initialize the adapter and set it to the list */

    //also add the new item from activity A
    Intent i = getIntent();
    if (i.hasExtra("myExtra")) {
        list.add(i.getStringExtra("myExtra"));
        adapter.notifyDataSetChanged();
    }
}

General note, instead of adding to the list and afterwards notifying the adapter, you can instead add your items directly to the adapter. The adapter will automatically update your list.

Edit: Yes, your list should be a member variable because it needs to be accessed in 2 methods.